view release on metacpan or  search on metacpan

erfasrc/src/bi00.c  view on Meta::CPAN

#include "erfa.h"

void eraBi00(double *dpsibi, double *depsbi, double *dra)
/*
**  - - - - - - - -
**   e r a B i 0 0
**  - - - - - - - -
**
**  Frame bias components of IAU 2000 precession-nutation models (part
**  of MHB2000 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 9th September 2002
**     from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
**
**  Copyright (C) 2013-2020, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
/* The frame bias corrections in longitude and obliquity */
   const double DPBIAS = -0.041775  * ERFA_DAS2R,
                DEBIAS = -0.0068192 * ERFA_DAS2R;

/* The ICRS RA of the J2000.0 equinox (Chapront et al., 2002) */
   const double DRA0 = -0.0146 * ERFA_DAS2R;


/* Return the results (which are fixed). */
   *dpsibi = DPBIAS;
   *depsbi = DEBIAS;
   *dra = DRA0;

   return;

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2020, NumFOCUS Foundation.
**  All rights reserved.
**  
**  This library is derived, with permission, from the International
**  Astronomical Union's "Standards of Fundamental Astronomy" library,
**  available from http://www.iausofa.org.
**  
**  The ERFA version is intended to retain identical functionality to
**  the SOFA library, but made distinct through different function and
**  file names, as set out in the SOFA license conditions.  The SOFA
**  original has a role as a reference standard for the IAU and IERS,
**  and consequently redistribution is permitted only in its unaltered
**  state.  The ERFA version is not subject to this restriction and
**  therefore can be included in distributions which do not support the
**  concept of "read only" software.
**  
**  Although the intent is to replicate the SOFA API (other than
**  replacement of prefix names) and results (with the exception of
**  bugs;  any that are discovered will be fixed), SOFA is not
**  responsible for any errors found in this version of the library.
**  
**  If you wish to acknowledge the SOFA heritage, please acknowledge
**  that you are using a library derived from SOFA, rather than SOFA
**  itself.
**  
**  
**  TERMS AND CONDITIONS
**  
**  Redistribution and use in source and binary forms, with or without
**  modification, are permitted provided that the following conditions
**  are met:
**  
**  1 Redistributions of source code must retain the above copyright