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sat_eph.c
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sat_eph.c
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#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include <math.h>
#include <time.h>
#include "watdefs.h"
#include "afuncs.h"
#include "comets.h"
#include "date.h"
#include "norad.h"
#include "mpc_func.h"
#include "observe.h"
/* Code to generate topocentric ephemerides from TLE data, mostly focussed
on the TLEs provided in https://www.github.com/Bill-Gray/tles. The program
can be compiled for standalone use or for use with the on-line artsat
ephemeris service at https://www.projectpluto.com/sat_eph.htm (q.v.). */
#define PI 3.1415926535897932384626433832795028841971693993751058209749445923
typedef struct
{
double lat, lon, alt, rho_sin_phi, rho_cos_phi;
double jd_start, jd_end, step_size;
int n_steps;
const char *desig;
} ephem_t;
static int verbose = 0;
static char *fgets_trimmed( char *buff, const int buffsize, FILE *ifile)
{
char *rval = fgets( buff, buffsize, ifile);
if( rval)
{
size_t i = 0;
while( rval[i] != 10 && rval[i] != 13 && rval[i])
i++;
while( i && rval[i - 1] == ' ')
i--; /* drop trailing spaces */
rval[i] = '\0';
}
return( rval);
}
static void show_base_60( char *buff, const unsigned n_millisec)
{
snprintf( buff, 15, "%03u %02u %02u.%03u",
n_millisec / 3600000u, (n_millisec / 60000u) % 60u,
(n_millisec / 1000u) % 60u, n_millisec % 1000u);
}
static void put_ra_in_buff( char *buff, double ra)
{
ra = fmod( ra, 2. * PI);
if( ra < 0.)
ra += PI + PI;
show_base_60( buff, (unsigned)( 3600. * 1000. * ra * 12. / PI));
memmove( buff, buff + 1, strlen( buff)); /* remove leading zero */
}
static void put_dec_in_buff( char *buff, const double dec)
{
show_base_60( buff, (unsigned)( 3600. * 1000. * fabs( dec) * 180. / PI));
*buff = (dec > 0. ? '+' : '-');
}
static double angle_between( const double *a, const double *b)
{
const double cos_ang = dot_product( a, b) /
sqrt( dot_product( a, a) * dot_product( b, b));
double rval = acose( cos_ang);
return( rval * 180. / PI);
}
static inline bool desig_match( const tle_t *tle, const char *desig)
{
size_t i = 0;
bool rval = false;
while( isdigit( desig[i]))
i++;
if( i == 5)
{
if( !desig[i]) /* desig is all digits -> it's the NORAD # */
rval = (atoi( desig) == tle->norad_number);
else
{
i = strlen( desig);
if( i > 5 && i < 9)
rval = !memcmp( tle->intl_desig, desig, i) && tle->intl_desig[i] <= ' ';
}
}
return( rval);
}
/* Generates unit vector in the direction of ivect and stores it in z_vect;
a unit vector perpendicular to that in the xy plane, stored in x_vect;
and a unit vector perpendicular to both, stored in y_vect. */
static double make_orthogonal_basis( const double *ivect,
double *x_vect, double *y_vect, double *z_vect)
{
double rval, len;
memcpy( z_vect, ivect, 3 * sizeof( double));
