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/*****************************************************************************
* Johns Hopkins University
* Center For Astrophysical Sciences
* FUSE
*****************************************************************************
*
* Synopsis: double helio_vel(double mjdate, double ra, double dec)
*
* Description: Computes the Earth's orbital velocity in the direction
* of ra,dec to convert to heliocentric velocity.
*
* Arguments: double mjdate Mod. Julian date of observation
* double ra (deg) J2000.0 right ascension
* double dec (deg) J2000.0 declination
*
* Returns: double (km/s) velocity in direction of source
*
* Calls: slaEvp evp.f
* slaDcs2c dcs2c.f
* slaDvdv dvdv.f
*
* History: 03/05/98 E. Murphy Begin work.
* 03/05/98 E. Murphy Initial version working
* 05/31/00 peb Implemented cfortran.h calls for slalib
* functions.
* 06/15/01 V. Dixon Correct sign of return value to agree
* with astronomical convention.
* 12/18/03 bjg Change calfusettag.h to calfuse.h
*
* References: This routine makes use of the Starlink set of astronomical
* subroutines (SLALIB). More information can be found at
* http://star-www.rl.ac.uk.
****************************************************************************/
#include <stdio.h>
#ifdef CFORTRAN
#include "cfortran.h"
PROTOCCALLSFSUB3(SLA_DCS2C, sla_dcs2c, DOUBLE, DOUBLE, DOUBLEV)
#define slaDcs2c(A, B, V) \
CCALLSFSUB3(SLA_DCS2C, sla_dcs2c, DOUBLE, DOUBLE, DOUBLEV, A, B, V)
PROTOCCALLSFFUN2(DOUBLE, SLA_DVDV, sla_dvdv, DOUBLEV, DOUBLEV)
#define slaDvdv(VA, VB) \
CCALLSFFUN2(SLA_DVDV, sla_dvdv, DOUBLEV, DOUBLEV, VA, VB)
PROTOCCALLSFSUB6(SLA_EVP, sla_evp, DOUBLE, DOUBLE, DOUBLEV, DOUBLEV, \
DOUBLEV, DOUBLEV)
#define slaEvp(DATE, DEQX, DVB, DPB, DVH, DPH) \
CCALLSFSUB6(SLA_EVP, sla_evp, DOUBLE, DOUBLE, DOUBLEV, DOUBLEV, \
DOUBLEV, DOUBLEV, DATE, DEQX, DVB, DPB, DVH, DPH)
#else
#include "slalib.h"
#include "slamac.h"
#endif
#include "calfuse.h"
double helio_vel(double mjdate, double ra, double dec)
{
/* Define variables. */
double dvb[3], dpb[3], dvh[3], dph[3], vect[3];
/*
* Evp returns four 3-vectors containing the barycentric velocity and
* position (dvb,dpb) and the heliocentric velocity and position
* (dvh,dph) of the Earth on the date mjdate. It requires a modified
* Julian date as input. Output has units of AU for positions and
* AU/s for velocities.
*/
slaEvp(mjdate, 2000.0, dvb, dpb, dvh, dph);
/* Convert the J2000.0 RA and DEC into a 3-vector position */
slaDcs2c(RADIAN*ra, RADIAN*dec, vect);
/*
* Compute the dot product of the RA DEC position vector and the
* heliocentric velocity vector. Mutliply by km/AU to get velocity
* in km/s.
*/
return slaDvdv(vect, dvh)*149.5978707E6;
}
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