spacecruft
/
sattools
1
0
Fork 0
Code Releases Activity
sattools/src/allnight.c

450 lines
8.5 KiB
C
Raw Permalink Blame History

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <getopt.h>
#include "sgdp4h.h"
#define LIM 384
#define D2R M_PI/180.0
#define R2D 180.0/M_PI
#define XKMPAU 149597879.691 // AU in km
struct map
{
int site_id;
double mjd;
float saltmin, alt;
char nfd[LIM], observer[32], datadir[LIM];
double lat, lng;
float length;
} m;
void allnight (void);
void sunpos_xyz (double, xyz_t *, double *, double *);
double modulo (double, double);
void equatorial2horizontal (double, double, double, double *, double *);
void mjd2date (double mjd, char *date);
double gmst (double mjd);
void nfd_now (char *s);
double nfd2mjd (char *date);
void get_site (int site_id);
double date2mjd (int year, int month, double day);
void usage (void);
int
main (int argc, char *argv[])
{
int arg = 0;
char *env;
// Default settings
strcpy (m.observer, "Unknown");
m.site_id = 0;
m.mjd = -1.0;
m.saltmin = -6.0;
m.alt = 0.0;
m.lat = 0.0;
m.lng = 0.0;
// Get default site
env = getenv ("ST_DATADIR");
if (env != NULL)
{
strcpy (m.datadir, env);
}
else
{
printf ("ST_DATADIR environment variable not found.\n");
}
env = getenv ("ST_COSPAR");
if (env != NULL)
{
get_site (atoi (env));
}
else
{
printf ("ST_COSPAR environment variable not found.\n");
}
// Get current time
nfd_now (m.nfd);
m.mjd = nfd2mjd (m.nfd);
// Decode options
while ((arg = getopt (argc, argv, "t:s:S:h")) != -1)
{
switch (arg)
{
case 't':
strcpy (m.nfd, optarg);
m.mjd = nfd2mjd (m.nfd);
break;
case 'S':
m.saltmin = atof (optarg);
break;
case 's':
get_site (atoi (optarg));
break;
case 'h':
usage ();
return 0;
break;
default:
usage ();
return 0;
}
}
// Compute set/rise times of sun
allnight ();
return 0;
}
// Usage
void
usage (void)
{
printf ("allnight t:s:S:\n\n");
printf ("t date/time (yyyy-mm-ddThh:mm:ss.sss) [default: now]\n");
printf ("S Minimum sun altitude\n");
printf ("s site (COSPAR)\n");
return;
}
// Convert equatorial into horizontal coordinates
void
equatorial2horizontal (double mjd, double ra, double de, double *azi,
double *alt)
{
double h;
h = gmst (mjd) + m.lng - ra;
*azi =
modulo (atan2
(sin (h * D2R),
cos (h * D2R) * sin (m.lat * D2R) -
tan (de * D2R) * cos (m.lat * D2R)) * R2D, 360.0);
*alt =
asin (sin (m.lat * D2R) * sin (de * D2R) +
cos (m.lat * D2R) * cos (de * D2R) * cos (h * D2R)) * R2D;
return;
}
// Return x modulo y [0,y)
double
modulo (double x, double y)
{
x = fmod (x, y);
if (x < 0.0)
x += y;
return x;
}
// Solar position
void
sunpos_xyz (double mjd, xyz_t * pos, double *ra, double *de)
{
double jd, t, l0, m, e, c, r;
double n, s, ecl;
jd = mjd + 2400000.5;
t = (jd - 2451545.0) / 36525.0;
l0 = modulo (280.46646 + t * (36000.76983 + t * 0.0003032), 360.0) * D2R;
m = modulo (357.52911 + t * (35999.05029 - t * 0.0001537), 360.0) * D2R;
e = 0.016708634 + t * (-0.000042037 - t * 0.0000001267);
c = (1.914602 + t * (-0.004817 - t * 0.000014)) * sin (m) * D2R;
c += (0.019993 - 0.000101 * t) * sin (2.0 * m) * D2R;
c += 0.000289 * sin (3.0 * m) * D2R;
r = 1.000001018 * (1.0 - e * e) / (1.0 + e * cos (m + c));
n = modulo (125.04 - 1934.136 * t, 360.0) * D2R;
s = l0 + c + (-0.00569 - 0.00478 * sin (n)) * D2R;
ecl =
(23.43929111 +
(-46.8150 * t - 0.00059 * t * t + 0.001813 * t * t * t) / 3600.0 +
0.00256 * cos (n)) * D2R;
*ra = atan2 (cos (ecl) * sin (s), cos (s)) * R2D;
*de = asin (sin (ecl) * sin (s)) * R2D;
pos->x = r * cos (*de * D2R) * cos (*ra * D2R) * XKMPAU;
pos->y = r * cos (*de * D2R) * sin (*ra * D2R) * XKMPAU;
pos->z = r * sin (*de * D2R) * XKMPAU;
return;
}
void
allnight (void)
{
int flag;
xyz_t sunpos;
double ra, de, azi, alt, alt0;
double mjd, mjdrise = -1.0, mjdset = -1.0;
char nfd[32];
// Find solar altitude at reference time
sunpos_xyz (m.mjd, &sunpos, &ra, &de);
equatorial2horizontal (m.mjd, ra, de, &azi, &alt);
// Sun below limit, find rise, then set
if (alt < m.saltmin)
{
