# Source code for erfa.core

```
# Licensed under a 3-clause BSD style license - see LICENSE.rst
# "core.py" is auto-generated by erfa_generator.py from the template
# "core.py.templ". Do *not* edit "core.py" directly, instead edit
# "core.py.templ" and run erfa_generator.py from the source directory to
# update it.
"""
Python wrappers for the ufunc wrappers of the ERFA library.
The key idea is that any function can be called with inputs that are arrays,
and the ufuncs will automatically vectorize and call the ERFA functions for
each item using broadcasting rules for numpy. So the return values are always
numpy arrays of some sort.
For ERFA functions that take/return vectors or matrices, the vector/matrix
dimension(s) are always the *last* dimension(s). For example, if you
want to give ten matrices (i.e., the ERFA input type is double[3][3]),
you would pass in a (10, 3, 3) numpy array. If the output of the ERFA
function is scalar, you'll get back a length-10 1D array.
(Note that the ufuncs take this into account using structured dtypes.)
Note that the ufunc part of these functions are implemented in a separate
module (compiled as ``ufunc``), derived from the ``ufunc.c`` file.
"""
import warnings
import numpy
from . import ufunc
__all__ = [
'ErfaError', 'ErfaWarning',
'cal2jd', 'epb', 'epb2jd', 'epj', 'epj2jd', 'jd2cal', 'jdcalf', 'ab', 'apcg',
'apcg13', 'apci', 'apci13', 'apco', 'apco13', 'apcs', 'apcs13', 'aper',
'aper13', 'apio', 'apio13', 'atci13', 'atciq', 'atciqn', 'atciqz', 'atco13',
'atic13', 'aticq', 'aticqn', 'atio13', 'atioq', 'atoc13', 'atoi13', 'atoiq',
'ld', 'ldn', 'ldsun', 'pmpx', 'pmsafe', 'pvtob', 'refco', 'epv00', 'plan94',
'fad03', 'fae03', 'faf03', 'faju03', 'fal03', 'falp03', 'fama03', 'fame03',
'fane03', 'faom03', 'fapa03', 'fasa03', 'faur03', 'fave03', 'bi00', 'bp00',
'bp06', 'bpn2xy', 'c2i00a', 'c2i00b', 'c2i06a', 'c2ibpn', 'c2ixy', 'c2ixys',
'c2t00a', 'c2t00b', 'c2t06a', 'c2tcio', 'c2teqx', 'c2tpe', 'c2txy', 'eo06a',
'eors', 'fw2m', 'fw2xy', 'ltp', 'ltpb', 'ltpecl', 'ltpequ', 'num00a', 'num00b',
'num06a', 'numat', 'nut00a', 'nut00b', 'nut06a', 'nut80', 'nutm80', 'obl06',
'obl80', 'p06e', 'pb06', 'pfw06', 'pmat00', 'pmat06', 'pmat76', 'pn00',
'pn00a', 'pn00b', 'pn06', 'pn06a', 'pnm00a', 'pnm00b', 'pnm06a', 'pnm80',
'pom00', 'pr00', 'prec76', 's00', 's00a', 's00b', 's06', 's06a', 'sp00',
'xy06', 'xys00a', 'xys00b', 'xys06a', 'ee00', 'ee00a', 'ee00b', 'ee06a',
'eect00', 'eqeq94', 'era00', 'gmst00', 'gmst06', 'gmst82', 'gst00a', 'gst00b',
'gst06', 'gst06a', 'gst94', 'pvstar', 'starpv', 'fk425', 'fk45z', 'fk524',
'fk52h', 'fk54z', 'fk5hip', 'fk5hz', 'h2fk5', 'hfk5z', 'starpm', 'eceq06',
'ecm06', 'eqec06', 'lteceq', 'ltecm', 'lteqec', 'g2icrs', 'icrs2g', 'eform',
'gc2gd', 'gc2gde', 'gd2gc', 'gd2gce', 'd2dtf', 'dat', 'dtdb', 'dtf2d', 'taitt',
'taiut1', 'taiutc', 'tcbtdb', 'tcgtt', 'tdbtcb', 'tdbtt', 'tttai', 'tttcg',
'tttdb', 'ttut1', 'ut1tai', 'ut1tt', 'ut1utc', 'utctai', 'utcut1', 'ae2hd',
'hd2ae', 'hd2pa', 'tpors', 'tporv', 'tpsts', 'tpstv', 'tpxes', 'tpxev', 'a2af',
'a2tf', 'af2a', 'anp', 'anpm', 'd2tf', 'tf2a', 'tf2d', 'rx', 'ry', 'rz', 'cp',
'cpv', 'cr', 'p2pv', 'pv2p', 'ir', 'zp', 'zpv', 'zr', 'rxr', 'tr', 'rxp',
'rxpv', 'trxp', 'trxpv', 'rm2v', 'rv2m', 'pap', 'pas', 'sepp', 'seps', 'c2s',
'p2s', 'pv2s', 's2c', 's2p', 's2pv', 'pdp', 'pm', 'pmp', 'pn', 'ppp', 'ppsp',
'pvdpv', 'pvm', 'pvmpv', 'pvppv', 'pvu', 'pvup', 'pvxpv', 'pxp', 's2xpv',
'sxp', 'sxpv',
'DPI', 'D2PI', 'DR2D', 'DD2R', 'DR2AS', 'DAS2R', 'DS2R', 'TURNAS', 'DMAS2R',
'DTY', 'DAYSEC', 'DJY', 'DJC', 'DJM', 'DJ00', 'DJM0', 'DJM00', 'DJM77',
'TTMTAI', 'DAU', 'CMPS', 'AULT', 'DC', 'ELG', 'ELB', 'TDB0', 'SRS', 'WGS84',
'GRS80', 'WGS72']
[docs]class ErfaError(ValueError):
"""
A class for errors triggered by ERFA functions (status codes < 0)
Note: this class should *not* be referenced by fully-qualified name, because
it may move to ERFA in a future version. In a future such move it will
still be imported here as an alias, but the true namespace of the class may
change.
"""
[docs]class ErfaWarning(UserWarning):
"""
A class for warnings triggered by ERFA functions (status codes > 0)
Note: this class should *not* be referenced by fully-qualified name, because
it may move to ERFA in a future version. In a future such move it will
still be imported here as an alias, but the true namespace of the class may
change.
"""
# <---------------------------------Error-handling---------------------------->
STATUS_CODES = {} # populated below before each function that returns an int
# This is a hard-coded list of status codes that need to be remapped,
# such as to turn errors into warnings.
STATUS_CODES_REMAP = {
'cal2jd': {-3: 3}
}
def check_errwarn(statcodes, func_name):
if not numpy.any(statcodes):
return
# Remap any errors into warnings in the STATUS_CODES_REMAP dict.
if func_name in STATUS_CODES_REMAP:
for before, after in STATUS_CODES_REMAP[func_name].items():
statcodes[statcodes == before] = after
STATUS_CODES[func_name][after] = STATUS_CODES[func_name][before]
if numpy.any(statcodes < 0):
# Errors present - only report the errors.
if statcodes.shape:
statcodes = statcodes[statcodes < 0]
errcodes = numpy.unique(statcodes)
errcounts = dict([(e, numpy.sum(statcodes == e)) for e in errcodes])
elsemsg = STATUS_CODES[func_name].get('else', None)
if elsemsg is None:
errmsgs = dict([(e, STATUS_CODES[func_name].get(
e, 'Return code ' + str(e))) for e in errcodes])
else:
errmsgs = dict([(e, STATUS_CODES[func_name].get(
e, elsemsg)) for e in errcodes])
emsg = ', '.join(['{0} of "{1}"'.format(errcounts[e], errmsgs[e])
for e in errcodes])
raise ErfaError('ERFA function "{}" yielded {}'
.format(func_name, emsg))
elif numpy.any(statcodes > 0):
# Only warnings present.
if statcodes.shape:
statcodes = statcodes[statcodes > 0]
warncodes = numpy.unique(statcodes)
warncounts = dict([(w, numpy.sum(statcodes == w)) for w in warncodes])
elsemsg = STATUS_CODES[func_name].get('else', None)
if elsemsg is None:
warnmsgs = dict([(w, STATUS_CODES[func_name].get(
w, 'Return code ' + str(w))) for w in warncodes])
else:
warnmsgs = dict([(w, STATUS_CODES[func_name].get(
w, elsemsg)) for w in warncodes])
wmsg = ', '.join(['{0} of "{1}"'.format(warncounts[w], warnmsgs[w])
for w in warncodes])
warnings.warn('ERFA function "{}" yielded {}'.format(func_name, wmsg),
ErfaWarning)
# <------------------------structured dtype conversion------------------------>
dt_bytes1 = numpy.dtype('S1')
dt_bytes12 = numpy.dtype('S12')
# <--------------------------Actual ERFA-wrapping code------------------------>
DPI = (3.141592653589793238462643)
"""Pi"""
D2PI = (6.283185307179586476925287)
"""2Pi"""
DR2D = (57.29577951308232087679815)
"""Radians to degrees"""
DD2R = (1.745329251994329576923691e-2)
"""Degrees to radians"""
DR2AS = (206264.8062470963551564734)
"""Radians to arcseconds"""
DAS2R = (4.848136811095359935899141e-6)
"""Arcseconds to radians"""
DS2R = (7.272205216643039903848712e-5)
"""Seconds of time to radians"""
TURNAS = (1296000.0)
"""Arcseconds in a full circle"""
DMAS2R = (DAS2R / 1e3)
"""Milliarcseconds to radians"""
DTY = (365.242198781)
"""Length of tropical year B1900 (days)"""
DAYSEC = (86400.0)
"""Seconds per day."""
DJY = (365.25)
"""Days per Julian year"""
DJC = (36525.0)
"""Days per Julian century"""
DJM = (365250.0)
"""Days per Julian millennium"""
DJ00 = (2451545.0)
"""Reference epoch (J2000.0), Julian Date"""
DJM0 = (2400000.5)
"""Julian Date of Modified Julian Date zero"""
DJM00 = (51544.5)
"""Reference epoch (J2000.0), Modified Julian Date"""
DJM77 = (43144.0)
"""1977 Jan 1.0 as MJD"""
TTMTAI = (32.184)
"""TT minus TAI (s)"""
DAU = (149597870.7e3)
"""Astronomical unit (m, IAU 2012)"""
CMPS = 299792458.0
"""Speed of light (m/s)"""
AULT = (DAU/CMPS)
"""Light time for 1 au (s)"""
DC = (DAYSEC/AULT)
"""Speed of light (au per day)"""
ELG = (6.969290134e-10)
"""L_G = 1 - d(TT)/d(TCG)"""
ELB = (1.550519768e-8)
"""L_B = 1 - d(TDB)/d(TCB), and TDB (s) at TAI 1977/1/1.0"""
TDB0 = (-6.55e-5)
"""L_B = 1 - d(TDB)/d(TCB), and TDB (s) at TAI 1977/1/1.0"""
SRS = 1.97412574336e-8
"""Schwarzschild radius of the Sun (au) = 2 * 1.32712440041e20 / (2.99792458e8)^2
/ 1.49597870700e11"""
WGS84 = 1
"""Reference ellipsoids"""
GRS80 = 2
"""Reference ellipsoids"""
WGS72 = 3
"""Reference ellipsoids"""
[docs]def cal2jd(iy, im, id):
"""
Gregorian Calendar to Julian Date.
Parameters
----------
iy : int array
im : int array
id : int array
Returns
-------
djm0 : double array
djm : double array
Notes
-----
Wraps ERFA function ``eraCal2jd``. The ERFA documentation is::
- - - - - - - - - -
e r a C a l 2 j d
- - - - - - - - - -
Gregorian Calendar to Julian Date.
Given:
iy,im,id int year, month, day in Gregorian calendar (Note 1)
Returned:
djm0 double MJD zero-point: always 2400000.5
djm double Modified Julian Date for 0 hrs
Returned (function value):
int status:
0 = OK
-1 = bad year (Note 3: JD not computed)
-2 = bad month (JD not computed)
-3 = bad day (JD computed)
Notes:
1) The algorithm used is valid from -4800 March 1, but this
implementation rejects dates before -4799 January 1.
2) The Julian Date is returned in two pieces, in the usual ERFA
manner, which is designed to preserve time resolution. The
Julian Date is available as a single number by adding djm0 and
djm.
3) In early eras the conversion is from the "Proleptic Gregorian
Calendar"; no account is taken of the date(s) of adoption of
the Gregorian Calendar, nor is the AD/BC numbering convention
observed.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 12.92 (p604).
This revision: 2013 August 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
djm0, djm, c_retval = ufunc.cal2jd(iy, im, id)
check_errwarn(c_retval, 'cal2jd')
return djm0, djm
STATUS_CODES['cal2jd'] = {
0: 'OK',
-1: 'bad year (Note 3: JD not computed)',
-2: 'bad month (JD not computed)',
-3: 'bad day (JD computed)',
}
[docs]def epb(dj1, dj2):
"""
Julian Date to Besselian Epoch.
Parameters
----------
dj1 : double array
dj2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEpb``. The ERFA documentation is::
- - - - - - -
e r a E p b
- - - - - - -
Julian Date to Besselian Epoch.
Given:
dj1,dj2 double Julian Date (see note)
Returned (function value):
double Besselian Epoch.
Note:
The Julian Date is supplied in two pieces, in the usual ERFA
manner, which is designed to preserve time resolution. The
Julian Date is available as a single number by adding dj1 and
dj2. The maximum resolution is achieved if dj1 is 2451545.0
(J2000.0).
Reference:
Lieske, J.H., 1979. Astron.Astrophys., 73, 282.
This revision: 2013 August 21
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.epb(dj1, dj2)
return c_retval
[docs]def epb2jd(epb):
"""
Besselian Epoch to Julian Date.
Parameters
----------
epb : double array
Returns
-------
djm0 : double array
djm : double array
Notes
-----
Wraps ERFA function ``eraEpb2jd``. The ERFA documentation is::
- - - - - - - - - -
e r a E p b 2 j d
- - - - - - - - - -
Besselian Epoch to Julian Date.
Given:
epb double Besselian Epoch (e.g. 1957.3)
Returned:
djm0 double MJD zero-point: always 2400000.5
djm double Modified Julian Date
Note:
The Julian Date is returned in two pieces, in the usual ERFA
manner, which is designed to preserve time resolution. The
Julian Date is available as a single number by adding djm0 and
djm.
Reference:
Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
This revision: 2013 August 13
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
djm0, djm = ufunc.epb2jd(epb)
return djm0, djm
[docs]def epj(dj1, dj2):
"""
Julian Date to Julian Epoch.
Parameters
----------
dj1 : double array
dj2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEpj``. The ERFA documentation is::
- - - - - - -
e r a E p j
- - - - - - -
Julian Date to Julian Epoch.
Given:
dj1,dj2 double Julian Date (see note)
Returned (function value):
double Julian Epoch
Note:
The Julian Date is supplied in two pieces, in the usual ERFA
manner, which is designed to preserve time resolution. The
Julian Date is available as a single number by adding dj1 and
dj2. The maximum resolution is achieved if dj1 is 2451545.0
(J2000.0).
Reference:
Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
This revision: 2013 August 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.epj(dj1, dj2)
return c_retval
[docs]def epj2jd(epj):
"""
Julian Epoch to Julian Date.
Parameters
----------
epj : double array
Returns
-------
djm0 : double array
djm : double array
Notes
-----
Wraps ERFA function ``eraEpj2jd``. The ERFA documentation is::
- - - - - - - - - -
e r a E p j 2 j d
- - - - - - - - - -
Julian Epoch to Julian Date.
Given:
epj double Julian Epoch (e.g. 1996.8)
Returned:
djm0 double MJD zero-point: always 2400000.5
djm double Modified Julian Date
Note:
The Julian Date is returned in two pieces, in the usual ERFA
manner, which is designed to preserve time resolution. The
Julian Date is available as a single number by adding djm0 and
djm.
Reference:
Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
This revision: 2013 August 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
djm0, djm = ufunc.epj2jd(epj)
return djm0, djm
[docs]def jd2cal(dj1, dj2):
"""
Julian Date to Gregorian year, month, day, and fraction of a day.
Parameters
----------
dj1 : double array
dj2 : double array
Returns
-------
iy : int array
im : int array
id : int array
fd : double array
Notes
-----
Wraps ERFA function ``eraJd2cal``. The ERFA documentation is::
- - - - - - - - - -
e r a J d 2 c a l
- - - - - - - - - -
Julian Date to Gregorian year, month, day, and fraction of a day.
Given:
dj1,dj2 double Julian Date (Notes 1, 2)
Returned (arguments):
iy int year
im int month
id int day
fd double fraction of day
Returned (function value):
int status:
0 = OK
-1 = unacceptable date (Note 1)
Notes:
1) The earliest valid date is -68569.5 (-4900 March 1). The
largest value accepted is 1e9.
2) The Julian Date is apportioned in any convenient way between
the arguments dj1 and dj2. For example, JD=2450123.7 could
be expressed in any of these ways, among others:
dj1 dj2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
Separating integer and fraction uses the "compensated summation"
algorithm of Kahan-Neumaier to preserve as much precision as
possible irrespective of the jd1+jd2 apportionment.
3) In early eras the conversion is from the "proleptic Gregorian
calendar"; no account is taken of the date(s) of adoption of
the Gregorian calendar, nor is the AD/BC numbering convention
observed.
References:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 12.92 (p604).
Klein, A., A Generalized Kahan-Babuska-Summation-Algorithm.
Computing, 76, 279-293 (2006), Section 3.
This revision: 2020 October 21
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
iy, im, id, fd, c_retval = ufunc.jd2cal(dj1, dj2)
check_errwarn(c_retval, 'jd2cal')
return iy, im, id, fd
STATUS_CODES['jd2cal'] = {
0: 'OK',
-1: 'unacceptable date (Note 1)',
}
[docs]def jdcalf(ndp, dj1, dj2):
"""
Julian Date to Gregorian Calendar, expressed in a form convenient
for formatting messages: rounded to a specified precision.
Parameters
----------
ndp : int array
dj1 : double array
dj2 : double array
Returns
-------
iymdf : int array
Notes
-----
Wraps ERFA function ``eraJdcalf``. The ERFA documentation is::
- - - - - - - - - -
e r a J d c a l f
- - - - - - - - - -
Julian Date to Gregorian Calendar, expressed in a form convenient
for formatting messages: rounded to a specified precision.
Given:
ndp int number of decimal places of days in fraction
dj1,dj2 double dj1+dj2 = Julian Date (Note 1)
Returned:
iymdf int[4] year, month, day, fraction in Gregorian
calendar
Returned (function value):
int status:
-1 = date out of range
0 = OK
+1 = NDP not 0-9 (interpreted as 0)
Notes:
1) The Julian Date is apportioned in any convenient way between
the arguments dj1 and dj2. For example, JD=2450123.7 could
be expressed in any of these ways, among others:
dj1 dj2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
2) In early eras the conversion is from the "Proleptic Gregorian
Calendar"; no account is taken of the date(s) of adoption of
the Gregorian Calendar, nor is the AD/BC numbering convention
observed.
3) See also the function eraJd2cal.
4) The number of decimal places ndp should be 4 or less if internal
overflows are to be avoided on platforms which use 16-bit
integers.
Called:
eraJd2cal JD to Gregorian calendar
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 12.92 (p604).
This revision: 2020 October 22
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
iymdf, c_retval = ufunc.jdcalf(ndp, dj1, dj2)
check_errwarn(c_retval, 'jdcalf')
return iymdf
STATUS_CODES['jdcalf'] = {
-1: 'date out of range',
0: 'OK',
1: 'NDP not 0-9 (interpreted as 0)',
}
[docs]def ab(pnat, v, s, bm1):
"""
Apply aberration to transform natural direction into proper
direction.
Parameters
----------
pnat : double array
v : double array
s : double array
bm1 : double array
Returns
-------
ppr : double array
Notes
-----
Wraps ERFA function ``eraAb``. The ERFA documentation is::
- - - - - -
e r a A b
- - - - - -
Apply aberration to transform natural direction into proper
direction.
Given:
pnat double[3] natural direction to the source (unit vector)
v double[3] observer barycentric velocity in units of c
s double distance between the Sun and the observer (au)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
Returned:
ppr double[3] proper direction to source (unit vector)
Notes:
1) The algorithm is based on Expr. (7.40) in the Explanatory
Supplement (Urban & Seidelmann 2013), but with the following
changes:
o Rigorous rather than approximate normalization is applied.
o The gravitational potential term from Expr. (7) in
Klioner (2003) is added, taking into account only the Sun's
contribution. This has a maximum effect of about
0.4 microarcsecond.
2) In almost all cases, the maximum accuracy will be limited by the
supplied velocity. For example, if the ERFA eraEpv00 function is
used, errors of up to 5 microarcseconds could occur.
References:
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013).
Klioner, Sergei A., "A practical relativistic model for micro-
arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).
Called:
eraPdp scalar product of two p-vectors
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ppr = ufunc.ab(pnat, v, s, bm1)
return ppr
[docs]def apcg(date1, date2, ebpv, ehp):
"""
For a geocentric observer, prepare star-independent astrometry
parameters for transformations between ICRS and GCRS coordinates.
Parameters
----------
date1 : double array
date2 : double array
ebpv : double array
ehp : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApcg``. The ERFA documentation is::
- - - - - - - -
e r a A p c g
- - - - - - - -
For a geocentric observer, prepare star-independent astrometry
parameters for transformations between ICRS and GCRS coordinates.
The Earth ephemeris is supplied by the caller.
The parameters produced by this function are required in the
parallax, light deflection and aberration parts of the astrometric
transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
ebpv double[2][3] Earth barycentric pos/vel (au, au/day)
ehp double[3] Earth heliocentric position (au)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
4) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraApcs astrometry parameters, ICRS-GCRS, space observer
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apcg(date1, date2, ebpv, ehp)
return astrom
[docs]def apcg13(date1, date2):
"""
For a geocentric observer, prepare star-independent astrometry
parameters for transformations between ICRS and GCRS coordinates.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApcg13``. The ERFA documentation is::
- - - - - - - - - -
e r a A p c g 1 3
- - - - - - - - - -
For a geocentric observer, prepare star-independent astrometry
parameters for transformations between ICRS and GCRS coordinates.
The caller supplies the date, and ERFA models are used to predict
the Earth ephemeris.
The parameters produced by this function are required in the
parallax, light deflection and aberration parts of the astrometric
transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
Returned:
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) In cases where the caller wishes to supply his own Earth
ephemeris, the function eraApcg can be used instead of the present
function.
4) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
5) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraEpv00 Earth position and velocity
eraApcg astrometry parameters, ICRS-GCRS, geocenter
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apcg13(date1, date2)
return astrom
[docs]def apci(date1, date2, ebpv, ehp, x, y, s):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and geocentric CIRS
coordinates.
Parameters
----------
date1 : double array
date2 : double array
ebpv : double array
ehp : double array
x : double array
y : double array
s : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApci``. The ERFA documentation is::
- - - - - - - -
e r a A p c i
- - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and geocentric CIRS
coordinates. The Earth ephemeris and CIP/CIO are supplied by the
caller.
The parameters produced by this function are required in the
parallax, light deflection, aberration, and bias-precession-nutation
parts of the astrometric transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
ebpv double[2][3] Earth barycentric position/velocity (au, au/day)
ehp double[3] Earth heliocentric position (au)
x,y double CIP X,Y (components of unit vector)
s double the CIO locator s (radians)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) In cases where the caller does not wish to provide the Earth
ephemeris and CIP/CIO, the function eraApci13 can be used instead
of the present function. This computes the required quantities
using other ERFA functions.
4) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
5) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraApcg astrometry parameters, ICRS-GCRS, geocenter
eraC2ixys celestial-to-intermediate matrix, given X,Y and s
This revision: 2013 September 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apci(date1, date2, ebpv, ehp, x, y, s)
return astrom
[docs]def apci13(date1, date2):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and geocentric CIRS
coordinates.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
astrom : eraASTROM array
eo : double array
Notes
-----
Wraps ERFA function ``eraApci13``. The ERFA documentation is::
- - - - - - - - - -
e r a A p c i 1 3
- - - - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and geocentric CIRS
coordinates. The caller supplies the date, and ERFA models are used
to predict the Earth ephemeris and CIP/CIO.
The parameters produced by this function are required in the
parallax, light deflection, aberration, and bias-precession-nutation
parts of the astrometric transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
eo double equation of the origins (ERA-GST)
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) In cases where the caller wishes to supply his own Earth
ephemeris and CIP/CIO, the function eraApci can be used instead
of the present function.
4) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
5) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraEpv00 Earth position and velocity
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
eraApci astrometry parameters, ICRS-CIRS
eraEors equation of the origins, given NPB matrix and s
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom, eo = ufunc.apci13(date1, date2)
return astrom, eo
[docs]def apco(date1, date2, ebpv, ehp, x, y, s, theta, elong, phi, hm, xp, yp, sp, refa, refb):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and observed
coordinates.
Parameters
----------
date1 : double array
date2 : double array
ebpv : double array
ehp : double array
x : double array
y : double array
s : double array
theta : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
sp : double array
refa : double array
refb : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApco``. The ERFA documentation is::
- - - - - - - -
e r a A p c o
- - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and observed
coordinates. The caller supplies the Earth ephemeris, the Earth
rotation information and the refraction constants as well as the
site coordinates.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
ebpv double[2][3] Earth barycentric PV (au, au/day, Note 2)
ehp double[3] Earth heliocentric P (au, Note 2)
x,y double CIP X,Y (components of unit vector)
s double the CIO locator s (radians)
theta double Earth rotation angle (radians)
elong double longitude (radians, east +ve, Note 3)
phi double latitude (geodetic, radians, Note 3)
hm double height above ellipsoid (m, geodetic, Note 3)
xp,yp double polar motion coordinates (radians, Note 4)
sp double the TIO locator s' (radians, Note 4)
refa double refraction constant A (radians, Note 5)
refb double refraction constant B (radians, Note 5)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double adjusted longitude (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) The vectors eb, eh, and all the astrom vectors, are with respect
to BCRS axes.
3) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN
CONVENTION: the longitude required by the present function is
right-handed, i.e. east-positive, in accordance with geographical
convention.
The adjusted longitude stored in the astrom array takes into
account the TIO locator and polar motion.
4) xp and yp are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions), measured along the
meridians 0 and 90 deg west respectively. sp is the TIO locator
s', in radians, which positions the Terrestrial Intermediate
Origin on the equator. For many applications, xp, yp and
(especially) sp can be set to zero.
Internally, the polar motion is stored in a form rotated onto the
local meridian.
5) The refraction constants refa and refb are for use in a
dZ = A*tan(Z)+B*tan^3(Z) model, where Z is the observed
(i.e. refracted) zenith distance and dZ is the amount of
refraction.
6) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
7) In cases where the caller does not wish to provide the Earth
Ephemeris, the Earth rotation information and refraction
constants, the function eraApco13 can be used instead of the
present function. This starts from UTC and weather readings etc.
and computes suitable values using other ERFA functions.
8) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
9) The context structure astrom produced by this function is used by
eraAtioq, eraAtoiq, eraAtciq* and eraAticq*.
Called:
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRy rotate around Y-axis
eraRx rotate around X-axis
eraAnpm normalize angle into range +/- pi
eraC2ixys celestial-to-intermediate matrix, given X,Y and s
eraPvtob position/velocity of terrestrial station
eraTrxpv product of transpose of r-matrix and pv-vector
eraApcs astrometry parameters, ICRS-GCRS, space observer
eraCr copy r-matrix
This revision: 2021 January 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apco(
date1, date2, ebpv, ehp, x, y, s, theta, elong, phi, hm, xp, yp, sp, refa, refb)
return astrom
[docs]def apco13(utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and observed
coordinates.
Parameters
----------
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
astrom : eraASTROM array
eo : double array
Notes
-----
Wraps ERFA function ``eraApco13``. The ERFA documentation is::
- - - - - - - - - -
e r a A p c o 1 3
- - - - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between ICRS and observed
coordinates. The caller supplies UTC, site coordinates, ambient air
conditions and observing wavelength, and ERFA models are used to
obtain the Earth ephemeris, CIP/CIO and refraction constants.
The parameters produced by this function are required in the
parallax, light deflection, aberration, and bias-precession-nutation
parts of the ICRS/CIRS transformations.
Given:
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 1,2)
dut1 double UT1-UTC (seconds, Note 3)
elong double longitude (radians, east +ve, Note 4)
phi double latitude (geodetic, radians, Note 4)
hm double height above ellipsoid (m, geodetic, Notes 4,6)
xp,yp double polar motion coordinates (radians, Note 5)
phpa double pressure at the observer (hPa = mB, Note 6)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 7)
Returned:
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
eo double equation of the origins (ERA-GST)
Returned (function value):
int status: +1 = dubious year (Note 2)
0 = OK
-1 = unacceptable date
Notes:
1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
2) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the
future to be trusted. See eraDat for further details.
3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
4) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
5) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many
applications, xp and yp can be set to zero.
Internally, the polar motion is stored in a form rotated onto
the local meridian.
6) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB), is
available, an adequate estimate of hm can be obtained from the
expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to
the pressure and that an accurate phpa value is important for
precise work.
7) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
8) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
9) In cases where the caller wishes to supply his own Earth
ephemeris, Earth rotation information and refraction constants,
the function eraApco can be used instead of the present function.
10) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
11) The context structure astrom produced by this function is used
by eraAtioq, eraAtoiq, eraAtciq* and eraAticq*.
Called:
eraUtctai UTC to TAI
eraTaitt TAI to TT
eraUtcut1 UTC to UT1
eraEpv00 Earth position and velocity
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
eraEra00 Earth rotation angle, IAU 2000
eraSp00 the TIO locator s', IERS 2000
eraRefco refraction constants for given ambient conditions
eraApco astrometry parameters, ICRS-observed
eraEors equation of the origins, given NPB matrix and s
This revision: 2013 December 5
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom, eo, c_retval = ufunc.apco13(
utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'apco13')
return astrom, eo
STATUS_CODES['apco13'] = {
1: 'dubious year (Note 2)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def apcs(date1, date2, pv, ebpv, ehp):
"""
For an observer whose geocentric position and velocity are known,
prepare star-independent astrometry parameters for transformations
between ICRS and GCRS.
Parameters
----------
date1 : double array
date2 : double array
pv : double array
ebpv : double array
ehp : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApcs``. The ERFA documentation is::
- - - - - - - -
e r a A p c s
- - - - - - - -
For an observer whose geocentric position and velocity are known,
prepare star-independent astrometry parameters for transformations
between ICRS and GCRS. The Earth ephemeris is supplied by the
caller.
The parameters produced by this function are required in the space
motion, parallax, light deflection and aberration parts of the
astrometric transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
pv double[2][3] observer's geocentric pos/vel (m, m/s)
ebpv double[2][3] Earth barycentric PV (au, au/day)
ehp double[3] Earth heliocentric P (au)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) Providing separate arguments for (i) the observer's geocentric
position and velocity and (ii) the Earth ephemeris is done for
convenience in the geocentric, terrestrial and Earth orbit cases.
For deep space applications it maybe more convenient to specify
zero geocentric position and velocity and to supply the
observer's position and velocity information directly instead of
with respect to the Earth. However, note the different units:
m and m/s for the geocentric vectors, au and au/day for the
heliocentric and barycentric vectors.
4) In cases where the caller does not wish to provide the Earth
ephemeris, the function eraApcs13 can be used instead of the
present function. This computes the Earth ephemeris using the
ERFA function eraEpv00.
5) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
6) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraCp copy p-vector
eraPm modulus of p-vector
eraPn decompose p-vector into modulus and direction
eraIr initialize r-matrix to identity
This revision: 2017 March 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apcs(date1, date2, pv, ebpv, ehp)
return astrom
[docs]def apcs13(date1, date2, pv):
"""
For an observer whose geocentric position and velocity are known,
prepare star-independent astrometry parameters for transformations
between ICRS and GCRS.
Parameters
----------
date1 : double array
date2 : double array
pv : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApcs13``. The ERFA documentation is::
- - - - - - - - - -
e r a A p c s 1 3
- - - - - - - - - -
For an observer whose geocentric position and velocity are known,
prepare star-independent astrometry parameters for transformations
between ICRS and GCRS. The Earth ephemeris is from ERFA models.
The parameters produced by this function are required in the space
motion, parallax, light deflection and aberration parts of the
astrometric transformation chain.
Given:
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
pv double[2][3] observer's geocentric pos/vel (Note 3)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double unchanged
refa double unchanged
refb double unchanged
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) All the vectors are with respect to BCRS axes.
3) The observer's position and velocity pv are geocentric but with
respect to BCRS axes, and in units of m and m/s. No assumptions
are made about proximity to the Earth, and the function can be
used for deep space applications as well as Earth orbit and
terrestrial.
4) In cases where the caller wishes to supply his own Earth
ephemeris, the function eraApcs can be used instead of the present
function.
5) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
6) The context structure astrom produced by this function is used by
eraAtciq* and eraAticq*.
Called:
eraEpv00 Earth position and velocity
eraApcs astrometry parameters, ICRS-GCRS, space observer
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apcs13(date1, date2, pv)
return astrom
[docs]def aper(theta, astrom):
"""
In the star-independent astrometry parameters, update only the
Earth rotation angle, supplied by the caller explicitly.
Parameters
----------
theta : double array
astrom : eraASTROM array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraAper``. Note that, unlike the erfa routine,
the python wrapper does not change astrom in-place. The ERFA documentation is::
- - - - - - - -
e r a A p e r
- - - - - - - -
In the star-independent astrometry parameters, update only the
Earth rotation angle, supplied by the caller explicitly.
Given:
theta double Earth rotation angle (radians, Note 2)
astrom eraASTROM star-independent astrometry parameters:
pmt double not used
eb double[3] not used
eh double[3] not used
em double not used
v double[3] not used
bm1 double not used
bpn double[3][3] not used
along double longitude + s' (radians)
xpl double not used
ypl double not used
sphi double not used
cphi double not used
diurab double not used
eral double not used
refa double not used
refb double not used
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double unchanged
eb double[3] unchanged
eh double[3] unchanged
em double unchanged
v double[3] unchanged
bm1 double unchanged
bpn double[3][3] unchanged
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double "local" Earth rotation angle (radians)
refa double unchanged
refb double unchanged
Notes:
1) This function exists to enable sidereal-tracking applications to
avoid wasteful recomputation of the bulk of the astrometry
parameters: only the Earth rotation is updated.
2) For targets expressed as equinox based positions, such as
classical geocentric apparent (RA,Dec), the supplied theta can be
Greenwich apparent sidereal time rather than Earth rotation
angle.
3) The function eraAper13 can be used instead of the present
function, and starts from UT1 rather than ERA itself.
4) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
This revision: 2013 September 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.aper(theta, astrom)
return astrom
[docs]def aper13(ut11, ut12, astrom):
"""
In the star-independent astrometry parameters, update only the
Earth rotation angle.
Parameters
----------
ut11 : double array
ut12 : double array
astrom : eraASTROM array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraAper13``. Note that, unlike the erfa routine,
the python wrapper does not change astrom in-place. The ERFA documentation is::
- - - - - - - - - -
e r a A p e r 1 3
- - - - - - - - - -
In the star-independent astrometry parameters, update only the
Earth rotation angle. The caller provides UT1, (n.b. not UTC).
Given:
ut11 double UT1 as a 2-part...
ut12 double ...Julian Date (Note 1)
astrom eraASTROM star-independent astrometry parameters:
pmt double not used
eb double[3] not used
eh double[3] not used
em double not used
v double[3] not used
bm1 double not used
bpn double[3][3] not used
along double longitude + s' (radians)
xpl double not used
ypl double not used
sphi double not used
cphi double not used
diurab double not used
eral double not used
refa double not used
refb double not used
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double unchanged
eb double[3] unchanged
eh double[3] unchanged
em double unchanged
v double[3] unchanged
bm1 double unchanged
bpn double[3][3] unchanged
along double unchanged
xpl double unchanged
ypl double unchanged
sphi double unchanged
cphi double unchanged
diurab double unchanged
eral double "local" Earth rotation angle (radians)
refa double unchanged
refb double unchanged
Notes:
1) The UT1 date (n.b. not UTC) ut11+ut12 is a Julian Date,
apportioned in any convenient way between the arguments ut11 and
ut12. For example, JD(UT1)=2450123.7 could be expressed in any
of these ways, among others:
ut11 ut12
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. The date & time method is
best matched to the algorithm used: maximum precision is
delivered when the ut11 argument is for 0hrs UT1 on the day in
question and the ut12 argument lies in the range 0 to 1, or vice
versa.
2) If the caller wishes to provide the Earth rotation angle itself,
the function eraAper can be used instead. One use of this
technique is to substitute Greenwich apparent sidereal time and
thereby to support equinox based transformations directly.
3) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
Called:
eraAper astrometry parameters: update ERA
eraEra00 Earth rotation angle, IAU 2000
This revision: 2013 September 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.aper13(ut11, ut12, astrom)
return astrom
[docs]def apio(sp, theta, elong, phi, hm, xp, yp, refa, refb):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between CIRS and observed
coordinates.
Parameters
----------
sp : double array
theta : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
refa : double array
refb : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApio``. The ERFA documentation is::
- - - - - - - -
e r a A p i o
- - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between CIRS and observed
coordinates. The caller supplies the Earth orientation information
and the refraction constants as well as the site coordinates.
Given:
sp double the TIO locator s' (radians, Note 1)
theta double Earth rotation angle (radians)
elong double longitude (radians, east +ve, Note 2)
phi double geodetic latitude (radians, Note 2)
hm double height above ellipsoid (m, geodetic Note 2)
xp,yp double polar motion coordinates (radians, Note 3)
refa double refraction constant A (radians, Note 4)
refb double refraction constant B (radians, Note 4)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double unchanged
eb double[3] unchanged
eh double[3] unchanged
em double unchanged
v double[3] unchanged
bm1 double unchanged
bpn double[3][3] unchanged
along double adjusted longitude (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Notes:
1) sp, the TIO locator s', is a tiny quantity needed only by the
most precise applications. It can either be set to zero or
predicted using the ERFA function eraSp00.
2) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
3) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many applications,
xp and yp can be set to zero.
Internally, the polar motion is stored in a form rotated onto the
local meridian.
4) The refraction constants refa and refb are for use in a
dZ = A*tan(Z)+B*tan^3(Z) model, where Z is the observed
(i.e. refracted) zenith distance and dZ is the amount of
refraction.
5) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
6) In cases where the caller does not wish to provide the Earth
rotation information and refraction constants, the function
eraApio13 can be used instead of the present function. This
starts from UTC and weather readings etc. and computes suitable
values using other ERFA functions.
7) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
8) The context structure astrom produced by this function is used by
eraAtioq and eraAtoiq.
Called:
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRy rotate around Y-axis
eraRx rotate around X-axis
eraAnpm normalize angle into range +/- pi
eraPvtob position/velocity of terrestrial station
This revision: 2021 January 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom = ufunc.apio(sp, theta, elong, phi, hm, xp, yp, refa, refb)
return astrom
[docs]def apio13(utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between CIRS and observed
coordinates.
Parameters
----------
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
astrom : eraASTROM array
Notes
-----
Wraps ERFA function ``eraApio13``. The ERFA documentation is::
- - - - - - - - - -
e r a A p i o 1 3
- - - - - - - - - -
For a terrestrial observer, prepare star-independent astrometry
parameters for transformations between CIRS and observed
coordinates. The caller supplies UTC, site coordinates, ambient air
conditions and observing wavelength.
Given:
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 1,2)
dut1 double UT1-UTC (seconds)
elong double longitude (radians, east +ve, Note 3)
phi double geodetic latitude (radians, Note 3)
hm double height above ellipsoid (m, geodetic Notes 4,6)
xp,yp double polar motion coordinates (radians, Note 5)
phpa double pressure at the observer (hPa = mB, Note 6)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 7)
Returned:
astrom eraASTROM star-independent astrometry parameters:
pmt double unchanged
eb double[3] unchanged
eh double[3] unchanged
em double unchanged
v double[3] unchanged
bm1 double unchanged
bpn double[3][3] unchanged
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned (function value):
int status: +1 = dubious year (Note 2)
0 = OK
-1 = unacceptable date
Notes:
1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
2) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
4) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
5) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many applications,
xp and yp can be set to zero.
Internally, the polar motion is stored in a form rotated onto
the local meridian.
6) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB), is
available, an adequate estimate of hm can be obtained from the
expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to the
pressure and that an accurate phpa value is important for
precise work.
7) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
8) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
9) In cases where the caller wishes to supply his own Earth
rotation information and refraction constants, the function
eraApc can be used instead of the present function.
10) This is one of several functions that inserts into the astrom
structure star-independent parameters needed for the chain of
astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
The various functions support different classes of observer and
portions of the transformation chain:
functions observer transformation
eraApcg eraApcg13 geocentric ICRS <-> GCRS
eraApci eraApci13 terrestrial ICRS <-> CIRS
eraApco eraApco13 terrestrial ICRS <-> observed
eraApcs eraApcs13 space ICRS <-> GCRS
eraAper eraAper13 terrestrial update Earth rotation
eraApio eraApio13 terrestrial CIRS <-> observed
Those with names ending in "13" use contemporary ERFA models to
compute the various ephemerides. The others accept ephemerides
supplied by the caller.
The transformation from ICRS to GCRS covers space motion,
parallax, light deflection, and aberration. From GCRS to CIRS
comprises frame bias and precession-nutation. From CIRS to
observed takes account of Earth rotation, polar motion, diurnal
aberration and parallax (unless subsumed into the ICRS <-> GCRS
transformation), and atmospheric refraction.
11) The context structure astrom produced by this function is used
by eraAtioq and eraAtoiq.
Called:
eraUtctai UTC to TAI
eraTaitt TAI to TT
eraUtcut1 UTC to UT1
eraSp00 the TIO locator s', IERS 2000
eraEra00 Earth rotation angle, IAU 2000
eraRefco refraction constants for given ambient conditions
eraApio astrometry parameters, CIRS-observed
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
astrom, c_retval = ufunc.apio13(
utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'apio13')
return astrom
STATUS_CODES['apio13'] = {
1: 'dubious year (Note 2)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def atci13(rc, dc, pr, pd, px, rv, date1, date2):
"""
Transform ICRS star data, epoch J2000.0, to CIRS.
Parameters
----------
rc : double array
dc : double array
pr : double array
pd : double array
px : double array
rv : double array
date1 : double array
date2 : double array
Returns
-------
ri : double array
di : double array
eo : double array
Notes
-----
Wraps ERFA function ``eraAtci13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t c i 1 3
- - - - - - - - - -
Transform ICRS star data, epoch J2000.0, to CIRS.
Given:
rc double ICRS right ascension at J2000.0 (radians, Note 1)
dc double ICRS declination at J2000.0 (radians, Note 1)
pr double RA proper motion (radians/year; Note 2)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 3)
Returned:
ri,di double CIRS geocentric RA,Dec (radians)
eo double equation of the origins (ERA-GST, Note 5)
Notes:
1) Star data for an epoch other than J2000.0 (for example from the
Hipparcos catalog, which has an epoch of J1991.25) will require a
preliminary call to eraPmsafe before use.
2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
3) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
4) The available accuracy is better than 1 milliarcsecond, limited
mainly by the precession-nutation model that is used, namely
IAU 2000A/2006. Very close to solar system bodies, additional
errors of up to several milliarcseconds can occur because of
unmodeled light deflection; however, the Sun's contribution is
taken into account, to first order. The accuracy limitations of
the ERFA function eraEpv00 (used to compute Earth position and
velocity) can contribute aberration errors of up to
5 microarcseconds. Light deflection at the Sun's limb is
uncertain at the 0.4 mas level.
5) Should the transformation to (equinox based) apparent place be
required rather than (CIO based) intermediate place, subtract the
equation of the origins from the returned right ascension:
RA = RI - EO. (The eraAnp function can then be applied, as
required, to keep the result in the conventional 0-2pi range.)
Called:
eraApci13 astrometry parameters, ICRS-CIRS, 2013
eraAtciq quick ICRS to CIRS
This revision: 2017 March 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di, eo = ufunc.atci13(rc, dc, pr, pd, px, rv, date1, date2)
return ri, di, eo
[docs]def atciq(rc, dc, pr, pd, px, rv, astrom):
"""
Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed
star-independent astrometry parameters.
Parameters
----------
rc : double array
dc : double array
pr : double array
pd : double array
px : double array
rv : double array
astrom : eraASTROM array
Returns
-------
ri : double array
di : double array
Notes
-----
Wraps ERFA function ``eraAtciq``. The ERFA documentation is::
- - - - - - - - -
e r a A t c i q
- - - - - - - - -
Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed
star-independent astrometry parameters.
Use of this function is appropriate when efficiency is important and
where many star positions are to be transformed for one date. The
star-independent parameters can be obtained by calling one of the
functions eraApci[13], eraApcg[13], eraApco[13] or eraApcs[13].
If the parallax and proper motions are zero the eraAtciqz function
can be used instead.
Given:
rc,dc double ICRS RA,Dec at J2000.0 (radians)
pr double RA proper motion (radians/year; Note 3)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned:
ri,di double CIRS RA,Dec (radians)
Notes:
1) All the vectors are with respect to BCRS axes.
2) Star data for an epoch other than J2000.0 (for example from the
Hipparcos catalog, which has an epoch of J1991.25) will require a
preliminary call to eraPmsafe before use.
3) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
Called:
eraPmpx proper motion and parallax
eraLdsun light deflection by the Sun
eraAb stellar aberration
eraRxp product of r-matrix and pv-vector
eraC2s p-vector to spherical
eraAnp normalize angle into range 0 to 2pi
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di = ufunc.atciq(rc, dc, pr, pd, px, rv, astrom)
return ri, di
[docs]def atciqn(rc, dc, pr, pd, px, rv, astrom, b):
"""
Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed
star-independent astrometry parameters plus a list of light-
deflecting bodies.
Parameters
----------
rc : double array
dc : double array
pr : double array
pd : double array
px : double array
rv : double array
astrom : eraASTROM array
b : eraLDBODY array
Returns
-------
ri : double array
di : double array
Notes
-----
Wraps ERFA function ``eraAtciqn``. The ERFA documentation is::
- - - - - - - - - -
e r a A t c i q n
- - - - - - - - - -
Quick ICRS, epoch J2000.0, to CIRS transformation, given precomputed
star-independent astrometry parameters plus a list of light-
deflecting bodies.
