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/*
*+
* Name:
* palEcmat
* Purpose:
* Form the equatorial to ecliptic rotation matrix - IAU 2006
* precession model.
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* palEcmat( double date, double rmat[3][3] )
* Arguments:
* date = double (Given)
* TT as Modified Julian Date (JD-2400000.5). The difference
* between TT and TDB is of the order of a millisecond or two
* (i.e. about 0.02 arc-seconds).
* rmat = double[3][3] (Returned)
* Rotation matrix
* Description:
* The equatorial to ecliptic rotation matrix is found and returned.
* The matrix is in the sense V(ecl) = RMAT * V(equ); the
* equator, equinox and ecliptic are mean of date.
* Authors:
* PTW: Pat Wallace (STFC)
* DSB: David Berry (JAC, Hawaii)
* {enter_new_authors_here}
* History:
* 2012-02-10 (DSB):
* Initial version with documentation taken from Fortran SLA
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 1996 Rutherford Appleton Laboratory
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* This program is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either
* version 3 of the License, or (at your option) any later
* version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "palmac.h"
#include "pal1sofa.h"
void palEcmat( double date, double rmat[3][3] ) {
/* Mean obliquity (the angle between the ecliptic and mean equator of
date). */
double eps0 = eraObl06( PAL__MJD0, date );
/* Matrix */
palDeuler( "X", eps0, 0.0, 0.0, rmat );
}
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