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/*
*+
* Name:
* palEvp
* Purpose:
* Returns the barycentric and heliocentric velocity and position of the
* Earth.
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* void palEvp( double date, double deqx, double dvb[3], double dpb[3],
* double dvh[3], double dph[3] )
* Arguments:
* date = double (Given)
* TDB (loosely ET) as a Modified Julian Date (JD-2400000.5)
* deqx = double (Given)
* Julian epoch (e.g. 2000.0) of mean equator and equinox of the
* vectors returned. If deqx <= 0.0, all vectors are referred to the
* mean equator and equinox (FK5) of epoch date.
* dvb = double[3] (Returned)
* Barycentric velocity (AU/s, AU)
* dpb = double[3] (Returned)
* Barycentric position (AU/s, AU)
* dvh = double[3] (Returned)
* heliocentric velocity (AU/s, AU)
* dph = double[3] (Returned)
* Heliocentric position (AU/s, AU)
* Description:
* Returns the barycentric and heliocentric velocity and position of the
* Earth at a given epoch, given with respect to a specified equinox.
* For information about accuracy, see the function eraEpv00.
* Authors:
* PTW: Pat Wallace (STFC)
* {enter_new_authors_here}
* History:
* 2012-02-13 (PTW):
* Initial version.
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 2005 Patrick T. Wallace
* 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 palEvp( double date, double deqx, double dvb[3], double dpb[3],
double dvh[3], double dph[3] ){
/* Local Variables; */
int i;
double pvh[2][3], pvb[2][3], d1, d2, r[3][3];
/* BCRS PV-vectors. */
eraEpv00 ( 2400000.5, date, pvh, pvb );
/* Was precession to another equinox requested? */
if ( deqx > 0.0 ) {
/* Yes: compute precession matrix from J2000.0 to deqx. */
eraEpj2jd ( deqx, &d1, &d2 );
eraPmat06 ( d1, d2, r );
/* Rotate the PV-vectors. */
eraRxpv ( r, pvh, pvh );
eraRxpv ( r, pvb, pvb );
}
/* Return the required vectors. */
for ( i = 0; i < 3; i++ ) {
dvh[i] = pvh[1][i] / PAL__SPD;
dvb[i] = pvb[1][i] / PAL__SPD;
dph[i] = pvh[0][i];
dpb[i] = pvb[0][i];
}
}
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