Use of this function is appropriate when efficiency is important and
where many star positions are to be transformed for one date. The
star-independent parameters can be obtained by calling one of the
functions eraApci[13], eraApcg[13], eraApco[13] or eraApcs[13].
If the only light-deflecting body to be taken into account is the
Sun, the eraAtciq function can be used instead. If in addition the
parallax and proper motions are zero, the eraAtciqz function can be
used.
Given:
rc,dc double ICRS RA,Dec at J2000.0 (radians)
pr double RA proper motion (radians/year; Note 3)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
n int number of bodies (Note 3)
b eraLDBODY[n] data for each of the n bodies (Notes 3,4):
bm double mass of the body (solar masses, Note 5)
dl double deflection limiter (Note 6)
pv [2][3] barycentric PV of the body (au, au/day)
Returned:
ri,di double CIRS RA,Dec (radians)
Notes:
1) Star data for an epoch other than J2000.0 (for example from the
Hipparcos catalog, which has an epoch of J1991.25) will require a
preliminary call to eraPmsafe before use.
2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
3) The struct b contains n entries, one for each body to be
considered. If n = 0, no gravitational light deflection will be
applied, not even for the Sun.
4) The struct b should include an entry for the Sun as well as for
any planet or other body to be taken into account. The entries
should be in the order in which the light passes the body.
5) In the entry in the b struct for body i, the mass parameter
b[i].bm can, as required, be adjusted in order to allow for such
effects as quadrupole field.
6) The deflection limiter parameter b[i].dl is phi^2/2, where phi is
the angular separation (in radians) between star and body at
which limiting is applied. As phi shrinks below the chosen
threshold, the deflection is artificially reduced, reaching zero
for phi = 0. Example values suitable for a terrestrial
observer, together with masses, are as follows:
body i b[i].bm b[i].dl
Sun 1.0 6e-6
Jupiter 0.00095435 3e-9
Saturn 0.00028574 3e-10
7) For efficiency, validation of the contents of the b array is
omitted. The supplied masses must be greater than zero, the
position and velocity vectors must be right, and the deflection
limiter greater than zero.
Called:
eraPmpx proper motion and parallax
eraLdn light deflection by n bodies
eraAb stellar aberration
eraRxp product of r-matrix and pv-vector
eraC2s p-vector to spherical
eraAnp normalize angle into range 0 to 2pi
This revision: 2021 January 6
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di = ufunc.atciqn(rc, dc, pr, pd, px, rv, astrom, b)
return ri, di
[docs]def atciqz(rc, dc, astrom):
"""
Quick ICRS to CIRS transformation, given precomputed star-
independent astrometry parameters, and assuming zero parallax and
proper motion.
Parameters
----------
rc : double array
dc : double array
astrom : eraASTROM array
Returns
-------
ri : double array
di : double array
Notes
-----
Wraps ERFA function ``eraAtciqz``. The ERFA documentation is::
- - - - - - - - - -
e r a A t c i q z
- - - - - - - - - -
Quick ICRS to CIRS transformation, given precomputed star-
independent astrometry parameters, and assuming zero parallax and
proper motion.
Use of this function is appropriate when efficiency is important and
where many star positions are to be transformed for one date. The
star-independent parameters can be obtained by calling one of the
functions eraApci[13], eraApcg[13], eraApco[13] or eraApcs[13].
The corresponding function for the case of non-zero parallax and
proper motion is eraAtciq.
Given:
rc,dc double ICRS astrometric RA,Dec (radians)
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned:
ri,di double CIRS RA,Dec (radians)
Note:
All the vectors are with respect to BCRS axes.
References:
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013).
Klioner, Sergei A., "A practical relativistic model for micro-
arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).
Called:
eraS2c spherical coordinates to unit vector
eraLdsun light deflection due to Sun
eraAb stellar aberration
eraRxp product of r-matrix and p-vector
eraC2s p-vector to spherical
eraAnp normalize angle into range +/- pi
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di = ufunc.atciqz(rc, dc, astrom)
return ri, di
[docs]def atco13(rc, dc, pr, pd, px, rv, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
ICRS RA,Dec to observed place. The caller supplies UTC, site
coordinates, ambient air conditions and observing wavelength.
Parameters
----------
rc : double array
dc : double array
pr : double array
pd : double array
px : double array
rv : double array
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
aob : double array
zob : double array
hob : double array
dob : double array
rob : double array
eo : double array
Notes
-----
Wraps ERFA function ``eraAtco13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t c o 1 3
- - - - - - - - - -
ICRS RA,Dec to observed place. The caller supplies UTC, site
coordinates, ambient air conditions and observing wavelength.
ERFA models are used for the Earth ephemeris, bias-precession-
nutation, Earth orientation and refraction.
Given:
rc,dc double ICRS right ascension at J2000.0 (radians, Note 1)
pr double RA proper motion (radians/year; Note 2)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 3-4)
dut1 double UT1-UTC (seconds, Note 5)
elong double longitude (radians, east +ve, Note 6)
phi double latitude (geodetic, radians, Note 6)
hm double height above ellipsoid (m, geodetic, Notes 6,8)
xp,yp double polar motion coordinates (radians, Note 7)
phpa double pressure at the observer (hPa = mB, Note 8)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 9)
Returned:
aob double observed azimuth (radians: N=0,E=90)
zob double observed zenith distance (radians)
hob double observed hour angle (radians)
dob double observed declination (radians)
rob double observed right ascension (CIO-based, radians)
eo double equation of the origins (ERA-GST)
Returned (function value):
int status: +1 = dubious year (Note 4)
0 = OK
-1 = unacceptable date
Notes:
1) Star data for an epoch other than J2000.0 (for example from the
Hipparcos catalog, which has an epoch of J1991.25) will require
a preliminary call to eraPmsafe before use.
2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
3) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
4) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the
future to be trusted. See eraDat for further details.
5) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
6) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
7) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many
applications, xp and yp can be set to zero.
8) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB),
is available, an adequate estimate of hm can be obtained from
the expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to
the pressure and that an accurate phpa value is important for
precise work.
9) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
10) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted observed
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better
than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
Without refraction, the complementary functions eraAtco13 and
eraAtoc13 are self-consistent to better than 1 microarcsecond
all over the celestial sphere. With refraction included,
consistency falls off at high zenith distances, but is still
better than 0.05 arcsec at 85 degrees.
11) "Observed" Az,ZD means the position that would be seen by a
perfect geodetically aligned theodolite. (Zenith distance is
used rather than altitude in order to reflect the fact that no
allowance is made for depression of the horizon.) This is
related to the observed HA,Dec via the standard rotation, using
the geodetic latitude (corrected for polar motion), while the
observed HA and RA are related simply through the Earth rotation
angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
means the position that would be seen by a perfect equatorial
with its polar axis aligned to the Earth's axis of rotation.
12) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
Called:
eraApco13 astrometry parameters, ICRS-observed, 2013
eraAtciq quick ICRS to CIRS
eraAtioq quick CIRS to observed
This revision: 2016 February 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
aob, zob, hob, dob, rob, eo, c_retval = ufunc.atco13(
rc, dc, pr, pd, px, rv, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'atco13')
return aob, zob, hob, dob, rob, eo
STATUS_CODES['atco13'] = {
1: 'dubious year (Note 4)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def atic13(ri, di, date1, date2):
"""
Transform star RA,Dec from geocentric CIRS to ICRS astrometric.
Parameters
----------
ri : double array
di : double array
date1 : double array
date2 : double array
Returns
-------
rc : double array
dc : double array
eo : double array
Notes
-----
Wraps ERFA function ``eraAtic13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t i c 1 3
- - - - - - - - - -
Transform star RA,Dec from geocentric CIRS to ICRS astrometric.
Given:
ri,di double CIRS geocentric RA,Dec (radians)
date1 double TDB as a 2-part...
date2 double ...Julian Date (Note 1)
Returned:
rc,dc double ICRS astrometric RA,Dec (radians)
eo double equation of the origins (ERA-GST, Note 4)
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. For most
applications of this function the choice will not be at all
critical.
TT can be used instead of TDB without any significant impact on
accuracy.
2) Iterative techniques are used for the aberration and light
deflection corrections so that the functions eraAtic13 (or
eraAticq) and eraAtci13 (or eraAtciq) are accurate inverses;
even at the edge of the Sun's disk the discrepancy is only about
1 nanoarcsecond.
3) The available accuracy is better than 1 milliarcsecond, limited
mainly by the precession-nutation model that is used, namely
IAU 2000A/2006. Very close to solar system bodies, additional
errors of up to several milliarcseconds can occur because of
unmodeled light deflection; however, the Sun's contribution is
taken into account, to first order. The accuracy limitations of
the ERFA function eraEpv00 (used to compute Earth position and
velocity) can contribute aberration errors of up to
5 microarcseconds. Light deflection at the Sun's limb is
uncertain at the 0.4 mas level.
4) Should the transformation to (equinox based) J2000.0 mean place
be required rather than (CIO based) ICRS coordinates, subtract the
equation of the origins from the returned right ascension:
RA = RI - EO. (The eraAnp function can then be applied, as
required, to keep the result in the conventional 0-2pi range.)
Called:
eraApci13 astrometry parameters, ICRS-CIRS, 2013
eraAticq quick CIRS to ICRS astrometric
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc, dc, eo = ufunc.atic13(ri, di, date1, date2)
return rc, dc, eo
[docs]def aticq(ri, di, astrom):
"""
Quick CIRS RA,Dec to ICRS astrometric place, given the star-
independent astrometry parameters.
Parameters
----------
ri : double array
di : double array
astrom : eraASTROM array
Returns
-------
rc : double array
dc : double array
Notes
-----
Wraps ERFA function ``eraAticq``. The ERFA documentation is::
- - - - - - - - -
e r a A t i c q
- - - - - - - - -
Quick CIRS RA,Dec to ICRS astrometric place, given the star-
independent astrometry parameters.
Use of this function is appropriate when efficiency is important and
where many star positions are all to be transformed for one date.
The star-independent astrometry parameters can be obtained by
calling one of the functions eraApci[13], eraApcg[13], eraApco[13]
or eraApcs[13].
Given:
ri,di double CIRS RA,Dec (radians)
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned:
rc,dc double ICRS astrometric RA,Dec (radians)
Notes:
1) Only the Sun is taken into account in the light deflection
correction.
2) Iterative techniques are used for the aberration and light
deflection corrections so that the functions eraAtic13 (or
eraAticq) and eraAtci13 (or eraAtciq) are accurate inverses;
even at the edge of the Sun's disk the discrepancy is only about
1 nanoarcsecond.
Called:
eraS2c spherical coordinates to unit vector
eraTrxp product of transpose of r-matrix and p-vector
eraZp zero p-vector
eraAb stellar aberration
eraLdsun light deflection by the Sun
eraC2s p-vector to spherical
eraAnp normalize angle into range +/- pi
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc, dc = ufunc.aticq(ri, di, astrom)
return rc, dc
[docs]def aticqn(ri, di, astrom, b):
"""
Quick CIRS to ICRS astrometric place transformation, given the star-
independent astrometry parameters plus a list of light-deflecting
bodies.
Parameters
----------
ri : double array
di : double array
astrom : eraASTROM array
b : eraLDBODY array
Returns
-------
rc : double array
dc : double array
Notes
-----
Wraps ERFA function ``eraAticqn``. The ERFA documentation is::
- - - - - - - - - -
e r a A t i c q n
- - - - - - - - - -
Quick CIRS to ICRS astrometric place transformation, given the star-
independent astrometry parameters plus a list of light-deflecting
bodies.
Use of this function is appropriate when efficiency is important and
where many star positions are all to be transformed for one date.
The star-independent astrometry parameters can be obtained by
calling one of the functions eraApci[13], eraApcg[13], eraApco[13]
or eraApcs[13].
If the only light-deflecting body to be taken into account is the
Sun, the eraAticq function can be used instead.
Given:
ri,di double CIRS RA,Dec (radians)
astrom eraASTROM star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
n int number of bodies (Note 3)
b eraLDBODY[n] data for each of the n bodies (Notes 3,4):
bm double mass of the body (solar masses, Note 5)
dl double deflection limiter (Note 6)
pv [2][3] barycentric PV of the body (au, au/day)
Returned:
rc,dc double ICRS astrometric RA,Dec (radians)
Notes:
1) Iterative techniques are used for the aberration and light
deflection corrections so that the functions eraAticqn and
eraAtciqn are accurate inverses; even at the edge of the Sun's
disk the discrepancy is only about 1 nanoarcsecond.
2) If the only light-deflecting body to be taken into account is the
Sun, the eraAticq function can be used instead.
3) The struct b contains n entries, one for each body to be
considered. If n = 0, no gravitational light deflection will be
applied, not even for the Sun.
4) The struct b should include an entry for the Sun as well as for
any planet or other body to be taken into account. The entries
should be in the order in which the light passes the body.
5) In the entry in the b struct for body i, the mass parameter
b[i].bm can, as required, be adjusted in order to allow for such
effects as quadrupole field.
6) The deflection limiter parameter b[i].dl is phi^2/2, where phi is
the angular separation (in radians) between star and body at
which limiting is applied. As phi shrinks below the chosen
threshold, the deflection is artificially reduced, reaching zero
for phi = 0. Example values suitable for a terrestrial
observer, together with masses, are as follows:
body i b[i].bm b[i].dl
Sun 1.0 6e-6
Jupiter 0.00095435 3e-9
Saturn 0.00028574 3e-10
7) For efficiency, validation of the contents of the b array is
omitted. The supplied masses must be greater than zero, the
position and velocity vectors must be right, and the deflection
limiter greater than zero.
Called:
eraS2c spherical coordinates to unit vector
eraTrxp product of transpose of r-matrix and p-vector
eraZp zero p-vector
eraAb stellar aberration
eraLdn light deflection by n bodies
eraC2s p-vector to spherical
eraAnp normalize angle into range +/- pi
This revision: 2021 January 6
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc, dc = ufunc.aticqn(ri, di, astrom, b)
return rc, dc
[docs]def atio13(ri, di, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
CIRS RA,Dec to observed place. The caller supplies UTC, site
coordinates, ambient air conditions and observing wavelength.
Parameters
----------
ri : double array
di : double array
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
aob : double array
zob : double array
hob : double array
dob : double array
rob : double array
Notes
-----
Wraps ERFA function ``eraAtio13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t i o 1 3
- - - - - - - - - -
CIRS RA,Dec to observed place. The caller supplies UTC, site
coordinates, ambient air conditions and observing wavelength.
Given:
ri double CIRS right ascension (CIO-based, radians)
di double CIRS declination (radians)
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 1,2)
dut1 double UT1-UTC (seconds, Note 3)
elong double longitude (radians, east +ve, Note 4)
phi double geodetic latitude (radians, Note 4)
hm double height above ellipsoid (m, geodetic Notes 4,6)
xp,yp double polar motion coordinates (radians, Note 5)
phpa double pressure at the observer (hPa = mB, Note 6)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 7)
Returned:
aob double observed azimuth (radians: N=0,E=90)
zob double observed zenith distance (radians)
hob double observed hour angle (radians)
dob double observed declination (radians)
rob double observed right ascension (CIO-based, radians)
Returned (function value):
int status: +1 = dubious year (Note 2)
0 = OK
-1 = unacceptable date
Notes:
1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
2) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the
future to be trusted. See eraDat for further details.
3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
4) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
5) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many
applications, xp and yp can be set to zero.
6) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB), is
available, an adequate estimate of hm can be obtained from the
expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to
the pressure and that an accurate phpa value is important for
precise work.
7) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
8) "Observed" Az,ZD means the position that would be seen by a
perfect geodetically aligned theodolite. (Zenith distance is
used rather than altitude in order to reflect the fact that no
allowance is made for depression of the horizon.) This is
related to the observed HA,Dec via the standard rotation, using
the geodetic latitude (corrected for polar motion), while the
observed HA and RA are related simply through the Earth rotation
angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
means the position that would be seen by a perfect equatorial
with its polar axis aligned to the Earth's axis of rotation.
9) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted astrometric
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better
than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
10) The complementary functions eraAtio13 and eraAtoi13 are self-
consistent to better than 1 microarcsecond all over the
celestial sphere.
11) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
Called:
eraApio13 astrometry parameters, CIRS-observed, 2013
eraAtioq quick CIRS to observed
This revision: 2016 February 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
aob, zob, hob, dob, rob, c_retval = ufunc.atio13(
ri, di, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'atio13')
return aob, zob, hob, dob, rob
STATUS_CODES['atio13'] = {
1: 'dubious year (Note 2)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def atioq(ri, di, astrom):
"""
Quick CIRS to observed place transformation.
Parameters
----------
ri : double array
di : double array
astrom : eraASTROM array
Returns
-------
aob : double array
zob : double array
hob : double array
dob : double array
rob : double array
Notes
-----
Wraps ERFA function ``eraAtioq``. The ERFA documentation is::
- - - - - - - - -
e r a A t i o q
- - - - - - - - -
Quick CIRS to observed place transformation.
Use of this function is appropriate when efficiency is important and
where many star positions are all to be transformed for one date.
The star-independent astrometry parameters can be obtained by
calling eraApio[13] or eraApco[13].
Given:
ri double CIRS right ascension
di double CIRS declination
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned:
aob double observed azimuth (radians: N=0,E=90)
zob double observed zenith distance (radians)
hob double observed hour angle (radians)
dob double observed declination (radians)
rob double observed right ascension (CIO-based, radians)
Notes:
1) This function returns zenith distance rather than altitude in
order to reflect the fact that no allowance is made for
depression of the horizon.
2) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted observed
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better
than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
Without refraction, the complementary functions eraAtioq and
eraAtoiq are self-consistent to better than 1 microarcsecond all
over the celestial sphere. With refraction included, consistency
falls off at high zenith distances, but is still better than
0.05 arcsec at 85 degrees.
3) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
4) The CIRS RA,Dec is obtained from a star catalog mean place by
allowing for space motion, parallax, the Sun's gravitational lens
effect, annual aberration and precession-nutation. For star
positions in the ICRS, these effects can be applied by means of
the eraAtci13 (etc.) functions. Starting from classical "mean
place" systems, additional transformations will be needed first.
5) "Observed" Az,El means the position that would be seen by a
perfect geodetically aligned theodolite. This is obtained from
the CIRS RA,Dec by allowing for Earth orientation and diurnal
aberration, rotating from equator to horizon coordinates, and
then adjusting for refraction. The HA,Dec is obtained by
rotating back into equatorial coordinates, and is the position
that would be seen by a perfect equatorial with its polar axis
aligned to the Earth's axis of rotation. Finally, the RA is
obtained by subtracting the HA from the local ERA.
6) The star-independent CIRS-to-observed-place parameters in ASTROM
may be computed with eraApio[13] or eraApco[13]. If nothing has
changed significantly except the time, eraAper[13] may be used to
perform the requisite adjustment to the astrom structure.
Called:
eraS2c spherical coordinates to unit vector
eraC2s p-vector to spherical
eraAnp normalize angle into range 0 to 2pi
This revision: 2020 December 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
aob, zob, hob, dob, rob = ufunc.atioq(ri, di, astrom)
return aob, zob, hob, dob, rob
[docs]def atoc13(type, ob1, ob2, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
Observed place at a groundbased site to to ICRS astrometric RA,Dec.
The caller supplies UTC, site coordinates, ambient air conditions
and observing wavelength.
Parameters
----------
type : const char array
ob1 : double array
ob2 : double array
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
rc : double array
dc : double array
Notes
-----
Wraps ERFA function ``eraAtoc13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t o c 1 3
- - - - - - - - - -
Observed place at a groundbased site to to ICRS astrometric RA,Dec.
The caller supplies UTC, site coordinates, ambient air conditions
and observing wavelength.
Given:
type char[] type of coordinates - "R", "H" or "A" (Notes 1,2)
ob1 double observed Az, HA or RA (radians; Az is N=0,E=90)
ob2 double observed ZD or Dec (radians)
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 3,4)
dut1 double UT1-UTC (seconds, Note 5)
elong double longitude (radians, east +ve, Note 6)
phi double geodetic latitude (radians, Note 6)
hm double height above ellipsoid (m, geodetic Notes 6,8)
xp,yp double polar motion coordinates (radians, Note 7)
phpa double pressure at the observer (hPa = mB, Note 8)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 9)
Returned:
rc,dc double ICRS astrometric RA,Dec (radians)
Returned (function value):
int status: +1 = dubious year (Note 4)
0 = OK
-1 = unacceptable date
Notes:
1) "Observed" Az,ZD means the position that would be seen by a
perfect geodetically aligned theodolite. (Zenith distance is
used rather than altitude in order to reflect the fact that no
allowance is made for depression of the horizon.) This is
related to the observed HA,Dec via the standard rotation, using
the geodetic latitude (corrected for polar motion), while the
observed HA and RA are related simply through the Earth rotation
angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
means the position that would be seen by a perfect equatorial
with its polar axis aligned to the Earth's axis of rotation.
2) Only the first character of the type argument is significant.
"R" or "r" indicates that ob1 and ob2 are the observed right
ascension and declination; "H" or "h" indicates that they are
hour angle (west +ve) and declination; anything else ("A" or
"a" is recommended) indicates that ob1 and ob2 are azimuth
(north zero, east 90 deg) and zenith distance.
3) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
4) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the
future to be trusted. See eraDat for further details.
5) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
6) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
7) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many
applications, xp and yp can be set to zero.
8) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB), is
available, an adequate estimate of hm can be obtained from the
expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to
the pressure and that an accurate phpa value is important for
precise work.
9) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
10) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted astrometric
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better
than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
Without refraction, the complementary functions eraAtco13 and
eraAtoc13 are self-consistent to better than 1 microarcsecond
all over the celestial sphere. With refraction included,
consistency falls off at high zenith distances, but is still
better than 0.05 arcsec at 85 degrees.
11) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
Called:
eraApco13 astrometry parameters, ICRS-observed
eraAtoiq quick observed to CIRS
eraAticq quick CIRS to ICRS
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc, dc, c_retval = ufunc.atoc13(
type, ob1, ob2, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'atoc13')
return rc, dc
STATUS_CODES['atoc13'] = {
1: 'dubious year (Note 4)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def atoi13(type, ob1, ob2, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl):
"""
Observed place to CIRS. The caller supplies UTC, site coordinates,
ambient air conditions and observing wavelength.
Parameters
----------
type : const char array
ob1 : double array
ob2 : double array
utc1 : double array
utc2 : double array
dut1 : double array
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
ri : double array
di : double array
Notes
-----
Wraps ERFA function ``eraAtoi13``. The ERFA documentation is::
- - - - - - - - - -
e r a A t o i 1 3
- - - - - - - - - -
Observed place to CIRS. The caller supplies UTC, site coordinates,
ambient air conditions and observing wavelength.
Given:
type char[] type of coordinates - "R", "H" or "A" (Notes 1,2)
ob1 double observed Az, HA or RA (radians; Az is N=0,E=90)
ob2 double observed ZD or Dec (radians)
utc1 double UTC as a 2-part...
utc2 double ...quasi Julian Date (Notes 3,4)
dut1 double UT1-UTC (seconds, Note 5)
elong double longitude (radians, east +ve, Note 6)
phi double geodetic latitude (radians, Note 6)
hm double height above the ellipsoid (meters, Notes 6,8)
xp,yp double polar motion coordinates (radians, Note 7)
phpa double pressure at the observer (hPa = mB, Note 8)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers, Note 9)
Returned:
ri double CIRS right ascension (CIO-based, radians)
di double CIRS declination (radians)
Returned (function value):
int status: +1 = dubious year (Note 2)
0 = OK
-1 = unacceptable date
Notes:
1) "Observed" Az,ZD means the position that would be seen by a
perfect geodetically aligned theodolite. (Zenith distance is
used rather than altitude in order to reflect the fact that no
allowance is made for depression of the horizon.) This is
related to the observed HA,Dec via the standard rotation, using
the geodetic latitude (corrected for polar motion), while the
observed HA and RA are related simply through the Earth rotation
angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
means the position that would be seen by a perfect equatorial
with its polar axis aligned to the Earth's axis of rotation.
2) Only the first character of the type argument is significant.
"R" or "r" indicates that ob1 and ob2 are the observed right
ascension and declination; "H" or "h" indicates that they are
hour angle (west +ve) and declination; anything else ("A" or
"a" is recommended) indicates that ob1 and ob2 are azimuth
(north zero, east 90 deg) and zenith distance.
3) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
However, JD cannot unambiguously represent UTC during a leap
second unless special measures are taken. The convention in the
present function is that the JD day represents UTC days whether
the length is 86399, 86400 or 86401 SI seconds.
Applications should use the function eraDtf2d to convert from
calendar date and time of day into 2-part quasi Julian Date, as
it implements the leap-second-ambiguity convention just
described.
4) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the
future to be trusted. See eraDat for further details.
5) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
one second at the end of each positive UTC leap second,
introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
practice is under review, and in the future UT1-UTC may grow
essentially without limit.
6) The geographical coordinates are with respect to the ERFA_WGS84
reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
longitude required by the present function is east-positive
(i.e. right-handed), in accordance with geographical convention.
7) The polar motion xp,yp can be obtained from IERS bulletins. The
values are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions 2003), measured along the
meridians 0 and 90 deg west respectively. For many
applications, xp and yp can be set to zero.
8) If hm, the height above the ellipsoid of the observing station
in meters, is not known but phpa, the pressure in hPa (=mB), is
available, an adequate estimate of hm can be obtained from the
expression
hm = -29.3 * tsl * log ( phpa / 1013.25 );
where tsl is the approximate sea-level air temperature in K
(See Astrophysical Quantities, C.W.Allen, 3rd edition, section
52). Similarly, if the pressure phpa is not known, it can be
estimated from the height of the observing station, hm, as
follows:
phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
Note, however, that the refraction is nearly proportional to
the pressure and that an accurate phpa value is important for
precise work.
9) The argument wl specifies the observing wavelength in
micrometers. The transition from optical to radio is assumed to
occur at 100 micrometers (about 3000 GHz).
10) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted astrometric
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better
than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
Without refraction, the complementary functions eraAtio13 and
eraAtoi13 are self-consistent to better than 1 microarcsecond
all over the celestial sphere. With refraction included,
consistency falls off at high zenith distances, but is still
better than 0.05 arcsec at 85 degrees.
12) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
Called:
eraApio13 astrometry parameters, CIRS-observed, 2013
eraAtoiq quick observed to CIRS
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di, c_retval = ufunc.atoi13(
type, ob1, ob2, utc1, utc2, dut1, elong, phi, hm, xp, yp, phpa, tc, rh, wl)
check_errwarn(c_retval, 'atoi13')
return ri, di
STATUS_CODES['atoi13'] = {
1: 'dubious year (Note 2)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def atoiq(type, ob1, ob2, astrom):
"""
Quick observed place to CIRS, given the star-independent astrometry
parameters.
Parameters
----------
type : const char array
ob1 : double array
ob2 : double array
astrom : eraASTROM array
Returns
-------
ri : double array
di : double array
Notes
-----
Wraps ERFA function ``eraAtoiq``. The ERFA documentation is::
- - - - - - - - -
e r a A t o i q
- - - - - - - - -
Quick observed place to CIRS, given the star-independent astrometry
parameters.
Use of this function is appropriate when efficiency is important and
where many star positions are all to be transformed for one date.
The star-independent astrometry parameters can be obtained by
calling eraApio[13] or eraApco[13].
Given:
type char[] type of coordinates: "R", "H" or "A" (Note 1)
ob1 double observed Az, HA or RA (radians; Az is N=0,E=90)
ob2 double observed ZD or Dec (radians)
astrom eraASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)
Returned:
ri double CIRS right ascension (CIO-based, radians)
di double CIRS declination (radians)
Notes:
1) "Observed" Az,El means the position that would be seen by a
perfect geodetically aligned theodolite. This is related to
the observed HA,Dec via the standard rotation, using the geodetic
latitude (corrected for polar motion), while the observed HA and
RA are related simply through the Earth rotation angle and the
site longitude. "Observed" RA,Dec or HA,Dec thus means the
position that would be seen by a perfect equatorial with its
polar axis aligned to the Earth's axis of rotation. By removing
from the observed place the effects of atmospheric refraction and
diurnal aberration, the CIRS RA,Dec is obtained.
2) Only the first character of the type argument is significant.
"R" or "r" indicates that ob1 and ob2 are the observed right
ascension and declination; "H" or "h" indicates that they are
hour angle (west +ve) and declination; anything else ("A" or
"a" is recommended) indicates that ob1 and ob2 are azimuth (north
zero, east 90 deg) and zenith distance. (Zenith distance is used
rather than altitude in order to reflect the fact that no
allowance is made for depression of the horizon.)
3) The accuracy of the result is limited by the corrections for
refraction, which use a simple A*tan(z) + B*tan^3(z) model.
Providing the meteorological parameters are known accurately and
there are no gross local effects, the predicted intermediate
coordinates should be within 0.05 arcsec (optical) or 1 arcsec
(radio) for a zenith distance of less than 70 degrees, better
than 30 arcsec (optical or radio) at 85 degrees and better than
20 arcmin (optical) or 25 arcmin (radio) at the horizon.
Without refraction, the complementary functions eraAtioq and
eraAtoiq are self-consistent to better than 1 microarcsecond all
over the celestial sphere. With refraction included, consistency
falls off at high zenith distances, but is still better than
0.05 arcsec at 85 degrees.
4) It is advisable to take great care with units, as even unlikely
values of the input parameters are accepted and processed in
accordance with the models used.
Called:
eraS2c spherical coordinates to unit vector
eraC2s p-vector to spherical
eraAnp normalize angle into range 0 to 2pi
This revision: 2020 December 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ri, di = ufunc.atoiq(type, ob1, ob2, astrom)
return ri, di
[docs]def ld(bm, p, q, e, em, dlim):
"""
Apply light deflection by a solar-system body, as part of
transforming coordinate direction into natural direction.
Parameters
----------
bm : double array
p : double array
q : double array
e : double array
em : double array
dlim : double array
Returns
-------
p1 : double array
Notes
-----
Wraps ERFA function ``eraLd``. The ERFA documentation is::
- - - - - -
e r a L d
- - - - - -
Apply light deflection by a solar-system body, as part of
transforming coordinate direction into natural direction.
Given:
bm double mass of the gravitating body (solar masses)
p double[3] direction from observer to source (unit vector)
q double[3] direction from body to source (unit vector)
e double[3] direction from body to observer (unit vector)
em double distance from body to observer (au)
dlim double deflection limiter (Note 4)
Returned:
p1 double[3] observer to deflected source (unit vector)
Notes:
1) The algorithm is based on Expr. (70) in Klioner (2003) and
Expr. (7.63) in the Explanatory Supplement (Urban & Seidelmann
2013), with some rearrangement to minimize the effects of machine
precision.
2) The mass parameter bm can, as required, be adjusted in order to
allow for such effects as quadrupole field.
3) The barycentric position of the deflecting body should ideally
correspond to the time of closest approach of the light ray to
the body.
4) The deflection limiter parameter dlim is phi^2/2, where phi is
the angular separation (in radians) between source and body at
which limiting is applied. As phi shrinks below the chosen
threshold, the deflection is artificially reduced, reaching zero
for phi = 0.
5) The returned vector p1 is not normalized, but the consequential
departure from unit magnitude is always negligible.
6) The arguments p and p1 can be the same array.
7) To accumulate total light deflection taking into account the
contributions from several bodies, call the present function for
each body in succession, in decreasing order of distance from the
observer.
8) For efficiency, validation is omitted. The supplied vectors must
be of unit magnitude, and the deflection limiter non-zero and
positive.
References:
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013).
Klioner, Sergei A., "A practical relativistic model for micro-
arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).
Called:
eraPdp scalar product of two p-vectors
eraPxp vector product of two p-vectors
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p1 = ufunc.ld(bm, p, q, e, em, dlim)
return p1
[docs]def ldn(b, ob, sc):
"""
For a star, apply light deflection by multiple solar-system bodies,
as part of transforming coordinate direction into natural direction.
Parameters
----------
b : eraLDBODY array
ob : double array
sc : double array
Returns
-------
sn : double array
Notes
-----
Wraps ERFA function ``eraLdn``. The ERFA documentation is::
- - - - - - -
e r a L d n
- - - - - - -
For a star, apply light deflection by multiple solar-system bodies,
as part of transforming coordinate direction into natural direction.
Given:
n int number of bodies (note 1)
b eraLDBODY[n] data for each of the n bodies (Notes 1,2):
bm double mass of the body (solar masses, Note 3)
dl double deflection limiter (Note 4)
pv [2][3] barycentric PV of the body (au, au/day)
ob double[3] barycentric position of the observer (au)
sc double[3] observer to star coord direction (unit vector)
Returned:
sn double[3] observer to deflected star (unit vector)
1) The array b contains n entries, one for each body to be
considered. If n = 0, no gravitational light deflection will be
applied, not even for the Sun.
2) The array b should include an entry for the Sun as well as for
any planet or other body to be taken into account. The entries
should be in the order in which the light passes the body.
3) In the entry in the b array for body i, the mass parameter
b[i].bm can, as required, be adjusted in order to allow for such
effects as quadrupole field.
4) The deflection limiter parameter b[i].dl is phi^2/2, where phi is
the angular separation (in radians) between star and body at
which limiting is applied. As phi shrinks below the chosen
threshold, the deflection is artificially reduced, reaching zero
for phi = 0. Example values suitable for a terrestrial
observer, together with masses, are as follows:
body i b[i].bm b[i].dl
Sun 1.0 6e-6
Jupiter 0.00095435 3e-9
Saturn 0.00028574 3e-10
5) For cases where the starlight passes the body before reaching the
observer, the body is placed back along its barycentric track by
the light time from that point to the observer. For cases where
the body is "behind" the observer no such shift is applied. If
a different treatment is preferred, the user has the option of
instead using the eraLd function. Similarly, eraLd can be used
for cases where the source is nearby, not a star.
6) The returned vector sn is not normalized, but the consequential
departure from unit magnitude is always negligible.
7) The arguments sc and sn can be the same array.
8) For efficiency, validation is omitted. The supplied masses must
be greater than zero, the position and velocity vectors must be
right, and the deflection limiter greater than zero.
Reference:
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013), Section 7.2.4.
Called:
eraCp copy p-vector
eraPdp scalar product of two p-vectors
eraPmp p-vector minus p-vector
eraPpsp p-vector plus scaled p-vector
eraPn decompose p-vector into modulus and direction
eraLd light deflection by a solar-system body
This revision: 2017 March 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
sn = ufunc.ldn(b, ob, sc)
return sn
[docs]def ldsun(p, e, em):
"""
Deflection of starlight by the Sun.
Parameters
----------
p : double array
e : double array
em : double array
Returns
-------
p1 : double array
Notes
-----
Wraps ERFA function ``eraLdsun``. The ERFA documentation is::
- - - - - - - - -
e r a L d s u n
- - - - - - - - -
Deflection of starlight by the Sun.
Given:
p double[3] direction from observer to star (unit vector)
e double[3] direction from Sun to observer (unit vector)
em double distance from Sun to observer (au)
Returned:
p1 double[3] observer to deflected star (unit vector)
Notes:
1) The source is presumed to be sufficiently distant that its
directions seen from the Sun and the observer are essentially
the same.
2) The deflection is restrained when the angle between the star and
the center of the Sun is less than a threshold value, falling to
zero deflection for zero separation. The chosen threshold value
is within the solar limb for all solar-system applications, and
is about 5 arcminutes for the case of a terrestrial observer.
3) The arguments p and p1 can be the same array.
Called:
eraLd light deflection by a solar-system body
This revision: 2016 June 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p1 = ufunc.ldsun(p, e, em)
return p1
[docs]def pmpx(rc, dc, pr, pd, px, rv, pmt, pob):
"""
Proper motion and parallax.
Parameters
----------
rc : double array
dc : double array
pr : double array
pd : double array
px : double array
rv : double array
pmt : double array
pob : double array
Returns
-------
pco : double array
Notes
-----
Wraps ERFA function ``eraPmpx``. The ERFA documentation is::
- - - - - - - -
e r a P m p x
- - - - - - - -
Proper motion and parallax.
Given:
rc,dc double ICRS RA,Dec at catalog epoch (radians)
pr double RA proper motion (radians/year; Note 1)
pd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, +ve if receding)
pmt double proper motion time interval (SSB, Julian years)
pob double[3] SSB to observer vector (au)
Returned:
pco double[3] coordinate direction (BCRS unit vector)
Notes:
1) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
2) The proper motion time interval is for when the starlight
reaches the solar system barycenter.
3) To avoid the need for iteration, the Roemer effect (i.e. the
small annual modulation of the proper motion coming from the
changing light time) is applied approximately, using the
direction of the star at the catalog epoch.
References:
1984 Astronomical Almanac, pp B39-B41.
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013), Section 7.2.
Called:
eraPdp scalar product of two p-vectors
eraPn decompose p-vector into modulus and direction
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pco = ufunc.pmpx(rc, dc, pr, pd, px, rv, pmt, pob)
return pco
[docs]def pmsafe(ra1, dec1, pmr1, pmd1, px1, rv1, ep1a, ep1b, ep2a, ep2b):
"""
Star proper motion: update star catalog data for space motion, with
special handling to handle the zero parallax case.
Parameters
----------
ra1 : double array
dec1 : double array
pmr1 : double array
pmd1 : double array
px1 : double array
rv1 : double array
ep1a : double array
ep1b : double array
ep2a : double array
ep2b : double array
Returns
-------
ra2 : double array
dec2 : double array
pmr2 : double array
pmd2 : double array
px2 : double array
rv2 : double array
Notes
-----
Wraps ERFA function ``eraPmsafe``. The ERFA documentation is::
- - - - - - - - - -
e r a P m s a f e
- - - - - - - - - -
Star proper motion: update star catalog data for space motion, with
special handling to handle the zero parallax case.
Given:
ra1 double right ascension (radians), before
dec1 double declination (radians), before
pmr1 double RA proper motion (radians/year), before
pmd1 double Dec proper motion (radians/year), before
px1 double parallax (arcseconds), before
rv1 double radial velocity (km/s, +ve = receding), before
ep1a double "before" epoch, part A (Note 1)
ep1b double "before" epoch, part B (Note 1)
ep2a double "after" epoch, part A (Note 1)
ep2b double "after" epoch, part B (Note 1)
Returned:
ra2 double right ascension (radians), after
dec2 double declination (radians), after
pmr2 double RA proper motion (radians/year), after
pmd2 double Dec proper motion (radians/year), after
px2 double parallax (arcseconds), after
rv2 double radial velocity (km/s, +ve = receding), after
Returned (function value):
int status:
-1 = system error (should not occur)
0 = no warnings or errors
1 = distance overridden (Note 6)
2 = excessive velocity (Note 7)
4 = solution didn't converge (Note 8)
else = binary logical OR of the above warnings
Notes:
1) The starting and ending TDB epochs ep1a+ep1b and ep2a+ep2b are
Julian Dates, apportioned in any convenient way between the two
parts (A and B). For example, JD(TDB)=2450123.7 could be
expressed in any of these ways, among others:
epNa epNb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience.
2) In accordance with normal star-catalog conventions, the object's
right ascension and declination are freed from the effects of
secular aberration. The frame, which is aligned to the catalog
equator and equinox, is Lorentzian and centered on the SSB.
The proper motions are the rate of change of the right ascension
and declination at the catalog epoch and are in radians per TDB
Julian year.
The parallax and radial velocity are in the same frame.
3) Care is needed with units. The star coordinates are in radians
and the proper motions in radians per Julian year, but the
parallax is in arcseconds.
4) The RA proper motion is in terms of coordinate angle, not true
angle. If the catalog uses arcseconds for both RA and Dec proper
motions, the RA proper motion will need to be divided by cos(Dec)
before use.
5) Straight-line motion at constant speed, in the inertial frame, is
assumed.
6) An extremely small (or zero or negative) parallax is overridden
to ensure that the object is at a finite but very large distance,
but not so large that the proper motion is equivalent to a large
but safe speed (about 0.1c using the chosen constant). A warning
status of 1 is added to the status if this action has been taken.
7) If the space velocity is a significant fraction of c (see the
constant VMAX in the function eraStarpv), it is arbitrarily set
to zero. When this action occurs, 2 is added to the status.
8) The relativistic adjustment carried out in the eraStarpv function
involves an iterative calculation. If the process fails to
converge within a set number of iterations, 4 is added to the
status.
Called:
eraSeps angle between two points
eraStarpm update star catalog data for space motion
This revision: 2014 July 1
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ra2, dec2, pmr2, pmd2, px2, rv2, c_retval = ufunc.pmsafe(
ra1, dec1, pmr1, pmd1, px1, rv1, ep1a, ep1b, ep2a, ep2b)
check_errwarn(c_retval, 'pmsafe')
return ra2, dec2, pmr2, pmd2, px2, rv2
STATUS_CODES['pmsafe'] = {
-1: 'system error (should not occur)',
0: 'no warnings or errors',
1: 'distance overridden (Note 6)',
2: 'excessive velocity (Note 7)',
4: "solution didn't converge (Note 8)",
'else': 'binary logical OR of the above warnings',
}
[docs]def pvtob(elong, phi, hm, xp, yp, sp, theta):
"""
Position and velocity of a terrestrial observing station.
Parameters
----------
elong : double array
phi : double array
hm : double array
xp : double array
yp : double array
sp : double array
theta : double array
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraPvtob``. The ERFA documentation is::
- - - - - - - - -
e r a P v t o b
- - - - - - - - -
Position and velocity of a terrestrial observing station.
Given:
elong double longitude (radians, east +ve, Note 1)
phi double latitude (geodetic, radians, Note 1)
hm double height above ref. ellipsoid (geodetic, m)
xp,yp double coordinates of the pole (radians, Note 2)
sp double the TIO locator s' (radians, Note 2)
theta double Earth rotation angle (radians, Note 3)
Returned:
pv double[2][3] position/velocity vector (m, m/s, CIRS)
Notes:
1) The terrestrial coordinates are with respect to the ERFA_WGS84
reference ellipsoid.
2) xp and yp are the coordinates (in radians) of the Celestial
Intermediate Pole with respect to the International Terrestrial
Reference System (see IERS Conventions), measured along the
meridians 0 and 90 deg west respectively. sp is the TIO locator
s', in radians, which positions the Terrestrial Intermediate
Origin on the equator. For many applications, xp, yp and
(especially) sp can be set to zero.
3) If theta is Greenwich apparent sidereal time instead of Earth
rotation angle, the result is with respect to the true equator
and equinox of date, i.e. with the x-axis at the equinox rather
than the celestial intermediate origin.
4) The velocity units are meters per UT1 second, not per SI second.
This is unlikely to have any practical consequences in the modern
era.
5) No validation is performed on the arguments. Error cases that
could lead to arithmetic exceptions are trapped by the eraGd2gc
function, and the result set to zeros.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
the Astronomical Almanac, 3rd ed., University Science Books
(2013), Section 7.4.3.3.
Called:
eraGd2gc geodetic to geocentric transformation
eraPom00 polar motion matrix
eraTrxp product of transpose of r-matrix and p-vector
This revision: 2013 October 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv = ufunc.pvtob(elong, phi, hm, xp, yp, sp, theta)
return pv
[docs]def refco(phpa, tc, rh, wl):
"""
Determine the constants A and B in the atmospheric refraction model
dZ = A tan Z + B tan^3 Z.
Parameters
----------
phpa : double array
tc : double array
rh : double array
wl : double array
Returns
-------
refa : double array
refb : double array
Notes
-----
Wraps ERFA function ``eraRefco``. The ERFA documentation is::
- - - - - - - - -
e r a R e f c o
- - - - - - - - -
Determine the constants A and B in the atmospheric refraction model
dZ = A tan Z + B tan^3 Z.
Z is the "observed" zenith distance (i.e. affected by refraction)
and dZ is what to add to Z to give the "topocentric" (i.e. in vacuo)
zenith distance.
Given:
phpa double pressure at the observer (hPa = millibar)
tc double ambient temperature at the observer (deg C)
rh double relative humidity at the observer (range 0-1)
wl double wavelength (micrometers)
Returned:
refa double tan Z coefficient (radians)
refb double tan^3 Z coefficient (radians)
Notes:
1) The model balances speed and accuracy to give good results in
applications where performance at low altitudes is not paramount.
Performance is maintained across a range of conditions, and
applies to both optical/IR and radio.
2) The model omits the effects of (i) height above sea level (apart
from the reduced pressure itself), (ii) latitude (i.e. the
flattening of the Earth), (iii) variations in tropospheric lapse
rate and (iv) dispersive effects in the radio.
The model was tested using the following range of conditions:
lapse rates 0.0055, 0.0065, 0.0075 deg/meter
latitudes 0, 25, 50, 75 degrees
heights 0, 2500, 5000 meters ASL
pressures mean for height -10% to +5% in steps of 5%
temperatures -10 deg to +20 deg with respect to 280 deg at SL
relative humidity 0, 0.5, 1
wavelengths 0.4, 0.6, ... 2 micron, + radio
zenith distances 15, 45, 75 degrees
The accuracy with respect to raytracing through a model
atmosphere was as follows:
worst RMS
optical/IR 62 mas 8 mas
radio 319 mas 49 mas
For this particular set of conditions:
lapse rate 0.0065 K/meter
latitude 50 degrees
sea level
pressure 1005 mb
temperature 280.15 K
humidity 80%
wavelength 5740 Angstroms
the results were as follows:
ZD raytrace eraRefco Saastamoinen
10 10.27 10.27 10.27
20 21.19 21.20 21.19
30 33.61 33.61 33.60
40 48.82 48.83 48.81
45 58.16 58.18 58.16
50 69.28 69.30 69.27
55 82.97 82.99 82.95
60 100.51 100.54 100.50
65 124.23 124.26 124.20
70 158.63 158.68 158.61
72 177.32 177.37 177.31
74 200.35 200.38 200.32
76 229.45 229.43 229.42
78 267.44 267.29 267.41
80 319.13 318.55 319.10
deg arcsec arcsec arcsec
The values for Saastamoinen's formula (which includes terms
up to tan^5) are taken from Hohenkerk and Sinclair (1985).
3) A wl value in the range 0-100 selects the optical/IR case and is
wavelength in micrometers. Any value outside this range selects
the radio case.
4) Outlandish input parameters are silently limited to
mathematically safe values. Zero pressure is permissible, and
causes zeroes to be returned.