for (flag = 0, mjd = m.mjd; mjd < m.mjd + 0.5; mjd += 1.0 / 86400)
{
sunpos_xyz (mjd, &sunpos, &ra, &de);
equatorial2horizontal (mjd, ra, de, &azi, &alt);
if (flag != 0)
{
if (alt > m.saltmin && alt0 <= m.saltmin)
mjdrise = mjd;
}
if (flag == 0)
flag = 1;
alt0 = alt;
}
for (flag = 0, mjd = m.mjd - 0.5; mjd < m.mjd; mjd += 1.0 / 86400)
{
sunpos_xyz (mjd, &sunpos, &ra, &de);
equatorial2horizontal (mjd, ra, de, &azi, &alt);
if (flag != 0)
{
if (alt < m.saltmin && alt0 >= m.saltmin)
mjdset = mjd;
}
if (flag == 0)
flag = 1;
alt0 = alt;
}
// Sun above limit, find set, and rise
}
else
{
for (flag = 0, mjd = m.mjd; mjd < m.mjd + 1.0; mjd += 1.0 / 86400)
{
sunpos_xyz (mjd, &sunpos, &ra, &de);
equatorial2horizontal (mjd, ra, de, &azi, &alt);
if (flag != 0)
{
if (alt > m.saltmin && alt0 <= m.saltmin)
mjdrise = mjd;
if (alt < m.saltmin && alt0 >= m.saltmin)
mjdset = mjd;
}
if (flag == 0)
flag = 1;
alt0 = alt;
}
}
m.mjd = mjdset;
mjd2date (m.mjd, m.nfd);
mjd2date (mjdrise, nfd);
printf ("%s %s\n", m.nfd, nfd);
return;
}
// Compute Date from Julian Day
void
mjd2date (double mjd, char *date)
{
double f, jd, dday;
int z, alpha, a, b, c, d, e;
int year, month, day, hour, min;
float sec, x;
jd = mjd + 2400000.5;
jd += 0.5;
z = floor (jd);
f = fmod (jd, 1.);
if (z < 2299161)
a = z;
else
{
alpha = floor ((z - 1867216.25) / 36524.25);
a = z + 1 + alpha - floor (alpha / 4.);
}
b = a + 1524;
c = floor ((b - 122.1) / 365.25);
d = floor (365.25 * c);
e = floor ((b - d) / 30.6001);
dday = b - d - floor (30.6001 * e) + f;
if (e < 14)
month = e - 1;
else
month = e - 13;
if (month > 2)
year = c - 4716;
else
year = c - 4715;
day = (int) floor (dday);
x = 24.0 * (dday - day);
x = 3600. * fabs (x) + 0.0001;
sec = fmod (x, 60.);
x = (x - sec) / 60.;
min = fmod (x, 60.);
x = (x - min) / 60.;
hour = x;
sec = floor (1000.0 * sec) / 1000.0;
sprintf (date, "%04d-%02d-%02dT%02d:%02d:%02.0f", year, month, day, hour,
min, sec);
return;
}
// Greenwich Mean Sidereal Time
double
gmst (double mjd)
{
double t, gmst;
t = (mjd - 51544.5) / 36525.0;
gmst =
modulo (280.46061837 + 360.98564736629 * (mjd - 51544.5) +
t * t * (0.000387933 - t / 38710000), 360.0);
return gmst;
}
// Present nfd
void
nfd_now (char *s)
{
time_t rawtime;
struct tm *ptm;
// Get UTC time
time (&rawtime);
ptm = gmtime (&rawtime);
sprintf (s, "%04d-%02d-%02dT%02d:%02d:%02d", ptm->tm_year + 1900,
ptm->tm_mon + 1, ptm->tm_mday, ptm->tm_hour, ptm->tm_min,
ptm->tm_sec);
return;
}
// nfd2mjd
double
nfd2mjd (char *date)
{
int year, month, day, hour, min, sec;
double mjd, dday;
sscanf (date, "%04d-%02d-%02dT%02d:%02d:%02d", &year, &month, &day, &hour,
&min, &sec);
dday = day + hour / 24.0 + min / 1440.0 + sec / 86400.0;
mjd = date2mjd (year, month, dday);
return mjd;
}
// Compute Julian Day from Date
double
date2mjd (int year, int month, double day)
{
int a, b;
double jd;
if (month < 3)
{
year--;
month += 12;
}
a = floor (year / 100.);
b = 2. - a + floor (a / 4.);
if (year < 1582)
b = 0;
if (year == 1582 && month < 10)
b = 0;
if (year == 1582 && month == 10 && day <= 4)
b = 0;
jd =
floor (365.25 * (year + 4716)) + floor (30.6001 * (month + 1)) + day + b -
1524.5;
return jd - 2400000.5;
}
// Get observing site
void
get_site (int site_id)
{
int i = 0;
char line[LIM];
FILE *file;
int id;
double lat, lng;
float alt;
char abbrev[3], observer[64], filename[LIM];
sprintf (filename, "%s/data/sites.txt", m.datadir);
file = fopen (filename, "r");
if (file == NULL)
{
printf ("File with site information not found!\n");
return;
}
while (fgets (line, LIM, file) != NULL)
{
// Skip
if (strstr (line, "#") != NULL)
continue;
// Strip newline
line[strlen (line) - 1] = '\0';
// Read data
sscanf (line, "%4d %2s %lf %lf %f", &id, abbrev, &lat, &lng, &alt);
strcpy (observer, line + 38);
// Change to km
alt /= 1000.0;
if (id == site_id)
{
m.lat = lat;
m.lng = lng;
m.alt = alt;
m.site_id = id;
strcpy (m.observer, observer);
}
}
fclose (file);
return;
}
View Git Blame Copy Permalink