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/*****************************************************************************
* Johns Hopkins University
* Center For Astrophysical Sciences
* FUSE
*****************************************************************************
*
* Synopsis: cf_limbang_calc(fitsfile *outfits, double mjd)
* cf_min_limbang(fitsfile *outfits,
* double mjd_start, double mjd_end)
* Description: cf_limbang_calc - Calculates the limb angle at a given mjd
* cf_min_limbang - determines the minimum limb angle between
* the start and end times. The limb angle is
* calculated every 8.6 seconds( .0001 MJD)
*
* Arguments: fitsfile *outfits Pointer to FITS file containing the
* input data and orbital elements
* double mjd The limb angle calculation is done for
* this time. The time is given as
* a Modified Julian Date.
* double mjd_start The range of times for which the minimum
* double mjd_end limb angle should be determined.
* Both are given as Modified Julian Dates.
*
* History: 08/09/99 mlr copied cf_velang.c to start
* 08/09/99 mlr removed excess calls then made the
* limb_ang calls - same as cf_check_point
*
****************************************************************************/
#include <stdio.h>
#include "calfuse.h"
#include "sgp4.h"
static char CF_PRGM_ID[] = "cf_limbang";
SGP4 set_orbit_parms(fitsfile *);
double cf_limbang_calc(fitsfile *outfits, double mjd)
{
int status=0, isday_dummy;
char comment[FLEN_CARD];
double ra, dec, pos[3], vel[3];
double lim_ang, zdist_dummy;
SGP4 sgp4;
sgp4 = set_orbit_parms(outfits);
/* get the state vector at time mjd */
SGP4_getStateVector(sgp4, mjd, pos, vel);
SGP4_precess(pos, mjd, MJD2000); SGP4_precess(vel, mjd, MJD2000);
FITS_read_key(outfits, TDOUBLE, "RA_TARG", &ra, comment, &status);
FITS_read_key(outfits, TDOUBLE, "DEC_TARG", &dec, comment, &status);
lim_ang = state_limb(pos, mjd, ra, dec, &zdist_dummy, &isday_dummy);
return(lim_ang);
}
void cf_min_limbang(fitsfile *outfits, double mjd_start, double mjd_end)
{
int status = 0;
double lim_ang, min_lim;
double mjd;
mjd = mjd_start;
min_lim = cf_limbang_calc(outfits, mjd);
#ifdef DEBUG
printf("mjd: %lf mjd_end = %lf minlim = %lf\n", mjd, mjd_end, min_lim);
#endif
/* .0001 = 8.6 seconds */
while ( (mjd_end - mjd) > .0001 )
{
mjd = mjd + .0001;
lim_ang = cf_limbang_calc(outfits, mjd);
#ifdef DEBUG
printf("mjd: %lf mjd_end = %lf minlim = %lf, limang = %lf\n",
mjd, mjd_end, min_lim, lim_ang);
#endif
if (lim_ang < min_lim) min_lim = lim_ang;
}
mjd = mjd_end;
lim_ang = cf_limbang_calc(outfits, mjd);
#ifdef DEBUG
printf("mjd: %lf mjd_end = %lf minlim = %lf, limang = %lf\n",
mjd, mjd_end, min_lim, lim_ang);
#endif
if (lim_ang < min_lim) min_lim = lim_ang;
#ifdef DEBUG
printf("mjd: %lf mjd_end = %lf minlim = %lf\n", mjd, mjd_end, min_lim);
#endif
FITS_update_key(outfits, TDOUBLE, "MIN_LIMB", &min_lim, NULL, &status);
}
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