5) The algorithm draws on several sources, as follows:
a) The formula for the saturation vapour pressure of water as
a function of temperature and temperature is taken from
Equations (A4.5-A4.7) of Gill (1982).
b) The formula for the water vapour pressure, given the
saturation pressure and the relative humidity, is from
Crane (1976), Equation (2.5.5).
c) The refractivity of air is a function of temperature,
total pressure, water-vapour pressure and, in the case
of optical/IR, wavelength. The formulae for the two cases are
developed from Hohenkerk & Sinclair (1985) and Rueger (2002).
The IAG (1999) optical refractivity for dry air is used.
d) The formula for beta, the ratio of the scale height of the
atmosphere to the geocentric distance of the observer, is
an adaption of Equation (9) from Stone (1996). The
adaptations, arrived at empirically, consist of (i) a small
adjustment to the coefficient and (ii) a humidity term for the
radio case only.
e) The formulae for the refraction constants as a function of
n-1 and beta are from Green (1987), Equation (4.31).
References:
Crane, R.K., Meeks, M.L. (ed), "Refraction Effects in the Neutral
Atmosphere", Methods of Experimental Physics: Astrophysics 12B,
Academic Press, 1976.
Gill, Adrian E., "Atmosphere-Ocean Dynamics", Academic Press,
1982.
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987.
Hohenkerk, C.Y., & Sinclair, A.T., NAO Technical Note No. 63,
1985.
IAG Resolutions adopted at the XXIIth General Assembly in
Birmingham, 1999, Resolution 3.
Rueger, J.M., "Refractive Index Formulae for Electronic Distance
Measurement with Radio and Millimetre Waves", in Unisurv Report
S-68, School of Surveying and Spatial Information Systems,
University of New South Wales, Sydney, Australia, 2002.
Stone, Ronald C., P.A.S.P. 108, 1051-1058, 1996.
This revision: 2020 August 17
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
refa, refb = ufunc.refco(phpa, tc, rh, wl)
return refa, refb
[docs]def epv00(date1, date2):
"""
Earth position and velocity, heliocentric and barycentric, with
respect to the Barycentric Celestial Reference System.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
pvh : double array
pvb : double array
Notes
-----
Wraps ERFA function ``eraEpv00``. The ERFA documentation is::
- - - - - - - - -
e r a E p v 0 0
- - - - - - - - -
Earth position and velocity, heliocentric and barycentric, with
respect to the Barycentric Celestial Reference System.
Given:
date1,date2 double TDB date (Note 1)
Returned:
pvh double[2][3] heliocentric Earth position/velocity
pvb double[2][3] barycentric Earth position/velocity
Returned (function value):
int status: 0 = OK
+1 = warning: date outside
the range 1900-2100 AD
Notes:
1) The TDB date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TDB)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. However,
the accuracy of the result is more likely to be limited by the
algorithm itself than the way the date has been expressed.
n.b. TT can be used instead of TDB in most applications.
2) On return, the arrays pvh and pvb contain the following:
pvh[0][0] x }
pvh[0][1] y } heliocentric position, au
pvh[0][2] z }
pvh[1][0] xdot }
pvh[1][1] ydot } heliocentric velocity, au/d
pvh[1][2] zdot }
pvb[0][0] x }
pvb[0][1] y } barycentric position, au
pvb[0][2] z }
pvb[1][0] xdot }
pvb[1][1] ydot } barycentric velocity, au/d
pvb[1][2] zdot }
The vectors are with respect to the Barycentric Celestial
Reference System. The time unit is one day in TDB.
3) The function is a SIMPLIFIED SOLUTION from the planetary theory
VSOP2000 (X. Moisson, P. Bretagnon, 2001, Celes. Mechanics &
Dyn. Astron., 80, 3/4, 205-213) and is an adaptation of original
Fortran code supplied by P. Bretagnon (private comm., 2000).
4) Comparisons over the time span 1900-2100 with this simplified
solution and the JPL DE405 ephemeris give the following results:
RMS max
Heliocentric:
position error 3.7 11.2 km
velocity error 1.4 5.0 mm/s
Barycentric:
position error 4.6 13.4 km
velocity error 1.4 4.9 mm/s
Comparisons with the JPL DE406 ephemeris show that by 1800 and
2200 the position errors are approximately double their 1900-2100
size. By 1500 and 2500 the deterioration is a factor of 10 and
by 1000 and 3000 a factor of 60. The velocity accuracy falls off
at about half that rate.
5) It is permissible to use the same array for pvh and pvb, which
will receive the barycentric values.
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pvh, pvb, c_retval = ufunc.epv00(date1, date2)
check_errwarn(c_retval, 'epv00')
return pvh, pvb
STATUS_CODES['epv00'] = {
0: 'OK',
1: 'warning: date outsidethe range 1900-2100 AD',
}
[docs]def plan94(date1, date2, np):
"""
Approximate heliocentric position and velocity of a nominated major
planet: Mercury, Venus, EMB, Mars, Jupiter, Saturn, Uranus or
Neptune (but not the Earth itself).
Parameters
----------
date1 : double array
date2 : double array
np : int array
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraPlan94``. The ERFA documentation is::
- - - - - - - - - -
e r a P l a n 9 4
- - - - - - - - - -
Approximate heliocentric position and velocity of a nominated major
planet: Mercury, Venus, EMB, Mars, Jupiter, Saturn, Uranus or
Neptune (but not the Earth itself).
Given:
date1 double TDB date part A (Note 1)
date2 double TDB date part B (Note 1)
np int planet (1=Mercury, 2=Venus, 3=EMB, 4=Mars,
5=Jupiter, 6=Saturn, 7=Uranus, 8=Neptune)
Returned (argument):
pv double[2][3] planet p,v (heliocentric, J2000.0, au,au/d)
Returned (function value):
int status: -1 = illegal NP (outside 1-8)
0 = OK
+1 = warning: year outside 1000-3000
+2 = warning: failed to converge
Notes:
1) The date date1+date2 is in the TDB time scale (in practice TT can
be used) and is a Julian Date, apportioned in any convenient way
between the two arguments. For example, JD(TDB)=2450123.7 could
be expressed in any of these ways, among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
resolution. The MJD method and the date & time methods are both
good compromises between resolution and convenience. The limited
accuracy of the present algorithm is such that any of the methods
is satisfactory.
2) If an np value outside the range 1-8 is supplied, an error status
(function value -1) is returned and the pv vector set to zeroes.
3) For np=3 the result is for the Earth-Moon Barycenter. To obtain
the heliocentric position and velocity of the Earth, use instead
the ERFA function eraEpv00.
4) On successful return, the array pv contains the following:
pv[0][0] x }
pv[0][1] y } heliocentric position, au
pv[0][2] z }
pv[1][0] xdot }
pv[1][1] ydot } heliocentric velocity, au/d
pv[1][2] zdot }
The reference frame is equatorial and is with respect to the
mean equator and equinox of epoch J2000.0.
5) The algorithm is due to J.L. Simon, P. Bretagnon, J. Chapront,
M. Chapront-Touze, G. Francou and J. Laskar (Bureau des
Longitudes, Paris, France). From comparisons with JPL
ephemeris DE102, they quote the following maximum errors
over the interval 1800-2050:
L (arcsec) B (arcsec) R (km)
Mercury 4 1 300
Venus 5 1 800
EMB 6 1 1000
Mars 17 1 7700
Jupiter 71 5 76000
Saturn 81 13 267000
Uranus 86 7 712000
Neptune 11 1 253000
Over the interval 1000-3000, they report that the accuracy is no
worse than 1.5 times that over 1800-2050. Outside 1000-3000 the
accuracy declines.
Comparisons of the present function with the JPL DE200 ephemeris
give the following RMS errors over the interval 1960-2025:
position (km) velocity (m/s)
Mercury 334 0.437
Venus 1060 0.855
EMB 2010 0.815
Mars 7690 1.98
Jupiter 71700 7.70
Saturn 199000 19.4
Uranus 564000 16.4
Neptune 158000 14.4
Comparisons against DE200 over the interval 1800-2100 gave the
following maximum absolute differences. (The results using
DE406 were essentially the same.)
L (arcsec) B (arcsec) R (km) Rdot (m/s)
Mercury 7 1 500 0.7
Venus 7 1 1100 0.9
EMB 9 1 1300 1.0
Mars 26 1 9000 2.5
Jupiter 78 6 82000 8.2
Saturn 87 14 263000 24.6
Uranus 86 7 661000 27.4
Neptune 11 2 248000 21.4
6) The present ERFA re-implementation of the original Simon et al.
Fortran code differs from the original in the following respects:
C instead of Fortran.
The date is supplied in two parts.
The result is returned only in equatorial Cartesian form;
the ecliptic longitude, latitude and radius vector are not
returned.
The result is in the J2000.0 equatorial frame, not ecliptic.
More is done in-line: there are fewer calls to subroutines.
Different error/warning status values are used.
A different Kepler's-equation-solver is used (avoiding
use of double precision complex).
Polynomials in t are nested to minimize rounding errors.
Explicit double constants are used to avoid mixed-mode
expressions.
None of the above changes affects the result significantly.
7) The returned status indicates the most serious condition
encountered during execution of the function. Illegal np is
considered the most serious, overriding failure to converge,
which in turn takes precedence over the remote date warning.
Called:
eraAnp normalize angle into range 0 to 2pi
Reference: Simon, J.L, Bretagnon, P., Chapront, J.,
Chapront-Touze, M., Francou, G., and Laskar, J.,
Astron.Astrophys., 282, 663 (1994).
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv, c_retval = ufunc.plan94(date1, date2, np)
check_errwarn(c_retval, 'plan94')
return pv
STATUS_CODES['plan94'] = {
-1: 'illegal NP (outside 1-8)',
0: 'OK',
1: 'warning: year outside 1000-3000',
2: 'warning: failed to converge',
}
[docs]def fad03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean elongation of the Moon from the Sun.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFad03``. The ERFA documentation is::
- - - - - - - - -
e r a F a d 0 3
- - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean elongation of the Moon from the Sun.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double D, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fad03(t)
return c_retval
[docs]def fae03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Earth.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFae03``. The ERFA documentation is::
- - - - - - - - -
e r a F a e 0 3
- - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Earth.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Earth, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fae03(t)
return c_retval
[docs]def faf03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of the Moon minus mean longitude of the ascending
node.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFaf03``. The ERFA documentation is::
- - - - - - - - -
e r a F a f 0 3
- - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of the Moon minus mean longitude of the ascending
node.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double F, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.faf03(t)
return c_retval
[docs]def faju03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Jupiter.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFaju03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a j u 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Jupiter.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Jupiter, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.faju03(t)
return c_retval
[docs]def fal03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean anomaly of the Moon.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFal03``. The ERFA documentation is::
- - - - - - - - -
e r a F a l 0 3
- - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean anomaly of the Moon.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double l, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fal03(t)
return c_retval
[docs]def falp03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean anomaly of the Sun.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFalp03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a l p 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean anomaly of the Sun.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double l', radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.falp03(t)
return c_retval
[docs]def fama03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Mars.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFama03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a m a 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Mars.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Mars, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fama03(t)
return c_retval
[docs]def fame03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Mercury.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFame03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a m e 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Mercury.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Mercury, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fame03(t)
return c_retval
[docs]def fane03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Neptune.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFane03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a n e 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Neptune.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Neptune, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is adapted from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fane03(t)
return c_retval
[docs]def faom03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of the Moon's ascending node.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFaom03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a o m 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of the Moon's ascending node.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double Omega, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J., 1994, Astron.Astrophys. 282, 663-683.
This revision: 2020 November 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.faom03(t)
return c_retval
[docs]def fapa03(t):
"""
Fundamental argument, IERS Conventions (2003):
general accumulated precession in longitude.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFapa03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a p a 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
general accumulated precession in longitude.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double general precession in longitude, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003). It
is taken from Kinoshita & Souchay (1990) and comes originally
from Lieske et al. (1977).
References:
Kinoshita, H. and Souchay J. 1990, Celest.Mech. and Dyn.Astron.
48, 187
Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
Astron.Astrophys. 58, 1-16
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fapa03(t)
return c_retval
[docs]def fasa03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Saturn.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFasa03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a s a 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Saturn.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Saturn, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fasa03(t)
return c_retval
[docs]def faur03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Uranus.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFaur03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a u r 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Uranus.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Uranus, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
is adapted from Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.faur03(t)
return c_retval
[docs]def fave03(t):
"""
Fundamental argument, IERS Conventions (2003):
mean longitude of Venus.
Parameters
----------
t : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraFave03``. The ERFA documentation is::
- - - - - - - - - -
e r a F a v e 0 3
- - - - - - - - - -
Fundamental argument, IERS Conventions (2003):
mean longitude of Venus.
Given:
t double TDB, Julian centuries since J2000.0 (Note 1)
Returned (function value):
double mean longitude of Venus, radians (Note 2)
Notes:
1) Though t is strictly TDB, it is usually more convenient to use
TT, which makes no significant difference.
2) The expression used is as adopted in IERS Conventions (2003) and
comes from Souchay et al. (1999) after Simon et al. (1994).
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.fave03(t)
return c_retval
[docs]def bi00():
"""
Frame bias components of IAU 2000 precession-nutation models; part
of the Mathews-Herring-Buffett (MHB2000) nutation series, with
additions.
Parameters
----------
Returns
-------
dpsibi : double array
depsbi : double array
dra : double array
Notes
-----
Wraps ERFA function ``eraBi00``. The ERFA documentation is::
- - - - - - - -
e r a B i 0 0
- - - - - - - -
Frame bias components of IAU 2000 precession-nutation models; part
of the Mathews-Herring-Buffett (MHB2000) nutation series, with
additions.
Returned:
dpsibi,depsbi double longitude and obliquity corrections
dra double the ICRS RA of the J2000.0 mean equinox
Notes:
1) The frame bias corrections in longitude and obliquity (radians)
are required in order to correct for the offset between the GCRS
pole and the mean J2000.0 pole. They define, with respect to the
GCRS frame, a J2000.0 mean pole that is consistent with the rest
of the IAU 2000A precession-nutation model.
2) In addition to the displacement of the pole, the complete
description of the frame bias requires also an offset in right
ascension. This is not part of the IAU 2000A model, and is from
Chapront et al. (2002). It is returned in radians.
3) This is a supplemented implementation of one aspect of the IAU
2000A nutation model, formally adopted by the IAU General
Assembly in 2000, namely MHB2000 (Mathews et al. 2002).
References:
Chapront, J., Chapront-Touze, M. & Francou, G., Astron.
Astrophys., 387, 700, 2002.
Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
and precession: New nutation series for nonrigid Earth and
insights into the Earth's interior", J.Geophys.Res., 107, B4,
2002. The MHB2000 code itself was obtained on 2002 September 9
from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
This revision: 2020 October 29
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsibi, depsbi, dra = ufunc.bi00()
return dpsibi, depsbi, dra
[docs]def bp00(date1, date2):
"""
Frame bias and precession, IAU 2000.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rb : double array
rp : double array
rbp : double array
Notes
-----
Wraps ERFA function ``eraBp00``. The ERFA documentation is::
- - - - - - - -
e r a B p 0 0
- - - - - - - -
Frame bias and precession, IAU 2000.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rb double[3][3] frame bias matrix (Note 2)
rp double[3][3] precession matrix (Note 3)
rbp double[3][3] bias-precession matrix (Note 4)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rb transforms vectors from GCRS to mean J2000.0 by
applying frame bias.
3) The matrix rp transforms vectors from J2000.0 mean equator and
equinox to mean equator and equinox of date by applying
precession.
4) The matrix rbp transforms vectors from GCRS to mean equator and
equinox of date by applying frame bias then precession. It is
the product rp x rb.
5) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the order given.
Called:
eraBi00 frame bias components, IAU 2000
eraPr00 IAU 2000 precession adjustments
eraIr initialize r-matrix to identity
eraRx rotate around X-axis
eraRy rotate around Y-axis
eraRz rotate around Z-axis
eraCr copy r-matrix
eraRxr product of two r-matrices
Reference:
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
This revision: 2013 August 21
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rb, rp, rbp = ufunc.bp00(date1, date2)
return rb, rp, rbp
[docs]def bp06(date1, date2):
"""
Frame bias and precession, IAU 2006.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rb : double array
rp : double array
rbp : double array
Notes
-----
Wraps ERFA function ``eraBp06``. The ERFA documentation is::
- - - - - - - -
e r a B p 0 6
- - - - - - - -
Frame bias and precession, IAU 2006.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rb double[3][3] frame bias matrix (Note 2)
rp double[3][3] precession matrix (Note 3)
rbp double[3][3] bias-precession matrix (Note 4)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rb transforms vectors from GCRS to mean J2000.0 by
applying frame bias.
3) The matrix rp transforms vectors from mean J2000.0 to mean of
date by applying precession.
4) The matrix rbp transforms vectors from GCRS to mean of date by
applying frame bias then precession. It is the product rp x rb.
5) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the order given.
Called:
eraPfw06 bias-precession F-W angles, IAU 2006
eraFw2m F-W angles to r-matrix
eraPmat06 PB matrix, IAU 2006
eraTr transpose r-matrix
eraRxr product of two r-matrices
eraCr copy r-matrix
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2013 August 21
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rb, rp, rbp = ufunc.bp06(date1, date2)
return rb, rp, rbp
[docs]def bpn2xy(rbpn):
"""
Extract from the bias-precession-nutation matrix the X,Y coordinates
of the Celestial Intermediate Pole.
Parameters
----------
rbpn : double array
Returns
-------
x : double array
y : double array
Notes
-----
Wraps ERFA function ``eraBpn2xy``. The ERFA documentation is::
- - - - - - - - - -
e r a B p n 2 x y
- - - - - - - - - -
Extract from the bias-precession-nutation matrix the X,Y coordinates
of the Celestial Intermediate Pole.
Given:
rbpn double[3][3] celestial-to-true matrix (Note 1)
Returned:
x,y double Celestial Intermediate Pole (Note 2)
Notes:
1) The matrix rbpn transforms vectors from GCRS to true equator (and
CIO or equinox) of date, and therefore the Celestial Intermediate
Pole unit vector is the bottom row of the matrix.
2) The arguments x,y are components of the Celestial Intermediate
Pole unit vector in the Geocentric Celestial Reference System.
Reference:
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154
(2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y = ufunc.bpn2xy(rbpn)
return x, y
[docs]def c2i00a(date1, date2):
"""
Form the celestial-to-intermediate matrix for a given date using the
IAU 2000A precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2i00a``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 i 0 0 a
- - - - - - - - - -
Form the celestial-to-intermediate matrix for a given date using the
IAU 2000A precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
3) A faster, but slightly less accurate, result (about 1 mas) can be
obtained by using instead the eraC2i00b function.
Called:
eraPnm00a classical NPB matrix, IAU 2000A
eraC2ibpn celestial-to-intermediate matrix, given NPB matrix
References:
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154
(2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2i00a(date1, date2)
return rc2i
[docs]def c2i00b(date1, date2):
"""
Form the celestial-to-intermediate matrix for a given date using the
IAU 2000B precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2i00b``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 i 0 0 b
- - - - - - - - - -
Form the celestial-to-intermediate matrix for a given date using the
IAU 2000B precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
3) The present function is faster, but slightly less accurate (about
1 mas), than the eraC2i00a function.
Called:
eraPnm00b classical NPB matrix, IAU 2000B
eraC2ibpn celestial-to-intermediate matrix, given NPB matrix
References:
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154
(2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2i00b(date1, date2)
return rc2i
[docs]def c2i06a(date1, date2):
"""
Form the celestial-to-intermediate matrix for a given date using the
IAU 2006 precession and IAU 2000A nutation models.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2i06a``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 i 0 6 a
- - - - - - - - - -
Form the celestial-to-intermediate matrix for a given date using the
IAU 2006 precession and IAU 2000A nutation models.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= RC2T * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
Called:
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
eraC2ixys celestial-to-intermediate matrix, given X,Y and s
References:
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2i06a(date1, date2)
return rc2i
[docs]def c2ibpn(date1, date2, rbpn):
"""
Form the celestial-to-intermediate matrix for a given date given
the bias-precession-nutation matrix.
Parameters
----------
date1 : double array
date2 : double array
rbpn : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2ibpn``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 i b p n
- - - - - - - - - -
Form the celestial-to-intermediate matrix for a given date given
the bias-precession-nutation matrix. IAU 2000.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
rbpn double[3][3] celestial-to-true matrix (Note 2)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix rbpn transforms vectors from GCRS to true equator (and
CIO or equinox) of date. Only the CIP (bottom row) is used.
3) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= RC2T * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
4) Although its name does not include "00", This function is in fact
specific to the IAU 2000 models.
Called:
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraC2ixy celestial-to-intermediate matrix, given X,Y
References:
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2ibpn(date1, date2, rbpn)
return rc2i
[docs]def c2ixy(date1, date2, x, y):
"""
Form the celestial to intermediate-frame-of-date matrix for a given
date when the CIP X,Y coordinates are known.
Parameters
----------
date1 : double array
date2 : double array
x : double array
y : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2ixy``. The ERFA documentation is::
- - - - - - - - -
e r a C 2 i x y
- - - - - - - - -
Form the celestial to intermediate-frame-of-date matrix for a given
date when the CIP X,Y coordinates are known. IAU 2000.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
x,y double Celestial Intermediate Pole (Note 2)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The Celestial Intermediate Pole coordinates are the x,y components
of the unit vector in the Geocentric Celestial Reference System.
3) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= RC2T * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
4) Although its name does not include "00", This function is in fact
specific to the IAU 2000 models.
Called:
eraC2ixys celestial-to-intermediate matrix, given X,Y and s
eraS00 the CIO locator s, given X,Y, IAU 2000A
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2ixy(date1, date2, x, y)
return rc2i
[docs]def c2ixys(x, y, s):
"""
Form the celestial to intermediate-frame-of-date matrix given the CIP
X,Y and the CIO locator s.
Parameters
----------
x : double array
y : double array
s : double array
Returns
-------
rc2i : double array
Notes
-----
Wraps ERFA function ``eraC2ixys``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 i x y s
- - - - - - - - - -
Form the celestial to intermediate-frame-of-date matrix given the CIP
X,Y and the CIO locator s.
Given:
x,y double Celestial Intermediate Pole (Note 1)
s double the CIO locator s (Note 2)
Returned:
rc2i double[3][3] celestial-to-intermediate matrix (Note 3)
Notes:
1) The Celestial Intermediate Pole coordinates are the x,y
components of the unit vector in the Geocentric Celestial
Reference System.
2) The CIO locator s (in radians) positions the Celestial
Intermediate Origin on the equator of the CIP.
3) The matrix rc2i is the first stage in the transformation from
celestial to terrestrial coordinates:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= RC2T * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
Called:
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRy rotate around Y-axis
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2014 November 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2i = ufunc.c2ixys(x, y, s)
return rc2i
[docs]def c2t00a(tta, ttb, uta, utb, xp, yp):
"""
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2000A precession-nutation model.
Parameters
----------
tta : double array
ttb : double array
uta : double array
utb : double array
xp : double array
yp : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2t00a``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 t 0 0 a
- - - - - - - - - -
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2000A precession-nutation model.
Given:
tta,ttb double TT as a 2-part Julian Date (Note 1)
uta,utb double UT1 as a 2-part Julian Date (Note 1)
xp,yp double CIP coordinates (radians, Note 2)
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 3)
Notes:
1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
apportioned in any convenient way between the arguments uta and
utb. For example, JD(UT1)=2450123.7 could be expressed in any of
these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. In the case of uta,utb, the
date & time method is best matched to the Earth rotation angle
algorithm used: maximum precision is delivered when the uta
argument is for 0hrs UT1 on the day in question and the utb
argument lies in the range 0 to 1, or vice versa.
2) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
3) The matrix rc2t transforms from celestial to terrestrial
coordinates:
[TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), RC2I is the
celestial-to-intermediate matrix, ERA is the Earth rotation
angle and RPOM is the polar motion matrix.
4) A faster, but slightly less accurate, result (about 1 mas) can
be obtained by using instead the eraC2t00b function.
Called:
eraC2i00a celestial-to-intermediate matrix, IAU 2000A
eraEra00 Earth rotation angle, IAU 2000
eraSp00 the TIO locator s', IERS 2000
eraPom00 polar motion matrix
eraC2tcio form CIO-based celestial-to-terrestrial matrix
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2t00a(tta, ttb, uta, utb, xp, yp)
return rc2t
[docs]def c2t00b(tta, ttb, uta, utb, xp, yp):
"""
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2000B precession-nutation model.
Parameters
----------
tta : double array
ttb : double array
uta : double array
utb : double array
xp : double array
yp : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2t00b``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 t 0 0 b
- - - - - - - - - -
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2000B precession-nutation model.
Given:
tta,ttb double TT as a 2-part Julian Date (Note 1)
uta,utb double UT1 as a 2-part Julian Date (Note 1)
xp,yp double coordinates of the pole (radians, Note 2)
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 3)
Notes:
1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
apportioned in any convenient way between the arguments uta and
utb. For example, JD(UT1)=2450123.7 could be expressed in any of
these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. In the case of uta,utb, the
date & time method is best matched to the Earth rotation angle
algorithm used: maximum precision is delivered when the uta
argument is for 0hrs UT1 on the day in question and the utb
argument lies in the range 0 to 1, or vice versa.
2) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
3) The matrix rc2t transforms from celestial to terrestrial
coordinates:
[TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), RC2I is the
celestial-to-intermediate matrix, ERA is the Earth rotation
angle and RPOM is the polar motion matrix.
4) The present function is faster, but slightly less accurate (about
1 mas), than the eraC2t00a function.
Called:
eraC2i00b celestial-to-intermediate matrix, IAU 2000B
eraEra00 Earth rotation angle, IAU 2000
eraPom00 polar motion matrix
eraC2tcio form CIO-based celestial-to-terrestrial matrix
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 October 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2t00b(tta, ttb, uta, utb, xp, yp)
return rc2t
[docs]def c2t06a(tta, ttb, uta, utb, xp, yp):
"""
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2006/2000A precession-nutation
model.
Parameters
----------
tta : double array
ttb : double array
uta : double array
utb : double array
xp : double array
yp : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2t06a``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 t 0 6 a
- - - - - - - - - -
Form the celestial to terrestrial matrix given the date, the UT1 and
the polar motion, using the IAU 2006/2000A precession-nutation
model.
Given:
tta,ttb double TT as a 2-part Julian Date (Note 1)
uta,utb double UT1 as a 2-part Julian Date (Note 1)
xp,yp double coordinates of the pole (radians, Note 2)
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 3)
Notes:
1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
apportioned in any convenient way between the arguments uta and
utb. For example, JD(UT1)=2450123.7 could be expressed in any of
these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. In the case of uta,utb, the
date & time method is best matched to the Earth rotation angle
algorithm used: maximum precision is delivered when the uta
argument is for 0hrs UT1 on the day in question and the utb
argument lies in the range 0 to 1, or vice versa.
2) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
3) The matrix rc2t transforms from celestial to terrestrial
coordinates:
[TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), RC2I is the
celestial-to-intermediate matrix, ERA is the Earth rotation
angle and RPOM is the polar motion matrix.
Called:
eraC2i06a celestial-to-intermediate matrix, IAU 2006/2000A
eraEra00 Earth rotation angle, IAU 2000
eraSp00 the TIO locator s', IERS 2000
eraPom00 polar motion matrix
eraC2tcio form CIO-based celestial-to-terrestrial matrix
Reference:
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
This revision: 2020 October 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2t06a(tta, ttb, uta, utb, xp, yp)
return rc2t
[docs]def c2tcio(rc2i, era, rpom):
"""
Assemble the celestial to terrestrial matrix from CIO-based
components (the celestial-to-intermediate matrix, the Earth Rotation
Angle and the polar motion matrix).
Parameters
----------
rc2i : double array
era : double array
rpom : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2tcio``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 t c i o
- - - - - - - - - -
Assemble the celestial to terrestrial matrix from CIO-based
components (the celestial-to-intermediate matrix, the Earth Rotation
Angle and the polar motion matrix).
Given:
rc2i double[3][3] celestial-to-intermediate matrix
era double Earth rotation angle (radians)
rpom double[3][3] polar-motion matrix
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix
Notes:
1) This function constructs the rotation matrix that transforms
vectors in the celestial system into vectors in the terrestrial
system. It does so starting from precomputed components, namely
the matrix which rotates from celestial coordinates to the
intermediate frame, the Earth rotation angle and the polar motion
matrix. One use of the present function is when generating a
series of celestial-to-terrestrial matrices where only the Earth
Rotation Angle changes, avoiding the considerable overhead of
recomputing the precession-nutation more often than necessary to
achieve given accuracy objectives.
2) The relationship between the arguments is as follows:
[TRS] = RPOM * R_3(ERA) * rc2i * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003).
Called:
eraCr copy r-matrix
eraRz rotate around Z-axis
eraRxr product of two r-matrices
Reference:
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
This revision: 2013 August 24
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2tcio(rc2i, era, rpom)
return rc2t
[docs]def c2teqx(rbpn, gst, rpom):
"""
Assemble the celestial to terrestrial matrix from equinox-based
components (the celestial-to-true matrix, the Greenwich Apparent
Sidereal Time and the polar motion matrix).
Parameters
----------
rbpn : double array
gst : double array
rpom : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2teqx``. The ERFA documentation is::
- - - - - - - - - -
e r a C 2 t e q x
- - - - - - - - - -
Assemble the celestial to terrestrial matrix from equinox-based
components (the celestial-to-true matrix, the Greenwich Apparent
Sidereal Time and the polar motion matrix).
Given:
rbpn double[3][3] celestial-to-true matrix
gst double Greenwich (apparent) Sidereal Time (radians)
rpom double[3][3] polar-motion matrix
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 2)
Notes:
1) This function constructs the rotation matrix that transforms
vectors in the celestial system into vectors in the terrestrial
system. It does so starting from precomputed components, namely
the matrix which rotates from celestial coordinates to the
true equator and equinox of date, the Greenwich Apparent Sidereal
Time and the polar motion matrix. One use of the present function
is when generating a series of celestial-to-terrestrial matrices
where only the Sidereal Time changes, avoiding the considerable
overhead of recomputing the precession-nutation more often than
necessary to achieve given accuracy objectives.
2) The relationship between the arguments is as follows:
[TRS] = rpom * R_3(gst) * rbpn * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003).
Called:
eraCr copy r-matrix
eraRz rotate around Z-axis
eraRxr product of two r-matrices
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 August 24
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2teqx(rbpn, gst, rpom)
return rc2t
[docs]def c2tpe(tta, ttb, uta, utb, dpsi, deps, xp, yp):
"""
Form the celestial to terrestrial matrix given the date, the UT1,
the nutation and the polar motion.
Parameters
----------
tta : double array
ttb : double array
uta : double array
utb : double array
dpsi : double array
deps : double array
xp : double array
yp : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2tpe``. The ERFA documentation is::
- - - - - - - - -
e r a C 2 t p e
- - - - - - - - -
Form the celestial to terrestrial matrix given the date, the UT1,
the nutation and the polar motion. IAU 2000.
Given:
tta,ttb double TT as a 2-part Julian Date (Note 1)
uta,utb double UT1 as a 2-part Julian Date (Note 1)
dpsi,deps double nutation (Note 2)
xp,yp double coordinates of the pole (radians, Note 3)
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 4)
Notes:
1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
apportioned in any convenient way between the arguments uta and
utb. For example, JD(UT1)=2450123.7 could be expressed in any of
these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. In the case of uta,utb, the
date & time method is best matched to the Earth rotation angle
algorithm used: maximum precision is delivered when the uta
argument is for 0hrs UT1 on the day in question and the utb
argument lies in the range 0 to 1, or vice versa.
2) The caller is responsible for providing the nutation components;
they are in longitude and obliquity, in radians and are with
respect to the equinox and ecliptic of date. For high-accuracy
applications, free core nutation should be included as well as
any other relevant corrections to the position of the CIP.
3) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
4) The matrix rc2t transforms from celestial to terrestrial
coordinates:
[TRS] = RPOM * R_3(GST) * RBPN * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), RBPN is the
bias-precession-nutation matrix, GST is the Greenwich (apparent)
Sidereal Time and RPOM is the polar motion matrix.
5) Although its name does not include "00", This function is in fact
specific to the IAU 2000 models.
Called:
eraPn00 bias/precession/nutation results, IAU 2000
eraGmst00 Greenwich mean sidereal time, IAU 2000
eraSp00 the TIO locator s', IERS 2000
eraEe00 equation of the equinoxes, IAU 2000
eraPom00 polar motion matrix
eraC2teqx form equinox-based celestial-to-terrestrial matrix
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 October 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2tpe(tta, ttb, uta, utb, dpsi, deps, xp, yp)
return rc2t
[docs]def c2txy(tta, ttb, uta, utb, x, y, xp, yp):
"""
Form the celestial to terrestrial matrix given the date, the UT1,
the CIP coordinates and the polar motion.
Parameters
----------
tta : double array
ttb : double array
uta : double array
utb : double array
x : double array
y : double array
xp : double array
yp : double array
Returns
-------
rc2t : double array
Notes
-----
Wraps ERFA function ``eraC2txy``. The ERFA documentation is::
- - - - - - - - -
e r a C 2 t x y
- - - - - - - - -
Form the celestial to terrestrial matrix given the date, the UT1,
the CIP coordinates and the polar motion. IAU 2000.
Given:
tta,ttb double TT as a 2-part Julian Date (Note 1)
uta,utb double UT1 as a 2-part Julian Date (Note 1)
x,y double Celestial Intermediate Pole (Note 2)
xp,yp double coordinates of the pole (radians, Note 3)
Returned:
rc2t double[3][3] celestial-to-terrestrial matrix (Note 4)
Notes:
1) The TT and UT1 dates tta+ttb and uta+utb are Julian Dates,
apportioned in any convenient way between the arguments uta and
utb. For example, JD(UT1)=2450123.7 could be expressed in any o
these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. In the case of uta,utb, the
date & time method is best matched to the Earth rotation angle
algorithm used: maximum precision is delivered when the uta
argument is for 0hrs UT1 on the day in question and the utb
argument lies in the range 0 to 1, or vice versa.
2) The Celestial Intermediate Pole coordinates are the x,y
components of the unit vector in the Geocentric Celestial
Reference System.
3) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
4) The matrix rc2t transforms from celestial to terrestrial
coordinates:
[TRS] = RPOM * R_3(ERA) * RC2I * [CRS]
= rc2t * [CRS]
where [CRS] is a vector in the Geocentric Celestial Reference
System and [TRS] is a vector in the International Terrestrial
Reference System (see IERS Conventions 2003), ERA is the Earth
Rotation Angle and RPOM is the polar motion matrix.
5) Although its name does not include "00", This function is in fact
specific to the IAU 2000 models.
Called:
eraC2ixy celestial-to-intermediate matrix, given X,Y
eraEra00 Earth rotation angle, IAU 2000
eraSp00 the TIO locator s', IERS 2000
eraPom00 polar motion matrix
eraC2tcio form CIO-based celestial-to-terrestrial matrix
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 October 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rc2t = ufunc.c2txy(tta, ttb, uta, utb, x, y, xp, yp)
return rc2t
[docs]def eo06a(date1, date2):
"""
Equation of the origins, IAU 2006 precession and IAU 2000A nutation.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEo06a``. The ERFA documentation is::
- - - - - - - - -
e r a E o 0 6 a
- - - - - - - - -
Equation of the origins, IAU 2006 precession and IAU 2000A nutation.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double the equation of the origins in radians
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The equation of the origins is the distance between the true
equinox and the celestial intermediate origin and, equivalently,
the difference between Earth rotation angle and Greenwich
apparent sidereal time (ERA-GST). It comprises the precession
(since J2000.0) in right ascension plus the equation of the
equinoxes (including the small correction terms).
Called:
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
eraEors equation of the origins, given NPB matrix and s
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 14
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.eo06a(date1, date2)
return c_retval
[docs]def eors(rnpb, s):
"""
Equation of the origins, given the classical NPB matrix and the
quantity s.
Parameters
----------
rnpb : double array
s : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEors``. The ERFA documentation is::
- - - - - - - -
e r a E o r s
- - - - - - - -
Equation of the origins, given the classical NPB matrix and the
quantity s.
Given:
rnpb double[3][3] classical nutation x precession x bias matrix
s double the quantity s (the CIO locator) in radians
Returned (function value):
double the equation of the origins in radians
Notes:
1) The equation of the origins is the distance between the true
equinox and the celestial intermediate origin and, equivalently,
the difference between Earth rotation angle and Greenwich
apparent sidereal time (ERA-GST). It comprises the precession
(since J2000.0) in right ascension plus the equation of the
equinoxes (including the small correction terms).
2) The algorithm is from Wallace & Capitaine (2006).
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Wallace, P. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 14
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.eors(rnpb, s)
return c_retval
[docs]def fw2m(gamb, phib, psi, eps):
"""
Form rotation matrix given the Fukushima-Williams angles.
Parameters
----------
gamb : double array
phib : double array
psi : double array
eps : double array
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraFw2m``. The ERFA documentation is::
- - - - - - - -
e r a F w 2 m
- - - - - - - -
Form rotation matrix given the Fukushima-Williams angles.
Given:
gamb double F-W angle gamma_bar (radians)
phib double F-W angle phi_bar (radians)
psi double F-W angle psi (radians)
eps double F-W angle epsilon (radians)
Returned:
r double[3][3] rotation matrix
Notes:
1) Naming the following points:
e = J2000.0 ecliptic pole,
p = GCRS pole,
E = ecliptic pole of date,
and P = CIP,
the four Fukushima-Williams angles are as follows:
gamb = gamma = epE
phib = phi = pE
psi = psi = pEP
eps = epsilon = EP
2) The matrix representing the combined effects of frame bias,
precession and nutation is:
NxPxB = R_1(-eps).R_3(-psi).R_1(phib).R_3(gamb)
3) The present function can construct three different matrices,
depending on which angles are supplied as the arguments gamb,
phib, psi and eps:
o To obtain the nutation x precession x frame bias matrix,
first generate the four precession angles known conventionally
as gamma_bar, phi_bar, psi_bar and epsilon_A, then generate
the nutation components Dpsi and Depsilon and add them to
psi_bar and epsilon_A, and finally call the present function
using those four angles as arguments.
o To obtain the precession x frame bias matrix, generate the
four precession angles and call the present function.
o To obtain the frame bias matrix, generate the four precession
angles for date J2000.0 and call the present function.
The nutation-only and precession-only matrices can if necessary
be obtained by combining these three appropriately.
Called:
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRx rotate around X-axis
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
This revision: 2020 November 17
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.fw2m(gamb, phib, psi, eps)
return r
[docs]def fw2xy(gamb, phib, psi, eps):
"""
CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
Parameters
----------
gamb : double array
phib : double array
psi : double array
eps : double array
Returns
-------
x : double array
y : double array
Notes
-----
Wraps ERFA function ``eraFw2xy``. The ERFA documentation is::
- - - - - - - - -
e r a F w 2 x y
- - - - - - - - -
CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
Given:
gamb double F-W angle gamma_bar (radians)
phib double F-W angle phi_bar (radians)
psi double F-W angle psi (radians)
eps double F-W angle epsilon (radians)
Returned:
x,y double CIP unit vector X,Y
Notes:
1) Naming the following points:
e = J2000.0 ecliptic pole,
p = GCRS pole
E = ecliptic pole of date,
and P = CIP,
the four Fukushima-Williams angles are as follows:
gamb = gamma = epE
phib = phi = pE
psi = psi = pEP
eps = epsilon = EP
2) The matrix representing the combined effects of frame bias,
precession and nutation is:
NxPxB = R_1(-epsA).R_3(-psi).R_1(phib).R_3(gamb)
The returned values x,y are elements [2][0] and [2][1] of the
matrix. Near J2000.0, they are essentially angles in radians.
Called:
eraFw2m F-W angles to r-matrix
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
Reference:
Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
This revision: 2013 September 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y = ufunc.fw2xy(gamb, phib, psi, eps)
return x, y
[docs]def ltp(epj):
"""
Long-term precession matrix.
Parameters
----------
epj : double array
Returns
-------
rp : double array
Notes
-----
Wraps ERFA function ``eraLtp``. The ERFA documentation is::
- - - - - - -
e r a L t p
- - - - - - -
Long-term precession matrix.
Given:
epj double Julian epoch (TT)
Returned:
rp double[3][3] precession matrix, J2000.0 to date
Notes:
1) The matrix is in the sense
P_date = rp x P_J2000,
where P_J2000 is a vector with respect to the J2000.0 mean
equator and equinox and P_date is the same vector with respect to
the equator and equinox of epoch epj.
2) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
Called:
eraLtpequ equator pole, long term
eraLtpecl ecliptic pole, long term
eraPxp vector product
eraPn normalize vector
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2015 December 6
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rp = ufunc.ltp(epj)
return rp
[docs]def ltpb(epj):
"""
Long-term precession matrix, including ICRS frame bias.
Parameters
----------
epj : double array
Returns
-------
rpb : double array
Notes
-----
Wraps ERFA function ``eraLtpb``. The ERFA documentation is::
- - - - - - - -
e r a L t p b
- - - - - - - -
Long-term precession matrix, including ICRS frame bias.
Given:
epj double Julian epoch (TT)
Returned:
rpb double[3][3] precession-bias matrix, J2000.0 to date
Notes:
1) The matrix is in the sense
P_date = rpb x P_ICRS,
where P_ICRS is a vector in the Geocentric Celestial Reference
System, and P_date is the vector with respect to the Celestial
Intermediate Reference System at that date but with nutation
neglected.
2) A first order frame bias formulation is used, of sub-
microarcsecond accuracy compared with a full 3D rotation.
3) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2015 December 6
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rpb = ufunc.ltpb(epj)
return rpb
[docs]def ltpecl(epj):
"""
Long-term precession of the ecliptic.
Parameters
----------
epj : double array
Returns
-------
vec : double array
Notes
-----
Wraps ERFA function ``eraLtpecl``. The ERFA documentation is::
- - - - - - - - - -
e r a L t p e c l
- - - - - - - - - -
Long-term precession of the ecliptic.
Given:
epj double Julian epoch (TT)
Returned:
vec double[3] ecliptic pole unit vector
Notes:
1) The returned vector is with respect to the J2000.0 mean equator
and equinox.
2) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
vec = ufunc.ltpecl(epj)
return vec
[docs]def ltpequ(epj):
"""
Long-term precession of the equator.
Parameters
----------
epj : double array
Returns
-------
veq : double array
Notes
-----
Wraps ERFA function ``eraLtpequ``. The ERFA documentation is::
- - - - - - - - - -
e r a L t p e q u
- - - - - - - - - -
Long-term precession of the equator.
Given:
epj double Julian epoch (TT)
Returned:
veq double[3] equator pole unit vector
Notes:
1) The returned vector is with respect to the J2000.0 mean equator
and equinox.
2) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
veq = ufunc.ltpequ(epj)
return veq
[docs]def num00a(date1, date2):
"""
Form the matrix of nutation for a given date, IAU 2000A model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatn : double array
Notes
-----
Wraps ERFA function ``eraNum00a``. The ERFA documentation is::
- - - - - - - - - -
e r a N u m 0 0 a
- - - - - - - - - -
Form the matrix of nutation for a given date, IAU 2000A model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rmatn double[3][3] nutation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(true) = rmatn * V(mean), where
the p-vector V(true) is with respect to the true equatorial triad
of date and the p-vector V(mean) is with respect to the mean
equatorial triad of date.
3) A faster, but slightly less accurate, result (about 1 mas) can be
obtained by using instead the eraNum00b function.
Called:
eraPn00a bias/precession/nutation, IAU 2000A
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.222-3 (p114).
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatn = ufunc.num00a(date1, date2)
return rmatn
[docs]def num00b(date1, date2):
"""
Form the matrix of nutation for a given date, IAU 2000B model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatn : double array
Notes
-----
Wraps ERFA function ``eraNum00b``. The ERFA documentation is::
- - - - - - - - - -
e r a N u m 0 0 b
- - - - - - - - - -
Form the matrix of nutation for a given date, IAU 2000B model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rmatn double[3][3] nutation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(true) = rmatn * V(mean), where
the p-vector V(true) is with respect to the true equatorial triad
of date and the p-vector V(mean) is with respect to the mean
equatorial triad of date.
3) The present function is faster, but slightly less accurate (about
1 mas), than the eraNum00a function.
Called:
eraPn00b bias/precession/nutation, IAU 2000B
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.222-3 (p114).
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatn = ufunc.num00b(date1, date2)
return rmatn
[docs]def num06a(date1, date2):
"""
Form the matrix of nutation for a given date, IAU 2006/2000A model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatn : double array
Notes
-----
Wraps ERFA function ``eraNum06a``. The ERFA documentation is::
- - - - - - - - - -
e r a N u m 0 6 a
- - - - - - - - - -
Form the matrix of nutation for a given date, IAU 2006/2000A model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rmatn double[3][3] nutation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(true) = rmatn * V(mean), where
the p-vector V(true) is with respect to the true equatorial triad
of date and the p-vector V(mean) is with respect to the mean
equatorial triad of date.
Called:
eraObl06 mean obliquity, IAU 2006
eraNut06a nutation, IAU 2006/2000A
eraNumat form nutation matrix
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.222-3 (p114).
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatn = ufunc.num06a(date1, date2)
return rmatn
[docs]def numat(epsa, dpsi, deps):
"""
Form the matrix of nutation.
Parameters
----------
epsa : double array
dpsi : double array
deps : double array
Returns
-------
rmatn : double array
Notes
-----
Wraps ERFA function ``eraNumat``. The ERFA documentation is::
- - - - - - - - -
e r a N u m a t
- - - - - - - - -
Form the matrix of nutation.
Given:
epsa double mean obliquity of date (Note 1)
dpsi,deps double nutation (Note 2)
Returned:
rmatn double[3][3] nutation matrix (Note 3)
Notes:
1) The supplied mean obliquity epsa, must be consistent with the
precession-nutation models from which dpsi and deps were obtained.
2) The caller is responsible for providing the nutation components;
they are in longitude and obliquity, in radians and are with
respect to the equinox and ecliptic of date.
3) The matrix operates in the sense V(true) = rmatn * V(mean),
where the p-vector V(true) is with respect to the true
equatorial triad of date and the p-vector V(mean) is with
respect to the mean equatorial triad of date.
Called:
eraIr initialize r-matrix to identity
eraRx rotate around X-axis
eraRz rotate around Z-axis
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.222-3 (p114).