rval = normalize_vect3( z_vect);
len = hypot( z_vect[0], z_vect[1]);
x_vect[0] = z_vect[1] / len;
x_vect[1] = -z_vect[0] / len;
x_vect[2] = 0.;
vector_cross_product( y_vect, z_vect, x_vect);
return( rval);
}
/* 'obs_pos' = observer position relative to the geocenter, km
'topo_posn' = artsat position relative to the observer, km
'sat_vel' = artsat vel, km/minute (usual, though somewhat oddball, SxPx units)
'*motion_pa' = returned posn angle of motion, degrees
apparent total angular motion is returned */
static double compute_angular_rates( const double *obs_pos, const double *topo_posn,
const double *sat_vel, double *motion_pa)
{
double vel[3]; /* velocity of sat relative to observer */
double x_vect[3]; /* unit vector in equatorial plane perpendicular to topo_posn */
double y_vect[3]; /* unit vector perpendicular to topo_posn & x_vect */
double z_vect[3]; /* unit vector version of topo_posn */
double xmotion, ymotion, total_motion, dist;
const double omega_E = 1.00273790934;
/* Earth rotations per sidereal day (non-constant) */
const double omega = omega_E * 2. * PI / minutes_per_day;
/* Earth rotational rate in radians/minute */
vel[0] = sat_vel[0] + omega * obs_pos[1];
vel[1] = sat_vel[1] - omega * obs_pos[0];
vel[2] = sat_vel[2];
dist = make_orthogonal_basis( topo_posn, x_vect, y_vect, z_vect);
xmotion = dot_product( vel, x_vect) / dist; /* all in radians/minute */
ymotion = dot_product( vel, y_vect) / dist;
total_motion = hypot( xmotion, ymotion);
*motion_pa = PI + atan2( xmotion, ymotion);
*motion_pa *= 180. / PI;
return( total_motion * (180. / PI) * 60.); /* cvt to arcmin/min = arcsec/sec */
}
static char _header[200];
static int motion_units = 1; /* default to '/minute = degrees/hr = "/sec */
static int show_ephems_from( const char *path_to_tles, const ephem_t *e,
const char *filename, int start_line)
{
FILE *ifile;
char line0[100], line1[100], line2[100];
int show_it = 1;
double jd_tle = 0., tle_range = 1e+10, abs_mag = 0.;
const bool is_geocentric = (e->rho_sin_phi == 0. && e->rho_cos_phi == 0.);
static const char *header_text =
"Date (UTC) Time R.A. (J2000) decl Azim Alt Elong"
" LuElo Dist(km) \"/sec PA";
static const char *geo_header_text =
"Date (UTC) Time R.A. (J2000) decl Elong LuElo Dist(km) \"/sec PA";
if( verbose)
printf( "Should examine '%s'; start line %d\n", filename, start_line);
snprintf( line0, sizeof( line0), "%s/%s", path_to_tles, filename);
ifile = fopen( line0, "rb");
if( !ifile)
{
fprintf( stderr, "'%s' not opened\n", line0);
exit( 0);
}
*line0 = *line1 = '\0';
while( fgets_trimmed( line2, sizeof( line2), ifile))
{
tle_t tle;
if( *line2 == '#')
{
char *tptr = strstr( line2, " H ");
if( !memcmp( line2, "# MJD ", 6))
{
jd_tle = atof( line2 + 6) + 2400000.5;
tle_range = 1.;
show_it = (jd_tle < e->jd_end && jd_tle + tle_range > e->jd_start);
}
else if( tptr)
{
abs_mag = atof( tptr + 2);
