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# pmat06

erfa.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:  2021 May 11

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