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatn = ufunc.numat(epsa, dpsi, deps)
return rmatn
[docs]def nut00a(date1, date2):
"""
Nutation, IAU 2000A model (MHB2000 luni-solar and planetary nutation
with free core nutation omitted).
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
Notes
-----
Wraps ERFA function ``eraNut00a``. The ERFA documentation is::
- - - - - - - - - -
e r a N u t 0 0 a
- - - - - - - - - -
Nutation, IAU 2000A model (MHB2000 luni-solar and planetary nutation
with free core nutation omitted).
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation, luni-solar + planetary (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components in longitude and obliquity are in radians
and with respect to the equinox and ecliptic of date. The
obliquity at J2000.0 is assumed to be the Lieske et al. (1977)
value of 84381.448 arcsec.
Both the luni-solar and planetary nutations are included. The
latter are due to direct planetary nutations and the
perturbations of the lunar and terrestrial orbits.
3) The function computes the MHB2000 nutation series with the
associated corrections for planetary nutations. It is an
implementation of the nutation part of the IAU 2000A precession-
nutation model, formally adopted by the IAU General Assembly in
2000, namely MHB2000 (Mathews et al. 2002), but with the free
core nutation (FCN - see Note 4) omitted.
4) The full MHB2000 model also contains contributions to the
nutations in longitude and obliquity due to the free-excitation
of the free-core-nutation during the period 1979-2000. These FCN
terms, which are time-dependent and unpredictable, are NOT
included in the present function and, if required, must be
independently computed. With the FCN corrections included, the
present function delivers a pole which is at current epochs
accurate to a few hundred microarcseconds. The omission of FCN
introduces further errors of about that size.
5) The present function provides classical nutation. The MHB2000
algorithm, from which it is adapted, deals also with (i) the
offsets between the GCRS and mean poles and (ii) the adjustments
in longitude and obliquity due to the changed precession rates.
These additional functions, namely frame bias and precession
adjustments, are supported by the ERFA functions eraBi00 and
eraPr00.
6) The MHB2000 algorithm also provides "total" nutations, comprising
the arithmetic sum of the frame bias, precession adjustments,
luni-solar nutation and planetary nutation. These total
nutations can be used in combination with an existing IAU 1976
precession implementation, such as eraPmat76, to deliver GCRS-
to-true predictions of sub-mas accuracy at current dates.
However, there are three shortcomings in the MHB2000 model that
must be taken into account if more accurate or definitive results
are required (see Wallace 2002):
(i) The MHB2000 total nutations are simply arithmetic sums,
yet in reality the various components are successive Euler
rotations. This slight lack of rigor leads to cross terms
that exceed 1 mas after a century. The rigorous procedure
is to form the GCRS-to-true rotation matrix by applying the
bias, precession and nutation in that order.
(ii) Although the precession adjustments are stated to be with
respect to Lieske et al. (1977), the MHB2000 model does
not specify which set of Euler angles are to be used and
how the adjustments are to be applied. The most literal
and straightforward procedure is to adopt the 4-rotation
epsilon_0, psi_A, omega_A, xi_A option, and to add DPSIPR
to psi_A and DEPSPR to both omega_A and eps_A.
(iii) The MHB2000 model predates the determination by Chapront
et al. (2002) of a 14.6 mas displacement between the
J2000.0 mean equinox and the origin of the ICRS frame. It
should, however, be noted that neglecting this displacement
when calculating star coordinates does not lead to a
14.6 mas change in right ascension, only a small second-
order distortion in the pattern of the precession-nutation
effect.
For these reasons, the ERFA functions do not generate the "total
nutations" directly, though they can of course easily be
generated by calling eraBi00, eraPr00 and the present function
and adding the results.
7) The MHB2000 model contains 41 instances where the same frequency
appears multiple times, of which 38 are duplicates and three are
triplicates. To keep the present code close to the original MHB
algorithm, this small inefficiency has not been corrected.
Called:
eraFal03 mean anomaly of the Moon
eraFaf03 mean argument of the latitude of the Moon
eraFaom03 mean longitude of the Moon's ascending node
eraFame03 mean longitude of Mercury
eraFave03 mean longitude of Venus
eraFae03 mean longitude of Earth
eraFama03 mean longitude of Mars
eraFaju03 mean longitude of Jupiter
eraFasa03 mean longitude of Saturn
eraFaur03 mean longitude of Uranus
eraFapa03 general accumulated precession in longitude
References:
Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
Astron.Astrophys. 387, 700
Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
Astron.Astrophys. 58, 1-16
Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
107, B4. The MHB_2000 code itself was obtained on 9th September
2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
Wallace, P.T., "Software for Implementing the IAU 2000
Resolutions", in IERS Workshop 5.1 (2002)
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps = ufunc.nut00a(date1, date2)
return dpsi, deps
[docs]def nut00b(date1, date2):
"""
Nutation, IAU 2000B model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
Notes
-----
Wraps ERFA function ``eraNut00b``. The ERFA documentation is::
- - - - - - - - - -
e r a N u t 0 0 b
- - - - - - - - - -
Nutation, IAU 2000B model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation, luni-solar + planetary (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components in longitude and obliquity are in radians
and with respect to the equinox and ecliptic of date. The
obliquity at J2000.0 is assumed to be the Lieske et al. (1977)
value of 84381.448 arcsec. (The errors that result from using
this function with the IAU 2006 value of 84381.406 arcsec can be
neglected.)
The nutation model consists only of luni-solar terms, but
includes also a fixed offset which compensates for certain long-
period planetary terms (Note 7).
3) This function is an implementation of the IAU 2000B abridged
nutation model formally adopted by the IAU General Assembly in
2000. The function computes the MHB_2000_SHORT luni-solar
nutation series (Luzum 2001), but without the associated
corrections for the precession rate adjustments and the offset
between the GCRS and J2000.0 mean poles.
4) The full IAU 2000A (MHB2000) nutation model contains nearly 1400
terms. The IAU 2000B model (McCarthy & Luzum 2003) contains only
77 terms, plus additional simplifications, yet still delivers
results of 1 mas accuracy at present epochs. This combination of
accuracy and size makes the IAU 2000B abridged nutation model
suitable for most practical applications.
The function delivers a pole accurate to 1 mas from 1900 to 2100
(usually better than 1 mas, very occasionally just outside
1 mas). The full IAU 2000A model, which is implemented in the
function eraNut00a (q.v.), delivers considerably greater accuracy
at current dates; however, to realize this improved accuracy,
corrections for the essentially unpredictable free-core-nutation
(FCN) must also be included.
5) The present function provides classical nutation. The
MHB_2000_SHORT algorithm, from which it is adapted, deals also
with (i) the offsets between the GCRS and mean poles and (ii) the
adjustments in longitude and obliquity due to the changed
precession rates. These additional functions, namely frame bias
and precession adjustments, are supported by the ERFA functions
eraBi00 and eraPr00.
6) The MHB_2000_SHORT algorithm also provides "total" nutations,
comprising the arithmetic sum of the frame bias, precession
adjustments, and nutation (luni-solar + planetary). These total
nutations can be used in combination with an existing IAU 1976
precession implementation, such as eraPmat76, to deliver GCRS-
to-true predictions of mas accuracy at current epochs. However,
for symmetry with the eraNut00a function (q.v. for the reasons),
the ERFA functions do not generate the "total nutations"
directly. Should they be required, they could of course easily
be generated by calling eraBi00, eraPr00 and the present function
and adding the results.
7) The IAU 2000B model includes "planetary bias" terms that are
fixed in size but compensate for long-period nutations. The
amplitudes quoted in McCarthy & Luzum (2003), namely
Dpsi = -1.5835 mas and Depsilon = +1.6339 mas, are optimized for
the "total nutations" method described in Note 6. The Luzum
(2001) values used in this ERFA implementation, namely -0.135 mas
and +0.388 mas, are optimized for the "rigorous" method, where
frame bias, precession and nutation are applied separately and in
that order. During the interval 1995-2050, the ERFA
implementation delivers a maximum error of 1.001 mas (not
including FCN).
References:
Lieske, J.H., Lederle, T., Fricke, W., Morando, B., "Expressions
for the precession quantities based upon the IAU /1976/ system of
astronomical constants", Astron.Astrophys. 58, 1-2, 1-16. (1977)
Luzum, B., private communication, 2001 (Fortran code
MHB_2000_SHORT)
McCarthy, D.D. & Luzum, B.J., "An abridged model of the
precession-nutation of the celestial pole", Cel.Mech.Dyn.Astron.
85, 37-49 (2003)
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J., Astron.Astrophys. 282, 663-683 (1994)
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps = ufunc.nut00b(date1, date2)
return dpsi, deps
[docs]def nut06a(date1, date2):
"""
IAU 2000A nutation with adjustments to match the IAU 2006
precession.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
Notes
-----
Wraps ERFA function ``eraNut06a``. The ERFA documentation is::
- - - - - - - - - -
e r a N u t 0 6 a
- - - - - - - - - -
IAU 2000A nutation with adjustments to match the IAU 2006
precession.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation, luni-solar + planetary (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components in longitude and obliquity are in radians
and with respect to the mean equinox and ecliptic of date,
IAU 2006 precession model (Hilton et al. 2006, Capitaine et al.
2005).
3) The function first computes the IAU 2000A nutation, then applies
adjustments for (i) the consequences of the change in obliquity
from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the
secular variation in the Earth's dynamical form factor J2.
4) The present function provides classical nutation, complementing
the IAU 2000 frame bias and IAU 2006 precession. It delivers a
pole which is at current epochs accurate to a few tens of
microarcseconds, apart from the free core nutation.
Called:
eraNut00a nutation, IAU 2000A
References:
Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
Astron.Astrophys. 387, 700
Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
Astron.Astrophys. 58, 1-16
Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
107, B4. The MHB_2000 code itself was obtained on 9th September
2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
Astron.Astrophys.Supp.Ser. 135, 111
Wallace, P.T., "Software for Implementing the IAU 2000
Resolutions", in IERS Workshop 5.1 (2002)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps = ufunc.nut06a(date1, date2)
return dpsi, deps
[docs]def nut80(date1, date2):
"""
Nutation, IAU 1980 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
Notes
-----
Wraps ERFA function ``eraNut80``. The ERFA documentation is::
- - - - - - - - -
e r a N u t 8 0
- - - - - - - - -
Nutation, IAU 1980 model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi double nutation in longitude (radians)
deps double nutation in obliquity (radians)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components are with respect to the ecliptic of
date.
Called:
eraAnpm normalize angle into range +/- pi
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.222 (p111).
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps = ufunc.nut80(date1, date2)
return dpsi, deps
[docs]def nutm80(date1, date2):
"""
Form the matrix of nutation for a given date, IAU 1980 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatn : double array
Notes
-----
Wraps ERFA function ``eraNutm80``. The ERFA documentation is::
- - - - - - - - - -
e r a N u t m 8 0
- - - - - - - - - -
Form the matrix of nutation for a given date, IAU 1980 model.
Given:
date1,date2 double TDB date (Note 1)
Returned:
rmatn double[3][3] nutation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(true) = rmatn * V(mean),
where the p-vector V(true) is with respect to the true
equatorial triad of date and the p-vector V(mean) is with
respect to the mean equatorial triad of date.
Called:
eraNut80 nutation, IAU 1980
eraObl80 mean obliquity, IAU 1980
eraNumat form nutation matrix
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatn = ufunc.nutm80(date1, date2)
return rmatn
[docs]def obl06(date1, date2):
"""
Mean obliquity of the ecliptic, IAU 2006 precession model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraObl06``. The ERFA documentation is::
- - - - - - - - -
e r a O b l 0 6
- - - - - - - - -
Mean obliquity of the ecliptic, IAU 2006 precession model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double obliquity of the ecliptic (radians, Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result is the angle between the ecliptic and mean equator of
date date1+date2.
Reference:
Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.obl06(date1, date2)
return c_retval
[docs]def obl80(date1, date2):
"""
Mean obliquity of the ecliptic, IAU 1980 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraObl80``. The ERFA documentation is::
- - - - - - - - -
e r a O b l 8 0
- - - - - - - - -
Mean obliquity of the ecliptic, IAU 1980 model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double obliquity of the ecliptic (radians, Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result is the angle between the ecliptic and mean equator of
date date1+date2.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Expression 3.222-1 (p114).
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.obl80(date1, date2)
return c_retval
[docs]def p06e(date1, date2):
"""
Precession angles, IAU 2006, equinox based.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
eps0 : double array
psia : double array
oma : double array
bpa : double array
bqa : double array
pia : double array
bpia : double array
epsa : double array
chia : double array
za : double array
zetaa : double array
thetaa : double array
pa : double array
gam : double array
phi : double array
psi : double array
Notes
-----
Wraps ERFA function ``eraP06e``. The ERFA documentation is::
- - - - - - - -
e r a P 0 6 e
- - - - - - - -
Precession angles, IAU 2006, equinox based.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (see Note 2):
eps0 double epsilon_0
psia double psi_A
oma double omega_A
bpa double P_A
bqa double Q_A
pia double pi_A
bpia double Pi_A
epsa double obliquity epsilon_A
chia double chi_A
za double z_A
zetaa double zeta_A
thetaa double theta_A
pa double p_A
gam double F-W angle gamma_J2000
phi double F-W angle phi_J2000
psi double F-W angle psi_J2000
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) This function returns the set of equinox based angles for the
Capitaine et al. "P03" precession theory, adopted by the IAU in
2006. The angles are set out in Table 1 of Hilton et al. (2006):
eps0 epsilon_0 obliquity at J2000.0
psia psi_A luni-solar precession
oma omega_A inclination of equator wrt J2000.0 ecliptic
bpa P_A ecliptic pole x, J2000.0 ecliptic triad
bqa Q_A ecliptic pole -y, J2000.0 ecliptic triad
pia pi_A angle between moving and J2000.0 ecliptics
bpia Pi_A longitude of ascending node of the ecliptic
epsa epsilon_A obliquity of the ecliptic
chia chi_A planetary precession
za z_A equatorial precession: -3rd 323 Euler angle
zetaa zeta_A equatorial precession: -1st 323 Euler angle
thetaa theta_A equatorial precession: 2nd 323 Euler angle
pa p_A general precession (n.b. see below)
gam gamma_J2000 J2000.0 RA difference of ecliptic poles
phi phi_J2000 J2000.0 codeclination of ecliptic pole
psi psi_J2000 longitude difference of equator poles, J2000.0
The returned values are all radians.
Note that the t^5 coefficient in the series for p_A from
Capitaine et al. (2003) is incorrectly signed in Hilton et al.
(2006).
3) Hilton et al. (2006) Table 1 also contains angles that depend on
models distinct from the P03 precession theory itself, namely the
IAU 2000A frame bias and nutation. The quoted polynomials are
used in other ERFA functions:
. eraXy06 contains the polynomial parts of the X and Y series.
. eraS06 contains the polynomial part of the s+XY/2 series.
. eraPfw06 implements the series for the Fukushima-Williams
angles that are with respect to the GCRS pole (i.e. the variants
that include frame bias).
4) The IAU resolution stipulated that the choice of parameterization
was left to the user, and so an IAU compliant precession
implementation can be constructed using various combinations of
the angles returned by the present function.
5) The parameterization used by ERFA is the version of the Fukushima-
Williams angles that refers directly to the GCRS pole. These
angles may be calculated by calling the function eraPfw06. ERFA
also supports the direct computation of the CIP GCRS X,Y by
series, available by calling eraXy06.
6) The agreement between the different parameterizations is at the
1 microarcsecond level in the present era.
7) When constructing a precession formulation that refers to the GCRS
pole rather than the dynamical pole, it may (depending on the
choice of angles) be necessary to introduce the frame bias
explicitly.
8) It is permissible to re-use the same variable in the returned
arguments. The quantities are stored in the stated order.
References:
Capitaine, N., Wallace, P.T. & Chapront, J., 2003,
Astron.Astrophys., 412, 567
Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
Called:
eraObl06 mean obliquity, IAU 2006
This revision: 2020 June 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
(eps0, psia, oma, bpa, bqa, pia, bpia, epsa, chia, za, zetaa, thetaa, pa,
gam, phi, psi) = ufunc.p06e(date1, date2)
return eps0, psia, oma, bpa, bqa, pia, bpia, epsa, chia, za, zetaa, thetaa, pa, gam, phi, psi
[docs]def pb06(date1, date2):
"""
This function forms three Euler angles which implement general
precession from epoch J2000.0, using the IAU 2006 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
bzeta : double array
bz : double array
btheta : double array
Notes
-----
Wraps ERFA function ``eraPb06``. The ERFA documentation is::
- - - - - - - -
e r a P b 0 6
- - - - - - - -
This function forms three Euler angles which implement general
precession from epoch J2000.0, using the IAU 2006 model. Frame
bias (the offset between ICRS and mean J2000.0) is included.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
bzeta double 1st rotation: radians cw around z
bz double 3rd rotation: radians cw around z
btheta double 2nd rotation: radians ccw around y
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The traditional accumulated precession angles zeta_A, z_A,
theta_A cannot be obtained in the usual way, namely through
polynomial expressions, because of the frame bias. The latter
means that two of the angles undergo rapid changes near this
date. They are instead the results of decomposing the
precession-bias matrix obtained by using the Fukushima-Williams
method, which does not suffer from the problem. The
decomposition returns values which can be used in the
conventional formulation and which include frame bias.
3) The three angles are returned in the conventional order, which
is not the same as the order of the corresponding Euler
rotations. The precession-bias matrix is
R_3(-z) x R_2(+theta) x R_3(-zeta).
4) Should zeta_A, z_A, theta_A angles be required that do not
contain frame bias, they are available by calling the ERFA
function eraP06e.
Called:
eraPmat06 PB matrix, IAU 2006
eraRz rotate around Z-axis
This revision: 2020 May 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
bzeta, bz, btheta = ufunc.pb06(date1, date2)
return bzeta, bz, btheta
[docs]def pfw06(date1, date2):
"""
Precession angles, IAU 2006 (Fukushima-Williams 4-angle formulation).
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
gamb : double array
phib : double array
psib : double array
epsa : double array
Notes
-----
Wraps ERFA function ``eraPfw06``. The ERFA documentation is::
- - - - - - - - -
e r a P f w 0 6
- - - - - - - - -
Precession angles, IAU 2006 (Fukushima-Williams 4-angle formulation).
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
gamb double F-W angle gamma_bar (radians)
phib double F-W angle phi_bar (radians)
psib double F-W angle psi_bar (radians)
epsa double F-W angle epsilon_A (radians)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) Naming the following points:
e = J2000.0 ecliptic pole,
p = GCRS pole,
E = mean ecliptic pole of date,
and P = mean pole of date,
the four Fukushima-Williams angles are as follows:
gamb = gamma_bar = epE
phib = phi_bar = pE
psib = psi_bar = pEP
epsa = epsilon_A = EP
3) The matrix representing the combined effects of frame bias and
precession is:
PxB = R_1(-epsa).R_3(-psib).R_1(phib).R_3(gamb)
4) The matrix representing the combined effects of frame bias,
precession and nutation is simply:
NxPxB = R_1(-epsa-dE).R_3(-psib-dP).R_1(phib).R_3(gamb)
where dP and dE are the nutation components with respect to the
ecliptic of date.
Reference:
Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
Called:
eraObl06 mean obliquity, IAU 2006
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
gamb, phib, psib, epsa = ufunc.pfw06(date1, date2)
return gamb, phib, psib, epsa
[docs]def pmat00(date1, date2):
"""
Precession matrix (including frame bias) from GCRS to a specified
date, IAU 2000 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rbp : double array
Notes
-----
Wraps ERFA function ``eraPmat00``. The ERFA documentation is::
- - - - - - - - - -
e r a P m a t 0 0
- - - - - - - - - -
Precession matrix (including frame bias) from GCRS to a specified
date, IAU 2000 model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rbp double[3][3] bias-precession matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rbp * V(GCRS), where
the p-vector V(GCRS) is with respect to the Geocentric Celestial
Reference System (IAU, 2000) and the p-vector V(date) is with
respect to the mean equatorial triad of the given date.
Called:
eraBp00 frame bias and precession matrices, IAU 2000
Reference:
IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc.
24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6.
(2000)
This revision: 2020 November 24
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rbp = ufunc.pmat00(date1, date2)
return rbp
[docs]def pmat06(date1, date2):
"""
Precession matrix (including frame bias) from GCRS to a specified
date, IAU 2006 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rbp : double array
Notes
-----
Wraps ERFA function ``eraPmat06``. The ERFA documentation is::
- - - - - - - - - -
e r a P m a t 0 6
- - - - - - - - - -
Precession matrix (including frame bias) from GCRS to a specified
date, IAU 2006 model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rbp double[3][3] bias-precession matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rbp * V(GCRS), where
the p-vector V(GCRS) is with respect to the Geocentric Celestial
Reference System (IAU, 2000) and the p-vector V(date) is with
respect to the mean equatorial triad of the given date.
Called:
eraPfw06 bias-precession F-W angles, IAU 2006
eraFw2m F-W angles to r-matrix
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc.
24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6.
(2000)
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 24
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rbp = ufunc.pmat06(date1, date2)
return rbp
[docs]def pmat76(date1, date2):
"""
Precession matrix from J2000.0 to a specified date, IAU 1976 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatp : double array
Notes
-----
Wraps ERFA function ``eraPmat76``. The ERFA documentation is::
- - - - - - - - - -
e r a P m a t 7 6
- - - - - - - - - -
Precession matrix from J2000.0 to a specified date, IAU 1976 model.
Given:
date1,date2 double ending date, TT (Note 1)
Returned:
rmatp double[3][3] precession matrix, J2000.0 -> date1+date2
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = RMATP * V(J2000),
where the p-vector V(J2000) is with respect to the mean
equatorial triad of epoch J2000.0 and the p-vector V(date)
is with respect to the mean equatorial triad of the given
date.
3) Though the matrix method itself is rigorous, the precession
angles are expressed through canonical polynomials which are
valid only for a limited time span. In addition, the IAU 1976
precession rate is known to be imperfect. The absolute accuracy
of the present formulation is better than 0.1 arcsec from
1960AD to 2040AD, better than 1 arcsec from 1640AD to 2360AD,
and remains below 3 arcsec for the whole of the period
500BC to 3000AD. The errors exceed 10 arcsec outside the
range 1200BC to 3900AD, exceed 100 arcsec outside 4200BC to
5600AD and exceed 1000 arcsec outside 6800BC to 8200AD.
Called:
eraPrec76 accumulated precession angles, IAU 1976
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRy rotate around Y-axis
eraCr copy r-matrix
References:
Lieske, J.H., 1979, Astron.Astrophys. 73, 282.
equations (6) & (7), p283.
Kaplan,G.H., 1981. USNO circular no. 163, pA2.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatp = ufunc.pmat76(date1, date2)
return rmatp
[docs]def pn00(date1, date2, dpsi, deps):
"""
Precession-nutation, IAU 2000 model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Parameters
----------
date1 : double array
date2 : double array
dpsi : double array
deps : double array
Returns
-------
epsa : double array
rb : double array
rp : double array
rbp : double array
rn : double array
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPn00``. The ERFA documentation is::
- - - - - - - -
e r a P n 0 0
- - - - - - - -
Precession-nutation, IAU 2000 model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
dpsi,deps double nutation (Note 2)
Returned:
epsa double mean obliquity (Note 3)
rb double[3][3] frame bias matrix (Note 4)
rp double[3][3] precession matrix (Note 5)
rbp double[3][3] bias-precession matrix (Note 6)
rn double[3][3] nutation matrix (Note 7)
rbpn double[3][3] GCRS-to-true matrix (Note 8)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The caller is responsible for providing the nutation components;
they are in longitude and obliquity, in radians and are with
respect to the equinox and ecliptic of date. For high-accuracy
applications, free core nutation should be included as well as
any other relevant corrections to the position of the CIP.
3) The returned mean obliquity is consistent with the IAU 2000
precession-nutation models.
4) The matrix rb transforms vectors from GCRS to J2000.0 mean
equator and equinox by applying frame bias.
5) The matrix rp transforms vectors from J2000.0 mean equator and
equinox to mean equator and equinox of date by applying
precession.
6) The matrix rbp transforms vectors from GCRS to mean equator and
equinox of date by applying frame bias then precession. It is
the product rp x rb.
7) The matrix rn transforms vectors from mean equator and equinox of
date to true equator and equinox of date by applying the nutation
(luni-solar + planetary).
8) The matrix rbpn transforms vectors from GCRS to true equator and
equinox of date. It is the product rn x rbp, applying frame
bias, precession and nutation in that order.
9) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the order given.
Called:
eraPr00 IAU 2000 precession adjustments
eraObl80 mean obliquity, IAU 1980
eraBp00 frame bias and precession matrices, IAU 2000
eraCr copy r-matrix
eraNumat form nutation matrix
eraRxr product of two r-matrices
Reference:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
epsa, rb, rp, rbp, rn, rbpn = ufunc.pn00(date1, date2, dpsi, deps)
return epsa, rb, rp, rbp, rn, rbpn
[docs]def pn00a(date1, date2):
"""
Precession-nutation, IAU 2000A model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
epsa : double array
rb : double array
rp : double array
rbp : double array
rn : double array
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPn00a``. The ERFA documentation is::
- - - - - - - - -
e r a P n 0 0 a
- - - - - - - - -
Precession-nutation, IAU 2000A model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation (Note 2)
epsa double mean obliquity (Note 3)
rb double[3][3] frame bias matrix (Note 4)
rp double[3][3] precession matrix (Note 5)
rbp double[3][3] bias-precession matrix (Note 6)
rn double[3][3] nutation matrix (Note 7)
rbpn double[3][3] GCRS-to-true matrix (Notes 8,9)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components (luni-solar + planetary, IAU 2000A) in
longitude and obliquity are in radians and with respect to the
equinox and ecliptic of date. Free core nutation is omitted;
for the utmost accuracy, use the eraPn00 function, where the
nutation components are caller-specified. For faster but
slightly less accurate results, use the eraPn00b function.
3) The mean obliquity is consistent with the IAU 2000 precession.
4) The matrix rb transforms vectors from GCRS to J2000.0 mean
equator and equinox by applying frame bias.
5) The matrix rp transforms vectors from J2000.0 mean equator and
equinox to mean equator and equinox of date by applying
precession.
6) The matrix rbp transforms vectors from GCRS to mean equator and
equinox of date by applying frame bias then precession. It is
the product rp x rb.
7) The matrix rn transforms vectors from mean equator and equinox
of date to true equator and equinox of date by applying the
nutation (luni-solar + planetary).
8) The matrix rbpn transforms vectors from GCRS to true equator and
equinox of date. It is the product rn x rbp, applying frame
bias, precession and nutation in that order.
9) The X,Y,Z coordinates of the IAU 2000A Celestial Intermediate
Pole are elements (3,1-3) of the GCRS-to-true matrix,
i.e. rbpn[2][0-2].
10) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the stated order.
Called:
eraNut00a nutation, IAU 2000A
eraPn00 bias/precession/nutation results, IAU 2000
Reference:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
This revision: 2020 November 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps, epsa, rb, rp, rbp, rn, rbpn = ufunc.pn00a(date1, date2)
return dpsi, deps, epsa, rb, rp, rbp, rn, rbpn
[docs]def pn00b(date1, date2):
"""
Precession-nutation, IAU 2000B model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
epsa : double array
rb : double array
rp : double array
rbp : double array
rn : double array
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPn00b``. The ERFA documentation is::
- - - - - - - - -
e r a P n 0 0 b
- - - - - - - - -
Precession-nutation, IAU 2000B model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based
use indirectly.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation (Note 2)
epsa double mean obliquity (Note 3)
rb double[3][3] frame bias matrix (Note 4)
rp double[3][3] precession matrix (Note 5)
rbp double[3][3] bias-precession matrix (Note 6)
rn double[3][3] nutation matrix (Note 7)
rbpn double[3][3] GCRS-to-true matrix (Notes 8,9)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components (luni-solar + planetary, IAU 2000B) in
longitude and obliquity are in radians and with respect to the
equinox and ecliptic of date. For more accurate results, but
at the cost of increased computation, use the eraPn00a function.
For the utmost accuracy, use the eraPn00 function, where the
nutation components are caller-specified.
3) The mean obliquity is consistent with the IAU 2000 precession.
4) The matrix rb transforms vectors from GCRS to J2000.0 mean
equator and equinox by applying frame bias.
5) The matrix rp transforms vectors from J2000.0 mean equator and
equinox to mean equator and equinox of date by applying
precession.
6) The matrix rbp transforms vectors from GCRS to mean equator and
equinox of date by applying frame bias then precession. It is
the product rp x rb.
7) The matrix rn transforms vectors from mean equator and equinox
of date to true equator and equinox of date by applying the
nutation (luni-solar + planetary).
8) The matrix rbpn transforms vectors from GCRS to true equator and
equinox of date. It is the product rn x rbp, applying frame
bias, precession and nutation in that order.
9) The X,Y,Z coordinates of the IAU 2000B Celestial Intermediate
Pole are elements (3,1-3) of the GCRS-to-true matrix,
i.e. rbpn[2][0-2].
10) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the stated order.
Called:
eraNut00b nutation, IAU 2000B
eraPn00 bias/precession/nutation results, IAU 2000
Reference:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003).
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
This revision: 2020 November 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps, epsa, rb, rp, rbp, rn, rbpn = ufunc.pn00b(date1, date2)
return dpsi, deps, epsa, rb, rp, rbp, rn, rbpn
[docs]def pn06(date1, date2, dpsi, deps):
"""
Precession-nutation, IAU 2006 model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based use
indirectly.
Parameters
----------
date1 : double array
date2 : double array
dpsi : double array
deps : double array
Returns
-------
epsa : double array
rb : double array
rp : double array
rbp : double array
rn : double array
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPn06``. The ERFA documentation is::
- - - - - - - -
e r a P n 0 6
- - - - - - - -
Precession-nutation, IAU 2006 model: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based use
indirectly.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
dpsi,deps double nutation (Note 2)
Returned:
epsa double mean obliquity (Note 3)
rb double[3][3] frame bias matrix (Note 4)
rp double[3][3] precession matrix (Note 5)
rbp double[3][3] bias-precession matrix (Note 6)
rn double[3][3] nutation matrix (Note 7)
rbpn double[3][3] GCRS-to-true matrix (Notes 8,9)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The caller is responsible for providing the nutation components;
they are in longitude and obliquity, in radians and are with
respect to the equinox and ecliptic of date. For high-accuracy
applications, free core nutation should be included as well as
any other relevant corrections to the position of the CIP.
3) The returned mean obliquity is consistent with the IAU 2006
precession.
4) The matrix rb transforms vectors from GCRS to J2000.0 mean
equator and equinox by applying frame bias.
5) The matrix rp transforms vectors from J2000.0 mean equator and
equinox to mean equator and equinox of date by applying
precession.
6) The matrix rbp transforms vectors from GCRS to mean equator and
equinox of date by applying frame bias then precession. It is
the product rp x rb.
7) The matrix rn transforms vectors from mean equator and equinox
of date to true equator and equinox of date by applying the
nutation (luni-solar + planetary).
8) The matrix rbpn transforms vectors from GCRS to true equator and
equinox of date. It is the product rn x rbp, applying frame
bias, precession and nutation in that order.
9) The X,Y,Z coordinates of the Celestial Intermediate Pole are
elements (3,1-3) of the GCRS-to-true matrix, i.e. rbpn[2][0-2].
10) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the stated order.
Called:
eraPfw06 bias-precession F-W angles, IAU 2006
eraFw2m F-W angles to r-matrix
eraCr copy r-matrix
eraTr transpose r-matrix
eraRxr product of two r-matrices
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
epsa, rb, rp, rbp, rn, rbpn = ufunc.pn06(date1, date2, dpsi, deps)
return epsa, rb, rp, rbp, rn, rbpn
[docs]def pn06a(date1, date2):
"""
Precession-nutation, IAU 2006/2000A models: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based use
indirectly.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsi : double array
deps : double array
epsa : double array
rb : double array
rp : double array
rbp : double array
rn : double array
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPn06a``. The ERFA documentation is::
- - - - - - - - -
e r a P n 0 6 a
- - - - - - - - -
Precession-nutation, IAU 2006/2000A models: a multi-purpose function,
supporting classical (equinox-based) use directly and CIO-based use
indirectly.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsi,deps double nutation (Note 2)
epsa double mean obliquity (Note 3)
rb double[3][3] frame bias matrix (Note 4)
rp double[3][3] precession matrix (Note 5)
rbp double[3][3] bias-precession matrix (Note 6)
rn double[3][3] nutation matrix (Note 7)
rbpn double[3][3] GCRS-to-true matrix (Notes 8,9)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The nutation components (luni-solar + planetary, IAU 2000A) in
longitude and obliquity are in radians and with respect to the
equinox and ecliptic of date. Free core nutation is omitted;
for the utmost accuracy, use the eraPn06 function, where the
nutation components are caller-specified.
3) The mean obliquity is consistent with the IAU 2006 precession.
4) The matrix rb transforms vectors from GCRS to mean J2000.0 by
applying frame bias.
5) The matrix rp transforms vectors from mean J2000.0 to mean of
date by applying precession.
6) The matrix rbp transforms vectors from GCRS to mean of date by
applying frame bias then precession. It is the product rp x rb.
7) The matrix rn transforms vectors from mean of date to true of
date by applying the nutation (luni-solar + planetary).
8) The matrix rbpn transforms vectors from GCRS to true of date
(CIP/equinox). It is the product rn x rbp, applying frame bias,
precession and nutation in that order.
9) The X,Y,Z coordinates of the IAU 2006/2000A Celestial
Intermediate Pole are elements (3,1-3) of the GCRS-to-true
matrix, i.e. rbpn[2][0-2].
10) It is permissible to re-use the same array in the returned
arguments. The arrays are filled in the stated order.
Called:
eraNut06a nutation, IAU 2006/2000A
eraPn06 bias/precession/nutation results, IAU 2006
Reference:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
This revision: 2013 November 13
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsi, deps, epsa, rb, rp, rbp, rn, rbpn = ufunc.pn06a(date1, date2)
return dpsi, deps, epsa, rb, rp, rbp, rn, rbpn
[docs]def pnm00a(date1, date2):
"""
Form the matrix of precession-nutation for a given date (including
frame bias), equinox based, IAU 2000A model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPnm00a``. The ERFA documentation is::
- - - - - - - - - -
e r a P n m 0 0 a
- - - - - - - - - -
Form the matrix of precession-nutation for a given date (including
frame bias), equinox based, IAU 2000A model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rbpn double[3][3] bias-precession-nutation matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rbpn * V(GCRS), where
the p-vector V(date) is with respect to the true equatorial triad
of date date1+date2 and the p-vector V(GCRS) is with respect to
the Geocentric Celestial Reference System (IAU, 2000).
3) A faster, but slightly less accurate, result (about 1 mas) can be
obtained by using instead the eraPnm00b function.
Called:
eraPn00a bias/precession/nutation, IAU 2000A
Reference:
IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc.
24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6.
(2000)
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rbpn = ufunc.pnm00a(date1, date2)
return rbpn
[docs]def pnm00b(date1, date2):
"""
Form the matrix of precession-nutation for a given date (including
frame bias), equinox-based, IAU 2000B model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPnm00b``. The ERFA documentation is::
- - - - - - - - - -
e r a P n m 0 0 b
- - - - - - - - - -
Form the matrix of precession-nutation for a given date (including
frame bias), equinox-based, IAU 2000B model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rbpn double[3][3] bias-precession-nutation matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rbpn * V(GCRS), where
the p-vector V(date) is with respect to the true equatorial triad
of date date1+date2 and the p-vector V(GCRS) is with respect to
the Geocentric Celestial Reference System (IAU, 2000).
3) The present function is faster, but slightly less accurate (about
1 mas), than the eraPnm00a function.
Called:
eraPn00b bias/precession/nutation, IAU 2000B
Reference:
IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc.
24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6.
(2000)
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rbpn = ufunc.pnm00b(date1, date2)
return rbpn
[docs]def pnm06a(date1, date2):
"""
Form the matrix of precession-nutation for a given date (including
frame bias), equinox based, IAU 2006 precession and IAU 2000A
nutation models.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rbpn : double array
Notes
-----
Wraps ERFA function ``eraPnm06a``. The ERFA documentation is::
- - - - - - - - - -
e r a P n m 0 6 a
- - - - - - - - - -
Form the matrix of precession-nutation for a given date (including
frame bias), equinox based, IAU 2006 precession and IAU 2000A
nutation models.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rbpn double[3][3] bias-precession-nutation matrix (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways, among
others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rbpn * V(GCRS), where
the p-vector V(date) is with respect to the true equatorial triad
of date date1+date2 and the p-vector V(GCRS) is with respect to
the Geocentric Celestial Reference System (IAU, 2000).
Called:
eraPfw06 bias-precession F-W angles, IAU 2006
eraNut06a nutation, IAU 2006/2000A
eraFw2m F-W angles to r-matrix
Reference:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855.
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rbpn = ufunc.pnm06a(date1, date2)
return rbpn
[docs]def pnm80(date1, date2):
"""
Form the matrix of precession/nutation for a given date, IAU 1976
precession model, IAU 1980 nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rmatpn : double array
Notes
-----
Wraps ERFA function ``eraPnm80``. The ERFA documentation is::
- - - - - - - - -
e r a P n m 8 0
- - - - - - - - -
Form the matrix of precession/nutation for a given date, IAU 1976
precession model, IAU 1980 nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
rmatpn double[3][3] combined precession/nutation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The matrix operates in the sense V(date) = rmatpn * V(J2000),
where the p-vector V(date) is with respect to the true equatorial
triad of date date1+date2 and the p-vector V(J2000) is with
respect to the mean equatorial triad of epoch J2000.0.
Called:
eraPmat76 precession matrix, IAU 1976
eraNutm80 nutation matrix, IAU 1980
eraRxr product of two r-matrices
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 3.3 (p145).
This revision: 2020 November 27
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rmatpn = ufunc.pnm80(date1, date2)
return rmatpn
[docs]def pom00(xp, yp, sp):
"""
Form the matrix of polar motion for a given date, IAU 2000.
Parameters
----------
xp : double array
yp : double array
sp : double array
Returns
-------
rpom : double array
Notes
-----
Wraps ERFA function ``eraPom00``. The ERFA documentation is::
- - - - - - - - - -
e r a P o m 0 0
- - - - - - - - - -
Form the matrix of polar motion for a given date, IAU 2000.
Given:
xp,yp double coordinates of the pole (radians, Note 1)
sp double the TIO locator s' (radians, Note 2)
Returned:
rpom double[3][3] polar-motion matrix (Note 3)
Notes:
1) The arguments xp and yp are the coordinates (in radians) of the
Celestial Intermediate Pole with respect to the International
Terrestrial Reference System (see IERS Conventions 2003),
measured along the meridians 0 and 90 deg west respectively.
2) The argument sp is the TIO locator s', in radians, which
positions the Terrestrial Intermediate Origin on the equator. It
is obtained from polar motion observations by numerical
integration, and so is in essence unpredictable. However, it is
dominated by a secular drift of about 47 microarcseconds per
century, and so can be taken into account by using s' = -47*t,
where t is centuries since J2000.0. The function eraSp00
implements this approximation.
3) The matrix operates in the sense V(TRS) = rpom * V(CIP), meaning
that it is the final rotation when computing the pointing
direction to a celestial source.
Called:
eraIr initialize r-matrix to identity
eraRz rotate around Z-axis
eraRy rotate around Y-axis
eraRx rotate around X-axis
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 October 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rpom = ufunc.pom00(xp, yp, sp)
return rpom
[docs]def pr00(date1, date2):
"""
Precession-rate part of the IAU 2000 precession-nutation models
(part of MHB2000).
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
dpsipr : double array
depspr : double array
Notes
-----
Wraps ERFA function ``eraPr00``. The ERFA documentation is::
- - - - - - - -
e r a P r 0 0
- - - - - - - -
Precession-rate part of the IAU 2000 precession-nutation models
(part of MHB2000).
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
dpsipr,depspr double precession corrections (Notes 2,3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The precession adjustments are expressed as "nutation
components", corrections in longitude and obliquity with respect
to the J2000.0 equinox and ecliptic.
3) Although the precession adjustments are stated to be with respect
to Lieske et al. (1977), the MHB2000 model does not specify which
set of Euler angles are to be used and how the adjustments are to
be applied. The most literal and straightforward procedure is to
adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
to add dpsipr to psi_A and depspr to both omega_A and eps_A.
4) This is an implementation of one aspect of the IAU 2000A nutation
model, formally adopted by the IAU General Assembly in 2000,
namely MHB2000 (Mathews et al. 2002).
References:
Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
for the precession quantities based upon the IAU (1976) System of
Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
and precession New nutation series for nonrigid Earth and
insights into the Earth's interior", J.Geophys.Res., 107, B4,
2002. The MHB2000 code itself was obtained on 9th September 2002
from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
Wallace, P.T., "Software for Implementing the IAU 2000
Resolutions", in IERS Workshop 5.1 (2002).
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dpsipr, depspr = ufunc.pr00(date1, date2)
return dpsipr, depspr
[docs]def prec76(date01, date02, date11, date12):
"""
IAU 1976 precession model.
Parameters
----------
date01 : double array
date02 : double array
date11 : double array
date12 : double array
Returns
-------
zeta : double array
z : double array
theta : double array
Notes
-----
Wraps ERFA function ``eraPrec76``. The ERFA documentation is::
- - - - - - - - - -
e r a P r e c 7 6
- - - - - - - - - -
IAU 1976 precession model.
This function forms the three Euler angles which implement general
precession between two dates, using the IAU 1976 model (as for the
FK5 catalog).
Given:
date01,date02 double TDB starting date (Note 1)
date11,date12 double TDB ending date (Note 1)
Returned:
zeta double 1st rotation: radians cw around z
z double 3rd rotation: radians cw around z
theta double 2nd rotation: radians ccw around y
Notes:
1) The dates date01+date02 and date11+date12 are Julian Dates,
apportioned in any convenient way between the arguments daten1
and daten2. For example, JD(TDB)=2450123.7 could be expressed in
any of these ways, among others:
daten1 daten2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 method is best matched to the way the
argument is handled internally and will deliver the optimum
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
The two dates may be expressed using different methods, but at
the risk of losing some resolution.
2) The accumulated precession angles zeta, z, theta are expressed
through canonical polynomials which are valid only for a limited
time span. In addition, the IAU 1976 precession rate is known to
be imperfect. The absolute accuracy of the present formulation
is better than 0.1 arcsec from 1960AD to 2040AD, better than
1 arcsec from 1640AD to 2360AD, and remains below 3 arcsec for
the whole of the period 500BC to 3000AD. The errors exceed
10 arcsec outside the range 1200BC to 3900AD, exceed 100 arcsec
outside 4200BC to 5600AD and exceed 1000 arcsec outside 6800BC to
8200AD.
3) The three angles are returned in the conventional order, which
is not the same as the order of the corresponding Euler
rotations. The precession matrix is
R_3(-z) x R_2(+theta) x R_3(-zeta).
Reference:
Lieske, J.H., 1979, Astron.Astrophys. 73, 282, equations
(6) & (7), p283.
This revision: 2013 November 19
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
zeta, z, theta = ufunc.prec76(date01, date02, date11, date12)
return zeta, z, theta
[docs]def s00(date1, date2, x, y):
"""
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, given the CIP's X,Y
coordinates.
Parameters
----------
date1 : double array
date2 : double array
x : double array
y : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraS00``. The ERFA documentation is::
- - - - - - -
e r a S 0 0
- - - - - - -
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, given the CIP's X,Y
coordinates. Compatible with IAU 2000A precession-nutation.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
x,y double CIP coordinates (Note 3)
Returned (function value):
double the CIO locator s in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The CIO locator s is the difference between the right ascensions
of the same point in two systems: the two systems are the GCRS
and the CIP,CIO, and the point is the ascending node of the
CIP equator. The quantity s remains below 0.1 arcsecond
throughout 1900-2100.
3) The series used to compute s is in fact for s+XY/2, where X and Y
are the x and y components of the CIP unit vector; this series
is more compact than a direct series for s would be. This
function requires X,Y to be supplied by the caller, who is
responsible for providing values that are consistent with the
supplied date.
4) The model is consistent with the IAU 2000A precession-nutation.
Called:
eraFal03 mean anomaly of the Moon
eraFalp03 mean anomaly of the Sun
eraFaf03 mean argument of the latitude of the Moon
eraFad03 mean elongation of the Moon from the Sun
eraFaom03 mean longitude of the Moon's ascending node
eraFave03 mean longitude of Venus
eraFae03 mean longitude of Earth
eraFapa03 general accumulated precession in longitude
References:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 4
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.s00(date1, date2, x, y)
return c_retval
[docs]def s00a(date1, date2):
"""
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2000A
precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraS00a``. The ERFA documentation is::
- - - - - - - -
e r a S 0 0 a
- - - - - - - -
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2000A
precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double the CIO locator s in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The CIO locator s is the difference between the right ascensions
of the same point in two systems. The two systems are the GCRS
and the CIP,CIO, and the point is the ascending node of the
CIP equator. The CIO locator s remains a small fraction of
1 arcsecond throughout 1900-2100.
3) The series used to compute s is in fact for s+XY/2, where X and Y
are the x and y components of the CIP unit vector; this series
is more compact than a direct series for s would be. The present
function uses the full IAU 2000A nutation model when predicting
the CIP position. Faster results, with no significant loss of
accuracy, can be obtained via the function eraS00b, which uses
instead the IAU 2000B truncated model.
Called:
eraPnm00a classical NPB matrix, IAU 2000A
eraBnp2xy extract CIP X,Y from the BPN matrix
eraS00 the CIO locator s, given X,Y, IAU 2000A
References:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.s00a(date1, date2)
return c_retval
[docs]def s00b(date1, date2):
"""
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2000B
precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraS00b``. The ERFA documentation is::
- - - - - - - -
e r a S 0 0 b
- - - - - - - -
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2000B
precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double the CIO locator s in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The CIO locator s is the difference between the right ascensions
of the same point in two systems. The two systems are the GCRS
and the CIP,CIO, and the point is the ascending node of the
CIP equator. The CIO locator s remains a small fraction of
1 arcsecond throughout 1900-2100.
3) The series used to compute s is in fact for s+XY/2, where X and Y
are the x and y components of the CIP unit vector; this series
is more compact than a direct series for s would be. The present
function uses the IAU 2000B truncated nutation model when
predicting the CIP position. The function eraS00a uses instead
the full IAU 2000A model, but with no significant increase in
accuracy and at some cost in speed.