if( verbose)
printf( "H = %.3f\n", abs_mag);
}
}
else if( show_it && parse_elements( line1, line2, &tle) >= 0
&& desig_match( &tle, e->desig))
{
double sat_params[N_SAT_PARAMS], jd = e->jd_start;
size_t i, j;
const int is_deep_type = select_ephemeris( &tle);
if( is_deep_type)
SDP4_init( sat_params, &tle);
else
SGP4_init( sat_params, &tle);
if( verbose > 1)
{
printf( "Got TLEs for %f :\n", jd);
printf( "%s\n%s\n%s\n", line0, line1, line2);
}
for( i = 0; i < (size_t)e->n_steps; i++,
jd = e->jd_start + (double)i * e->step_size)
if( (int)i >= start_line && jd >= jd_tle && jd < jd_tle + tle_range)
{
char buff[90], dec_buff[20], ra_buff[20], alt_buff[17];
double pos[3], vel[3], obs_pos[3], ra, dec, dist;
const double t_since = (jd - tle.epoch) * minutes_per_day;
double solar_xyzr[4], lunar_xyzr[4], topo_posn[3], elong;
double motion_rate, motion_pa;
const char *format_string;
if( !i)
{
printf( "\nEphemerides for %05d = %s%.2s-%s\n",
tle.norad_number,
(atoi( tle.intl_desig) > 57000) ? "19" : "20",
tle.intl_desig, tle.intl_desig + 2);
snprintf( _header, sizeof( _header),
"%s\n%s", line0, (is_geocentric ? geo_header_text : header_text));
strcat( _header, abs_mag ? " Mag\n" : "\n");
if( motion_units == 60)
{
char *tptr = strstr( _header, "/sec ");
assert( tptr);
memcpy( tptr, "/min", 4);
}
printf( "%s", _header);
}
full_ctime( buff, jd, FULL_CTIME_YMD | FULL_CTIME_MONTHS_AS_DIGITS
| FULL_CTIME_LEADING_ZEROES);
if( is_deep_type)
SDP4( t_since, &tle, sat_params, pos, vel);
else
SGP4( t_since, &tle, sat_params, pos, vel);
observer_cartesian_coords( jd, e->lon, e->rho_cos_phi,
e->rho_sin_phi, obs_pos);
get_satellite_ra_dec_delta( obs_pos, pos, &ra, &dec, &dist);
epoch_of_date_to_j2000( jd, &ra, &dec);
put_ra_in_buff( ra_buff, ra);
put_dec_in_buff( dec_buff, dec);
ra_buff[10] = dec_buff[9] = '\0';
for( j = 0; j < 3; j++)
topo_posn[j] = pos[j] - obs_pos[j];
motion_rate = compute_angular_rates( obs_pos, topo_posn, vel, &motion_pa);
lunar_solar_position( jd, lunar_xyzr, solar_xyzr);
ecliptic_to_equatorial( solar_xyzr);
ecliptic_to_equatorial( lunar_xyzr);
if( !is_geocentric)
{
double x_vect[3], y_vect[3], z_vect[3], alt, az;
make_orthogonal_basis( obs_pos, x_vect, y_vect, z_vect);
az = PI + atan2( dot_product( x_vect, topo_posn),
dot_product( y_vect, topo_posn));
az *= 180. / PI;
alt = 90. - angle_between( topo_posn, obs_pos);
snprintf( alt_buff, sizeof( alt_buff), " %5.1f %+05.1f",
az, alt);
}
else
*alt_buff = '\0';
elong = angle_between( topo_posn, solar_xyzr);
printf( "%s %s %s%s %6.1f %6.1f %8.0f", buff, ra_buff, dec_buff,
alt_buff, elong, angle_between( topo_posn, lunar_xyzr), dist);
motion_rate *= (double)motion_units;
if( motion_rate < 9.999)
format_string = " %6.4f %6.1f";
else if( motion_rate < 99.99)
format_string = " %6.3f %6.1f";
else if( motion_rate < 999.9)
format_string = " %6.2f %6.1f";
else if( motion_rate < 9999.)
