pn06¶

erfa.pn06(date1, date2, dpsi, deps)[source]¶

Precession-nutation, IAU 2006 model: a multi-purpose function, supporting classical (equinox-based) use directly and CIO-based use indirectly.

Parameters:

date1double array
date2double array
dpsidouble array
depsdouble array

Returns:

epsadouble array
rbdouble array
rpdouble array
rbpdouble array
rndouble array
rbpndouble 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:  2021 May 11

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

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pn06¶