Called:
eraPnm00b classical NPB matrix, IAU 2000B
eraBnp2xy extract CIP X,Y from the BPN matrix
eraS00 the CIO locator s, given X,Y, IAU 2000A
References:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.s00b(date1, date2)
return c_retval
[docs]def s06(date1, date2, x, y):
"""
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, given the CIP's X,Y
coordinates.
Parameters
----------
date1 : double array
date2 : double array
x : double array
y : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraS06``. The ERFA documentation is::
- - - - - - -
e r a S 0 6
- - - - - - -
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, given the CIP's X,Y
coordinates. Compatible with IAU 2006/2000A precession-nutation.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
x,y double CIP coordinates (Note 3)
Returned (function value):
double the CIO locator s in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The CIO locator s is the difference between the right ascensions
of the same point in two systems: the two systems are the GCRS
and the CIP,CIO, and the point is the ascending node of the
CIP equator. The quantity s remains below 0.1 arcsecond
throughout 1900-2100.
3) The series used to compute s is in fact for s+XY/2, where X and Y
are the x and y components of the CIP unit vector; this series
is more compact than a direct series for s would be. This
function requires X,Y to be supplied by the caller, who is
responsible for providing values that are consistent with the
supplied date.
4) The model is consistent with the "P03" precession (Capitaine et
al. 2003), adopted by IAU 2006 Resolution 1, 2006, and the
IAU 2000A nutation (with P03 adjustments).
Called:
eraFal03 mean anomaly of the Moon
eraFalp03 mean anomaly of the Sun
eraFaf03 mean argument of the latitude of the Moon
eraFad03 mean elongation of the Moon from the Sun
eraFaom03 mean longitude of the Moon's ascending node
eraFave03 mean longitude of Venus
eraFae03 mean longitude of Earth
eraFapa03 general accumulated precession in longitude
References:
Capitaine, N., Wallace, P.T. & Chapront, J., 2003, Astron.
Astrophys. 432, 355
McCarthy, D.D., Petit, G. (eds.) 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.s06(date1, date2, x, y)
return c_retval
[docs]def s06a(date1, date2):
"""
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2006
precession and IAU 2000A nutation models.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraS06a``. The ERFA documentation is::
- - - - - - - -
e r a S 0 6 a
- - - - - - - -
The CIO locator s, positioning the Celestial Intermediate Origin on
the equator of the Celestial Intermediate Pole, using the IAU 2006
precession and IAU 2000A nutation models.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double the CIO locator s in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The CIO locator s is the difference between the right ascensions
of the same point in two systems. The two systems are the GCRS
and the CIP,CIO, and the point is the ascending node of the
CIP equator. The CIO locator s remains a small fraction of
1 arcsecond throughout 1900-2100.
3) The series used to compute s is in fact for s+XY/2, where X and Y
are the x and y components of the CIP unit vector; this series is
more compact than a direct series for s would be. The present
function uses the full IAU 2000A nutation model when predicting
the CIP position.
Called:
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
References:
Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
"Expressions for the Celestial Intermediate Pole and Celestial
Ephemeris Origin consistent with the IAU 2000A precession-
nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
n.b. The celestial ephemeris origin (CEO) was renamed "celestial
intermediate origin" (CIO) by IAU 2006 Resolution 2.
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.s06a(date1, date2)
return c_retval
[docs]def sp00(date1, date2):
"""
The TIO locator s', positioning the Terrestrial Intermediate Origin
on the equator of the Celestial Intermediate Pole.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraSp00``. The ERFA documentation is::
- - - - - - - -
e r a S p 0 0
- - - - - - - -
The TIO locator s', positioning the Terrestrial Intermediate Origin
on the equator of the Celestial Intermediate Pole.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double the TIO locator s' in radians (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The TIO locator s' is obtained from polar motion observations by
numerical integration, and so is in essence unpredictable.
However, it is dominated by a secular drift of about
47 microarcseconds per century, which is the approximation
evaluated by the present function.
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.sp00(date1, date2)
return c_retval
[docs]def xy06(date1, date2):
"""
X,Y coordinates of celestial intermediate pole from series based
on IAU 2006 precession and IAU 2000A nutation.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
x : double array
y : double array
Notes
-----
Wraps ERFA function ``eraXy06``. The ERFA documentation is::
- - - - - - - -
e r a X y 0 6
- - - - - - - -
X,Y coordinates of celestial intermediate pole from series based
on IAU 2006 precession and IAU 2000A nutation.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
x,y double CIP X,Y coordinates (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The X,Y coordinates are those of the unit vector towards the
celestial intermediate pole. They represent the combined effects
of frame bias, precession and nutation.
3) The fundamental arguments used are as adopted in IERS Conventions
(2003) and are from Simon et al. (1994) and Souchay et al.
(1999).
4) This is an alternative to the angles-based method, via the ERFA
function eraFw2xy and as used in eraXys06a for example. The two
methods agree at the 1 microarcsecond level (at present), a
negligible amount compared with the intrinsic accuracy of the
models. However, it would be unwise to mix the two methods
(angles-based and series-based) in a single application.
Called:
eraFal03 mean anomaly of the Moon
eraFalp03 mean anomaly of the Sun
eraFaf03 mean argument of the latitude of the Moon
eraFad03 mean elongation of the Moon from the Sun
eraFaom03 mean longitude of the Moon's ascending node
eraFame03 mean longitude of Mercury
eraFave03 mean longitude of Venus
eraFae03 mean longitude of Earth
eraFama03 mean longitude of Mars
eraFaju03 mean longitude of Jupiter
eraFasa03 mean longitude of Saturn
eraFaur03 mean longitude of Uranus
eraFane03 mean longitude of Neptune
eraFapa03 general accumulated precession in longitude
References:
Capitaine, N., Wallace, P.T. & Chapront, J., 2003,
Astron.Astrophys., 412, 567
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
Simon, J.L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G. & Laskar, J., Astron.Astrophys., 1994, 282, 663
Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M., 1999,
Astron.Astrophys.Supp.Ser. 135, 111
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y = ufunc.xy06(date1, date2)
return x, y
[docs]def xys00a(date1, date2):
"""
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2000A
precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
x : double array
y : double array
s : double array
Notes
-----
Wraps ERFA function ``eraXys00a``. The ERFA documentation is::
- - - - - - - - - -
e r a X y s 0 0 a
- - - - - - - - - -
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2000A
precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
x,y double Celestial Intermediate Pole (Note 2)
s double the CIO locator s (Note 3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The Celestial Intermediate Pole coordinates are the x,y
components of the unit vector in the Geocentric Celestial
Reference System.
3) The CIO locator s (in radians) positions the Celestial
Intermediate Origin on the equator of the CIP.
4) A faster, but slightly less accurate result (about 1 mas for
X,Y), can be obtained by using instead the eraXys00b function.
Called:
eraPnm00a classical NPB matrix, IAU 2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS00 the CIO locator s, given X,Y, IAU 2000A
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2019 November 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y, s = ufunc.xys00a(date1, date2)
return x, y, s
[docs]def xys00b(date1, date2):
"""
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2000B
precession-nutation model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
x : double array
y : double array
s : double array
Notes
-----
Wraps ERFA function ``eraXys00b``. The ERFA documentation is::
- - - - - - - - - -
e r a X y s 0 0 b
- - - - - - - - - -
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2000B
precession-nutation model.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
x,y double Celestial Intermediate Pole (Note 2)
s double the CIO locator s (Note 3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The Celestial Intermediate Pole coordinates are the x,y
components of the unit vector in the Geocentric Celestial
Reference System.
3) The CIO locator s (in radians) positions the Celestial
Intermediate Origin on the equator of the CIP.
4) The present function is faster, but slightly less accurate (about
1 mas in X,Y), than the eraXys00a function.
Called:
eraPnm00b classical NPB matrix, IAU 2000B
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS00 the CIO locator s, given X,Y, IAU 2000A
Reference:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 December 4
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y, s = ufunc.xys00b(date1, date2)
return x, y, s
[docs]def xys06a(date1, date2):
"""
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2006
precession and IAU 2000A nutation models.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
x : double array
y : double array
s : double array
Notes
-----
Wraps ERFA function ``eraXys06a``. The ERFA documentation is::
- - - - - - - - - -
e r a X y s 0 6 a
- - - - - - - - - -
For a given TT date, compute the X,Y coordinates of the Celestial
Intermediate Pole and the CIO locator s, using the IAU 2006
precession and IAU 2000A nutation models.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned:
x,y double Celestial Intermediate Pole (Note 2)
s double the CIO locator s (Note 3)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The Celestial Intermediate Pole coordinates are the x,y components
of the unit vector in the Geocentric Celestial Reference System.
3) The CIO locator s (in radians) positions the Celestial
Intermediate Origin on the equator of the CIP.
4) Series-based solutions for generating X and Y are also available:
see Capitaine & Wallace (2006) and eraXy06.
Called:
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
References:
Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 December 4
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
x, y, s = ufunc.xys06a(date1, date2)
return x, y, s
[docs]def ee00(date1, date2, epsa, dpsi):
"""
The equation of the equinoxes, compatible with IAU 2000 resolutions,
given the nutation in longitude and the mean obliquity.
Parameters
----------
date1 : double array
date2 : double array
epsa : double array
dpsi : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEe00``. The ERFA documentation is::
- - - - - - - -
e r a E e 0 0
- - - - - - - -
The equation of the equinoxes, compatible with IAU 2000 resolutions,
given the nutation in longitude and the mean obliquity.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
epsa double mean obliquity (Note 2)
dpsi double nutation in longitude (Note 3)
Returned (function value):
double equation of the equinoxes (Note 4)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The obliquity, in radians, is mean of date.
3) The result, which is in radians, operates in the following sense:
Greenwich apparent ST = GMST + equation of the equinoxes
4) The result is compatible with the IAU 2000 resolutions. For
further details, see IERS Conventions 2003 and Capitaine et al.
(2002).
Called:
eraEect00 equation of the equinoxes complementary terms
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2008 May 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.ee00(date1, date2, epsa, dpsi)
return c_retval
[docs]def ee00a(date1, date2):
"""
Equation of the equinoxes, compatible with IAU 2000 resolutions.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEe00a``. The ERFA documentation is::
- - - - - - - - -
e r a E e 0 0 a
- - - - - - - - -
Equation of the equinoxes, compatible with IAU 2000 resolutions.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double equation of the equinoxes (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result, which is in radians, operates in the following sense:
Greenwich apparent ST = GMST + equation of the equinoxes
3) The result is compatible with the IAU 2000 resolutions. For
further details, see IERS Conventions 2003 and Capitaine et al.
(2002).
Called:
eraPr00 IAU 2000 precession adjustments
eraObl80 mean obliquity, IAU 1980
eraNut00a nutation, IAU 2000A
eraEe00 equation of the equinoxes, IAU 2000
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003).
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004).
This revision: 2008 May 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.ee00a(date1, date2)
return c_retval
[docs]def ee00b(date1, date2):
"""
Equation of the equinoxes, compatible with IAU 2000 resolutions but
using the truncated nutation model IAU 2000B.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEe00b``. The ERFA documentation is::
- - - - - - - - -
e r a E e 0 0 b
- - - - - - - - -
Equation of the equinoxes, compatible with IAU 2000 resolutions but
using the truncated nutation model IAU 2000B.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double equation of the equinoxes (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result, which is in radians, operates in the following sense:
Greenwich apparent ST = GMST + equation of the equinoxes
3) The result is compatible with the IAU 2000 resolutions except
that accuracy has been compromised (1 mas) for the sake of speed.
For further details, see McCarthy & Luzum (2003), IERS
Conventions 2003 and Capitaine et al. (2003).
Called:
eraPr00 IAU 2000 precession adjustments
eraObl80 mean obliquity, IAU 1980
eraNut00b nutation, IAU 2000B
eraEe00 equation of the equinoxes, IAU 2000
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)
McCarthy, D.D. & Luzum, B.J., "An abridged model of the
precession-nutation of the celestial pole", Celestial Mechanics &
Dynamical Astronomy, 85, 37-49 (2003)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 3
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.ee00b(date1, date2)
return c_retval
[docs]def ee06a(date1, date2):
"""
Equation of the equinoxes, compatible with IAU 2000 resolutions and
IAU 2006/2000A precession-nutation.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEe06a``. The ERFA documentation is::
- - - - - - - - -
e r a E e 0 6 a
- - - - - - - - -
Equation of the equinoxes, compatible with IAU 2000 resolutions and
IAU 2006/2000A precession-nutation.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double equation of the equinoxes (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result, which is in radians, operates in the following sense:
Greenwich apparent ST = GMST + equation of the equinoxes
Called:
eraAnpm normalize angle into range +/- pi
eraGst06a Greenwich apparent sidereal time, IAU 2006/2000A
eraGmst06 Greenwich mean sidereal time, IAU 2006
Reference:
McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
IERS Technical Note No. 32, BKG
This revision: 2008 May 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.ee06a(date1, date2)
return c_retval
[docs]def eect00(date1, date2):
"""
Equation of the equinoxes complementary terms, consistent with
IAU 2000 resolutions.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEect00``. The ERFA documentation is::
- - - - - - - - - -
e r a E e c t 0 0
- - - - - - - - - -
Equation of the equinoxes complementary terms, consistent with
IAU 2000 resolutions.
Given:
date1,date2 double TT as a 2-part Julian Date (Note 1)
Returned (function value):
double complementary terms (Note 2)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The "complementary terms" are part of the equation of the
equinoxes (EE), classically the difference between apparent and
mean Sidereal Time:
GAST = GMST + EE
with:
EE = dpsi * cos(eps)
where dpsi is the nutation in longitude and eps is the obliquity
of date. However, if the rotation of the Earth were constant in
an inertial frame the classical formulation would lead to
apparent irregularities in the UT1 timescale traceable to side-
effects of precession-nutation. In order to eliminate these
effects from UT1, "complementary terms" were introduced in 1994
(IAU, 1994) and took effect from 1997 (Capitaine and Gontier,
1993):
GAST = GMST + CT + EE
By convention, the complementary terms are included as part of
the equation of the equinoxes rather than as part of the mean
Sidereal Time. This slightly compromises the "geometrical"
interpretation of mean sidereal time but is otherwise
inconsequential.
The present function computes CT in the above expression,
compatible with IAU 2000 resolutions (Capitaine et al., 2002, and
IERS Conventions 2003).
Called:
eraFal03 mean anomaly of the Moon
eraFalp03 mean anomaly of the Sun
eraFaf03 mean argument of the latitude of the Moon
eraFad03 mean elongation of the Moon from the Sun
eraFaom03 mean longitude of the Moon's ascending node
eraFave03 mean longitude of Venus
eraFae03 mean longitude of Earth
eraFapa03 general accumulated precession in longitude
References:
Capitaine, N. & Gontier, A.-M., Astron.Astrophys., 275,
645-650 (1993)
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astron.Astrophys., 406,
1135-1149 (2003)
IAU Resolution C7, Recommendation 3 (1994)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2019 June 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.eect00(date1, date2)
return c_retval
[docs]def eqeq94(date1, date2):
"""
Equation of the equinoxes, IAU 1994 model.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEqeq94``. The ERFA documentation is::
- - - - - - - - - -
e r a E q e q 9 4
- - - - - - - - - -
Equation of the equinoxes, IAU 1994 model.
Given:
date1,date2 double TDB date (Note 1)
Returned (function value):
double equation of the equinoxes (Note 2)
Notes:
1) The date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The result, which is in radians, operates in the following sense:
Greenwich apparent ST = GMST + equation of the equinoxes
Called:
eraAnpm normalize angle into range +/- pi
eraNut80 nutation, IAU 1980
eraObl80 mean obliquity, IAU 1980
References:
IAU Resolution C7, Recommendation 3 (1994).
Capitaine, N. & Gontier, A.-M., 1993, Astron.Astrophys., 275,
645-650.
This revision: 2017 October 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.eqeq94(date1, date2)
return c_retval
[docs]def era00(dj1, dj2):
"""
Earth rotation angle (IAU 2000 model).
Parameters
----------
dj1 : double array
dj2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraEra00``. The ERFA documentation is::
- - - - - - - - -
e r a E r a 0 0
- - - - - - - - -
Earth rotation angle (IAU 2000 model).
Given:
dj1,dj2 double UT1 as a 2-part Julian Date (see note)
Returned (function value):
double Earth rotation angle (radians), range 0-2pi
Notes:
1) The UT1 date dj1+dj2 is a Julian Date, apportioned in any
convenient way between the arguments dj1 and dj2. For example,
JD(UT1)=2450123.7 could be expressed in any of these ways,
among others:
dj1 dj2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. The date & time method is
best matched to the algorithm used: maximum precision is
delivered when the dj1 argument is for 0hrs UT1 on the day in
question and the dj2 argument lies in the range 0 to 1, or vice
versa.
2) The algorithm is adapted from Expression 22 of Capitaine et al.
2000. The time argument has been expressed in days directly,
and, to retain precision, integer contributions have been
eliminated. The same formulation is given in IERS Conventions
(2003), Chap. 5, Eq. 14.
Called:
eraAnp normalize angle into range 0 to 2pi
References:
Capitaine N., Guinot B. and McCarthy D.D, 2000, Astron.
Astrophys., 355, 398-405.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.era00(dj1, dj2)
return c_retval
[docs]def gmst00(uta, utb, tta, ttb):
"""
Greenwich mean sidereal time (model consistent with IAU 2000
resolutions).
Parameters
----------
uta : double array
utb : double array
tta : double array
ttb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGmst00``. The ERFA documentation is::
- - - - - - - - - -
e r a G m s t 0 0
- - - - - - - - - -
Greenwich mean sidereal time (model consistent with IAU 2000
resolutions).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich mean sidereal time (radians)
Notes:
1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs. For example, JD(UT1)=2450123.7 could be
expressed in any of these ways, among others:
Part A Part B
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable (in the case of UT; the TT is not at all critical
in this respect). The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
Rotation Angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession. If UT1 is used for
both purposes, errors of order 100 microarcseconds result.
3) This GMST is compatible with the IAU 2000 resolutions and must be
used only in conjunction with other IAU 2000 compatible
components such as precession-nutation and equation of the
equinoxes.
4) The result is returned in the range 0 to 2pi.
5) The algorithm is from Capitaine et al. (2003) and IERS
Conventions 2003.
Called:
eraEra00 Earth rotation angle, IAU 2000
eraAnp normalize angle into range 0 to 2pi
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 17
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gmst00(uta, utb, tta, ttb)
return c_retval
[docs]def gmst06(uta, utb, tta, ttb):
"""
Greenwich mean sidereal time (consistent with IAU 2006 precession).
Parameters
----------
uta : double array
utb : double array
tta : double array
ttb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGmst06``. The ERFA documentation is::
- - - - - - - - - -
e r a G m s t 0 6
- - - - - - - - - -
Greenwich mean sidereal time (consistent with IAU 2006 precession).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich mean sidereal time (radians)
Notes:
1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs. For example, JD=2450123.7 could be expressed in
any of these ways, among others:
Part A Part B
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable (in the case of UT; the TT is not at all critical
in this respect). The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
rotation angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession. If UT1 is used for
both purposes, errors of order 100 microarcseconds result.
3) This GMST is compatible with the IAU 2006 precession and must not
be used with other precession models.
4) The result is returned in the range 0 to 2pi.
Called:
eraEra00 Earth rotation angle, IAU 2000
eraAnp normalize angle into range 0 to 2pi
Reference:
Capitaine, N., Wallace, P.T. & Chapront, J., 2005,
Astron.Astrophys. 432, 355
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gmst06(uta, utb, tta, ttb)
return c_retval
[docs]def gmst82(dj1, dj2):
"""
Universal Time to Greenwich mean sidereal time (IAU 1982 model).
Parameters
----------
dj1 : double array
dj2 : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGmst82``. The ERFA documentation is::
- - - - - - - - - -
e r a G m s t 8 2
- - - - - - - - - -
Universal Time to Greenwich mean sidereal time (IAU 1982 model).
Given:
dj1,dj2 double UT1 Julian Date (see note)
Returned (function value):
double Greenwich mean sidereal time (radians)
Notes:
1) The UT1 date dj1+dj2 is a Julian Date, apportioned in any
convenient way between the arguments dj1 and dj2. For example,
JD(UT1)=2450123.7 could be expressed in any of these ways,
among others:
dj1 dj2
2450123.7 0 (JD method)
2451545 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. The date & time method is
best matched to the algorithm used: maximum accuracy (or, at
least, minimum noise) is delivered when the dj1 argument is for
0hrs UT1 on the day in question and the dj2 argument lies in the
range 0 to 1, or vice versa.
2) The algorithm is based on the IAU 1982 expression. This is
always described as giving the GMST at 0 hours UT1. In fact, it
gives the difference between the GMST and the UT, the steady
4-minutes-per-day drawing-ahead of ST with respect to UT. When
whole days are ignored, the expression happens to equal the GMST
at 0 hours UT1 each day.
3) In this function, the entire UT1 (the sum of the two arguments
dj1 and dj2) is used directly as the argument for the standard
formula, the constant term of which is adjusted by 12 hours to
take account of the noon phasing of Julian Date. The UT1 is then
added, but omitting whole days to conserve accuracy.
Called:
eraAnp normalize angle into range 0 to 2pi
References:
Transactions of the International Astronomical Union,
XVIII B, 67 (1983).
Aoki et al., Astron.Astrophys., 105, 359-361 (1982).
This revision: 2020 January 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gmst82(dj1, dj2)
return c_retval
[docs]def gst00a(uta, utb, tta, ttb):
"""
Greenwich apparent sidereal time (consistent with IAU 2000
resolutions).
Parameters
----------
uta : double array
utb : double array
tta : double array
ttb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGst00a``. The ERFA documentation is::
- - - - - - - - - -
e r a G s t 0 0 a
- - - - - - - - - -
Greenwich apparent sidereal time (consistent with IAU 2000
resolutions).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich apparent sidereal time (radians)
Notes:
1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs. For example, JD(UT1)=2450123.7 could be
expressed in any of these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable (in the case of UT; the TT is not at all critical
in this respect). The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
Rotation Angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession-nutation. If UT1 is
used for both purposes, errors of order 100 microarcseconds
result.
3) This GAST is compatible with the IAU 2000 resolutions and must be
used only in conjunction with other IAU 2000 compatible
components such as precession-nutation.
4) The result is returned in the range 0 to 2pi.
5) The algorithm is from Capitaine et al. (2003) and IERS
Conventions 2003.
Called:
eraGmst00 Greenwich mean sidereal time, IAU 2000
eraEe00a equation of the equinoxes, IAU 2000A
eraAnp normalize angle into range 0 to 2pi
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gst00a(uta, utb, tta, ttb)
return c_retval
[docs]def gst00b(uta, utb):
"""
Greenwich apparent sidereal time (consistent with IAU 2000
resolutions but using the truncated nutation model IAU 2000B).
Parameters
----------
uta : double array
utb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGst00b``. The ERFA documentation is::
- - - - - - - - - -
e r a G s t 0 0 b
- - - - - - - - - -
Greenwich apparent sidereal time (consistent with IAU 2000
resolutions but using the truncated nutation model IAU 2000B).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich apparent sidereal time (radians)
Notes:
1) The UT1 date uta+utb is a Julian Date, apportioned in any
convenient way between the argument pair. For example,
JD(UT1)=2450123.7 could be expressed in any of these ways,
among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
Rotation Angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) The result is compatible with the IAU 2000 resolutions, except
that accuracy has been compromised for the sake of speed and
convenience in two respects:
. UT is used instead of TDB (or TT) to compute the precession
component of GMST and the equation of the equinoxes. This
results in errors of order 0.1 mas at present.
. The IAU 2000B abridged nutation model (McCarthy & Luzum, 2003)
is used, introducing errors of up to 1 mas.
3) This GAST is compatible with the IAU 2000 resolutions and must be
used only in conjunction with other IAU 2000 compatible
components such as precession-nutation.
4) The result is returned in the range 0 to 2pi.
5) The algorithm is from Capitaine et al. (2003) and IERS
Conventions 2003.
Called:
eraGmst00 Greenwich mean sidereal time, IAU 2000
eraEe00b equation of the equinoxes, IAU 2000B
eraAnp normalize angle into range 0 to 2pi
References:
Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)
McCarthy, D.D. & Luzum, B.J., "An abridged model of the
precession-nutation of the celestial pole", Celestial Mechanics &
Dynamical Astronomy, 85, 37-49 (2003)
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
This revision: 2020 November 19
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gst00b(uta, utb)
return c_retval
[docs]def gst06(uta, utb, tta, ttb, rnpb):
"""
Greenwich apparent sidereal time, IAU 2006, given the NPB matrix.
Parameters
----------
uta : double array
utb : double array
tta : double array
ttb : double array
rnpb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGst06``. The ERFA documentation is::
- - - - - - - - -
e r a G s t 0 6
- - - - - - - - -
Greenwich apparent sidereal time, IAU 2006, given the NPB matrix.
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
rnpb double[3][3] nutation x precession x bias matrix
Returned (function value):
double Greenwich apparent sidereal time (radians)
Notes:
1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs. For example, JD(UT1)=2450123.7 could be
expressed in any of these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable (in the case of UT; the TT is not at all critical
in this respect). The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
rotation angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession-nutation. If UT1 is
used for both purposes, errors of order 100 microarcseconds
result.
3) Although the function uses the IAU 2006 series for s+XY/2, it is
otherwise independent of the precession-nutation model and can in
practice be used with any equinox-based NPB matrix.
4) The result is returned in the range 0 to 2pi.
Called:
eraBpn2xy extract CIP X,Y coordinates from NPB matrix
eraS06 the CIO locator s, given X,Y, IAU 2006
eraAnp normalize angle into range 0 to 2pi
eraEra00 Earth rotation angle, IAU 2000
eraEors equation of the origins, given NPB matrix and s
Reference:
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gst06(uta, utb, tta, ttb, rnpb)
return c_retval
[docs]def gst06a(uta, utb, tta, ttb):
"""
Greenwich apparent sidereal time (consistent with IAU 2000 and 2006
resolutions).
Parameters
----------
uta : double array
utb : double array
tta : double array
ttb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGst06a``. The ERFA documentation is::
- - - - - - - - - -
e r a G s t 0 6 a
- - - - - - - - - -
Greenwich apparent sidereal time (consistent with IAU 2000 and 2006
resolutions).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
tta,ttb double TT as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich apparent sidereal time (radians)
Notes:
1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
Julian Dates, apportioned in any convenient way between the
argument pairs. For example, JD(UT1)=2450123.7 could be
expressed in any of these ways, among others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable (in the case of UT; the TT is not at all critical
in this respect). The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
rotation angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) Both UT1 and TT are required, UT1 to predict the Earth rotation
and TT to predict the effects of precession-nutation. If UT1 is
used for both purposes, errors of order 100 microarcseconds
result.
3) This GAST is compatible with the IAU 2000/2006 resolutions and
must be used only in conjunction with IAU 2006 precession and
IAU 2000A nutation.
4) The result is returned in the range 0 to 2pi.
Called:
eraPnm06a classical NPB matrix, IAU 2006/2000A
eraGst06 Greenwich apparent ST, IAU 2006, given NPB matrix
Reference:
Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
This revision: 2020 November 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gst06a(uta, utb, tta, ttb)
return c_retval
[docs]def gst94(uta, utb):
"""
Greenwich apparent sidereal time (consistent with IAU 1982/94
resolutions).
Parameters
----------
uta : double array
utb : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraGst94``. The ERFA documentation is::
- - - - - - - - -
e r a G s t 9 4
- - - - - - - - -
Greenwich apparent sidereal time (consistent with IAU 1982/94
resolutions).
Given:
uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
Returned (function value):
double Greenwich apparent sidereal time (radians)
Notes:
1) The UT1 date uta+utb is a Julian Date, apportioned in any
convenient way between the argument pair. For example,
JD(UT1)=2450123.7 could be expressed in any of these ways, among
others:
uta utb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in cases
where the loss of several decimal digits of resolution is
acceptable. The J2000 and MJD methods are good compromises
between resolution and convenience. For UT, the date & time
method is best matched to the algorithm that is used by the Earth
Rotation Angle function, called internally: maximum precision is
delivered when the uta argument is for 0hrs UT1 on the day in
question and the utb argument lies in the range 0 to 1, or vice
versa.
2) The result is compatible with the IAU 1982 and 1994 resolutions,
except that accuracy has been compromised for the sake of
convenience in that UT is used instead of TDB (or TT) to compute
the equation of the equinoxes.
3) This GAST must be used only in conjunction with contemporaneous
IAU standards such as 1976 precession, 1980 obliquity and 1982
nutation. It is not compatible with the IAU 2000 resolutions.
4) The result is returned in the range 0 to 2pi.
Called:
eraGmst82 Greenwich mean sidereal time, IAU 1982
eraEqeq94 equation of the equinoxes, IAU 1994
eraAnp normalize angle into range 0 to 2pi
References:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
IAU Resolution C7, Recommendation 3 (1994)
This revision: 2020 November 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.gst94(uta, utb)
return c_retval
[docs]def pvstar(pv):
"""
Convert star position+velocity vector to catalog coordinates.
Parameters
----------
pv : double array
Returns
-------
ra : double array
dec : double array
pmr : double array
pmd : double array
px : double array
rv : double array
Notes
-----
Wraps ERFA function ``eraPvstar``. The ERFA documentation is::
- - - - - - - - - -
e r a P v s t a r
- - - - - - - - - -
Convert star position+velocity vector to catalog coordinates.
Given (Note 1):
pv double[2][3] pv-vector (au, au/day)
Returned (Note 2):
ra double right ascension (radians)
dec double declination (radians)
pmr double RA proper motion (radians/year)
pmd double Dec proper motion (radians/year)
px double parallax (arcsec)
rv double radial velocity (km/s, positive = receding)
Returned (function value):
int status:
0 = OK
-1 = superluminal speed (Note 5)
-2 = null position vector
Notes:
1) The specified pv-vector is the coordinate direction (and its rate
of change) for the date at which the light leaving the star
reached the solar-system barycenter.
2) The star data returned by this function are "observables" for an
imaginary observer at the solar-system barycenter. Proper motion
and radial velocity are, strictly, in terms of barycentric
coordinate time, TCB. For most practical applications, it is
permissible to neglect the distinction between TCB and ordinary
"proper" time on Earth (TT/TAI). The result will, as a rule, be
limited by the intrinsic accuracy of the proper-motion and
radial-velocity data; moreover, the supplied pv-vector is likely
to be merely an intermediate result (for example generated by the
function eraStarpv), so that a change of time unit will cancel
out overall.
In accordance with normal star-catalog conventions, the object's
right ascension and declination are freed from the effects of
secular aberration. The frame, which is aligned to the catalog
equator and equinox, is Lorentzian and centered on the SSB.
Summarizing, the specified pv-vector is for most stars almost
identical to the result of applying the standard geometrical
"space motion" transformation to the catalog data. The
differences, which are the subject of the Stumpff paper cited
below, are:
(i) In stars with significant radial velocity and proper motion,
the constantly changing light-time distorts the apparent proper
motion. Note that this is a classical, not a relativistic,
effect.
(ii) The transformation complies with special relativity.
3) Care is needed with units. The star coordinates are in radians
and the proper motions in radians per Julian year, but the
parallax is in arcseconds; the radial velocity is in km/s, but
the pv-vector result is in au and au/day.
4) The proper motions are the rate of change of the right ascension
and declination at the catalog epoch and are in radians per Julian
year. The RA proper motion is in terms of coordinate angle, not
true angle, and will thus be numerically larger at high
declinations.
5) Straight-line motion at constant speed in the inertial frame is
assumed. If the speed is greater than or equal to the speed of
light, the function aborts with an error status.
6) The inverse transformation is performed by the function eraStarpv.
Called:
eraPn decompose p-vector into modulus and direction
eraPdp scalar product of two p-vectors
eraSxp multiply p-vector by scalar
eraPmp p-vector minus p-vector
eraPm modulus of p-vector
eraPpp p-vector plus p-vector
eraPv2s pv-vector to spherical
eraAnp normalize angle into range 0 to 2pi
Reference:
Stumpff, P., 1985, Astron.Astrophys. 144, 232-240.
This revision: 2017 March 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ra, dec, pmr, pmd, px, rv, c_retval = ufunc.pvstar(pv)
check_errwarn(c_retval, 'pvstar')
return ra, dec, pmr, pmd, px, rv
STATUS_CODES['pvstar'] = {
0: 'OK',
-1: 'superluminal speed (Note 5)',
-2: 'null position vector',
}
[docs]def starpv(ra, dec, pmr, pmd, px, rv):
"""
Convert star catalog coordinates to position+velocity vector.
Parameters
----------
ra : double array
dec : double array
pmr : double array
pmd : double array
px : double array
rv : double array
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraStarpv``. The ERFA documentation is::
- - - - - - - - - -
e r a S t a r p v
- - - - - - - - - -
Convert star catalog coordinates to position+velocity vector.
Given (Note 1):
ra double right ascension (radians)
dec double declination (radians)
pmr double RA proper motion (radians/year)
pmd double Dec proper motion (radians/year)
px double parallax (arcseconds)
rv double radial velocity (km/s, positive = receding)
Returned (Note 2):
pv double[2][3] pv-vector (au, au/day)
Returned (function value):
int status:
0 = no warnings
1 = distance overridden (Note 6)
2 = excessive speed (Note 7)
4 = solution didn't converge (Note 8)
else = binary logical OR of the above
Notes:
1) The star data accepted by this function are "observables" for an
imaginary observer at the solar-system barycenter. Proper motion
and radial velocity are, strictly, in terms of barycentric
coordinate time, TCB. For most practical applications, it is
permissible to neglect the distinction between TCB and ordinary
"proper" time on Earth (TT/TAI). The result will, as a rule, be
limited by the intrinsic accuracy of the proper-motion and
radial-velocity data; moreover, the pv-vector is likely to be
merely an intermediate result, so that a change of time unit
would cancel out overall.
In accordance with normal star-catalog conventions, the object's
right ascension and declination are freed from the effects of
secular aberration. The frame, which is aligned to the catalog
equator and equinox, is Lorentzian and centered on the SSB.
2) The resulting position and velocity pv-vector is with respect to
the same frame and, like the catalog coordinates, is freed from
the effects of secular aberration. Should the "coordinate
direction", where the object was located at the catalog epoch, be
required, it may be obtained by calculating the magnitude of the
position vector pv[0][0-2] dividing by the speed of light in
au/day to give the light-time, and then multiplying the space
velocity pv[1][0-2] by this light-time and adding the result to
pv[0][0-2].
Summarizing, the pv-vector returned is for most stars almost
identical to the result of applying the standard geometrical
"space motion" transformation. The differences, which are the
subject of the Stumpff paper referenced below, are:
(i) In stars with significant radial velocity and proper motion,
the constantly changing light-time distorts the apparent proper
motion. Note that this is a classical, not a relativistic,
effect.
(ii) The transformation complies with special relativity.
3) Care is needed with units. The star coordinates are in radians
and the proper motions in radians per Julian year, but the
parallax is in arcseconds; the radial velocity is in km/s, but
the pv-vector result is in au and au/day.
4) The RA proper motion is in terms of coordinate angle, not true
angle. If the catalog uses arcseconds for both RA and Dec proper
motions, the RA proper motion will need to be divided by cos(Dec)
before use.
5) Straight-line motion at constant speed, in the inertial frame,
is assumed.
6) An extremely small (or zero or negative) parallax is interpreted
to mean that the object is on the "celestial sphere", the radius
of which is an arbitrary (large) value (see the constant PXMIN).
When the distance is overridden in this way, the status,
initially zero, has 1 added to it.
7) If the space velocity is a significant fraction of c (see the
constant VMAX), it is arbitrarily set to zero. When this action
occurs, 2 is added to the status.
8) The relativistic adjustment involves an iterative calculation.
If the process fails to converge within a set number (IMAX) of
iterations, 4 is added to the status.
9) The inverse transformation is performed by the function
eraPvstar.
Called:
eraS2pv spherical coordinates to pv-vector
eraPm modulus of p-vector
eraZp zero p-vector
eraPn decompose p-vector into modulus and direction
eraPdp scalar product of two p-vectors
eraSxp multiply p-vector by scalar
eraPmp p-vector minus p-vector
eraPpp p-vector plus p-vector
Reference:
Stumpff, P., 1985, Astron.Astrophys. 144, 232-240.
This revision: 2017 March 16
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv, c_retval = ufunc.starpv(ra, dec, pmr, pmd, px, rv)
check_errwarn(c_retval, 'starpv')
return pv
STATUS_CODES['starpv'] = {
0: 'no warnings',
1: 'distance overridden (Note 6)',
2: 'excessive speed (Note 7)',
4: "solution didn't converge (Note 8)",
'else': 'binary logical OR of the above',
}
[docs]def fk425(r1950, d1950, dr1950, dd1950, p1950, v1950):
"""
Convert B1950.0 FK4 star catalog data to J2000.0 FK5.
Parameters
----------
r1950 : double array
d1950 : double array
dr1950 : double array
dd1950 : double array
p1950 : double array
v1950 : double array
Returns
-------
r2000 : double array
d2000 : double array
dr2000 : double array
dd2000 : double array
p2000 : double array
v2000 : double array
Notes
-----
Wraps ERFA function ``eraFk425``. The ERFA documentation is::
- - - - - - - - -
e r a F k 4 2 5
- - - - - - - - -
Convert B1950.0 FK4 star catalog data to J2000.0 FK5.
This function converts a star's catalog data from the old FK4
(Bessel-Newcomb) system to the later IAU 1976 FK5 (Fricke) system.
Given: (all B1950.0, FK4)
r1950,d1950 double B1950.0 RA,Dec (rad)
dr1950,dd1950 double B1950.0 proper motions (rad/trop.yr)
p1950 double parallax (arcsec)
v1950 double radial velocity (km/s, +ve = moving away)
Returned: (all J2000.0, FK5)
r2000,d2000 double J2000.0 RA,Dec (rad)
dr2000,dd2000 double J2000.0 proper motions (rad/Jul.yr)
p2000 double parallax (arcsec)
v2000 double radial velocity (km/s, +ve = moving away)
Notes:
1) The proper motions in RA are dRA/dt rather than cos(Dec)*dRA/dt,
and are per year rather than per century.
2) The conversion is somewhat complicated, for several reasons:
. Change of standard epoch from B1950.0 to J2000.0.
. An intermediate transition date of 1984 January 1.0 TT.
. A change of precession model.
. Change of time unit for proper motion (tropical to Julian).
. FK4 positions include the E-terms of aberration, to simplify
the hand computation of annual aberration. FK5 positions
assume a rigorous aberration computation based on the Earth's
barycentric velocity.
. The E-terms also affect proper motions, and in particular cause
objects at large distances to exhibit fictitious proper
motions.
The algorithm is based on Smith et al. (1989) and Yallop et al.
(1989), which presented a matrix method due to Standish (1982) as
developed by Aoki et al. (1983), using Kinoshita's development of
Andoyer's post-Newcomb precession. The numerical constants from
Seidelmann (1992) are used canonically.
3) Conversion from B1950.0 FK4 to J2000.0 FK5 only is provided for.
Conversions for different epochs and equinoxes would require
additional treatment for precession, proper motion and E-terms.
4) In the FK4 catalog the proper motions of stars within 10 degrees
of the poles do not embody differential E-terms effects and
should, strictly speaking, be handled in a different manner from
stars outside these regions. However, given the general lack of
homogeneity of the star data available for routine astrometry,
the difficulties of handling positions that may have been
determined from astrometric fields spanning the polar and non-
polar regions, the likelihood that the differential E-terms
effect was not taken into account when allowing for proper motion
in past astrometry, and the undesirability of a discontinuity in
the algorithm, the decision has been made in this ERFA algorithm
to include the effects of differential E-terms on the proper
motions for all stars, whether polar or not. At epoch J2000.0,
and measuring "on the sky" rather than in terms of RA change, the
errors resulting from this simplification are less than
1 milliarcsecond in position and 1 milliarcsecond per century in
proper motion.
Called:
eraAnp normalize angle into range 0 to 2pi
eraPv2s pv-vector to spherical coordinates
eraPdp scalar product of two p-vectors
eraPvmpv pv-vector minus pv_vector
eraPvppv pv-vector plus pv_vector
eraS2pv spherical coordinates to pv-vector
eraSxp multiply p-vector by scalar
References:
Aoki, S. et al., 1983, "Conversion matrix of epoch B1950.0
FK4-based positions of stars to epoch J2000.0 positions in
accordance with the new IAU resolutions". Astron.Astrophys.
128, 263-267.
Seidelmann, P.K. (ed), 1992, "Explanatory Supplement to the
Astronomical Almanac", ISBN 0-935702-68-7.
Smith, C.A. et al., 1989, "The transformation of astrometric
catalog systems to the equinox J2000.0". Astron.J. 97, 265.
Standish, E.M., 1982, "Conversion of positions and proper motions
from B1950.0 to the IAU system at J2000.0". Astron.Astrophys.,
115, 1, 20-22.
Yallop, B.D. et al., 1989, "Transformation of mean star places
from FK4 B1950.0 to FK5 J2000.0 using matrices in 6-space".
Astron.J. 97, 274.
This revision: 2018 December 5
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r2000, d2000, dr2000, dd2000, p2000, v2000 = ufunc.fk425(
r1950, d1950, dr1950, dd1950, p1950, v1950)
return r2000, d2000, dr2000, dd2000, p2000, v2000
[docs]def fk45z(r1950, d1950, bepoch):
"""
Convert a B1950.0 FK4 star position to J2000.0 FK5, assuming zero
proper motion in the FK5 system.
Parameters
----------
r1950 : double array
d1950 : double array
bepoch : double array
Returns
-------
r2000 : double array
d2000 : double array
Notes
-----
Wraps ERFA function ``eraFk45z``. The ERFA documentation is::
- - - - - - - - -
e r a F k 4 5 z
- - - - - - - - -
Convert a B1950.0 FK4 star position to J2000.0 FK5, assuming zero
proper motion in the FK5 system.
This function converts a star's catalog data from the old FK4
(Bessel-Newcomb) system to the later IAU 1976 FK5 (Fricke) system,
in such a way that the FK5 proper motion is zero. Because such a
star has, in general, a non-zero proper motion in the FK4 system,
the function requires the epoch at which the position in the FK4
system was determined.
Given:
r1950,d1950 double B1950.0 FK4 RA,Dec at epoch (rad)
bepoch double Besselian epoch (e.g. 1979.3)
Returned:
r2000,d2000 double J2000.0 FK5 RA,Dec (rad)
Notes:
1) The epoch bepoch is strictly speaking Besselian, but if a
Julian epoch is supplied the result will be affected only to a
negligible extent.
2) The method is from Appendix 2 of Aoki et al. (1983), but using
the constants of Seidelmann (1992). See the function eraFk425
for a general introduction to the FK4 to FK5 conversion.
3) Conversion from equinox B1950.0 FK4 to equinox J2000.0 FK5 only
is provided for. Conversions for different starting and/or
ending epochs would require additional treatment for precession,
proper motion and E-terms.
4) In the FK4 catalog the proper motions of stars within 10 degrees
of the poles do not embody differential E-terms effects and
should, strictly speaking, be handled in a different manner from
stars outside these regions. However, given the general lack of
homogeneity of the star data available for routine astrometry,
the difficulties of handling positions that may have been
determined from astrometric fields spanning the polar and non-
polar regions, the likelihood that the differential E-terms
effect was not taken into account when allowing for proper motion
in past astrometry, and the undesirability of a discontinuity in
the algorithm, the decision has been made in this ERFA algorithm
to include the effects of differential E-terms on the proper
motions for all stars, whether polar or not. At epoch 2000.0,
and measuring "on the sky" rather than in terms of RA change, the
errors resulting from this simplification are less than
1 milliarcsecond in position and 1 milliarcsecond per century in
proper motion.
References:
Aoki, S. et al., 1983, "Conversion matrix of epoch B1950.0
FK4-based positions of stars to epoch J2000.0 positions in
accordance with the new IAU resolutions". Astron.Astrophys.
128, 263-267.
Seidelmann, P.K. (ed), 1992, "Explanatory Supplement to the
Astronomical Almanac", ISBN 0-935702-68-7.
Called:
eraAnp normalize angle into range 0 to 2pi
eraC2s p-vector to spherical
eraEpb2jd Besselian epoch to Julian date
eraEpj Julian date to Julian epoch
eraPdp scalar product of two p-vectors
eraPmp p-vector minus p-vector
eraPpsp p-vector plus scaled p-vector
eraPvu update a pv-vector
eraS2c spherical to p-vector
This revision: 2020 November 19
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r2000, d2000 = ufunc.fk45z(r1950, d1950, bepoch)
return r2000, d2000
[docs]def fk524(r2000, d2000, dr2000, dd2000, p2000, v2000):
"""
Convert J2000.0 FK5 star catalog data to B1950.0 FK4.
Parameters
----------
r2000 : double array
d2000 : double array
dr2000 : double array
dd2000 : double array
p2000 : double array
v2000 : double array
Returns
-------
r1950 : double array
d1950 : double array
dr1950 : double array
dd1950 : double array
p1950 : double array
v1950 : double array
Notes
-----
Wraps ERFA function ``eraFk524``. The ERFA documentation is::
- - - - - - - - -
e r a F k 5 2 4
- - - - - - - - -
Convert J2000.0 FK5 star catalog data to B1950.0 FK4.
Given: (all J2000.0, FK5)
r2000,d2000 double J2000.0 RA,Dec (rad)
dr2000,dd2000 double J2000.0 proper motions (rad/Jul.yr)
p2000 double parallax (arcsec)
v2000 double radial velocity (km/s, +ve = moving away)
Returned: (all B1950.0, FK4)
r1950,d1950 double B1950.0 RA,Dec (rad)
dr1950,dd1950 double B1950.0 proper motions (rad/trop.yr)
p1950 double parallax (arcsec)
v1950 double radial velocity (km/s, +ve = moving away)
Notes:
1) The proper motions in RA are dRA/dt rather than cos(Dec)*dRA/dt,
and are per year rather than per century.
2) The conversion is somewhat complicated, for several reasons:
. Change of standard epoch from J2000.0 to B1950.0.
. An intermediate transition date of 1984 January 1.0 TT.
. A change of precession model.
. Change of time unit for proper motion (Julian to tropical).