format_string = " %6.1f %6.1f";
else
format_string = " %6.0f %6.1f";
printf( format_string, motion_rate, motion_pa);
if( !abs_mag)
printf( "\n");
else
{
const double phase_ang = (180. - elong) * (PI / 180.);
double mag = abs_mag + 5. * log10( dist / AU_IN_KM)
+ phase_angle_correction_to_magnitude(
phase_ang, 0.15);
printf( "%8.1f\n", mag);
}
start_line = (int)i + 1;
}
}
strcpy( line0, line1);
strcpy( line1, line2);
}
fclose( ifile);
return( start_line);
}
static const char *tle_list_filename = "tle_list.txt";
int generate_artsat_ephems( const char *path_to_tles, const ephem_t *e)
{
FILE *ifile;
char buff[100];
int is_in_range = 0, id_matches = 1, start_line = 0;
snprintf( buff, sizeof( buff), "%s/%s", path_to_tles, tle_list_filename);
if( verbose > 1)
printf( "Opening '%s'\n", buff);
ifile = fopen( buff, "rb");
if( !ifile)
{
fprintf( stderr, "'%s' not opened\n", buff);
exit( 0);
}
while( start_line != e->n_steps &&
fgets_trimmed( buff, sizeof( buff), ifile))
{
if( !memcmp( buff, "# Range:", 8))
{
char t_start[40], t_end[40];
int n_scanned = sscanf( buff + 8, "%39s %39s", t_start, t_end);
assert( 2 == n_scanned);
if( get_time_from_string( 0., t_start, FULL_CTIME_YMD, NULL) < e->jd_end
&& get_time_from_string( 0., t_end, FULL_CTIME_YMD, NULL) > e->jd_start)
is_in_range = 1;
}
if( !memcmp( buff, "# ID:", 5))
if( strcmp( e->desig, buff + 13) && atoi( buff + 5) != atoi( e->desig))
id_matches = 0;
if( !memcmp( buff, "# Include ", 10))
{
if( is_in_range && id_matches)
start_line = show_ephems_from( path_to_tles, e, buff + 10, start_line);
is_in_range = 0;
id_matches = 1;
}
}
fclose( ifile);
if( start_line)
printf( "%s", _header);
return( start_line);
}
static int set_location( ephem_t *e, const char *mpc_code, const char *obscode_file_name)
{
mpc_code_t c;
int rval = get_lat_lon_info( &c, mpc_code);
if( rval)
{
FILE *ifile = fopen( obscode_file_name, "rb");
char buff[200];
if( !ifile)
{
fprintf( stderr, "'%s' not found\n", obscode_file_name);
exit( 0);
}
while( rval && fgets_trimmed( buff, sizeof( buff), ifile))
if( !memcmp( mpc_code, buff, 3))
{
const int planet = get_mpc_code_info( &c, buff);
if( planet != 3)
{
fprintf( stderr, "MPC code '%s' is for planet %d\n",
mpc_code, planet);
exit( 0);
}
rval = 0;
printf( "%s\n", c.name);
}
fclose( ifile);
}
if( !rval)
{
e->lat = c.lat;
e->lon = c.lon;
e->alt = c.alt;
e->rho_cos_phi = c.rho_cos_phi;
e->rho_sin_phi = c.rho_sin_phi;
if( c.lon > PI)
c.lon -= PI + PI;
if( c.rho_sin_phi || c.rho_cos_phi)
printf( "Latitude %c %f, Longitude %c %f\nAltitude %.1f meters (above WGS84 ellipsoid)\n",
(c.lat > 0. ? 'N' : 'S'), fabs( c.lat) * 180. / PI,
(c.lon > 0. ? 'E' : 'W'), fabs( c.lon) * 180. / PI,
c.alt);
}
return( rval);
}
#ifdef ON_LINE_VERSION
#define OBSCODES_DOT_HTML_FILENAME "/home/projectp/public_html/cgi-bin/fo/ObsCodes.htm"
#define ROVERS_DOT_TXT_FILENAME "/home/projectp/public_html/cgi-bin/fo/rovers.txt"
#define PATH_TO_TLES "/home/projectp/public_html/tles"
#else
#define OBSCODES_DOT_HTML_FILENAME "/home/phred/.find_orb/ObsCodes.htm"
#define ROVERS_DOT_TXT_FILENAME "/home/phred/.find_orb/rovers.txt"
#define PATH_TO_TLES "/home/phred/tles"
#endif
static const char *get_arg( const char **argv)
{
const char *rval;
if( argv[0][0] == '-' && argv[0][1])
{
if( !argv[0][2] && argv[1])
