nutm80.c

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#include "erfa.h"

void eraNutm80(double date1, double date2, double rmatn[3][3])
/*
**  - - - - - - - - - -
**   e r a N u t m 8 0
**  - - - - - - - - - -
**
**  Form the matrix of nutation for a given date, IAU 1980 model.
**
**  Given:
**     date1,date2    double          TDB date (Note 1)
**
**  Returned:
**     rmatn          double[3][3]    nutation matrix
**
**  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(true) = rmatn * V(mean),
**     where the p-vector V(true) is with respect to the true
**     equatorial triad of date and the p-vector V(mean) is with
**     respect to the mean equatorial triad of date.
**
**  Called:
**     eraNut80     nutation, IAU 1980
**     eraObl80     mean obliquity, IAU 1980
**     eraNumat     form nutation matrix
**
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
   double dpsi, deps, epsa;

/* Nutation components and mean obliquity. */
   eraNut80(date1, date2, &dpsi, &deps);
   epsa = eraObl80(date1, date2);

/* Build the rotation matrix. */
   eraNumat(epsa, dpsi, deps, rmatn);

   return;

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2015, 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.
**  
**  
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