. FK4 positions include the E-terms of aberration, to simplify
the hand computation of annual aberration. FK5 positions
assume a rigorous aberration computation based on the Earth's
barycentric velocity.
. The E-terms also affect proper motions, and in particular cause
objects at large distances to exhibit fictitious proper
motions.
The algorithm is based on Smith et al. (1989) and Yallop et al.
(1989), which presented a matrix method due to Standish (1982) as
developed by Aoki et al. (1983), using Kinoshita's development of
Andoyer's post-Newcomb precession. The numerical constants from
Seidelmann (1992) are used canonically.
4) In the FK4 catalog the proper motions of stars within 10 degrees
of the poles do not embody differential E-terms effects and
should, strictly speaking, be handled in a different manner from
stars outside these regions. However, given the general lack of
homogeneity of the star data available for routine astrometry,
the difficulties of handling positions that may have been
determined from astrometric fields spanning the polar and non-
polar regions, the likelihood that the differential E-terms
effect was not taken into account when allowing for proper motion
in past astrometry, and the undesirability of a discontinuity in
the algorithm, the decision has been made in this ERFA algorithm
to include the effects of differential E-terms on the proper
motions for all stars, whether polar or not. At epoch J2000.0,
and measuring "on the sky" rather than in terms of RA change, the
errors resulting from this simplification are less than
1 milliarcsecond in position and 1 milliarcsecond per century in
proper motion.
Called:
eraAnp normalize angle into range 0 to 2pi
eraPdp scalar product of two p-vectors
eraPm modulus of p-vector
eraPmp p-vector minus p-vector
eraPpp p-vector pluus p-vector
eraPv2s pv-vector to spherical coordinates
eraS2pv spherical coordinates to pv-vector
eraSxp multiply p-vector by scalar
References:
Aoki, S. et al., 1983, "Conversion matrix of epoch B1950.0
FK4-based positions of stars to epoch J2000.0 positions in
accordance with the new IAU resolutions". Astron.Astrophys.
128, 263-267.
Seidelmann, P.K. (ed), 1992, "Explanatory Supplement to the
Astronomical Almanac", ISBN 0-935702-68-7.
Smith, C.A. et al., 1989, "The transformation of astrometric
catalog systems to the equinox J2000.0". Astron.J. 97, 265.
Standish, E.M., 1982, "Conversion of positions and proper motions
from B1950.0 to the IAU system at J2000.0". Astron.Astrophys.,
115, 1, 20-22.
Yallop, B.D. et al., 1989, "Transformation of mean star places
from FK4 B1950.0 to FK5 J2000.0 using matrices in 6-space".
Astron.J. 97, 274.
This revision: 2019 October 3
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r1950, d1950, dr1950, dd1950, p1950, v1950 = ufunc.fk524(
r2000, d2000, dr2000, dd2000, p2000, v2000)
return r1950, d1950, dr1950, dd1950, p1950, v1950
[docs]def fk52h(r5, d5, dr5, dd5, px5, rv5):
"""
Transform FK5 (J2000.0) star data into the Hipparcos system.
Parameters
----------
r5 : double array
d5 : double array
dr5 : double array
dd5 : double array
px5 : double array
rv5 : double array
Returns
-------
rh : double array
dh : double array
drh : double array
ddh : double array
pxh : double array
rvh : double array
Notes
-----
Wraps ERFA function ``eraFk52h``. The ERFA documentation is::
- - - - - - - - -
e r a F k 5 2 h
- - - - - - - - -
Transform FK5 (J2000.0) star data into the Hipparcos system.
Given (all FK5, equinox J2000.0, epoch J2000.0):
r5 double RA (radians)
d5 double Dec (radians)
dr5 double proper motion in RA (dRA/dt, rad/Jyear)
dd5 double proper motion in Dec (dDec/dt, rad/Jyear)
px5 double parallax (arcsec)
rv5 double radial velocity (km/s, positive = receding)
Returned (all Hipparcos, epoch J2000.0):
rh double RA (radians)
dh double Dec (radians)
drh double proper motion in RA (dRA/dt, rad/Jyear)
ddh double proper motion in Dec (dDec/dt, rad/Jyear)
pxh double parallax (arcsec)
rvh double radial velocity (km/s, positive = receding)
Notes:
1) This function transforms FK5 star positions and proper motions
into the system of the Hipparcos catalog.
2) The proper motions in RA are dRA/dt rather than
cos(Dec)*dRA/dt, and are per year rather than per century.
3) The FK5 to Hipparcos transformation is modeled as a pure
rotation and spin; zonal errors in the FK5 catalog are not
taken into account.
4) See also eraH2fk5, eraFk5hz, eraHfk5z.
Called:
eraStarpv star catalog data to space motion pv-vector
eraFk5hip FK5 to Hipparcos rotation and spin
eraRxp product of r-matrix and p-vector
eraPxp vector product of two p-vectors
eraPpp p-vector plus p-vector
eraPvstar space motion pv-vector to star catalog data
Reference:
F.Mignard & M.Froeschle, Astron.Astrophys., 354, 732-739 (2000).
This revision: 2017 October 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rh, dh, drh, ddh, pxh, rvh = ufunc.fk52h(r5, d5, dr5, dd5, px5, rv5)
return rh, dh, drh, ddh, pxh, rvh
[docs]def fk54z(r2000, d2000, bepoch):
"""
Convert a J2000.0 FK5 star position to B1950.0 FK4, assuming zero
proper motion in FK5 and parallax.
Parameters
----------
r2000 : double array
d2000 : double array
bepoch : double array
Returns
-------
r1950 : double array
d1950 : double array
dr1950 : double array
dd1950 : double array
Notes
-----
Wraps ERFA function ``eraFk54z``. The ERFA documentation is::
- - - - - - - - -
e r a F k 5 4 z
- - - - - - - - -
Convert a J2000.0 FK5 star position to B1950.0 FK4, assuming zero
proper motion in FK5 and parallax.
Given:
r2000,d2000 double J2000.0 FK5 RA,Dec (rad)
bepoch double Besselian epoch (e.g. 1950.0)
Returned:
r1950,d1950 double B1950.0 FK4 RA,Dec (rad) at epoch BEPOCH
dr1950,dd1950 double B1950.0 FK4 proper motions (rad/trop.yr)
Notes:
1) In contrast to the eraFk524 function, here the FK5 proper
motions, the parallax and the radial velocity are presumed zero.
2) This function converts a star position from the IAU 1976 FK5
(Fricke) system to the former FK4 (Bessel-Newcomb) system, for
cases such as distant radio sources where it is presumed there is
zero parallax and no proper motion. Because of the E-terms of
aberration, such objects have (in general) non-zero proper motion
in FK4, and the present function returns those fictitious proper
motions.
3) Conversion from B1950.0 FK4 to J2000.0 FK5 only is provided for.
Conversions involving other equinoxes would require additional
treatment for precession.
4) The position returned by this function is in the B1950.0 FK4
reference system but at Besselian epoch BEPOCH. For comparison
with catalogs the BEPOCH argument will frequently be 1950.0. (In
this context the distinction between Besselian and Julian epoch
is insignificant.)
5) The RA component of the returned (fictitious) proper motion is
dRA/dt rather than cos(Dec)*dRA/dt.
Called:
eraAnp normalize angle into range 0 to 2pi
eraC2s p-vector to spherical
eraFk524 FK4 to FK5
eraS2c spherical to p-vector
This revision: 2020 November 19
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r1950, d1950, dr1950, dd1950 = ufunc.fk54z(r2000, d2000, bepoch)
return r1950, d1950, dr1950, dd1950
[docs]def fk5hip():
"""
FK5 to Hipparcos rotation and spin.
Parameters
----------
Returns
-------
r5h : double array
s5h : double array
Notes
-----
Wraps ERFA function ``eraFk5hip``. The ERFA documentation is::
- - - - - - - - - -
e r a F k 5 h i p
- - - - - - - - - -
FK5 to Hipparcos rotation and spin.
Returned:
r5h double[3][3] r-matrix: FK5 rotation wrt Hipparcos (Note 2)
s5h double[3] r-vector: FK5 spin wrt Hipparcos (Note 3)
Notes:
1) This function models the FK5 to Hipparcos transformation as a
pure rotation and spin; zonal errors in the FK5 catalogue are
not taken into account.
2) The r-matrix r5h operates in the sense:
P_Hipparcos = r5h x P_FK5
where P_FK5 is a p-vector in the FK5 frame, and P_Hipparcos is
the equivalent Hipparcos p-vector.
3) The r-vector s5h represents the time derivative of the FK5 to
Hipparcos rotation. The units are radians per year (Julian,
TDB).
Called:
eraRv2m r-vector to r-matrix
Reference:
F.Mignard & M.Froeschle, Astron.Astrophys., 354, 732-739 (2000).
This revision: 2017 October 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r5h, s5h = ufunc.fk5hip()
return r5h, s5h
[docs]def fk5hz(r5, d5, date1, date2):
"""
Transform an FK5 (J2000.0) star position into the system of the
Hipparcos catalogue, assuming zero Hipparcos proper motion.
Parameters
----------
r5 : double array
d5 : double array
date1 : double array
date2 : double array
Returns
-------
rh : double array
dh : double array
Notes
-----
Wraps ERFA function ``eraFk5hz``. The ERFA documentation is::
- - - - - - - - -
e r a F k 5 h z
- - - - - - - - -
Transform an FK5 (J2000.0) star position into the system of the
Hipparcos catalogue, assuming zero Hipparcos proper motion.
Given:
r5 double FK5 RA (radians), equinox J2000.0, at date
d5 double FK5 Dec (radians), equinox J2000.0, at date
date1,date2 double TDB date (Notes 1,2)
Returned:
rh double Hipparcos RA (radians)
dh double Hipparcos Dec (radians)
Notes:
1) This function converts a star position from the FK5 system to
the Hipparcos system, in such a way that the Hipparcos proper
motion is zero. Because such a star has, in general, a non-zero
proper motion in the FK5 system, the function requires the date
at which the position in the FK5 system was determined.
2) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
3) The FK5 to Hipparcos transformation is modeled as a pure
rotation and spin; zonal errors in the FK5 catalogue are not
taken into account.
4) The position returned by this function is in the Hipparcos
reference system but at date date1+date2.
5) See also eraFk52h, eraH2fk5, eraHfk5z.
Called:
eraS2c spherical coordinates to unit vector
eraFk5hip FK5 to Hipparcos rotation and spin
eraSxp multiply p-vector by scalar
eraRv2m r-vector to r-matrix
eraTrxp product of transpose of r-matrix and p-vector
eraPxp vector product of two p-vectors
eraC2s p-vector to spherical
eraAnp normalize angle into range 0 to 2pi
Reference:
F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rh, dh = ufunc.fk5hz(r5, d5, date1, date2)
return rh, dh
[docs]def h2fk5(rh, dh, drh, ddh, pxh, rvh):
"""
Transform Hipparcos star data into the FK5 (J2000.0) system.
Parameters
----------
rh : double array
dh : double array
drh : double array
ddh : double array
pxh : double array
rvh : double array
Returns
-------
r5 : double array
d5 : double array
dr5 : double array
dd5 : double array
px5 : double array
rv5 : double array
Notes
-----
Wraps ERFA function ``eraH2fk5``. The ERFA documentation is::
- - - - - - - - -
e r a H 2 f k 5
- - - - - - - - -
Transform Hipparcos star data into the FK5 (J2000.0) system.
Given (all Hipparcos, epoch J2000.0):
rh double RA (radians)
dh double Dec (radians)
drh double proper motion in RA (dRA/dt, rad/Jyear)
ddh double proper motion in Dec (dDec/dt, rad/Jyear)
pxh double parallax (arcsec)
rvh double radial velocity (km/s, positive = receding)
Returned (all FK5, equinox J2000.0, epoch J2000.0):
r5 double RA (radians)
d5 double Dec (radians)
dr5 double proper motion in RA (dRA/dt, rad/Jyear)
dd5 double proper motion in Dec (dDec/dt, rad/Jyear)
px5 double parallax (arcsec)
rv5 double radial velocity (km/s, positive = receding)
Notes:
1) This function transforms Hipparcos star positions and proper
motions into FK5 J2000.0.
2) The proper motions in RA are dRA/dt rather than
cos(Dec)*dRA/dt, and are per year rather than per century.
3) The FK5 to Hipparcos transformation is modeled as a pure
rotation and spin; zonal errors in the FK5 catalog are not
taken into account.
4) See also eraFk52h, eraFk5hz, eraHfk5z.
Called:
eraStarpv star catalog data to space motion pv-vector
eraFk5hip FK5 to Hipparcos rotation and spin
eraRv2m r-vector to r-matrix
eraRxp product of r-matrix and p-vector
eraTrxp product of transpose of r-matrix and p-vector
eraPxp vector product of two p-vectors
eraPmp p-vector minus p-vector
eraPvstar space motion pv-vector to star catalog data
Reference:
F.Mignard & M.Froeschle, Astron.Astrophys., 354, 732-739 (2000).
This revision: 2017 October 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r5, d5, dr5, dd5, px5, rv5 = ufunc.h2fk5(rh, dh, drh, ddh, pxh, rvh)
return r5, d5, dr5, dd5, px5, rv5
[docs]def hfk5z(rh, dh, date1, date2):
"""
Transform a Hipparcos star position into FK5 J2000.0, assuming
zero Hipparcos proper motion.
Parameters
----------
rh : double array
dh : double array
date1 : double array
date2 : double array
Returns
-------
r5 : double array
d5 : double array
dr5 : double array
dd5 : double array
Notes
-----
Wraps ERFA function ``eraHfk5z``. The ERFA documentation is::
- - - - - - - - -
e r a H f k 5 z
- - - - - - - - -
Transform a Hipparcos star position into FK5 J2000.0, assuming
zero Hipparcos proper motion.
Given:
rh double Hipparcos RA (radians)
dh double Hipparcos Dec (radians)
date1,date2 double TDB date (Note 1)
Returned (all FK5, equinox J2000.0, date date1+date2):
r5 double RA (radians)
d5 double Dec (radians)
dr5 double FK5 RA proper motion (rad/year, Note 4)
dd5 double Dec proper motion (rad/year, Note 4)
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) The proper motion in RA is dRA/dt rather than cos(Dec)*dRA/dt.
3) The FK5 to Hipparcos transformation is modeled as a pure rotation
and spin; zonal errors in the FK5 catalogue are not taken into
account.
4) It was the intention that Hipparcos should be a close
approximation to an inertial frame, so that distant objects have
zero proper motion; such objects have (in general) non-zero
proper motion in FK5, and this function returns those fictitious
proper motions.
5) The position returned by this function is in the FK5 J2000.0
reference system but at date date1+date2.
6) See also eraFk52h, eraH2fk5, eraFk5zhz.
Called:
eraS2c spherical coordinates to unit vector
eraFk5hip FK5 to Hipparcos rotation and spin
eraRxp product of r-matrix and p-vector
eraSxp multiply p-vector by scalar
eraRxr product of two r-matrices
eraTrxp product of transpose of r-matrix and p-vector
eraPxp vector product of two p-vectors
eraPv2s pv-vector to spherical
eraAnp normalize angle into range 0 to 2pi
Reference:
F.Mignard & M.Froeschle, 2000, Astron.Astrophys. 354, 732-739.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r5, d5, dr5, dd5 = ufunc.hfk5z(rh, dh, date1, date2)
return r5, d5, dr5, dd5
[docs]def starpm(ra1, dec1, pmr1, pmd1, px1, rv1, ep1a, ep1b, ep2a, ep2b):
"""
Star proper motion: update star catalog data for space motion.
Parameters
----------
ra1 : double array
dec1 : double array
pmr1 : double array
pmd1 : double array
px1 : double array
rv1 : double array
ep1a : double array
ep1b : double array
ep2a : double array
ep2b : double array
Returns
-------
ra2 : double array
dec2 : double array
pmr2 : double array
pmd2 : double array
px2 : double array
rv2 : double array
Notes
-----
Wraps ERFA function ``eraStarpm``. The ERFA documentation is::
- - - - - - - - - -
e r a S t a r p m
- - - - - - - - - -
Star proper motion: update star catalog data for space motion.
Given:
ra1 double right ascension (radians), before
dec1 double declination (radians), before
pmr1 double RA proper motion (radians/year), before
pmd1 double Dec proper motion (radians/year), before
px1 double parallax (arcseconds), before
rv1 double radial velocity (km/s, +ve = receding), before
ep1a double "before" epoch, part A (Note 1)
ep1b double "before" epoch, part B (Note 1)
ep2a double "after" epoch, part A (Note 1)
ep2b double "after" epoch, part B (Note 1)
Returned:
ra2 double right ascension (radians), after
dec2 double declination (radians), after
pmr2 double RA proper motion (radians/year), after
pmd2 double Dec proper motion (radians/year), after
px2 double parallax (arcseconds), after
rv2 double radial velocity (km/s, +ve = receding), after
Returned (function value):
int status:
-1 = system error (should not occur)
0 = no warnings or errors
1 = distance overridden (Note 6)
2 = excessive velocity (Note 7)
4 = solution didn't converge (Note 8)
else = binary logical OR of the above warnings
Notes:
1) The starting and ending TDB dates ep1a+ep1b and ep2a+ep2b are
Julian Dates, apportioned in any convenient way between the two
parts (A and B). For example, JD(TDB)=2450123.7 could be
expressed in any of these ways, among others:
epna epnb
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) In accordance with normal star-catalog conventions, the object's
right ascension and declination are freed from the effects of
secular aberration. The frame, which is aligned to the catalog
equator and equinox, is Lorentzian and centered on the SSB.
The proper motions are the rate of change of the right ascension
and declination at the catalog epoch and are in radians per TDB
Julian year.
The parallax and radial velocity are in the same frame.
3) Care is needed with units. The star coordinates are in radians
and the proper motions in radians per Julian year, but the
parallax is in arcseconds.
4) The RA proper motion is in terms of coordinate angle, not true
angle. If the catalog uses arcseconds for both RA and Dec proper
motions, the RA proper motion will need to be divided by cos(Dec)
before use.
5) Straight-line motion at constant speed, in the inertial frame,
is assumed.
6) An extremely small (or zero or negative) parallax is interpreted
to mean that the object is on the "celestial sphere", the radius
of which is an arbitrary (large) value (see the eraStarpv
function for the value used). When the distance is overridden in
this way, the status, initially zero, has 1 added to it.
7) If the space velocity is a significant fraction of c (see the
constant VMAX in the function eraStarpv), it is arbitrarily set
to zero. When this action occurs, 2 is added to the status.
8) The relativistic adjustment carried out in the eraStarpv function
involves an iterative calculation. If the process fails to
converge within a set number of iterations, 4 is added to the
status.
Called:
eraStarpv star catalog data to space motion pv-vector
eraPvu update a pv-vector
eraPdp scalar product of two p-vectors
eraPvstar space motion pv-vector to star catalog data
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ra2, dec2, pmr2, pmd2, px2, rv2, c_retval = ufunc.starpm(
ra1, dec1, pmr1, pmd1, px1, rv1, ep1a, ep1b, ep2a, ep2b)
check_errwarn(c_retval, 'starpm')
return ra2, dec2, pmr2, pmd2, px2, rv2
STATUS_CODES['starpm'] = {
-1: 'system error (should not occur)',
0: 'no warnings or errors',
1: 'distance overridden (Note 6)',
2: 'excessive velocity (Note 7)',
4: "solution didn't converge (Note 8)",
'else': 'binary logical OR of the above warnings',
}
[docs]def eceq06(date1, date2, dl, db):
"""
Transformation from ecliptic coordinates (mean equinox and ecliptic
of date) to ICRS RA,Dec, using the IAU 2006 precession model.
Parameters
----------
date1 : double array
date2 : double array
dl : double array
db : double array
Returns
-------
dr : double array
dd : double array
Notes
-----
Wraps ERFA function ``eraEceq06``. The ERFA documentation is::
- - - - - - - - - -
e r a E c e q 0 6
- - - - - - - - - -
Transformation from ecliptic coordinates (mean equinox and ecliptic
of date) to ICRS RA,Dec, using the IAU 2006 precession model.
Given:
date1,date2 double TT as a 2-part Julian date (Note 1)
dl,db double ecliptic longitude and latitude (radians)
Returned:
dr,dd double ICRS right ascension and declination (radians)
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) No assumptions are made about whether the coordinates represent
starlight and embody astrometric effects such as parallax or
aberration.
3) The transformation is approximately that from ecliptic longitude
and latitude (mean equinox and ecliptic of date) to mean J2000.0
right ascension and declination, with only frame bias (always
less than 25 mas) to disturb this classical picture.
Called:
eraS2c spherical coordinates to unit vector
eraEcm06 J2000.0 to ecliptic rotation matrix, IAU 2006
eraTrxp product of transpose of r-matrix and p-vector
eraC2s unit vector to spherical coordinates
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dr, dd = ufunc.eceq06(date1, date2, dl, db)
return dr, dd
[docs]def ecm06(date1, date2):
"""
ICRS equatorial to ecliptic rotation matrix, IAU 2006.
Parameters
----------
date1 : double array
date2 : double array
Returns
-------
rm : double array
Notes
-----
Wraps ERFA function ``eraEcm06``. The ERFA documentation is::
- - - - - - - - -
e r a E c m 0 6
- - - - - - - - -
ICRS equatorial to ecliptic rotation matrix, IAU 2006.
Given:
date1,date2 double TT as a 2-part Julian date (Note 1)
Returned:
rm double[3][3] ICRS to ecliptic rotation matrix
Notes:
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
1) The matrix is in the sense
E_ep = rm x P_ICRS,
where P_ICRS is a vector with respect to ICRS right ascension
and declination axes and E_ep is the same vector with respect to
the (inertial) ecliptic and equinox of date.
2) P_ICRS is a free vector, merely a direction, typically of unit
magnitude, and not bound to any particular spatial origin, such
as the Earth, Sun or SSB. No assumptions are made about whether
it represents starlight and embodies astrometric effects such as
parallax or aberration. The transformation is approximately that
between mean J2000.0 right ascension and declination and ecliptic
longitude and latitude, with only frame bias (always less than
25 mas) to disturb this classical picture.
Called:
eraObl06 mean obliquity, IAU 2006
eraPmat06 PB matrix, IAU 2006
eraIr initialize r-matrix to identity
eraRx rotate around X-axis
eraRxr product of two r-matrices
This revision: 2015 December 11
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rm = ufunc.ecm06(date1, date2)
return rm
[docs]def eqec06(date1, date2, dr, dd):
"""
Transformation from ICRS equatorial coordinates to ecliptic
coordinates (mean equinox and ecliptic of date) using IAU 2006
precession model.
Parameters
----------
date1 : double array
date2 : double array
dr : double array
dd : double array
Returns
-------
dl : double array
db : double array
Notes
-----
Wraps ERFA function ``eraEqec06``. The ERFA documentation is::
- - - - - - - - - -
e r a E q e c 0 6
- - - - - - - - - -
Transformation from ICRS equatorial coordinates to ecliptic
coordinates (mean equinox and ecliptic of date) using IAU 2006
precession model.
Given:
date1,date2 double TT as a 2-part Julian date (Note 1)
dr,dd double ICRS right ascension and declination (radians)
Returned:
dl,db double ecliptic longitude and latitude (radians)
1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
2) No assumptions are made about whether the coordinates represent
starlight and embody astrometric effects such as parallax or
aberration.
3) The transformation is approximately that from mean J2000.0 right
ascension and declination to ecliptic longitude and latitude
(mean equinox and ecliptic of date), with only frame bias (always
less than 25 mas) to disturb this classical picture.
Called:
eraS2c spherical coordinates to unit vector
eraEcm06 J2000.0 to ecliptic rotation matrix, IAU 2006
eraRxp product of r-matrix and p-vector
eraC2s unit vector to spherical coordinates
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dl, db = ufunc.eqec06(date1, date2, dr, dd)
return dl, db
[docs]def lteceq(epj, dl, db):
"""
Transformation from ecliptic coordinates (mean equinox and ecliptic
of date) to ICRS RA,Dec, using a long-term precession model.
Parameters
----------
epj : double array
dl : double array
db : double array
Returns
-------
dr : double array
dd : double array
Notes
-----
Wraps ERFA function ``eraLteceq``. The ERFA documentation is::
- - - - - - - - - -
e r a L t e c e q
- - - - - - - - - -
Transformation from ecliptic coordinates (mean equinox and ecliptic
of date) to ICRS RA,Dec, using a long-term precession model.
Given:
epj double Julian epoch (TT)
dl,db double ecliptic longitude and latitude (radians)
Returned:
dr,dd double ICRS right ascension and declination (radians)
1) No assumptions are made about whether the coordinates represent
starlight and embody astrometric effects such as parallax or
aberration.
2) The transformation is approximately that from ecliptic longitude
and latitude (mean equinox and ecliptic of date) to mean J2000.0
right ascension and declination, with only frame bias (always
less than 25 mas) to disturb this classical picture.
3) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
Called:
eraS2c spherical coordinates to unit vector
eraLtecm J2000.0 to ecliptic rotation matrix, long term
eraTrxp product of transpose of r-matrix and p-vector
eraC2s unit vector to spherical coordinates
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dr, dd = ufunc.lteceq(epj, dl, db)
return dr, dd
[docs]def ltecm(epj):
"""
ICRS equatorial to ecliptic rotation matrix, long-term.
Parameters
----------
epj : double array
Returns
-------
rm : double array
Notes
-----
Wraps ERFA function ``eraLtecm``. The ERFA documentation is::
- - - - - - - - -
e r a L t e c m
- - - - - - - - -
ICRS equatorial to ecliptic rotation matrix, long-term.
Given:
epj double Julian epoch (TT)
Returned:
rm double[3][3] ICRS to ecliptic rotation matrix
Notes:
1) The matrix is in the sense
E_ep = rm x P_ICRS,
where P_ICRS is a vector with respect to ICRS right ascension
and declination axes and E_ep is the same vector with respect to
the (inertial) ecliptic and equinox of epoch epj.
2) P_ICRS is a free vector, merely a direction, typically of unit
magnitude, and not bound to any particular spatial origin, such
as the Earth, Sun or SSB. No assumptions are made about whether
it represents starlight and embodies astrometric effects such as
parallax or aberration. The transformation is approximately that
between mean J2000.0 right ascension and declination and ecliptic
longitude and latitude, with only frame bias (always less than
25 mas) to disturb this classical picture.
3) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
Called:
eraLtpequ equator pole, long term
eraLtpecl ecliptic pole, long term
eraPxp vector product
eraPn normalize vector
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2015 December 6
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rm = ufunc.ltecm(epj)
return rm
[docs]def lteqec(epj, dr, dd):
"""
Transformation from ICRS equatorial coordinates to ecliptic
coordinates (mean equinox and ecliptic of date) using a long-term
precession model.
Parameters
----------
epj : double array
dr : double array
dd : double array
Returns
-------
dl : double array
db : double array
Notes
-----
Wraps ERFA function ``eraLteqec``. The ERFA documentation is::
- - - - - - - - - -
e r a L t e q e c
- - - - - - - - - -
Transformation from ICRS equatorial coordinates to ecliptic
coordinates (mean equinox and ecliptic of date) using a long-term
precession model.
Given:
epj double Julian epoch (TT)
dr,dd double ICRS right ascension and declination (radians)
Returned:
dl,db double ecliptic longitude and latitude (radians)
1) No assumptions are made about whether the coordinates represent
starlight and embody astrometric effects such as parallax or
aberration.
2) The transformation is approximately that from mean J2000.0 right
ascension and declination to ecliptic longitude and latitude
(mean equinox and ecliptic of date), with only frame bias (always
less than 25 mas) to disturb this classical picture.
3) The Vondrak et al. (2011, 2012) 400 millennia precession model
agrees with the IAU 2006 precession at J2000.0 and stays within
100 microarcseconds during the 20th and 21st centuries. It is
accurate to a few arcseconds throughout the historical period,
worsening to a few tenths of a degree at the end of the
+/- 200,000 year time span.
Called:
eraS2c spherical coordinates to unit vector
eraLtecm J2000.0 to ecliptic rotation matrix, long term
eraRxp product of r-matrix and p-vector
eraC2s unit vector to spherical coordinates
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
References:
Vondrak, J., Capitaine, N. and Wallace, P., 2011, New precession
expressions, valid for long time intervals, Astron.Astrophys. 534,
A22
Vondrak, J., Capitaine, N. and Wallace, P., 2012, New precession
expressions, valid for long time intervals (Corrigendum),
Astron.Astrophys. 541, C1
This revision: 2016 February 9
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dl, db = ufunc.lteqec(epj, dr, dd)
return dl, db
[docs]def g2icrs(dl, db):
"""
Transformation from Galactic Coordinates to ICRS.
Parameters
----------
dl : double array
db : double array
Returns
-------
dr : double array
dd : double array
Notes
-----
Wraps ERFA function ``eraG2icrs``. The ERFA documentation is::
- - - - - - - - - -
e r a G 2 i c r s
- - - - - - - - - -
Transformation from Galactic Coordinates to ICRS.
Given:
dl double galactic longitude (radians)
db double galactic latitude (radians)
Returned:
dr double ICRS right ascension (radians)
dd double ICRS declination (radians)
Notes:
1) The IAU 1958 system of Galactic coordinates was defined with
respect to the now obsolete reference system FK4 B1950.0. When
interpreting the system in a modern context, several factors have
to be taken into account:
. The inclusion in FK4 positions of the E-terms of aberration.
. The distortion of the FK4 proper motion system by differential
Galactic rotation.
. The use of the B1950.0 equinox rather than the now-standard
J2000.0.
. The frame bias between ICRS and the J2000.0 mean place system.
The Hipparcos Catalogue (Perryman & ESA 1997) provides a rotation
matrix that transforms directly between ICRS and Galactic
coordinates with the above factors taken into account. The
matrix is derived from three angles, namely the ICRS coordinates
of the Galactic pole and the longitude of the ascending node of
the galactic equator on the ICRS equator. They are given in
degrees to five decimal places and for canonical purposes are
regarded as exact. In the Hipparcos Catalogue the matrix
elements are given to 10 decimal places (about 20 microarcsec).
In the present ERFA function the matrix elements have been
recomputed from the canonical three angles and are given to 30
decimal places.
2) The inverse transformation is performed by the function eraIcrs2g.
Called:
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
eraS2c spherical coordinates to unit vector
eraTrxp product of transpose of r-matrix and p-vector
eraC2s p-vector to spherical
Reference:
Perryman M.A.C. & ESA, 1997, ESA SP-1200, The Hipparcos and Tycho
catalogues. Astrometric and photometric star catalogues
derived from the ESA Hipparcos Space Astrometry Mission. ESA
Publications Division, Noordwijk, Netherlands.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dr, dd = ufunc.g2icrs(dl, db)
return dr, dd
[docs]def icrs2g(dr, dd):
"""
Transformation from ICRS to Galactic Coordinates.
Parameters
----------
dr : double array
dd : double array
Returns
-------
dl : double array
db : double array
Notes
-----
Wraps ERFA function ``eraIcrs2g``. The ERFA documentation is::
- - - - - - - - - -
e r a I c r s 2 g
- - - - - - - - - -
Transformation from ICRS to Galactic Coordinates.
Given:
dr double ICRS right ascension (radians)
dd double ICRS declination (radians)
Returned:
dl double galactic longitude (radians)
db double galactic latitude (radians)
Notes:
1) The IAU 1958 system of Galactic coordinates was defined with
respect to the now obsolete reference system FK4 B1950.0. When
interpreting the system in a modern context, several factors have
to be taken into account:
. The inclusion in FK4 positions of the E-terms of aberration.
. The distortion of the FK4 proper motion system by differential
Galactic rotation.
. The use of the B1950.0 equinox rather than the now-standard
J2000.0.
. The frame bias between ICRS and the J2000.0 mean place system.
The Hipparcos Catalogue (Perryman & ESA 1997) provides a rotation
matrix that transforms directly between ICRS and Galactic
coordinates with the above factors taken into account. The
matrix is derived from three angles, namely the ICRS coordinates
of the Galactic pole and the longitude of the ascending node of
the galactic equator on the ICRS equator. They are given in
degrees to five decimal places and for canonical purposes are
regarded as exact. In the Hipparcos Catalogue the matrix
elements are given to 10 decimal places (about 20 microarcsec).
In the present ERFA function the matrix elements have been
recomputed from the canonical three angles and are given to 30
decimal places.
2) The inverse transformation is performed by the function eraG2icrs.
Called:
eraAnp normalize angle into range 0 to 2pi
eraAnpm normalize angle into range +/- pi
eraS2c spherical coordinates to unit vector
eraRxp product of r-matrix and p-vector
eraC2s p-vector to spherical
Reference:
Perryman M.A.C. & ESA, 1997, ESA SP-1200, The Hipparcos and Tycho
catalogues. Astrometric and photometric star catalogues
derived from the ESA Hipparcos Space Astrometry Mission. ESA
Publications Division, Noordwijk, Netherlands.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
dl, db = ufunc.icrs2g(dr, dd)
return dl, db
[docs]def eform(n):
"""
Earth reference ellipsoids.
Parameters
----------
n : int array
Returns
-------
a : double array
f : double array
Notes
-----
Wraps ERFA function ``eraEform``. The ERFA documentation is::
- - - - - - - - -
e r a E f o r m
- - - - - - - - -
Earth reference ellipsoids.
Given:
n int ellipsoid identifier (Note 1)
Returned:
a double equatorial radius (meters, Note 2)
f double flattening (Note 2)
Returned (function value):
int status: 0 = OK
-1 = illegal identifier (Note 3)
Notes:
1) The identifier n is a number that specifies the choice of
reference ellipsoid. The following are supported:
n ellipsoid
1 ERFA_WGS84
2 ERFA_GRS80
3 ERFA_WGS72
The n value has no significance outside the ERFA software. For
convenience, symbols ERFA_WGS84 etc. are defined in erfam.h.
2) The ellipsoid parameters are returned in the form of equatorial
radius in meters (a) and flattening (f). The latter is a number
around 0.00335, i.e. around 1/298.
3) For the case where an unsupported n value is supplied, zero a and
f are returned, as well as error status.
References:
Department of Defense World Geodetic System 1984, National
Imagery and Mapping Agency Technical Report 8350.2, Third
Edition, p3-2.
Moritz, H., Bull. Geodesique 66-2, 187 (1992).
The Department of Defense World Geodetic System 1972, World
Geodetic System Committee, May 1974.
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
p220.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
a, f, c_retval = ufunc.eform(n)
check_errwarn(c_retval, 'eform')
return a, f
STATUS_CODES['eform'] = {
0: 'OK',
-1: 'illegal identifier (Note 3)',
}
[docs]def gc2gd(n, xyz):
"""
Transform geocentric coordinates to geodetic using the specified
reference ellipsoid.
Parameters
----------
n : int array
xyz : double array
Returns
-------
elong : double array
phi : double array
height : double array
Notes
-----
Wraps ERFA function ``eraGc2gd``. The ERFA documentation is::
- - - - - - - - -
e r a G c 2 g d
- - - - - - - - -
Transform geocentric coordinates to geodetic using the specified
reference ellipsoid.
Given:
n int ellipsoid identifier (Note 1)
xyz double[3] geocentric vector (Note 2)
Returned:
elong double longitude (radians, east +ve, Note 3)
phi double latitude (geodetic, radians, Note 3)
height double height above ellipsoid (geodetic, Notes 2,3)
Returned (function value):
int status: 0 = OK
-1 = illegal identifier (Note 3)
-2 = internal error (Note 3)
Notes:
1) The identifier n is a number that specifies the choice of
reference ellipsoid. The following are supported:
n ellipsoid
1 ERFA_WGS84
2 ERFA_GRS80
3 ERFA_WGS72
The n value has no significance outside the ERFA software. For
convenience, symbols ERFA_WGS84 etc. are defined in erfam.h.
2) The geocentric vector (xyz, given) and height (height, returned)
are in meters.
3) An error status -1 means that the identifier n is illegal. An
error status -2 is theoretically impossible. In all error cases,
all three results are set to -1e9.
4) The inverse transformation is performed in the function eraGd2gc.
Called:
eraEform Earth reference ellipsoids
eraGc2gde geocentric to geodetic transformation, general
This revision: 2013 September 1
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
elong, phi, height, c_retval = ufunc.gc2gd(n, xyz)
check_errwarn(c_retval, 'gc2gd')
return elong, phi, height
STATUS_CODES['gc2gd'] = {
0: 'OK',
-1: 'illegal identifier (Note 3)',
-2: 'internal error (Note 3)',
}
[docs]def gc2gde(a, f, xyz):
"""
Transform geocentric coordinates to geodetic for a reference
ellipsoid of specified form.
Parameters
----------
a : double array
f : double array
xyz : double array
Returns
-------
elong : double array
phi : double array
height : double array
Notes
-----
Wraps ERFA function ``eraGc2gde``. The ERFA documentation is::
- - - - - - - - - -
e r a G c 2 g d e
- - - - - - - - - -
Transform geocentric coordinates to geodetic for a reference
ellipsoid of specified form.
Given:
a double equatorial radius (Notes 2,4)
f double flattening (Note 3)
xyz double[3] geocentric vector (Note 4)
Returned:
elong double longitude (radians, east +ve)
phi double latitude (geodetic, radians)
height double height above ellipsoid (geodetic, Note 4)
Returned (function value):
int status: 0 = OK
-1 = illegal f
-2 = illegal a
Notes:
1) This function is based on the GCONV2H Fortran subroutine by
Toshio Fukushima (see reference).
2) The equatorial radius, a, can be in any units, but meters is
the conventional choice.
3) The flattening, f, is (for the Earth) a value around 0.00335,
i.e. around 1/298.
4) The equatorial radius, a, and the geocentric vector, xyz,
must be given in the same units, and determine the units of
the returned height, height.
5) If an error occurs (status < 0), elong, phi and height are
unchanged.
6) The inverse transformation is performed in the function
eraGd2gce.
7) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
more conveniently be performed by calling eraGc2gd, which uses a
numerical code to identify the required A and F values.
Reference:
Fukushima, T., "Transformation from Cartesian to geodetic
coordinates accelerated by Halley's method", J.Geodesy (2006)
79: 689-693
This revision: 2014 November 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
elong, phi, height, c_retval = ufunc.gc2gde(a, f, xyz)
check_errwarn(c_retval, 'gc2gde')
return elong, phi, height
STATUS_CODES['gc2gde'] = {
0: 'OK',
-1: 'illegal f',
-2: 'illegal a',
}
[docs]def gd2gc(n, elong, phi, height):
"""
Transform geodetic coordinates to geocentric using the specified
reference ellipsoid.
Parameters
----------
n : int array
elong : double array
phi : double array
height : double array
Returns
-------
xyz : double array
Notes
-----
Wraps ERFA function ``eraGd2gc``. The ERFA documentation is::
- - - - - - - - -
e r a G d 2 g c
- - - - - - - - -
Transform geodetic coordinates to geocentric using the specified
reference ellipsoid.
Given:
n int ellipsoid identifier (Note 1)
elong double longitude (radians, east +ve)
phi double latitude (geodetic, radians, Note 3)
height double height above ellipsoid (geodetic, Notes 2,3)
Returned:
xyz double[3] geocentric vector (Note 2)
Returned (function value):
int status: 0 = OK
-1 = illegal identifier (Note 3)
-2 = illegal case (Note 3)
Notes:
1) The identifier n is a number that specifies the choice of
reference ellipsoid. The following are supported:
n ellipsoid
1 ERFA_WGS84
2 ERFA_GRS80
3 ERFA_WGS72
The n value has no significance outside the ERFA software. For
convenience, symbols ERFA_WGS84 etc. are defined in erfam.h.
2) The height (height, given) and the geocentric vector (xyz,
returned) are in meters.
3) No validation is performed on the arguments elong, phi and
height. An error status -1 means that the identifier n is
illegal. An error status -2 protects against cases that would
lead to arithmetic exceptions. In all error cases, xyz is set
to zeros.
4) The inverse transformation is performed in the function eraGc2gd.
Called:
eraEform Earth reference ellipsoids
eraGd2gce geodetic to geocentric transformation, general
eraZp zero p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
xyz, c_retval = ufunc.gd2gc(n, elong, phi, height)
check_errwarn(c_retval, 'gd2gc')
return xyz
STATUS_CODES['gd2gc'] = {
0: 'OK',
-1: 'illegal identifier (Note 3)',
-2: 'illegal case (Note 3)',
}
[docs]def gd2gce(a, f, elong, phi, height):
"""
Transform geodetic coordinates to geocentric for a reference
ellipsoid of specified form.
Parameters
----------
a : double array
f : double array
elong : double array
phi : double array
height : double array
Returns
-------
xyz : double array
Notes
-----
Wraps ERFA function ``eraGd2gce``. The ERFA documentation is::
- - - - - - - - - -
e r a G d 2 g c e
- - - - - - - - - -
Transform geodetic coordinates to geocentric for a reference
ellipsoid of specified form.
Given:
a double equatorial radius (Notes 1,4)
f double flattening (Notes 2,4)
elong double longitude (radians, east +ve)
phi double latitude (geodetic, radians, Note 4)
height double height above ellipsoid (geodetic, Notes 3,4)
Returned:
xyz double[3] geocentric vector (Note 3)
Returned (function value):
int status: 0 = OK
-1 = illegal case (Note 4)
Notes:
1) The equatorial radius, a, can be in any units, but meters is
the conventional choice.
2) The flattening, f, is (for the Earth) a value around 0.00335,
i.e. around 1/298.
3) The equatorial radius, a, and the height, height, must be
given in the same units, and determine the units of the
returned geocentric vector, xyz.
4) No validation is performed on individual arguments. The error
status -1 protects against (unrealistic) cases that would lead
to arithmetic exceptions. If an error occurs, xyz is unchanged.
5) The inverse transformation is performed in the function
eraGc2gde.
6) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
more conveniently be performed by calling eraGd2gc, which uses a
numerical code to identify the required a and f values.
References:
Green, R.M., Spherical Astronomy, Cambridge University Press,
(1985) Section 4.5, p96.
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992),
Section 4.22, p202.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
xyz, c_retval = ufunc.gd2gce(a, f, elong, phi, height)
check_errwarn(c_retval, 'gd2gce')
return xyz
STATUS_CODES['gd2gce'] = {
0: 'OK',
-1: 'illegal case (Note 4)Notes:',
}
[docs]def d2dtf(scale, ndp, d1, d2):
"""
Format for output a 2-part Julian Date (or in the case of UTC a
quasi-JD form that includes special provision for leap seconds).
Parameters
----------
scale : const char array
ndp : int array
d1 : double array
d2 : double array
Returns
-------
iy : int array
im : int array
id : int array
ihmsf : int array
Notes
-----
Wraps ERFA function ``eraD2dtf``. The ERFA documentation is::
- - - - - - - - -
e r a D 2 d t f
- - - - - - - - -
Format for output a 2-part Julian Date (or in the case of UTC a
quasi-JD form that includes special provision for leap seconds).
Given:
scale char[] time scale ID (Note 1)
ndp int resolution (Note 2)
d1,d2 double time as a 2-part Julian Date (Notes 3,4)
Returned:
iy,im,id int year, month, day in Gregorian calendar (Note 5)
ihmsf int[4] hours, minutes, seconds, fraction (Note 1)
Returned (function value):
int status: +1 = dubious year (Note 5)
0 = OK
-1 = unacceptable date (Note 6)
Notes:
1) scale identifies the time scale. Only the value "UTC" (in upper
case) is significant, and enables handling of leap seconds (see
Note 4).
2) ndp is the number of decimal places in the seconds field, and can
have negative as well as positive values, such as:
ndp resolution
-4 1 00 00
-3 0 10 00
-2 0 01 00
-1 0 00 10
0 0 00 01
1 0 00 00.1
2 0 00 00.01
3 0 00 00.001
The limits are platform dependent, but a safe range is -5 to +9.
3) d1+d2 is Julian Date, apportioned in any convenient way between
the two arguments, for example where d1 is the Julian Day Number
and d2 is the fraction of a day. In the case of UTC, where the
use of JD is problematical, special conventions apply: see the
next note.
4) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The ERFA internal convention is that
the quasi-JD day represents UTC days whether the length is 86399,
86400 or 86401 SI seconds. In the 1960-1972 era there were
smaller jumps (in either direction) each time the linear UTC(TAI)
expression was changed, and these "mini-leaps" are also included
in the ERFA convention.
5) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
6) For calendar conventions and limitations, see eraCal2jd.
Called:
eraJd2cal JD to Gregorian calendar
eraD2tf decompose days to hms
eraDat delta(AT) = TAI-UTC
This revision: 2021 February 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
iy, im, id, ihmsf, c_retval = ufunc.d2dtf(scale, ndp, d1, d2)
check_errwarn(c_retval, 'd2dtf')
return iy, im, id, ihmsf
STATUS_CODES['d2dtf'] = {
1: 'dubious year (Note 5)',
0: 'OK',
-1: 'unacceptable date (Note 6)',
}
[docs]def dat(iy, im, id, fd):
"""
For a given UTC date, calculate Delta(AT) = TAI-UTC.
Parameters
----------
iy : int array
im : int array
id : int array
fd : double array
Returns
-------
deltat : double array
Notes
-----
Wraps ERFA function ``eraDat``. The ERFA documentation is::
- - - - - - -
e r a D a t
- - - - - - -
For a given UTC date, calculate Delta(AT) = TAI-UTC.
:------------------------------------------:
: :
: IMPORTANT :
: :
: A new version of this function must be :
: produced whenever a new leap second is :
: announced. There are four items to :
: change on each such occasion: :
: :
: 1) A new line must be added to the set :
: of statements that initialize the :
: array "changes". :
: :
: 2) The constant IYV must be set to the :
: current year. :
: :
: 3) The "Latest leap second" comment :
: below must be set to the new leap :
: second date. :
: :
: 4) The "This revision" comment, later, :
: must be set to the current date. :
: :
: Change (2) must also be carried out :
: whenever the function is re-issued, :
: even if no leap seconds have been :
: added. :
: :
: Latest leap second: 2016 December 31 :
: :
:__________________________________________:
Given:
iy int UTC: year (Notes 1 and 2)
im int month (Note 2)
id int day (Notes 2 and 3)
fd double fraction of day (Note 4)
Returned:
deltat double TAI minus UTC, seconds
Returned (function value):
int status (Note 5):
1 = dubious year (Note 1)
0 = OK
-1 = bad year
-2 = bad month
-3 = bad day (Note 3)
-4 = bad fraction (Note 4)
-5 = internal error (Note 5)
Notes:
1) UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper
to call the function with an earlier date. If this is attempted,
zero is returned together with a warning status.
