From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001
From: Joseph Hunkeler <jhunkeler@gmail.com>
Date: Wed, 4 Mar 2015 21:21:30 -0500
Subject: Initial commit

---
 src/fes/cf_limbang.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 src/fes/cf_limbang.c

(limited to 'src/fes/cf_limbang.c')

diff --git a/src/fes/cf_limbang.c b/src/fes/cf_limbang.c
new file mode 100644
index 0000000..8bd230f
--- /dev/null
+++ b/src/fes/cf_limbang.c
@@ -0,0 +1,100 @@
+/*****************************************************************************
+ *              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);
+
+}
-- 
cgit