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# pr00

erfa.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:  2021 May 11

      Copyright (C) 2013-2021, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.