rval = argv[1];
else
rval = argv[0] + 2;
}
else
rval = NULL;
if( !rval)
{
fprintf( stderr, "Can't get an argument : '%s'\n", argv[0]);
exit( 0);
}
return( rval);
}
static void fix_desig( char *desig)
{
size_t i;
int bitmask = 0;
for( i = 0; i < 10 && desig[i]; i++)
if( isdigit( desig[i]))
bitmask |= (1 << (int)i);
if( i >= 9 && bitmask == 0xef && desig[4] == '-')
{
desig[0] = desig[2]; /* it's in YYYY-NNNA form; */
desig[1] = desig[3]; /* cvt to YYNNNA form */
for( i = 5; desig[i - 1]; i++)
desig[i - 3] = desig[i];
}
}
static void error_help( void)
{
printf( "Mandatory 'sat_eph' arguments:\n"
" -c(MPC code) : specify location\n"
" -t(date/time) : starting time of ephemeris\n"
" -n(#) : number of ephemeris steps\n"
" -s(#) : ephemeris step size in days\n"
" -o(#) : five digit NORAD number\n"
"Optional arguments:\n"
" -v(#) : level of verbosity\n");
}
int dummy_main( const int argc, const char **argv)
{
int i;
ephem_t e;
bool round_to_nearest_step = true;
const char *mpc_code = "500";
const char *override_tle_filename = NULL;
if( argc < 2)
{
error_help( );
return( 0);
}
memset( &e, 0, sizeof( ephem_t));
e.jd_start = current_jd( );
e.n_steps = 20;
e.step_size = 1. / 24.;
for( i = 1; i < argc; i++)
if( argv[i][0] == '-' && argv[i][1])
{
const char *arg = get_arg( argv + i);
switch( argv[i][1])
{
case 'c':
mpc_code = arg;
break;
case 'f':
tle_list_filename = arg;
break;
case 'F':
override_tle_filename = arg;
break;
case 't':
e.jd_start = get_time_from_string( e.jd_start, arg, FULL_CTIME_YMD, NULL);
break;
case 'n':
e.n_steps = atoi( arg);
break;
case 'r':
round_to_nearest_step = true;
break;
case 's':
if( arg && *arg)
{
const char end_char = arg[strlen( arg) - 1];
e.step_size = atof( arg);
switch( end_char)
{
case 'h':
e.step_size /= hours_per_day;
break;
case 'm':
e.step_size /= minutes_per_day;
break;
case 's':
e.step_size /= seconds_per_day;
break;
}
}
break;
case 'u':
motion_units = 60;
break;
case 'o':
/* Will handle below */
break;
case 'v':
verbose = 1 + atoi( arg);
break;
default:
fprintf( stderr, "Unrecognized option '%s'\n", argv[i]);
error_help( );
return( 0);
}
}
if( set_location( &e, mpc_code, OBSCODES_DOT_HTML_FILENAME))
if( set_location( &e, mpc_code, ROVERS_DOT_TXT_FILENAME))
fprintf( stderr, "WARNING: Could not parse location '%s'\n", mpc_code);
if( round_to_nearest_step && e.step_size)
e.jd_start = floor( (e.jd_start - 0.5) / e.step_size) * e.step_size + 0.5;
e.jd_end = e.jd_start + (double)e.n_steps * e.step_size;
if( verbose)
printf( "arguments parsed; JDs %f to %f\n", e.jd_start, e.jd_end);
for( i = 1; i < argc; i++)
if( argv[i][0] == '-' && argv[i][1] == 'o')
{
char desig[30];
strncpy( desig, get_arg( argv + i), 29);
fix_desig( desig);
e.desig = desig;
if( override_tle_filename)
show_ephems_from( PATH_TO_TLES, &e, override_tle_filename, 0);
else
generate_artsat_ephems( PATH_TO_TLES, &e);
}
return( 0);
}
#ifndef ON_LINE_VERSION
int main( const int argc, const char **argv)
{
return( dummy_main( argc, argv));
}
#else
#include <errno.h>
#ifdef __has_include
#if __has_include(<cgi_func.h>)
#include "cgi_func.h"
#else
#error \
'cgi_func.h' not found. This project depends on the 'lunar'\
library. See www.github.com/Bill-Gray/lunar .\
Clone that repository, 'make' and 'make install' it.
