c2tpe¶
- erfa.c2tpe(tta, ttb, uta, utb, dpsi, deps, xp, yp)[source]¶
Form the celestial to terrestrial matrix given the date, the UT1, the nutation and the polar motion.
- Parameters:
- ttadouble array
- ttbdouble array
- utadouble array
- utbdouble array
- dpsidouble array
- depsdouble array
- xpdouble array
- ypdouble array
- Returns:
- rc2tdouble 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: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.