#include "sofam.h"
 
void iauPr00(double date1, double date2, double *dpsipr, double *depspr)
/*
**  - - - - - - - -
**   i a u P r 0 0
**  - - - - - - - -
**
**  Precession-rate part of the IAU 2000 precession-nutation models
**  (part of MHB2000).
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  canonical model.
**
**  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 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:  2008 May 27
**
**  Copyright (C) 2008 IAU SOFA Review Board.  See notes at end.
*/
{
   double t;

/* Precession and obliquity corrections (radians per century) */
   static const double PRECOR = -0.29965 * DAS2R,
                       OBLCOR = -0.02524 * DAS2R;


/* Interval between fundamental epoch J2000.0 and given date (JC). */
   t = ((date1 - DJ00) + date2) / DJC;
 
/* Precession rate contributions with respect to IAU 1976/80. */
   *dpsipr = PRECOR * t;
   *depspr = OBLCOR * t;
 
   return;

/*-----------------------------------------------------------------------
**
**  Copyright (C) 2008
**  Standards Of Fundamental Astronomy Review Board
**  of the International Astronomical Union.
**
**  =====================
**  SOFA Software License
**  =====================
**
**  NOTICE TO USER:
**
**  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS
**  WHICH APPLY TO ITS USE.
**
**  1. The Software is owned by the IAU SOFA Review Board ("the Board").
**
**  2. Permission is granted to anyone to use the SOFA software for any
**     purpose, including commercial applications, free of charge and
**     without payment of royalties, subject to the conditions and 
**     restrictions listed below.
**
**  3. You (the user) may copy and adapt the SOFA software and its 
**     algorithms for your own purposes and you may copy and distribute
**     a resulting "derived work" to others on a world-wide, royalty-free 
**     basis, provided that the derived work complies with the following
**     requirements: 
**
**     a) Your work shall be marked or carry a statement that it (i) uses
**        routines and computations derived by you from software provided 
**        by SOFA under license to you; and (ii) does not contain
**        software provided by SOFA or software that has been distributed
**        by or endorsed by SOFA.
**
**     b) The source code of your derived work must contain descriptions
**        of how the derived work is based upon and/or differs from the
**        original SOFA software.
**
**     c) The name(s) of all routine(s) that you distribute shall differ
**        from the SOFA names, even when the SOFA content has not been
**        otherwise changed.
**
**     d) The routine-naming prefix "iau" shall not be used.
**
**     e) The origin of the SOFA components of your derived work must not
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**        software or algorithms embedded in the SOFA software.
**
**     f) These requirements must be reproduced intact in any source
**        distribution and shall apply to anyone to whom you have granted 
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**
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**     results achieved by using the SOFA software, you shall acknowledge
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**
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**
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**
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**
**  Correspondence concerning SOFA software should be addressed as
**  follows:
**
**     Internet email: sofa@rl.ac.uk
**     Postal address: IAU SOFA Center
**                     Rutherford Appleton Laboratory
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**
**---------------------------------------------------------------------*/
}