Because leap seconds cannot, in principle, be predicted in
advance, a reliable check for dates beyond the valid range is
impossible. To guard against gross errors, a year five or more
after the release year of the present function (see the constant
IYV) is considered dubious. In this case a warning status is
returned but the result is computed in the normal way.
For both too-early and too-late years, the warning status is +1.
This is distinct from the error status -1, which signifies a year
so early that JD could not be computed.
2) If the specified date is for a day which ends with a leap second,
the TAI-UTC value returned is for the period leading up to the
leap second. If the date is for a day which begins as a leap
second ends, the TAI-UTC returned is for the period following the
leap second.
3) The day number must be in the normal calendar range, for example
1 through 30 for April. The "almanac" convention of allowing
such dates as January 0 and December 32 is not supported in this
function, in order to avoid confusion near leap seconds.
4) The fraction of day is used only for dates before the
introduction of leap seconds, the first of which occurred at the
end of 1971. It is tested for validity (0 to 1 is the valid
range) even if not used; if invalid, zero is used and status -4
is returned. For many applications, setting fd to zero is
acceptable; the resulting error is always less than 3 ms (and
occurs only pre-1972).
5) The status value returned in the case where there are multiple
errors refers to the first error detected. For example, if the
month and day are 13 and 32 respectively, status -2 (bad month)
will be returned. The "internal error" status refers to a
case that is impossible but causes some compilers to issue a
warning.
6) In cases where a valid result is not available, zero is returned.
References:
1) For dates from 1961 January 1 onwards, the expressions from the
file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used.
2) The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of
the 1992 Explanatory Supplement.
Called:
eraCal2jd Gregorian calendar to JD
This revision: 2020 May 31
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
deltat, c_retval = ufunc.dat(iy, im, id, fd)
check_errwarn(c_retval, 'dat')
return deltat
STATUS_CODES['dat'] = {
1: 'dubious year (Note 1)',
0: 'OK',
-1: 'bad year',
-2: 'bad month',
-3: 'bad day (Note 3)',
-4: 'bad fraction (Note 4)',
-5: 'internal error (Note 5)',
}
[docs]def dtdb(date1, date2, ut, elong, u, v):
"""
An approximation to TDB-TT, the difference between barycentric
dynamical time and terrestrial time, for an observer on the Earth.
Parameters
----------
date1 : double array
date2 : double array
ut : double array
elong : double array
u : double array
v : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraDtdb``. The ERFA documentation is::
- - - - - - - -
e r a D t d b
- - - - - - - -
An approximation to TDB-TT, the difference between barycentric
dynamical time and terrestrial time, for an observer on the Earth.
The different time scales - proper, coordinate and realized - are
related to each other:
TAI <- physically realized
:
offset <- observed (nominally +32.184s)
:
TT <- terrestrial time
:
rate adjustment (L_G) <- definition of TT
:
TCG <- time scale for GCRS
:
"periodic" terms <- eraDtdb is an implementation
:
rate adjustment (L_C) <- function of solar-system ephemeris
:
TCB <- time scale for BCRS
:
rate adjustment (-L_B) <- definition of TDB
:
TDB <- TCB scaled to track TT
:
"periodic" terms <- -eraDtdb is an approximation
:
TT <- terrestrial time
Adopted values for the various constants can be found in the IERS
Conventions (McCarthy & Petit 2003).
Given:
date1,date2 double date, TDB (Notes 1-3)
ut double universal time (UT1, fraction of one day)
elong double longitude (east positive, radians)
u double distance from Earth spin axis (km)
v double distance north of equatorial plane (km)
Returned (function value):
double TDB-TT (seconds)
Notes:
1) The date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments. For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:
date1 date2
2450123.7 0.0 (JD method)
2451545.0 -1421.3 (J2000 method)
2400000.5 50123.2 (MJD method)
2450123.5 0.2 (date & time method)
The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable. The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution. The MJD method and the date & time methods
are both good compromises between resolution and convenience.
Although the date is, formally, barycentric dynamical time (TDB),
the terrestrial dynamical time (TT) can be used with no practical
effect on the accuracy of the prediction.
2) TT can be regarded as a coordinate time that is realized as an
offset of 32.184s from International Atomic Time, TAI. TT is a
specific linear transformation of geocentric coordinate time TCG,
which is the time scale for the Geocentric Celestial Reference
System, GCRS.
3) TDB is a coordinate time, and is a specific linear transformation
of barycentric coordinate time TCB, which is the time scale for
the Barycentric Celestial Reference System, BCRS.
4) The difference TCG-TCB depends on the masses and positions of the
bodies of the solar system and the velocity of the Earth. It is
dominated by a rate difference, the residual being of a periodic
character. The latter, which is modeled by the present function,
comprises a main (annual) sinusoidal term of amplitude
approximately 0.00166 seconds, plus planetary terms up to about
20 microseconds, and lunar and diurnal terms up to 2 microseconds.
These effects come from the changing transverse Doppler effect
and gravitational red-shift as the observer (on the Earth's
surface) experiences variations in speed (with respect to the
BCRS) and gravitational potential.
5) TDB can be regarded as the same as TCB but with a rate adjustment
to keep it close to TT, which is convenient for many applications.
The history of successive attempts to define TDB is set out in
Resolution 3 adopted by the IAU General Assembly in 2006, which
defines a fixed TDB(TCB) transformation that is consistent with
contemporary solar-system ephemerides. Future ephemerides will
imply slightly changed transformations between TCG and TCB, which
could introduce a linear drift between TDB and TT; however, any
such drift is unlikely to exceed 1 nanosecond per century.
6) The geocentric TDB-TT model used in the present function is that of
Fairhead & Bretagnon (1990), in its full form. It was originally
supplied by Fairhead (private communications with P.T.Wallace,
1990) as a Fortran subroutine. The present C function contains an
adaptation of the Fairhead code. The numerical results are
essentially unaffected by the changes, the differences with
respect to the Fairhead & Bretagnon original being at the 1e-20 s
level.
The topocentric part of the model is from Moyer (1981) and
Murray (1983), with fundamental arguments adapted from
Simon et al. 1994. It is an approximation to the expression
( v / c ) . ( r / c ), where v is the barycentric velocity of
the Earth, r is the geocentric position of the observer and
c is the speed of light.
By supplying zeroes for u and v, the topocentric part of the
model can be nullified, and the function will return the Fairhead
& Bretagnon result alone.
7) During the interval 1950-2050, the absolute accuracy is better
than +/- 3 nanoseconds relative to time ephemerides obtained by
direct numerical integrations based on the JPL DE405 solar system
ephemeris.
8) It must be stressed that the present function is merely a model,
and that numerical integration of solar-system ephemerides is the
definitive method for predicting the relationship between TCG and
TCB and hence between TT and TDB.
References:
Fairhead, L., & Bretagnon, P., Astron.Astrophys., 229, 240-247
(1990).
IAU 2006 Resolution 3.
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Moyer, T.D., Cel.Mech., 23, 33 (1981).
Murray, C.A., Vectorial Astrometry, Adam Hilger (1983).
Seidelmann, P.K. et al., Explanatory Supplement to the
Astronomical Almanac, Chapter 2, University Science Books (1992).
Simon, J.L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
Francou, G. & Laskar, J., Astron.Astrophys., 282, 663-683 (1994).
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.dtdb(date1, date2, ut, elong, u, v)
return c_retval
[docs]def dtf2d(scale, iy, im, id, ihr, imn, sec):
"""
Encode date and time fields into 2-part Julian Date (or in the case
of UTC a quasi-JD form that includes special provision for leap
seconds).
Parameters
----------
scale : const char array
iy : int array
im : int array
id : int array
ihr : int array
imn : int array
sec : double array
Returns
-------
d1 : double array
d2 : double array
Notes
-----
Wraps ERFA function ``eraDtf2d``. The ERFA documentation is::
- - - - - - - - -
e r a D t f 2 d
- - - - - - - - -
Encode date and time fields into 2-part Julian Date (or in the case
of UTC a quasi-JD form that includes special provision for leap
seconds).
Given:
scale char[] time scale ID (Note 1)
iy,im,id int year, month, day in Gregorian calendar (Note 2)
ihr,imn int hour, minute
sec double seconds
Returned:
d1,d2 double 2-part Julian Date (Notes 3,4)
Returned (function value):
int status: +3 = both of next two
+2 = time is after end of day (Note 5)
+1 = dubious year (Note 6)
0 = OK
-1 = bad year
-2 = bad month
-3 = bad day
-4 = bad hour
-5 = bad minute
-6 = bad second (<0)
Notes:
1) scale identifies the time scale. Only the value "UTC" (in upper
case) is significant, and enables handling of leap seconds (see
Note 4).
2) For calendar conventions and limitations, see eraCal2jd.
3) The sum of the results, d1+d2, is Julian Date, where normally d1
is the Julian Day Number and d2 is the fraction of a day. In the
case of UTC, where the use of JD is problematical, special
conventions apply: see the next note.
4) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The ERFA internal convention is that
the quasi-JD day represents UTC days whether the length is 86399,
86400 or 86401 SI seconds. In the 1960-1972 era there were
smaller jumps (in either direction) each time the linear UTC(TAI)
expression was changed, and these "mini-leaps" are also included
in the ERFA convention.
5) The warning status "time is after end of day" usually means that
the sec argument is greater than 60.0. However, in a day ending
in a leap second the limit changes to 61.0 (or 59.0 in the case
of a negative leap second).
6) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
7) Only in the case of continuous and regular time scales (TAI, TT,
TCG, TCB and TDB) is the result d1+d2 a Julian Date, strictly
speaking. In the other cases (UT1 and UTC) the result must be
used with circumspection; in particular the difference between
two such results cannot be interpreted as a precise time
interval.
Called:
eraCal2jd Gregorian calendar to JD
eraDat delta(AT) = TAI-UTC
eraJd2cal JD to Gregorian calendar
This revision: 2013 July 26
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
d1, d2, c_retval = ufunc.dtf2d(scale, iy, im, id, ihr, imn, sec)
check_errwarn(c_retval, 'dtf2d')
return d1, d2
STATUS_CODES['dtf2d'] = {
3: 'both of next two',
2: 'time is after end of day (Note 5)',
1: 'dubious year (Note 6)',
0: 'OK',
-1: 'bad year',
-2: 'bad month',
-3: 'bad day',
-4: 'bad hour',
-5: 'bad minute',
-6: 'bad second (<0)',
}
[docs]def taitt(tai1, tai2):
"""
Time scale transformation: International Atomic Time, TAI, to
Terrestrial Time, TT.
Parameters
----------
tai1 : double array
tai2 : double array
Returns
-------
tt1 : double array
tt2 : double array
Notes
-----
Wraps ERFA function ``eraTaitt``. The ERFA documentation is::
- - - - - - - - -
e r a T a i t t
- - - - - - - - -
Time scale transformation: International Atomic Time, TAI, to
Terrestrial Time, TT.
Given:
tai1,tai2 double TAI as a 2-part Julian Date
Returned:
tt1,tt2 double TT as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Note:
tai1+tai2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tai1 is the Julian
Day Number and tai2 is the fraction of a day. The returned
tt1,tt2 follow suit.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tt1, tt2, c_retval = ufunc.taitt(tai1, tai2)
check_errwarn(c_retval, 'taitt')
return tt1, tt2
STATUS_CODES['taitt'] = {
0: 'OK',
}
[docs]def taiut1(tai1, tai2, dta):
"""
Time scale transformation: International Atomic Time, TAI, to
Universal Time, UT1.
Parameters
----------
tai1 : double array
tai2 : double array
dta : double array
Returns
-------
ut11 : double array
ut12 : double array
Notes
-----
Wraps ERFA function ``eraTaiut1``. The ERFA documentation is::
- - - - - - - - - -
e r a T a i u t 1
- - - - - - - - - -
Time scale transformation: International Atomic Time, TAI, to
Universal Time, UT1.
Given:
tai1,tai2 double TAI as a 2-part Julian Date
dta double UT1-TAI in seconds
Returned:
ut11,ut12 double UT1 as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tai1+tai2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tai1 is the Julian
Day Number and tai2 is the fraction of a day. The returned
UT11,UT12 follow suit.
2) The argument dta, i.e. UT1-TAI, is an observed quantity, and is
available from IERS tabulations.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ut11, ut12, c_retval = ufunc.taiut1(tai1, tai2, dta)
check_errwarn(c_retval, 'taiut1')
return ut11, ut12
STATUS_CODES['taiut1'] = {
0: 'OK',
}
[docs]def taiutc(tai1, tai2):
"""
Time scale transformation: International Atomic Time, TAI, to
Coordinated Universal Time, UTC.
Parameters
----------
tai1 : double array
tai2 : double array
Returns
-------
utc1 : double array
utc2 : double array
Notes
-----
Wraps ERFA function ``eraTaiutc``. The ERFA documentation is::
- - - - - - - - - -
e r a T a i u t c
- - - - - - - - - -
Time scale transformation: International Atomic Time, TAI, to
Coordinated Universal Time, UTC.
Given:
tai1,tai2 double TAI as a 2-part Julian Date (Note 1)
Returned:
utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-3)
Returned (function value):
int status: +1 = dubious year (Note 4)
0 = OK
-1 = unacceptable date
Notes:
1) tai1+tai2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tai1 is the Julian
Day Number and tai2 is the fraction of a day. The returned utc1
and utc2 form an analogous pair, except that a special convention
is used, to deal with the problem of leap seconds - see the next
note.
2) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The convention in the present
function is that the JD day represents UTC days whether the
length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era
there were smaller jumps (in either direction) each time the
linear UTC(TAI) expression was changed, and these "mini-leaps"
are also included in the ERFA convention.
3) The function eraD2dtf can be used to transform the UTC quasi-JD
into calendar date and clock time, including UTC leap second
handling.
4) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
Called:
eraUtctai UTC to TAI
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
utc1, utc2, c_retval = ufunc.taiutc(tai1, tai2)
check_errwarn(c_retval, 'taiutc')
return utc1, utc2
STATUS_CODES['taiutc'] = {
1: 'dubious year (Note 4)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def tcbtdb(tcb1, tcb2):
"""
Time scale transformation: Barycentric Coordinate Time, TCB, to
Barycentric Dynamical Time, TDB.
Parameters
----------
tcb1 : double array
tcb2 : double array
Returns
-------
tdb1 : double array
tdb2 : double array
Notes
-----
Wraps ERFA function ``eraTcbtdb``. The ERFA documentation is::
- - - - - - - - - -
e r a T c b t d b
- - - - - - - - - -
Time scale transformation: Barycentric Coordinate Time, TCB, to
Barycentric Dynamical Time, TDB.
Given:
tcb1,tcb2 double TCB as a 2-part Julian Date
Returned:
tdb1,tdb2 double TDB as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tcb1+tcb2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tcb1 is the Julian
Day Number and tcb2 is the fraction of a day. The returned
tdb1,tdb2 follow suit.
2) The 2006 IAU General Assembly introduced a conventional linear
transformation between TDB and TCB. This transformation
compensates for the drift between TCB and terrestrial time TT,
and keeps TDB approximately centered on TT. Because the
relationship between TT and TCB depends on the adopted solar
system ephemeris, the degree of alignment between TDB and TT over
long intervals will vary according to which ephemeris is used.
Former definitions of TDB attempted to avoid this problem by
stipulating that TDB and TT should differ only by periodic
effects. This is a good description of the nature of the
relationship but eluded precise mathematical formulation. The
conventional linear relationship adopted in 2006 sidestepped
these difficulties whilst delivering a TDB that in practice was
consistent with values before that date.
3) TDB is essentially the same as Teph, the time argument for the
JPL solar system ephemerides.
Reference:
IAU 2006 Resolution B3
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tdb1, tdb2, c_retval = ufunc.tcbtdb(tcb1, tcb2)
check_errwarn(c_retval, 'tcbtdb')
return tdb1, tdb2
STATUS_CODES['tcbtdb'] = {
0: 'OK',
}
[docs]def tcgtt(tcg1, tcg2):
"""
Time scale transformation: Geocentric Coordinate Time, TCG, to
Terrestrial Time, TT.
Parameters
----------
tcg1 : double array
tcg2 : double array
Returns
-------
tt1 : double array
tt2 : double array
Notes
-----
Wraps ERFA function ``eraTcgtt``. The ERFA documentation is::
- - - - - - - - -
e r a T c g t t
- - - - - - - - -
Time scale transformation: Geocentric Coordinate Time, TCG, to
Terrestrial Time, TT.
Given:
tcg1,tcg2 double TCG as a 2-part Julian Date
Returned:
tt1,tt2 double TT as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Note:
tcg1+tcg2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tcg1 is the Julian
Day Number and tcg22 is the fraction of a day. The returned
tt1,tt2 follow suit.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
IAU 2000 Resolution B1.9
This revision: 2020 October 23
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tt1, tt2, c_retval = ufunc.tcgtt(tcg1, tcg2)
check_errwarn(c_retval, 'tcgtt')
return tt1, tt2
STATUS_CODES['tcgtt'] = {
0: 'OK',
}
[docs]def tdbtcb(tdb1, tdb2):
"""
Time scale transformation: Barycentric Dynamical Time, TDB, to
Barycentric Coordinate Time, TCB.
Parameters
----------
tdb1 : double array
tdb2 : double array
Returns
-------
tcb1 : double array
tcb2 : double array
Notes
-----
Wraps ERFA function ``eraTdbtcb``. The ERFA documentation is::
- - - - - - - - - -
e r a T d b t c b
- - - - - - - - - -
Time scale transformation: Barycentric Dynamical Time, TDB, to
Barycentric Coordinate Time, TCB.
Given:
tdb1,tdb2 double TDB as a 2-part Julian Date
Returned:
tcb1,tcb2 double TCB as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tdb1+tdb2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tdb1 is the Julian
Day Number and tdb2 is the fraction of a day. The returned
tcb1,tcb2 follow suit.
2) The 2006 IAU General Assembly introduced a conventional linear
transformation between TDB and TCB. This transformation
compensates for the drift between TCB and terrestrial time TT,
and keeps TDB approximately centered on TT. Because the
relationship between TT and TCB depends on the adopted solar
system ephemeris, the degree of alignment between TDB and TT over
long intervals will vary according to which ephemeris is used.
Former definitions of TDB attempted to avoid this problem by
stipulating that TDB and TT should differ only by periodic
effects. This is a good description of the nature of the
relationship but eluded precise mathematical formulation. The
conventional linear relationship adopted in 2006 sidestepped
these difficulties whilst delivering a TDB that in practice was
consistent with values before that date.
3) TDB is essentially the same as Teph, the time argument for the
JPL solar system ephemerides.
Reference:
IAU 2006 Resolution B3
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tcb1, tcb2, c_retval = ufunc.tdbtcb(tdb1, tdb2)
check_errwarn(c_retval, 'tdbtcb')
return tcb1, tcb2
STATUS_CODES['tdbtcb'] = {
0: 'OK',
}
[docs]def tdbtt(tdb1, tdb2, dtr):
"""
Time scale transformation: Barycentric Dynamical Time, TDB, to
Terrestrial Time, TT.
Parameters
----------
tdb1 : double array
tdb2 : double array
dtr : double array
Returns
-------
tt1 : double array
tt2 : double array
Notes
-----
Wraps ERFA function ``eraTdbtt``. The ERFA documentation is::
- - - - - - - - -
e r a T d b t t
- - - - - - - - -
Time scale transformation: Barycentric Dynamical Time, TDB, to
Terrestrial Time, TT.
Given:
tdb1,tdb2 double TDB as a 2-part Julian Date
dtr double TDB-TT in seconds
Returned:
tt1,tt2 double TT as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tdb1+tdb2 is Julian Date, apportioned in any convenient way
between the two arguments, for example where tdb1 is the Julian
Day Number and tdb2 is the fraction of a day. The returned
tt1,tt2 follow suit.
2) The argument dtr represents the quasi-periodic component of the
GR transformation between TT and TCB. It is dependent upon the
adopted solar-system ephemeris, and can be obtained by numerical
integration, by interrogating a precomputed time ephemeris or by
evaluating a model such as that implemented in the ERFA function
eraDtdb. The quantity is dominated by an annual term of 1.7 ms
amplitude.
3) TDB is essentially the same as Teph, the time argument for the
JPL solar system ephemerides.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
IAU 2006 Resolution 3
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tt1, tt2, c_retval = ufunc.tdbtt(tdb1, tdb2, dtr)
check_errwarn(c_retval, 'tdbtt')
return tt1, tt2
STATUS_CODES['tdbtt'] = {
0: 'OK',
}
[docs]def tttai(tt1, tt2):
"""
Time scale transformation: Terrestrial Time, TT, to International
Atomic Time, TAI.
Parameters
----------
tt1 : double array
tt2 : double array
Returns
-------
tai1 : double array
tai2 : double array
Notes
-----
Wraps ERFA function ``eraTttai``. The ERFA documentation is::
- - - - - - - - -
e r a T t t a i
- - - - - - - - -
Time scale transformation: Terrestrial Time, TT, to International
Atomic Time, TAI.
Given:
tt1,tt2 double TT as a 2-part Julian Date
Returned:
tai1,tai2 double TAI as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Note:
tt1+tt2 is Julian Date, apportioned in any convenient way between
the two arguments, for example where tt1 is the Julian Day Number
and tt2 is the fraction of a day. The returned tai1,tai2 follow
suit.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tai1, tai2, c_retval = ufunc.tttai(tt1, tt2)
check_errwarn(c_retval, 'tttai')
return tai1, tai2
STATUS_CODES['tttai'] = {
0: 'OK',
}
[docs]def tttcg(tt1, tt2):
"""
Time scale transformation: Terrestrial Time, TT, to Geocentric
Coordinate Time, TCG.
Parameters
----------
tt1 : double array
tt2 : double array
Returns
-------
tcg1 : double array
tcg2 : double array
Notes
-----
Wraps ERFA function ``eraTttcg``. The ERFA documentation is::
- - - - - - - - -
e r a T t t c g
- - - - - - - - -
Time scale transformation: Terrestrial Time, TT, to Geocentric
Coordinate Time, TCG.
Given:
tt1,tt2 double TT as a 2-part Julian Date
Returned:
tcg1,tcg2 double TCG as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Note:
tt1+tt2 is Julian Date, apportioned in any convenient way between
the two arguments, for example where tt1 is the Julian Day Number
and tt2 is the fraction of a day. The returned tcg1,tcg2 follow
suit.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
IAU 2000 Resolution B1.9
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tcg1, tcg2, c_retval = ufunc.tttcg(tt1, tt2)
check_errwarn(c_retval, 'tttcg')
return tcg1, tcg2
STATUS_CODES['tttcg'] = {
0: 'OK',
}
[docs]def tttdb(tt1, tt2, dtr):
"""
Time scale transformation: Terrestrial Time, TT, to Barycentric
Dynamical Time, TDB.
Parameters
----------
tt1 : double array
tt2 : double array
dtr : double array
Returns
-------
tdb1 : double array
tdb2 : double array
Notes
-----
Wraps ERFA function ``eraTttdb``. The ERFA documentation is::
- - - - - - - - -
e r a T t t d b
- - - - - - - - -
Time scale transformation: Terrestrial Time, TT, to Barycentric
Dynamical Time, TDB.
Given:
tt1,tt2 double TT as a 2-part Julian Date
dtr double TDB-TT in seconds
Returned:
tdb1,tdb2 double TDB as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tt1+tt2 is Julian Date, apportioned in any convenient way between
the two arguments, for example where tt1 is the Julian Day Number
and tt2 is the fraction of a day. The returned tdb1,tdb2 follow
suit.
2) The argument dtr represents the quasi-periodic component of the
GR transformation between TT and TCB. It is dependent upon the
adopted solar-system ephemeris, and can be obtained by numerical
integration, by interrogating a precomputed time ephemeris or by
evaluating a model such as that implemented in the ERFA function
eraDtdb. The quantity is dominated by an annual term of 1.7 ms
amplitude.
3) TDB is essentially the same as Teph, the time argument for the JPL
solar system ephemerides.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
IAU 2006 Resolution 3
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tdb1, tdb2, c_retval = ufunc.tttdb(tt1, tt2, dtr)
check_errwarn(c_retval, 'tttdb')
return tdb1, tdb2
STATUS_CODES['tttdb'] = {
0: 'OK',
}
[docs]def ttut1(tt1, tt2, dt):
"""
Time scale transformation: Terrestrial Time, TT, to Universal Time,
UT1.
Parameters
----------
tt1 : double array
tt2 : double array
dt : double array
Returns
-------
ut11 : double array
ut12 : double array
Notes
-----
Wraps ERFA function ``eraTtut1``. The ERFA documentation is::
- - - - - - - - -
e r a T t u t 1
- - - - - - - - -
Time scale transformation: Terrestrial Time, TT, to Universal Time,
UT1.
Given:
tt1,tt2 double TT as a 2-part Julian Date
dt double TT-UT1 in seconds
Returned:
ut11,ut12 double UT1 as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) tt1+tt2 is Julian Date, apportioned in any convenient way between
the two arguments, for example where tt1 is the Julian Day Number
and tt2 is the fraction of a day. The returned ut11,ut12 follow
suit.
2) The argument dt is classical Delta T.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ut11, ut12, c_retval = ufunc.ttut1(tt1, tt2, dt)
check_errwarn(c_retval, 'ttut1')
return ut11, ut12
STATUS_CODES['ttut1'] = {
0: 'OK',
}
[docs]def ut1tai(ut11, ut12, dta):
"""
Time scale transformation: Universal Time, UT1, to International
Atomic Time, TAI.
Parameters
----------
ut11 : double array
ut12 : double array
dta : double array
Returns
-------
tai1 : double array
tai2 : double array
Notes
-----
Wraps ERFA function ``eraUt1tai``. The ERFA documentation is::
- - - - - - - - - -
e r a U t 1 t a i
- - - - - - - - - -
Time scale transformation: Universal Time, UT1, to International
Atomic Time, TAI.
Given:
ut11,ut12 double UT1 as a 2-part Julian Date
dta double UT1-TAI in seconds
Returned:
tai1,tai2 double TAI as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) ut11+ut12 is Julian Date, apportioned in any convenient way
between the two arguments, for example where ut11 is the Julian
Day Number and ut12 is the fraction of a day. The returned
tai1,tai2 follow suit.
2) The argument dta, i.e. UT1-TAI, is an observed quantity, and is
available from IERS tabulations.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tai1, tai2, c_retval = ufunc.ut1tai(ut11, ut12, dta)
check_errwarn(c_retval, 'ut1tai')
return tai1, tai2
STATUS_CODES['ut1tai'] = {
0: 'OK',
}
[docs]def ut1tt(ut11, ut12, dt):
"""
Time scale transformation: Universal Time, UT1, to Terrestrial
Time, TT.
Parameters
----------
ut11 : double array
ut12 : double array
dt : double array
Returns
-------
tt1 : double array
tt2 : double array
Notes
-----
Wraps ERFA function ``eraUt1tt``. The ERFA documentation is::
- - - - - - - - -
e r a U t 1 t t
- - - - - - - - -
Time scale transformation: Universal Time, UT1, to Terrestrial
Time, TT.
Given:
ut11,ut12 double UT1 as a 2-part Julian Date
dt double TT-UT1 in seconds
Returned:
tt1,tt2 double TT as a 2-part Julian Date
Returned (function value):
int status: 0 = OK
Notes:
1) ut11+ut12 is Julian Date, apportioned in any convenient way
between the two arguments, for example where ut11 is the Julian
Day Number and ut12 is the fraction of a day. The returned
tt1,tt2 follow suit.
2) The argument dt is classical Delta T.
Reference:
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tt1, tt2, c_retval = ufunc.ut1tt(ut11, ut12, dt)
check_errwarn(c_retval, 'ut1tt')
return tt1, tt2
STATUS_CODES['ut1tt'] = {
0: 'OK',
}
[docs]def ut1utc(ut11, ut12, dut1):
"""
Time scale transformation: Universal Time, UT1, to Coordinated
Universal Time, UTC.
Parameters
----------
ut11 : double array
ut12 : double array
dut1 : double array
Returns
-------
utc1 : double array
utc2 : double array
Notes
-----
Wraps ERFA function ``eraUt1utc``. The ERFA documentation is::
- - - - - - - - - -
e r a U t 1 u t c
- - - - - - - - - -
Time scale transformation: Universal Time, UT1, to Coordinated
Universal Time, UTC.
Given:
ut11,ut12 double UT1 as a 2-part Julian Date (Note 1)
dut1 double Delta UT1: UT1-UTC in seconds (Note 2)
Returned:
utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 3,4)
Returned (function value):
int status: +1 = dubious year (Note 5)
0 = OK
-1 = unacceptable date
Notes:
1) ut11+ut12 is Julian Date, apportioned in any convenient way
between the two arguments, for example where ut11 is the Julian
Day Number and ut12 is the fraction of a day. The returned utc1
and utc2 form an analogous pair, except that a special convention
is used, to deal with the problem of leap seconds - see Note 3.
2) Delta UT1 can be obtained from tabulations provided by the
International Earth Rotation and Reference Systems Service. The
value changes abruptly by 1s at a leap second; however, close to
a leap second the algorithm used here is tolerant of the "wrong"
choice of value being made.
3) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The convention in the present
function is that the returned quasi-JD UTC1+UTC2 represents UTC
days whether the length is 86399, 86400 or 86401 SI seconds.
4) The function eraD2dtf can be used to transform the UTC quasi-JD
into calendar date and clock time, including UTC leap second
handling.
5) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
Called:
eraJd2cal JD to Gregorian calendar
eraDat delta(AT) = TAI-UTC
eraCal2jd Gregorian calendar to JD
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2020 October 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
utc1, utc2, c_retval = ufunc.ut1utc(ut11, ut12, dut1)
check_errwarn(c_retval, 'ut1utc')
return utc1, utc2
STATUS_CODES['ut1utc'] = {
1: 'dubious year (Note 5)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def utctai(utc1, utc2):
"""
Time scale transformation: Coordinated Universal Time, UTC, to
International Atomic Time, TAI.
Parameters
----------
utc1 : double array
utc2 : double array
Returns
-------
tai1 : double array
tai2 : double array
Notes
-----
Wraps ERFA function ``eraUtctai``. The ERFA documentation is::
- - - - - - - - - -
e r a U t c t a i
- - - - - - - - - -
Time scale transformation: Coordinated Universal Time, UTC, to
International Atomic Time, TAI.
Given:
utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-4)
Returned:
tai1,tai2 double TAI as a 2-part Julian Date (Note 5)
Returned (function value):
int status: +1 = dubious year (Note 3)
0 = OK
-1 = unacceptable date
Notes:
1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
2) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The convention in the present
function is that the JD day represents UTC days whether the
length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era
there were smaller jumps (in either direction) each time the
linear UTC(TAI) expression was changed, and these "mini-leaps"
are also included in the ERFA convention.
3) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
4) The function eraDtf2d converts from calendar date and time of day
into 2-part Julian Date, and in the case of UTC implements the
leap-second-ambiguity convention described above.
5) The returned TAI1,TAI2 are such that their sum is the TAI Julian
Date.
Called:
eraJd2cal JD to Gregorian calendar
eraDat delta(AT) = TAI-UTC
eraCal2jd Gregorian calendar to JD
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
This revision: 2019 June 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
tai1, tai2, c_retval = ufunc.utctai(utc1, utc2)
check_errwarn(c_retval, 'utctai')
return tai1, tai2
STATUS_CODES['utctai'] = {
1: 'dubious year (Note 3)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def utcut1(utc1, utc2, dut1):
"""
Time scale transformation: Coordinated Universal Time, UTC, to
Universal Time, UT1.
Parameters
----------
utc1 : double array
utc2 : double array
dut1 : double array
Returns
-------
ut11 : double array
ut12 : double array
Notes
-----
Wraps ERFA function ``eraUtcut1``. The ERFA documentation is::
- - - - - - - - - -
e r a U t c u t 1
- - - - - - - - - -
Time scale transformation: Coordinated Universal Time, UTC, to
Universal Time, UT1.
Given:
utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-4)
dut1 double Delta UT1 = UT1-UTC in seconds (Note 5)
Returned:
ut11,ut12 double UT1 as a 2-part Julian Date (Note 6)
Returned (function value):
int status: +1 = dubious year (Note 3)
0 = OK
-1 = unacceptable date
Notes:
1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
convenient way between the two arguments, for example where utc1
is the Julian Day Number and utc2 is the fraction of a day.
2) JD cannot unambiguously represent UTC during a leap second unless
special measures are taken. The convention in the present
function is that the JD day represents UTC days whether the
length is 86399, 86400 or 86401 SI seconds.
3) The warning status "dubious year" flags UTCs that predate the
introduction of the time scale or that are too far in the future
to be trusted. See eraDat for further details.
4) The function eraDtf2d converts from calendar date and time of
day into 2-part Julian Date, and in the case of UTC implements
the leap-second-ambiguity convention described above.
5) Delta UT1 can be obtained from tabulations provided by the
International Earth Rotation and Reference Systems Service.
It is the caller's responsibility to supply a dut1 argument
containing the UT1-UTC value that matches the given UTC.
6) The returned ut11,ut12 are such that their sum is the UT1 Julian
Date.
References:
McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)
Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann (ed), University Science Books (1992)
Called:
eraJd2cal JD to Gregorian calendar
eraDat delta(AT) = TAI-UTC
eraUtctai UTC to TAI
eraTaiut1 TAI to UT1
This revision: 2013 August 12
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
ut11, ut12, c_retval = ufunc.utcut1(utc1, utc2, dut1)
check_errwarn(c_retval, 'utcut1')
return ut11, ut12
STATUS_CODES['utcut1'] = {
1: 'dubious year (Note 3)',
0: 'OK',
-1: 'unacceptable date',
}
[docs]def ae2hd(az, el, phi):
"""
Horizon to equatorial coordinates: transform azimuth and altitude
to hour angle and declination.
Parameters
----------
az : double array
el : double array
phi : double array
Returns
-------
ha : double array
dec : double array
Notes
-----
Wraps ERFA function ``eraAe2hd``. The ERFA documentation is::
- - - - - - - - -
e r a A e 2 h d
- - - - - - - - -
Horizon to equatorial coordinates: transform azimuth and altitude
to hour angle and declination.
Given:
az double azimuth
el double altitude (informally, elevation)
phi double site latitude
Returned:
ha double hour angle (local)
dec double declination
Notes:
1) All the arguments are angles in radians.
2) The sign convention for azimuth is north zero, east +pi/2.
3) HA is returned in the range +/-pi. Declination is returned in
the range +/-pi/2.
4) The latitude phi is pi/2 minus the angle between the Earth's
rotation axis and the adopted zenith. In many applications it
will be sufficient to use the published geodetic latitude of the
site. In very precise (sub-arcsecond) applications, phi can be
corrected for polar motion.
5) The azimuth az must be with respect to the rotational north pole,
as opposed to the ITRS pole, and an azimuth with respect to north
on a map of the Earth's surface will need to be adjusted for
polar motion if sub-arcsecond accuracy is required.
6) Should the user wish to work with respect to the astronomical
zenith rather than the geodetic zenith, phi will need to be
adjusted for deflection of the vertical (often tens of
arcseconds), and the zero point of ha will also be affected.
7) The transformation is the same as Ve = Ry(phi-pi/2)*Rz(pi)*Vh,
where Ve and Vh are lefthanded unit vectors in the (ha,dec) and
(az,el) systems respectively and Rz and Ry are rotations about
first the z-axis and then the y-axis. (n.b. Rz(pi) simply
reverses the signs of the x and y components.) For efficiency,
the algorithm is written out rather than calling other utility
functions. For applications that require even greater
efficiency, additional savings are possible if constant terms
such as functions of latitude are computed once and for all.
8) Again for efficiency, no range checking of arguments is carried
out.
Last revision: 2017 September 12
ERFA release 2021-01-25
Copyright (C) 2021 IAU ERFA Board. See notes at end.
"""
ha, dec = ufunc.ae2hd(az, el, phi)
return ha, dec
[docs]def hd2ae(ha, dec, phi):
"""
Equatorial to horizon coordinates: transform hour angle and
declination to azimuth and altitude.
Parameters
----------
ha : double array
dec : double array
phi : double array
Returns
-------
az : double array
el : double array
Notes
-----
Wraps ERFA function ``eraHd2ae``. The ERFA documentation is::
- - - - - - - - -
e r a H d 2 a e
- - - - - - - - -
Equatorial to horizon coordinates: transform hour angle and
declination to azimuth and altitude.
Given:
ha double hour angle (local)
dec double declination
phi double site latitude
Returned:
*az double azimuth
*el double altitude (informally, elevation)
Notes:
1) All the arguments are angles in radians.
2) Azimuth is returned in the range 0-2pi; north is zero, and east
is +pi/2. Altitude is returned in the range +/- pi/2.
3) The latitude phi is pi/2 minus the angle between the Earth's
rotation axis and the adopted zenith. In many applications it
will be sufficient to use the published geodetic latitude of the
site. In very precise (sub-arcsecond) applications, phi can be
corrected for polar motion.
4) The returned azimuth az is with respect to the rotational north
pole, as opposed to the ITRS pole, and for sub-arcsecond
accuracy will need to be adjusted for polar motion if it is to
be with respect to north on a map of the Earth's surface.
5) Should the user wish to work with respect to the astronomical
zenith rather than the geodetic zenith, phi will need to be
adjusted for deflection of the vertical (often tens of
arcseconds), and the zero point of the hour angle ha will also
be affected.
6) The transformation is the same as Vh = Rz(pi)*Ry(pi/2-phi)*Ve,
where Vh and Ve are lefthanded unit vectors in the (az,el) and
(ha,dec) systems respectively and Ry and Rz are rotations about
first the y-axis and then the z-axis. (n.b. Rz(pi) simply
reverses the signs of the x and y components.) For efficiency,
the algorithm is written out rather than calling other utility
functions. For applications that require even greater
efficiency, additional savings are possible if constant terms
such as functions of latitude are computed once and for all.
7) Again for efficiency, no range checking of arguments is carried
out.
Last revision: 2017 September 12
ERFA release 2021-01-25
Copyright (C) 2021 IAU ERFA Board. See notes at end.
"""
az, el = ufunc.hd2ae(ha, dec, phi)
return az, el
[docs]def hd2pa(ha, dec, phi):
"""
Parallactic angle for a given hour angle and declination.
Parameters
----------
ha : double array
dec : double array
phi : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraHd2pa``. The ERFA documentation is::
- - - - - - - - -
e r a H d 2 p a
- - - - - - - - -
Parallactic angle for a given hour angle and declination.
Given:
ha double hour angle
dec double declination
phi double site latitude
Returned (function value):
double parallactic angle
Notes:
1) All the arguments are angles in radians.
2) The parallactic angle at a point in the sky is the position
angle of the vertical, i.e. the angle between the directions to
the north celestial pole and to the zenith respectively.
3) The result is returned in the range -pi to +pi.
4) At the pole itself a zero result is returned.
5) The latitude phi is pi/2 minus the angle between the Earth's
rotation axis and the adopted zenith. In many applications it
will be sufficient to use the published geodetic latitude of the
site. In very precise (sub-arcsecond) applications, phi can be
corrected for polar motion.
6) Should the user wish to work with respect to the astronomical
zenith rather than the geodetic zenith, phi will need to be
adjusted for deflection of the vertical (often tens of
arcseconds), and the zero point of the hour angle ha will also
be affected.
Reference:
Smart, W.M., "Spherical Astronomy", Cambridge University Press,
6th edition (Green, 1977), p49.
Last revision: 2017 September 12
ERFA release 2021-01-25
Copyright (C) 2021 IAU ERFA Board. See notes at end.
"""
c_retval = ufunc.hd2pa(ha, dec, phi)
return c_retval
[docs]def tpors(xi, eta, a, b):
"""
In the tangent plane projection, given the rectangular coordinates
of a star and its spherical coordinates, determine the spherical
coordinates of the tangent point.
Parameters
----------
xi : double array
eta : double array
a : double array
b : double array
Returns
-------
a01 : double array
b01 : double array
a02 : double array
b02 : double array
Notes
-----
Wraps ERFA function ``eraTpors``. The ERFA documentation is::
- - - - - - - - -
e r a T p o r s
- - - - - - - - -
In the tangent plane projection, given the rectangular coordinates
of a star and its spherical coordinates, determine the spherical
coordinates of the tangent point.
Given:
xi,eta double rectangular coordinates of star image (Note 2)
a,b double star's spherical coordinates (Note 3)
Returned:
*a01,*b01 double tangent point's spherical coordinates, Soln. 1
*a02,*b02 double tangent point's spherical coordinates, Soln. 2
Returned (function value):
int number of solutions:
0 = no solutions returned (Note 5)
1 = only the first solution is useful (Note 6)
2 = both solutions are useful (Note 6)
Notes:
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the spherical coordinates are observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". If the spherical coordinates are with
respect to a right-handed triad, (xi,eta) are also right-handed.
The units of (xi,eta) are, effectively, radians at the tangent
point.
3) All angular arguments are in radians.
4) The angles a01 and a02 are returned in the range 0-2pi. The
angles b01 and b02 are returned in the range +/-pi, but in the
usual, non-pole-crossing, case, the range is +/-pi/2.
5) Cases where there is no solution can arise only near the poles.
For example, it is clearly impossible for a star at the pole
itself to have a non-zero xi value, and hence it is meaningless
to ask where the tangent point would have to be to bring about
this combination of xi and dec.
6) Also near the poles, cases can arise where there are two useful
solutions. The return value indicates whether the second of the
two solutions returned is useful; 1 indicates only one useful
solution, the usual case.
7) The basis of the algorithm is to solve the spherical triangle PSC,
where P is the north celestial pole, S is the star and C is the
tangent point. The spherical coordinates of the tangent point are
[a0,b0]; writing rho^2 = (xi^2+eta^2) and r^2 = (1+rho^2), side c
is then (pi/2-b), side p is sqrt(xi^2+eta^2) and side s (to be
found) is (pi/2-b0). Angle C is given by sin(C) = xi/rho and
cos(C) = eta/rho. Angle P (to be found) is the longitude
difference between star and tangent point (a-a0).
8) This function is a member of the following set:
spherical vector solve for
eraTpxes eraTpxev xi,eta
eraTpsts eraTpstv star
> eraTpors < eraTporv origin
Called:
eraAnp normalize angle into range 0 to 2pi
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
a01, b01, a02, b02, c_retval = ufunc.tpors(xi, eta, a, b)
check_errwarn(c_retval, 'tpors')
return a01, b01, a02, b02
[docs]def tporv(xi, eta, v):
"""
In the tangent plane projection, given the rectangular coordinates
of a star and its direction cosines, determine the direction
cosines of the tangent point.
Parameters
----------
xi : double array
eta : double array
v : double array
Returns
-------
v01 : double array
v02 : double array
Notes
-----
Wraps ERFA function ``eraTporv``. The ERFA documentation is::
- - - - - - - - -
e r a T p o r v
- - - - - - - - -
In the tangent plane projection, given the rectangular coordinates
of a star and its direction cosines, determine the direction
cosines of the tangent point.
Given:
xi,eta double rectangular coordinates of star image (Note 2)
v double[3] star's direction cosines (Note 3)
Returned:
v01 double[3] tangent point's direction cosines, Solution 1
v02 double[3] tangent point's direction cosines, Solution 2
Returned (function value):
int number of solutions:
0 = no solutions returned (Note 4)
1 = only the first solution is useful (Note 5)
2 = both solutions are useful (Note 5)
Notes:
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the direction cosines represent observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". If the direction cosines are with
respect to a right-handed triad, (xi,eta) are also right-handed.
The units of (xi,eta) are, effectively, radians at the tangent
point.
3) The vector v must be of unit length or the result will be wrong.
4) Cases where there is no solution can arise only near the poles.
For example, it is clearly impossible for a star at the pole
itself to have a non-zero xi value, and hence it is meaningless
to ask where the tangent point would have to be.
5) Also near the poles, cases can arise where there are two useful
solutions. The return value indicates whether the second of the
two solutions returned is useful; 1 indicates only one useful
solution, the usual case.
6) The basis of the algorithm is to solve the spherical triangle
PSC, where P is the north celestial pole, S is the star and C is
the tangent point. Calling the celestial spherical coordinates
of the star and tangent point (a,b) and (a0,b0) respectively, and
writing rho^2 = (xi^2+eta^2) and r^2 = (1+rho^2), and
transforming the vector v into (a,b) in the normal way, side c is
then (pi/2-b), side p is sqrt(xi^2+eta^2) and side s (to be
found) is (pi/2-b0), while angle C is given by sin(C) = xi/rho
and cos(C) = eta/rho; angle P (to be found) is (a-a0). After
solving the spherical triangle, the result (a0,b0) can be
expressed in vector form as v0.
7) This function is a member of the following set:
spherical vector solve for
eraTpxes eraTpxev xi,eta
eraTpsts eraTpstv star
eraTpors > eraTporv < origin
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
v01, v02, c_retval = ufunc.tporv(xi, eta, v)
check_errwarn(c_retval, 'tporv')
return v01, v02
[docs]def tpsts(xi, eta, a0, b0):
"""
In the tangent plane projection, given the star's rectangular
coordinates and the spherical coordinates of the tangent point,
solve for the spherical coordinates of the star.
Parameters
----------
xi : double array
eta : double array
a0 : double array
b0 : double array
Returns
-------
a : double array
b : double array
Notes
-----
Wraps ERFA function ``eraTpsts``. The ERFA documentation is::
- - - - - - - - -
e r a T p s t s
- - - - - - - - -
In the tangent plane projection, given the star's rectangular
coordinates and the spherical coordinates of the tangent point,
solve for the spherical coordinates of the star.
Given:
xi,eta double rectangular coordinates of star image (Note 2)
a0,b0 double tangent point's spherical coordinates
Returned:
*a,*b double star's spherical coordinates
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the spherical coordinates are observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". If the spherical coordinates are with
respect to a right-handed triad, (xi,eta) are also right-handed.
The units of (xi,eta) are, effectively, radians at the tangent
point.
3) All angular arguments are in radians.
4) This function is a member of the following set:
spherical vector solve for
eraTpxes eraTpxev xi,eta
> eraTpsts < eraTpstv star
eraTpors eraTporv origin
Called:
eraAnp normalize angle into range 0 to 2pi
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
a, b = ufunc.tpsts(xi, eta, a0, b0)
return a, b
[docs]def tpstv(xi, eta, v0):
"""
In the tangent plane projection, given the star's rectangular
coordinates and the direction cosines of the tangent point, solve
for the direction cosines of the star.
