erfa.pmat00(date1, date2)[source]

Precession matrix (including frame bias) from GCRS to a specified date, IAU 2000 model.

date1double array
date2double array
rbpdouble array


Wraps ERFA function eraPmat00. The ERFA documentation is:

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 e r a P m a t 0 0
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Precession matrix (including frame bias) from GCRS to a specified
date, IAU 2000 model.

   date1,date2  double          TT as a 2-part Julian Date (Note 1)

   rbp          double[3][3]    bias-precession matrix (Note 2)


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.

   eraBp00      frame bias and precession matrices, IAU 2000


   IAU: Trans. International Astronomical Union, Vol. XXIVB;  Proc.
   24th General Assembly, Manchester, UK.  Resolutions B1.3, B1.6.

This revision:  2021 May 11

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