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# bi00

erfa.bi00()

  Frame bias components of IAU 2000 precession-nutation models; part of the Mathews-Herring-Buffett (MHB2000) nutation series, with additions.

  Returns:
    dpsibi double array
    depsbi double array
    dra double array

  Notes

  Wraps ERFA function `eraBi00`. The ERFA documentation is:

      - - - - - - - -
       e r a B i 0 0
      - - - - - - - -

      Frame bias components of IAU 2000 precession-nutation models;  part
      of the Mathews-Herring-Buffett (MHB2000) nutation series, with
      additions.

      Returned:
         dpsibi,depsbi  double  longitude and obliquity corrections
         dra            double  the ICRS RA of the J2000.0 mean equinox

      Notes:

      1) The frame bias corrections in longitude and obliquity (radians)
         are required in order to correct for the offset between the GCRS
         pole and the mean J2000.0 pole.  They define, with respect to the
         GCRS frame, a J2000.0 mean pole that is consistent with the rest
         of the IAU 2000A precession-nutation model.

      2) In addition to the displacement of the pole, the complete
         description of the frame bias requires also an offset in right
         ascension.  This is not part of the IAU 2000A model, and is from
         Chapront et al. (2002).  It is returned in radians.

      3) This is a supplemented 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:

         Chapront, J., Chapront-Touze, M. & Francou, G., Astron.
         Astrophys., 387, 700, 2002.

         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 2002 September 9
         from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.

      This revision:  2021 May 11

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