Parameters
----------
xi : double array
eta : double array
v0 : double array
Returns
-------
v : double array
Notes
-----
Wraps ERFA function ``eraTpstv``. The ERFA documentation is::
- - - - - - - - -
e r a T p s t v
- - - - - - - - -
In the tangent plane projection, given the star's rectangular
coordinates and the direction cosines of the tangent point, solve
for the direction cosines of the star.
Given:
xi,eta double rectangular coordinates of star image (Note 2)
v0 double[3] tangent point's direction cosines
Returned:
v double[3] star's direction cosines
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the direction cosines represent observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". If the direction cosines are with
respect to a right-handed triad, (xi,eta) are also right-handed.
The units of (xi,eta) are, effectively, radians at the tangent
point.
3) The method used is to complete the star vector in the (xi,eta)
based triad and normalize it, then rotate the triad to put the
tangent point at the pole with the x-axis aligned to zero
longitude. Writing (a0,b0) for the celestial spherical
coordinates of the tangent point, the sequence of rotations is
(b-pi/2) around the x-axis followed by (-a-pi/2) around the
z-axis.
4) If vector v0 is not of unit length, the returned vector v will
be wrong.
5) If vector v0 points at a pole, the returned vector v will be
based on the arbitrary assumption that the longitude coordinate
of the tangent point is zero.
6) This function is a member of the following set:
spherical vector solve for
eraTpxes eraTpxev xi,eta
eraTpsts > eraTpstv < star
eraTpors eraTporv origin
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
v = ufunc.tpstv(xi, eta, v0)
return v
[docs]def tpxes(a, b, a0, b0):
"""
In the tangent plane projection, given celestial spherical
coordinates for a star and the tangent point, solve for the star's
rectangular coordinates in the tangent plane.
Parameters
----------
a : double array
b : double array
a0 : double array
b0 : double array
Returns
-------
xi : double array
eta : double array
Notes
-----
Wraps ERFA function ``eraTpxes``. The ERFA documentation is::
- - - - - - - - -
e r a T p x e s
- - - - - - - - -
In the tangent plane projection, given celestial spherical
coordinates for a star and the tangent point, solve for the star's
rectangular coordinates in the tangent plane.
Given:
a,b double star's spherical coordinates
a0,b0 double tangent point's spherical coordinates
Returned:
*xi,*eta double rectangular coordinates of star image (Note 2)
Returned (function value):
int status: 0 = OK
1 = star too far from axis
2 = antistar on tangent plane
3 = antistar too far from axis
Notes:
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the spherical coordinates are observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". For right-handed spherical coordinates,
(xi,eta) are also right-handed. The units of (xi,eta) are,
effectively, radians at the tangent point.
3) All angular arguments are in radians.
4) This function is a member of the following set:
spherical vector solve for
> eraTpxes < eraTpxev xi,eta
eraTpsts eraTpstv star
eraTpors eraTporv origin
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
xi, eta, c_retval = ufunc.tpxes(a, b, a0, b0)
check_errwarn(c_retval, 'tpxes')
return xi, eta
STATUS_CODES['tpxes'] = {
0: 'OK',
1: 'star too far from axis',
2: 'antistar on tangent plane',
3: 'antistar too far from axis',
}
[docs]def tpxev(v, v0):
"""
In the tangent plane projection, given celestial direction cosines
for a star and the tangent point, solve for the star's rectangular
coordinates in the tangent plane.
Parameters
----------
v : double array
v0 : double array
Returns
-------
xi : double array
eta : double array
Notes
-----
Wraps ERFA function ``eraTpxev``. The ERFA documentation is::
- - - - - - - - -
e r a T p x e v
- - - - - - - - -
In the tangent plane projection, given celestial direction cosines
for a star and the tangent point, solve for the star's rectangular
coordinates in the tangent plane.
Given:
v double[3] direction cosines of star (Note 4)
v0 double[3] direction cosines of tangent point (Note 4)
Returned:
*xi,*eta double tangent plane coordinates of star
Returned (function value):
int status: 0 = OK
1 = star too far from axis
2 = antistar on tangent plane
3 = antistar too far from axis
Notes:
1) The tangent plane projection is also called the "gnomonic
projection" and the "central projection".
2) The eta axis points due north in the adopted coordinate system.
If the direction cosines represent observed (RA,Dec), the tangent
plane coordinates (xi,eta) are conventionally called the
"standard coordinates". If the direction cosines are with
respect to a right-handed triad, (xi,eta) are also right-handed.
The units of (xi,eta) are, effectively, radians at the tangent
point.
3) The method used is to extend the star vector to the tangent
plane and then rotate the triad so that (x,y) becomes (xi,eta).
Writing (a,b) for the celestial spherical coordinates of the
star, the sequence of rotations is (a+pi/2) around the z-axis
followed by (pi/2-b) around the x-axis.
4) If vector v0 is not of unit length, or if vector v is of zero
length, the results will be wrong.
5) If v0 points at a pole, the returned (xi,eta) will be based on
the arbitrary assumption that the longitude coordinate of the
tangent point is zero.
6) This function is a member of the following set:
spherical vector solve for
eraTpxes > eraTpxev < xi,eta
eraTpsts eraTpstv star
eraTpors eraTporv origin
References:
Calabretta M.R. & Greisen, E.W., 2002, "Representations of
celestial coordinates in FITS", Astron.Astrophys. 395, 1077
Green, R.M., "Spherical Astronomy", Cambridge University Press,
1987, Chapter 13.
This revision: 2018 January 2
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
xi, eta, c_retval = ufunc.tpxev(v, v0)
check_errwarn(c_retval, 'tpxev')
return xi, eta
STATUS_CODES['tpxev'] = {
0: 'OK',
1: 'star too far from axis',
2: 'antistar on tangent plane',
3: 'antistar too far from axis',
}
[docs]def a2af(ndp, angle):
"""
Decompose radians into degrees, arcminutes, arcseconds, fraction.
Parameters
----------
ndp : int array
angle : double array
Returns
-------
sign : char array
idmsf : int array
Notes
-----
Wraps ERFA function ``eraA2af``. The ERFA documentation is::
- - - - - - - -
e r a A 2 a f
- - - - - - - -
Decompose radians into degrees, arcminutes, arcseconds, fraction.
Given:
ndp int resolution (Note 1)
angle double angle in radians
Returned:
sign char '+' or '-'
idmsf int[4] degrees, arcminutes, arcseconds, fraction
Notes:
1) The argument ndp is interpreted as follows:
ndp resolution
: ...0000 00 00
-7 1000 00 00
-6 100 00 00
-5 10 00 00
-4 1 00 00
-3 0 10 00
-2 0 01 00
-1 0 00 10
0 0 00 01
1 0 00 00.1
2 0 00 00.01
3 0 00 00.001
: 0 00 00.000...
2) The largest positive useful value for ndp is determined by the
size of angle, the format of doubles on the target platform, and
the risk of overflowing idmsf[3]. On a typical platform, for
angle up to 2pi, the available floating-point precision might
correspond to ndp=12. However, the practical limit is typically
ndp=9, set by the capacity of a 32-bit int, or ndp=4 if int is
only 16 bits.
3) The absolute value of angle may exceed 2pi. In cases where it
does not, it is up to the caller to test for and handle the
case where angle is very nearly 2pi and rounds up to 360 degrees,
by testing for idmsf[0]=360 and setting idmsf[0-3] to zero.
Called:
eraD2tf decompose days to hms
This revision: 2020 April 1
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
sign, idmsf = ufunc.a2af(ndp, angle)
sign = sign.view(dt_bytes1)
return sign, idmsf
[docs]def a2tf(ndp, angle):
"""
Decompose radians into hours, minutes, seconds, fraction.
Parameters
----------
ndp : int array
angle : double array
Returns
-------
sign : char array
ihmsf : int array
Notes
-----
Wraps ERFA function ``eraA2tf``. The ERFA documentation is::
- - - - - - - -
e r a A 2 t f
- - - - - - - -
Decompose radians into hours, minutes, seconds, fraction.
Given:
ndp int resolution (Note 1)
angle double angle in radians
Returned:
sign char '+' or '-'
ihmsf int[4] hours, minutes, seconds, fraction
Notes:
1) The argument ndp is interpreted as follows:
ndp resolution
: ...0000 00 00
-7 1000 00 00
-6 100 00 00
-5 10 00 00
-4 1 00 00
-3 0 10 00
-2 0 01 00
-1 0 00 10
0 0 00 01
1 0 00 00.1
2 0 00 00.01
3 0 00 00.001
: 0 00 00.000...
2) The largest positive useful value for ndp is determined by the
size of angle, the format of doubles on the target platform, and
the risk of overflowing ihmsf[3]. On a typical platform, for
angle up to 2pi, the available floating-point precision might
correspond to ndp=12. However, the practical limit is typically
ndp=9, set by the capacity of a 32-bit int, or ndp=4 if int is
only 16 bits.
3) The absolute value of angle may exceed 2pi. In cases where it
does not, it is up to the caller to test for and handle the
case where angle is very nearly 2pi and rounds up to 24 hours,
by testing for ihmsf[0]=24 and setting ihmsf[0-3] to zero.
Called:
eraD2tf decompose days to hms
This revision: 2020 April 1
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
sign, ihmsf = ufunc.a2tf(ndp, angle)
sign = sign.view(dt_bytes1)
return sign, ihmsf
[docs]def af2a(s, ideg, iamin, asec):
"""
Convert degrees, arcminutes, arcseconds to radians.
Parameters
----------
s : char array
ideg : int array
iamin : int array
asec : double array
Returns
-------
rad : double array
Notes
-----
Wraps ERFA function ``eraAf2a``. The ERFA documentation is::
- - - - - - - -
e r a A f 2 a
- - - - - - - -
Convert degrees, arcminutes, arcseconds to radians.
Given:
s char sign: '-' = negative, otherwise positive
ideg int degrees
iamin int arcminutes
asec double arcseconds
Returned:
rad double angle in radians
Returned (function value):
int status: 0 = OK
1 = ideg outside range 0-359
2 = iamin outside range 0-59
3 = asec outside range 0-59.999...
Notes:
1) The result is computed even if any of the range checks fail.
2) Negative ideg, iamin and/or asec produce a warning status, but
the absolute value is used in the conversion.
3) If there are multiple errors, the status value reflects only the
first, the smallest taking precedence.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rad, c_retval = ufunc.af2a(s, ideg, iamin, asec)
check_errwarn(c_retval, 'af2a')
return rad
STATUS_CODES['af2a'] = {
0: 'OK',
1: 'ideg outside range 0-359',
2: 'iamin outside range 0-59',
3: 'asec outside range 0-59.999...',
}
[docs]def anp(a):
"""
Normalize angle into the range 0 <= a < 2pi.
Parameters
----------
a : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraAnp``. The ERFA documentation is::
- - - - - - -
e r a A n p
- - - - - - -
Normalize angle into the range 0 <= a < 2pi.
Given:
a double angle (radians)
Returned (function value):
double angle in range 0-2pi
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.anp(a)
return c_retval
[docs]def anpm(a):
"""
Normalize angle into the range -pi <= a < +pi.
Parameters
----------
a : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraAnpm``. The ERFA documentation is::
- - - - - - - -
e r a A n p m
- - - - - - - -
Normalize angle into the range -pi <= a < +pi.
Given:
a double angle (radians)
Returned (function value):
double angle in range +/-pi
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.anpm(a)
return c_retval
[docs]def d2tf(ndp, days):
"""
Decompose days to hours, minutes, seconds, fraction.
Parameters
----------
ndp : int array
days : double array
Returns
-------
sign : char array
ihmsf : int array
Notes
-----
Wraps ERFA function ``eraD2tf``. The ERFA documentation is::
- - - - - - - -
e r a D 2 t f
- - - - - - - -
Decompose days to hours, minutes, seconds, fraction.
Given:
ndp int resolution (Note 1)
days double interval in days
Returned:
sign char '+' or '-'
ihmsf int[4] hours, minutes, seconds, fraction
Notes:
1) The argument ndp is interpreted as follows:
ndp resolution
: ...0000 00 00
-7 1000 00 00
-6 100 00 00
-5 10 00 00
-4 1 00 00
-3 0 10 00
-2 0 01 00
-1 0 00 10
0 0 00 01
1 0 00 00.1
2 0 00 00.01
3 0 00 00.001
: 0 00 00.000...
2) The largest positive useful value for ndp is determined by the
size of days, the format of double on the target platform, and
the risk of overflowing ihmsf[3]. On a typical platform, for
days up to 1.0, the available floating-point precision might
correspond to ndp=12. However, the practical limit is typically
ndp=9, set by the capacity of a 32-bit int, or ndp=4 if int is
only 16 bits.
3) The absolute value of days may exceed 1.0. In cases where it
does not, it is up to the caller to test for and handle the
case where days is very nearly 1.0 and rounds up to 24 hours,
by testing for ihmsf[0]=24 and setting ihmsf[0-3] to zero.
This revision: 2020 April 20
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
sign, ihmsf = ufunc.d2tf(ndp, days)
sign = sign.view(dt_bytes1)
return sign, ihmsf
[docs]def tf2a(s, ihour, imin, sec):
"""
Convert hours, minutes, seconds to radians.
Parameters
----------
s : char array
ihour : int array
imin : int array
sec : double array
Returns
-------
rad : double array
Notes
-----
Wraps ERFA function ``eraTf2a``. The ERFA documentation is::
- - - - - - - -
e r a T f 2 a
- - - - - - - -
Convert hours, minutes, seconds to radians.
Given:
s char sign: '-' = negative, otherwise positive
ihour int hours
imin int minutes
sec double seconds
Returned:
rad double angle in radians
Returned (function value):
int status: 0 = OK
1 = ihour outside range 0-23
2 = imin outside range 0-59
3 = sec outside range 0-59.999...
Notes:
1) The result is computed even if any of the range checks fail.
2) Negative ihour, imin and/or sec produce a warning status, but
the absolute value is used in the conversion.
3) If there are multiple errors, the status value reflects only the
first, the smallest taking precedence.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rad, c_retval = ufunc.tf2a(s, ihour, imin, sec)
check_errwarn(c_retval, 'tf2a')
return rad
STATUS_CODES['tf2a'] = {
0: 'OK',
1: 'ihour outside range 0-23',
2: 'imin outside range 0-59',
3: 'sec outside range 0-59.999...',
}
[docs]def tf2d(s, ihour, imin, sec):
"""
Convert hours, minutes, seconds to days.
Parameters
----------
s : char array
ihour : int array
imin : int array
sec : double array
Returns
-------
days : double array
Notes
-----
Wraps ERFA function ``eraTf2d``. The ERFA documentation is::
- - - - - - - -
e r a T f 2 d
- - - - - - - -
Convert hours, minutes, seconds to days.
Given:
s char sign: '-' = negative, otherwise positive
ihour int hours
imin int minutes
sec double seconds
Returned:
days double interval in days
Returned (function value):
int status: 0 = OK
1 = ihour outside range 0-23
2 = imin outside range 0-59
3 = sec outside range 0-59.999...
Notes:
1) The result is computed even if any of the range checks fail.
2) Negative ihour, imin and/or sec produce a warning status, but
the absolute value is used in the conversion.
3) If there are multiple errors, the status value reflects only the
first, the smallest taking precedence.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
days, c_retval = ufunc.tf2d(s, ihour, imin, sec)
check_errwarn(c_retval, 'tf2d')
return days
STATUS_CODES['tf2d'] = {
0: 'OK',
1: 'ihour outside range 0-23',
2: 'imin outside range 0-59',
3: 'sec outside range 0-59.999...',
}
[docs]def rx(phi, r):
"""
Rotate an r-matrix about the x-axis.
Parameters
----------
phi : double array
r : double array
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraRx``. Note that, unlike the erfa routine,
the python wrapper does not change r in-place. The ERFA documentation is::
- - - - - -
e r a R x
- - - - - -
Rotate an r-matrix about the x-axis.
Given:
phi double angle (radians)
Given and returned:
r double[3][3] r-matrix, rotated
Notes:
1) Calling this function with positive phi incorporates in the
supplied r-matrix r an additional rotation, about the x-axis,
anticlockwise as seen looking towards the origin from positive x.
2) The additional rotation can be represented by this matrix:
( 1 0 0 )
( )
( 0 + cos(phi) + sin(phi) )
( )
( 0 - sin(phi) + cos(phi) )
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.rx(phi, r)
return r
[docs]def ry(theta, r):
"""
Rotate an r-matrix about the y-axis.
Parameters
----------
theta : double array
r : double array
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraRy``. Note that, unlike the erfa routine,
the python wrapper does not change r in-place. The ERFA documentation is::
- - - - - -
e r a R y
- - - - - -
Rotate an r-matrix about the y-axis.
Given:
theta double angle (radians)
Given and returned:
r double[3][3] r-matrix, rotated
Notes:
1) Calling this function with positive theta incorporates in the
supplied r-matrix r an additional rotation, about the y-axis,
anticlockwise as seen looking towards the origin from positive y.
2) The additional rotation can be represented by this matrix:
( + cos(theta) 0 - sin(theta) )
( )
( 0 1 0 )
( )
( + sin(theta) 0 + cos(theta) )
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.ry(theta, r)
return r
[docs]def rz(psi, r):
"""
Rotate an r-matrix about the z-axis.
Parameters
----------
psi : double array
r : double array
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraRz``. Note that, unlike the erfa routine,
the python wrapper does not change r in-place. The ERFA documentation is::
- - - - - -
e r a R z
- - - - - -
Rotate an r-matrix about the z-axis.
Given:
psi double angle (radians)
Given and returned:
r double[3][3] r-matrix, rotated
Notes:
1) Calling this function with positive psi incorporates in the
supplied r-matrix r an additional rotation, about the z-axis,
anticlockwise as seen looking towards the origin from positive z.
2) The additional rotation can be represented by this matrix:
( + cos(psi) + sin(psi) 0 )
( )
( - sin(psi) + cos(psi) 0 )
( )
( 0 0 1 )
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.rz(psi, r)
return r
[docs]def cp(p):
"""
Copy a p-vector.
Parameters
----------
p : double array
Returns
-------
c : double array
Notes
-----
Wraps ERFA function ``eraCp``. The ERFA documentation is::
- - - - - -
e r a C p
- - - - - -
Copy a p-vector.
Given:
p double[3] p-vector to be copied
Returned:
c double[3] copy
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c = ufunc.cp(p)
return c
[docs]def cpv(pv):
"""
Copy a position/velocity vector.
Parameters
----------
pv : double array
Returns
-------
c : double array
Notes
-----
Wraps ERFA function ``eraCpv``. The ERFA documentation is::
- - - - - - -
e r a C p v
- - - - - - -
Copy a position/velocity vector.
Given:
pv double[2][3] position/velocity vector to be copied
Returned:
c double[2][3] copy
Called:
eraCp copy p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c = ufunc.cpv(pv)
return c
[docs]def cr(r):
"""
Copy an r-matrix.
Parameters
----------
r : double array
Returns
-------
c : double array
Notes
-----
Wraps ERFA function ``eraCr``. The ERFA documentation is::
- - - - - -
e r a C r
- - - - - -
Copy an r-matrix.
Given:
r double[3][3] r-matrix to be copied
Returned:
c double[3][3] copy
Called:
eraCp copy p-vector
This revision: 2016 May 19
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c = ufunc.cr(r)
return c
[docs]def p2pv(p):
"""
Extend a p-vector to a pv-vector by appending a zero velocity.
Parameters
----------
p : double array
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraP2pv``. The ERFA documentation is::
- - - - - - - -
e r a P 2 p v
- - - - - - - -
Extend a p-vector to a pv-vector by appending a zero velocity.
Given:
p double[3] p-vector
Returned:
pv double[2][3] pv-vector
Called:
eraCp copy p-vector
eraZp zero p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv = ufunc.p2pv(p)
return pv
[docs]def pv2p(pv):
"""
Discard velocity component of a pv-vector.
Parameters
----------
pv : double array
Returns
-------
p : double array
Notes
-----
Wraps ERFA function ``eraPv2p``. The ERFA documentation is::
- - - - - - - -
e r a P v 2 p
- - - - - - - -
Discard velocity component of a pv-vector.
Given:
pv double[2][3] pv-vector
Returned:
p double[3] p-vector
Called:
eraCp copy p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p = ufunc.pv2p(pv)
return p
[docs]def ir():
"""
Initialize an r-matrix to the identity matrix.
Parameters
----------
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraIr``. The ERFA documentation is::
- - - - - -
e r a I r
- - - - - -
Initialize an r-matrix to the identity matrix.
Returned:
r double[3][3] r-matrix
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.ir()
return r
[docs]def zp():
"""
Zero a p-vector.
Parameters
----------
Returns
-------
p : double array
Notes
-----
Wraps ERFA function ``eraZp``. The ERFA documentation is::
- - - - - -
e r a Z p
- - - - - -
Zero a p-vector.
Returned:
p double[3] zero p-vector
This revision: 2020 August 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p = ufunc.zp()
return p
[docs]def zpv():
"""
Zero a pv-vector.
Parameters
----------
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraZpv``. The ERFA documentation is::
- - - - - - -
e r a Z p v
- - - - - - -
Zero a pv-vector.
Returned:
pv double[2][3] zero pv-vector
Called:
eraZp zero p-vector
This revision: 2020 August 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv = ufunc.zpv()
return pv
[docs]def zr():
"""
Initialize an r-matrix to the null matrix.
Parameters
----------
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraZr``. The ERFA documentation is::
- - - - - -
e r a Z r
- - - - - -
Initialize an r-matrix to the null matrix.
Returned:
r double[3][3] r-matrix
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.zr()
return r
[docs]def rxr(a, b):
"""
Multiply two r-matrices.
Parameters
----------
a : double array
b : double array
Returns
-------
atb : double array
Notes
-----
Wraps ERFA function ``eraRxr``. The ERFA documentation is::
- - - - - - -
e r a R x r
- - - - - - -
Multiply two r-matrices.
Given:
a double[3][3] first r-matrix
b double[3][3] second r-matrix
Returned:
atb double[3][3] a * b
Note:
It is permissible to re-use the same array for any of the
arguments.
Called:
eraCr copy r-matrix
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
atb = ufunc.rxr(a, b)
return atb
[docs]def tr(r):
"""
Transpose an r-matrix.
Parameters
----------
r : double array
Returns
-------
rt : double array
Notes
-----
Wraps ERFA function ``eraTr``. The ERFA documentation is::
- - - - - -
e r a T r
- - - - - -
Transpose an r-matrix.
Given:
r double[3][3] r-matrix
Returned:
rt double[3][3] transpose
Note:
It is permissible for r and rt to be the same array.
Called:
eraCr copy r-matrix
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rt = ufunc.tr(r)
return rt
[docs]def rxp(r, p):
"""
Multiply a p-vector by an r-matrix.
Parameters
----------
r : double array
p : double array
Returns
-------
rp : double array
Notes
-----
Wraps ERFA function ``eraRxp``. The ERFA documentation is::
- - - - - - -
e r a R x p
- - - - - - -
Multiply a p-vector by an r-matrix.
Given:
r double[3][3] r-matrix
p double[3] p-vector
Returned:
rp double[3] r * p
Note:
It is permissible for p and rp to be the same array.
Called:
eraCp copy p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rp = ufunc.rxp(r, p)
return rp
[docs]def rxpv(r, pv):
"""
Multiply a pv-vector by an r-matrix.
Parameters
----------
r : double array
pv : double array
Returns
-------
rpv : double array
Notes
-----
Wraps ERFA function ``eraRxpv``. The ERFA documentation is::
- - - - - - - -
e r a R x p v
- - - - - - - -
Multiply a pv-vector by an r-matrix.
Given:
r double[3][3] r-matrix
pv double[2][3] pv-vector
Returned:
rpv double[2][3] r * pv
Notes:
1) The algorithm is for the simple case where the r-matrix r is not
a function of time. The case where r is a function of time leads
to an additional velocity component equal to the product of the
derivative of r and the position vector.
2) It is permissible for pv and rpv to be the same array.
Called:
eraRxp product of r-matrix and p-vector
This revision: 2020 September 26
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
rpv = ufunc.rxpv(r, pv)
return rpv
[docs]def trxp(r, p):
"""
Multiply a p-vector by the transpose of an r-matrix.
Parameters
----------
r : double array
p : double array
Returns
-------
trp : double array
Notes
-----
Wraps ERFA function ``eraTrxp``. The ERFA documentation is::
- - - - - - - -
e r a T r x p
- - - - - - - -
Multiply a p-vector by the transpose of an r-matrix.
Given:
r double[3][3] r-matrix
p double[3] p-vector
Returned:
trp double[3] r^T * p
Note:
It is permissible for p and trp to be the same array.
Called:
eraTr transpose r-matrix
eraRxp product of r-matrix and p-vector
This revision: 2020 May 24
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
trp = ufunc.trxp(r, p)
return trp
[docs]def trxpv(r, pv):
"""
Multiply a pv-vector by the transpose of an r-matrix.
Parameters
----------
r : double array
pv : double array
Returns
-------
trpv : double array
Notes
-----
Wraps ERFA function ``eraTrxpv``. The ERFA documentation is::
- - - - - - - - -
e r a T r x p v
- - - - - - - - -
Multiply a pv-vector by the transpose of an r-matrix.
Given:
r double[3][3] r-matrix
pv double[2][3] pv-vector
Returned:
trpv double[2][3] r^T * pv
Notes:
1) The algorithm is for the simple case where the r-matrix r is not
a function of time. The case where r is a function of time leads
to an additional velocity component equal to the product of the
derivative of the transpose of r and the position vector.
2) It is permissible for pv and rpv to be the same array.
Called:
eraTr transpose r-matrix
eraRxpv product of r-matrix and pv-vector
This revision: 2020 September 26
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
trpv = ufunc.trxpv(r, pv)
return trpv
[docs]def rm2v(r):
"""
Express an r-matrix as an r-vector.
Parameters
----------
r : double array
Returns
-------
w : double array
Notes
-----
Wraps ERFA function ``eraRm2v``. The ERFA documentation is::
- - - - - - - -
e r a R m 2 v
- - - - - - - -
Express an r-matrix as an r-vector.
Given:
r double[3][3] rotation matrix
Returned:
w double[3] rotation vector (Note 1)
Notes:
1) A rotation matrix describes a rotation through some angle about
some arbitrary axis called the Euler axis. The "rotation vector"
returned by this function has the same direction as the Euler axis,
and its magnitude is the angle in radians. (The magnitude and
direction can be separated by means of the function eraPn.)
2) If r is null, so is the result. If r is not a rotation matrix
the result is undefined; r must be proper (i.e. have a positive
determinant) and real orthogonal (inverse = transpose).
3) The reference frame rotates clockwise as seen looking along
the rotation vector from the origin.
This revision: 2015 January 30
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
w = ufunc.rm2v(r)
return w
[docs]def rv2m(w):
"""
Form the r-matrix corresponding to a given r-vector.
Parameters
----------
w : double array
Returns
-------
r : double array
Notes
-----
Wraps ERFA function ``eraRv2m``. The ERFA documentation is::
- - - - - - - -
e r a R v 2 m
- - - - - - - -
Form the r-matrix corresponding to a given r-vector.
Given:
w double[3] rotation vector (Note 1)
Returned:
r double[3][3] rotation matrix
Notes:
1) A rotation matrix describes a rotation through some angle about
some arbitrary axis called the Euler axis. The "rotation vector"
supplied to This function has the same direction as the Euler
axis, and its magnitude is the angle in radians.
2) If w is null, the identity matrix is returned.
3) The reference frame rotates clockwise as seen looking along the
rotation vector from the origin.
This revision: 2020 August 21
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r = ufunc.rv2m(w)
return r
[docs]def pap(a, b):
"""
Position-angle from two p-vectors.
Parameters
----------
a : double array
b : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraPap``. The ERFA documentation is::
- - - - - - -
e r a P a p
- - - - - - -
Position-angle from two p-vectors.
Given:
a double[3] direction of reference point
b double[3] direction of point whose PA is required
Returned (function value):
double position angle of b with respect to a (radians)
Notes:
1) The result is the position angle, in radians, of direction b with
respect to direction a. It is in the range -pi to +pi. The
sense is such that if b is a small distance "north" of a the
position angle is approximately zero, and if b is a small
distance "east" of a the position angle is approximately +pi/2.
2) The vectors a and b need not be of unit length.
3) Zero is returned if the two directions are the same or if either
vector is null.
4) If vector a is at a pole, the result is ill-defined.
Called:
eraPn decompose p-vector into modulus and direction
eraPm modulus of p-vector
eraPxp vector product of two p-vectors
eraPmp p-vector minus p-vector
eraPdp scalar product of two p-vectors
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.pap(a, b)
return c_retval
[docs]def pas(al, ap, bl, bp):
"""
Position-angle from spherical coordinates.
Parameters
----------
al : double array
ap : double array
bl : double array
bp : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraPas``. The ERFA documentation is::
- - - - - - -
e r a P a s
- - - - - - -
Position-angle from spherical coordinates.
Given:
al double longitude of point A (e.g. RA) in radians
ap double latitude of point A (e.g. Dec) in radians
bl double longitude of point B
bp double latitude of point B
Returned (function value):
double position angle of B with respect to A
Notes:
1) The result is the bearing (position angle), in radians, of point
B with respect to point A. It is in the range -pi to +pi. The
sense is such that if B is a small distance "east" of point A,
the bearing is approximately +pi/2.
2) Zero is returned if the two points are coincident.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.pas(al, ap, bl, bp)
return c_retval
[docs]def sepp(a, b):
"""
Angular separation between two p-vectors.
Parameters
----------
a : double array
b : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraSepp``. The ERFA documentation is::
- - - - - - - -
e r a S e p p
- - - - - - - -
Angular separation between two p-vectors.
Given:
a double[3] first p-vector (not necessarily unit length)
b double[3] second p-vector (not necessarily unit length)
Returned (function value):
double angular separation (radians, always positive)
Notes:
1) If either vector is null, a zero result is returned.
2) The angular separation is most simply formulated in terms of
scalar product. However, this gives poor accuracy for angles
near zero and pi. The present algorithm uses both cross product
and dot product, to deliver full accuracy whatever the size of
the angle.
Called:
eraPxp vector product of two p-vectors
eraPm modulus of p-vector
eraPdp scalar product of two p-vectors
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.sepp(a, b)
return c_retval
[docs]def seps(al, ap, bl, bp):
"""
Angular separation between two sets of spherical coordinates.
Parameters
----------
al : double array
ap : double array
bl : double array
bp : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraSeps``. The ERFA documentation is::
- - - - - - - -
e r a S e p s
- - - - - - - -
Angular separation between two sets of spherical coordinates.
Given:
al double first longitude (radians)
ap double first latitude (radians)
bl double second longitude (radians)
bp double second latitude (radians)
Returned (function value):
double angular separation (radians)
Called:
eraS2c spherical coordinates to unit vector
eraSepp angular separation between two p-vectors
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.seps(al, ap, bl, bp)
return c_retval
[docs]def c2s(p):
"""
P-vector to spherical coordinates.
Parameters
----------
p : double array
Returns
-------
theta : double array
phi : double array
Notes
-----
Wraps ERFA function ``eraC2s``. The ERFA documentation is::
- - - - - - -
e r a C 2 s
- - - - - - -
P-vector to spherical coordinates.
Given:
p double[3] p-vector
Returned:
theta double longitude angle (radians)
phi double latitude angle (radians)
Notes:
1) The vector p can have any magnitude; only its direction is used.
2) If p is null, zero theta and phi are returned.
3) At either pole, zero theta is returned.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
theta, phi = ufunc.c2s(p)
return theta, phi
[docs]def p2s(p):
"""
P-vector to spherical polar coordinates.
Parameters
----------
p : double array
Returns
-------
theta : double array
phi : double array
r : double array
Notes
-----
Wraps ERFA function ``eraP2s``. The ERFA documentation is::
- - - - - - -
e r a P 2 s
- - - - - - -
P-vector to spherical polar coordinates.
Given:
p double[3] p-vector
Returned:
theta double longitude angle (radians)
phi double latitude angle (radians)
r double radial distance
Notes:
1) If P is null, zero theta, phi and r are returned.
2) At either pole, zero theta is returned.
Called:
eraC2s p-vector to spherical
eraPm modulus of p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
theta, phi, r = ufunc.p2s(p)
return theta, phi, r
[docs]def pv2s(pv):
"""
Convert position/velocity from Cartesian to spherical coordinates.
Parameters
----------
pv : double array
Returns
-------
theta : double array
phi : double array
r : double array
td : double array
pd : double array
rd : double array
Notes
-----
Wraps ERFA function ``eraPv2s``. The ERFA documentation is::
- - - - - - - -
e r a P v 2 s
- - - - - - - -
Convert position/velocity from Cartesian to spherical coordinates.
Given:
pv double[2][3] pv-vector
Returned:
theta double longitude angle (radians)
phi double latitude angle (radians)
r double radial distance
td double rate of change of theta
pd double rate of change of phi
rd double rate of change of r
Notes:
1) If the position part of pv is null, theta, phi, td and pd
are indeterminate. This is handled by extrapolating the
position through unit time by using the velocity part of
pv. This moves the origin without changing the direction
of the velocity component. If the position and velocity
components of pv are both null, zeroes are returned for all
six results.
2) If the position is a pole, theta, td and pd are indeterminate.
In such cases zeroes are returned for all three.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
theta, phi, r, td, pd, rd = ufunc.pv2s(pv)
return theta, phi, r, td, pd, rd
[docs]def s2c(theta, phi):
"""
Convert spherical coordinates to Cartesian.
Parameters
----------
theta : double array
phi : double array
Returns
-------
c : double array
Notes
-----
Wraps ERFA function ``eraS2c``. The ERFA documentation is::
- - - - - - -
e r a S 2 c
- - - - - - -
Convert spherical coordinates to Cartesian.
Given:
theta double longitude angle (radians)
phi double latitude angle (radians)
Returned:
c double[3] direction cosines
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c = ufunc.s2c(theta, phi)
return c
[docs]def s2p(theta, phi, r):
"""
Convert spherical polar coordinates to p-vector.
Parameters
----------
theta : double array
phi : double array
r : double array
Returns
-------
p : double array
Notes
-----
Wraps ERFA function ``eraS2p``. The ERFA documentation is::
- - - - - - -
e r a S 2 p
- - - - - - -
Convert spherical polar coordinates to p-vector.
Given:
theta double longitude angle (radians)
phi double latitude angle (radians)
r double radial distance
Returned:
p double[3] Cartesian coordinates
Called:
eraS2c spherical coordinates to unit vector
eraSxp multiply p-vector by scalar
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p = ufunc.s2p(theta, phi, r)
return p
[docs]def s2pv(theta, phi, r, td, pd, rd):
"""
Convert position/velocity from spherical to Cartesian coordinates.
Parameters
----------
theta : double array
phi : double array
r : double array
td : double array
pd : double array
rd : double array
Returns
-------
pv : double array
Notes
-----
Wraps ERFA function ``eraS2pv``. The ERFA documentation is::
- - - - - - - -
e r a S 2 p v
- - - - - - - -
Convert position/velocity from spherical to Cartesian coordinates.
Given:
theta double longitude angle (radians)
phi double latitude angle (radians)
r double radial distance
td double rate of change of theta
pd double rate of change of phi
rd double rate of change of r
Returned:
pv double[2][3] pv-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
pv = ufunc.s2pv(theta, phi, r, td, pd, rd)
return pv
[docs]def pdp(a, b):
"""
p-vector inner (=scalar=dot) product.
Parameters
----------
a : double array
b : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraPdp``. The ERFA documentation is::
- - - - - - -
e r a P d p
- - - - - - -
p-vector inner (=scalar=dot) product.
Given:
a double[3] first p-vector
b double[3] second p-vector
Returned (function value):
double a . b
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.pdp(a, b)
return c_retval
[docs]def pm(p):
"""
Modulus of p-vector.
Parameters
----------
p : double array
Returns
-------
c_retval : double array
Notes
-----
Wraps ERFA function ``eraPm``. The ERFA documentation is::
- - - - - -
e r a P m
- - - - - -
Modulus of p-vector.
Given:
p double[3] p-vector
Returned (function value):
double modulus
This revision: 2013 August 7
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
c_retval = ufunc.pm(p)
return c_retval
[docs]def pmp(a, b):
"""
P-vector subtraction.
Parameters
----------
a : double array
b : double array
Returns
-------
amb : double array
Notes
-----
Wraps ERFA function ``eraPmp``. The ERFA documentation is::
- - - - - - -
e r a P m p
- - - - - - -
P-vector subtraction.
Given:
a double[3] first p-vector
b double[3] second p-vector
Returned:
amb double[3] a - b
Note:
It is permissible to re-use the same array for any of the
arguments.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
amb = ufunc.pmp(a, b)
return amb
[docs]def pn(p):
"""
Convert a p-vector into modulus and unit vector.
Parameters
----------
p : double array
Returns
-------
r : double array
u : double array
Notes
-----
Wraps ERFA function ``eraPn``. The ERFA documentation is::
- - - - - -
e r a P n
- - - - - -
Convert a p-vector into modulus and unit vector.
Given:
p double[3] p-vector
Returned:
r double modulus
u double[3] unit vector
Notes:
1) If p is null, the result is null. Otherwise the result is a unit
vector.
2) It is permissible to re-use the same array for any of the
arguments.
Called:
eraPm modulus of p-vector
eraZp zero p-vector
eraSxp multiply p-vector by scalar
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r, u = ufunc.pn(p)
return r, u
[docs]def ppp(a, b):
"""
P-vector addition.
Parameters
----------
a : double array
b : double array
Returns
-------
apb : double array
Notes
-----
Wraps ERFA function ``eraPpp``. The ERFA documentation is::
- - - - - - -
e r a P p p
- - - - - - -
P-vector addition.
Given:
a double[3] first p-vector
b double[3] second p-vector
Returned:
apb double[3] a + b
Note:
It is permissible to re-use the same array for any of the
arguments.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
apb = ufunc.ppp(a, b)
return apb
[docs]def ppsp(a, s, b):
"""
P-vector plus scaled p-vector.
Parameters
----------
a : double array
s : double array
b : double array
Returns
-------
apsb : double array
Notes
-----
Wraps ERFA function ``eraPpsp``. The ERFA documentation is::
- - - - - - - -
e r a P p s p
- - - - - - - -
P-vector plus scaled p-vector.
Given:
a double[3] first p-vector
s double scalar (multiplier for b)
b double[3] second p-vector
Returned:
apsb double[3] a + s*b
Note:
It is permissible for any of a, b and apsb to be the same array.
Called:
eraSxp multiply p-vector by scalar
eraPpp p-vector plus p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
apsb = ufunc.ppsp(a, s, b)
return apsb
[docs]def pvdpv(a, b):
"""
Inner (=scalar=dot) product of two pv-vectors.
Parameters
----------
a : double array
b : double array
Returns
-------
adb : double array
Notes
-----
Wraps ERFA function ``eraPvdpv``. The ERFA documentation is::
- - - - - - - - -
e r a P v d p v
- - - - - - - - -
Inner (=scalar=dot) product of two pv-vectors.
Given:
a double[2][3] first pv-vector
b double[2][3] second pv-vector
Returned:
adb double[2] a . b (see note)
Note:
If the position and velocity components of the two pv-vectors are
( ap, av ) and ( bp, bv ), the result, a . b, is the pair of
numbers ( ap . bp , ap . bv + av . bp ). The two numbers are the
dot-product of the two p-vectors and its derivative.
Called:
eraPdp scalar product of two p-vectors
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
adb = ufunc.pvdpv(a, b)
return adb
[docs]def pvm(pv):
"""
Modulus of pv-vector.
Parameters
----------
pv : double array
Returns
-------
r : double array
s : double array
Notes
-----
Wraps ERFA function ``eraPvm``. The ERFA documentation is::
- - - - - - -
e r a P v m
- - - - - - -
Modulus of pv-vector.
Given:
pv double[2][3] pv-vector
Returned:
r double modulus of position component
s double modulus of velocity component
Called:
eraPm modulus of p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
r, s = ufunc.pvm(pv)
return r, s
[docs]def pvmpv(a, b):
"""
Subtract one pv-vector from another.
Parameters
----------
a : double array
b : double array
Returns
-------
amb : double array
Notes
-----
Wraps ERFA function ``eraPvmpv``. The ERFA documentation is::
- - - - - - - - -
e r a P v m p v
- - - - - - - - -
Subtract one pv-vector from another.
Given:
a double[2][3] first pv-vector
b double[2][3] second pv-vector
Returned:
amb double[2][3] a - b
Note:
It is permissible to re-use the same array for any of the
arguments.
Called:
eraPmp p-vector minus p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
amb = ufunc.pvmpv(a, b)
return amb
[docs]def pvppv(a, b):
"""
Add one pv-vector to another.
Parameters
----------
a : double array
b : double array
Returns
-------
apb : double array
Notes
-----
Wraps ERFA function ``eraPvppv``. The ERFA documentation is::
- - - - - - - - -
e r a P v p p v
- - - - - - - - -
Add one pv-vector to another.
Given:
a double[2][3] first pv-vector
b double[2][3] second pv-vector
Returned:
apb double[2][3] a + b
Note:
It is permissible to re-use the same array for any of the
arguments.
Called:
eraPpp p-vector plus p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
apb = ufunc.pvppv(a, b)
return apb
[docs]def pvu(dt, pv):
"""
Update a pv-vector.
Parameters
----------
dt : double array
pv : double array
Returns
-------
upv : double array
Notes
-----
Wraps ERFA function ``eraPvu``. The ERFA documentation is::
- - - - - - -
e r a P v u
- - - - - - -
Update a pv-vector.
Given:
dt double time interval
pv double[2][3] pv-vector
Returned:
upv double[2][3] p updated, v unchanged
Notes:
1) "Update" means "refer the position component of the vector
to a new date dt time units from the existing date".
2) The time units of dt must match those of the velocity.
3) It is permissible for pv and upv to be the same array.
Called:
eraPpsp p-vector plus scaled p-vector
eraCp copy p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
upv = ufunc.pvu(dt, pv)
return upv
[docs]def pvup(dt, pv):
"""
Update a pv-vector, discarding the velocity component.
Parameters
----------
dt : double array
pv : double array
Returns
-------
p : double array
Notes
-----
Wraps ERFA function ``eraPvup``. The ERFA documentation is::
- - - - - - - -
e r a P v u p
- - - - - - - -
Update a pv-vector, discarding the velocity component.
Given:
dt double time interval
pv double[2][3] pv-vector
Returned:
p double[3] p-vector
Notes:
1) "Update" means "refer the position component of the vector to a
new date dt time units from the existing date".
2) The time units of dt must match those of the velocity.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
p = ufunc.pvup(dt, pv)
return p
[docs]def pvxpv(a, b):
"""
Outer (=vector=cross) product of two pv-vectors.
Parameters
----------
a : double array
b : double array
Returns
-------
axb : double array
Notes
-----
Wraps ERFA function ``eraPvxpv``. The ERFA documentation is::
- - - - - - - - -
e r a P v x p v
- - - - - - - - -
Outer (=vector=cross) product of two pv-vectors.
Given:
a double[2][3] first pv-vector
b double[2][3] second pv-vector
Returned:
axb double[2][3] a x b
Notes:
1) If the position and velocity components of the two pv-vectors are
( ap, av ) and ( bp, bv ), the result, a x b, is the pair of
vectors ( ap x bp, ap x bv + av x bp ). The two vectors are the
cross-product of the two p-vectors and its derivative.
2) It is permissible to re-use the same array for any of the
arguments.
Called:
eraCpv copy pv-vector
eraPxp vector product of two p-vectors
eraPpp p-vector plus p-vector
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
axb = ufunc.pvxpv(a, b)
return axb
[docs]def pxp(a, b):
"""
p-vector outer (=vector=cross) product.
Parameters
----------
a : double array
b : double array
Returns
-------
axb : double array
Notes
-----
Wraps ERFA function ``eraPxp``. The ERFA documentation is::
- - - - - - -
e r a P x p
- - - - - - -
p-vector outer (=vector=cross) product.
Given:
a double[3] first p-vector
b double[3] second p-vector
Returned:
axb double[3] a x b
Note:
It is permissible to re-use the same array for any of the
arguments.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
axb = ufunc.pxp(a, b)
return axb
[docs]def s2xpv(s1, s2, pv):
"""
Multiply a pv-vector by two scalars.
Parameters
----------
s1 : double array
s2 : double array
pv : double array
Returns
-------
spv : double array
Notes
-----
Wraps ERFA function ``eraS2xpv``. The ERFA documentation is::
- - - - - - - - -
e r a S 2 x p v
- - - - - - - - -
Multiply a pv-vector by two scalars.
Given:
s1 double scalar to multiply position component by
s2 double scalar to multiply velocity component by
pv double[2][3] pv-vector
Returned:
spv double[2][3] pv-vector: p scaled by s1, v scaled by s2
Note:
It is permissible for pv and spv to be the same array.
Called:
eraSxp multiply p-vector by scalar
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
spv = ufunc.s2xpv(s1, s2, pv)
return spv
[docs]def sxp(s, p):
"""
Multiply a p-vector by a scalar.
Parameters
----------
s : double array
p : double array
Returns
-------
sp : double array
Notes
-----
Wraps ERFA function ``eraSxp``. The ERFA documentation is::
- - - - - - -
e r a S x p
- - - - - - -
Multiply a p-vector by a scalar.
Given:
s double scalar
p double[3] p-vector
Returned:
sp double[3] s * p
Note:
It is permissible for p and sp to be the same array.
This revision: 2013 June 18
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
sp = ufunc.sxp(s, p)
return sp
[docs]def sxpv(s, pv):
"""
Multiply a pv-vector by a scalar.
Parameters
----------
s : double array
pv : double array
Returns
-------
spv : double array
Notes
-----
Wraps ERFA function ``eraSxpv``. The ERFA documentation is::
- - - - - - - -
e r a S x p v
- - - - - - - -
Multiply a pv-vector by a scalar.
Given:
s double scalar
pv double[2][3] pv-vector
Returned:
spv double[2][3] s * pv
Note:
It is permissible for pv and spv to be the same array.
Called:
eraS2xpv multiply pv-vector by two scalars
This revision: 2020 August 25
Copyright (C) 2013-2021, NumFOCUS Foundation.
Derived, with permission, from the SOFA library. See notes at end of file.
"""
spv = ufunc.sxpv(s, pv)
return spv
```