#endif
#else
#include "cgi_func.h"
#endif
int main( const int unused_argc, const char **unused_argv)
{
const char *argv[2000];
const size_t max_buff_size = 40000; /* room for 500 obs */
char *buff = (char *)malloc( max_buff_size);
char field[30], time_text[80];
char num_steps[30], step_size[30], obs_code[40];
FILE *lock_file = fopen( "lock.txt", "w");
int cgi_status, i, argc = 9;
#ifndef _WIN32
extern char **environ;
avoid_runaway_process( 15);
#endif /* _WIN32 */
setbuf( lock_file, NULL);
INTENTIONALLY_UNUSED_PARAMETER( unused_argc);
INTENTIONALLY_UNUSED_PARAMETER( unused_argv);
printf( "Content-type: text/html\n\n");
printf( "<html> <body> <pre>\n");
if( !lock_file)
{
printf( "<p> Server is busy. Try again in a minute or two. </p>");
printf( "<p> Your artsat ephemerides are very important to us! </p>");
return( 0);
}
fprintf( lock_file, "We're in\n");
*time_text = *num_steps = *step_size = *obs_code = '\0';
#ifndef _WIN32
for( size_t i = 0; environ[i]; i++)
fprintf( lock_file, "%s\n", environ[i]);
#endif
cgi_status = initialize_cgi_reading( );
fprintf( lock_file, "CGI status %d\n", cgi_status);
if( cgi_status <= 0)
{
printf( "<p> <b> CGI data reading failed : error %d </b>", cgi_status);
printf( "This isn't supposed to happen.</p>\n");
return( 0);
}
while( !get_cgi_data( field, buff, NULL, max_buff_size))
{
fprintf( lock_file, "Field '%s'\n", field);
if( !strcmp( field, "time") && strlen( buff) < sizeof( time_text))
strcpy( time_text, buff);
if( !strcmp( field, "obj_name"))
{
char *obj_name = (char *)malloc( strlen( buff) + 1);
strcpy( obj_name, buff);
argv[argc++] = "-o";
argv[argc++] = obj_name;
}
else if( !memcmp( field, "obj_", 4)) /* selected an object check-box */
{
char *obj_name = (char *)malloc( strlen( field) - 3);
strcpy( obj_name, field + 4);
argv[argc++] = "-o";
argv[argc++] = obj_name;
}
else if( !strcmp( field, "motion60"))
motion_units = 60;
if( !strcmp( field, "num_steps") && strlen( buff) < sizeof( num_steps))
strcpy( num_steps, buff);
if( !strcmp( field, "step_size") && strlen( buff) < sizeof( step_size))
{
char *tptr = strchr( buff, 'v');
if( tptr)
{
verbose = atoi( tptr + 1);
*tptr = '\0';
}
strcpy( step_size, buff);
}
if( !strcmp( field, "obs_code") && strlen( buff) < sizeof( obs_code))
strcpy( obs_code, buff);
if( !strcmp( field, "round_step"))
argv[argc++] = "-r";
}
fprintf( lock_file, "Fields read\n");
argv[0] = "sat_eph";
argv[1] = "-t";
argv[2] = time_text;
argv[3] = "-c";
argv[4] = obs_code;
argv[5] = "-n";
argv[6] = num_steps;
argv[7] = "-s";
argv[8] = step_size;
argv[argc] = NULL;
for( i = 0; argv[i]; i++)
fprintf( lock_file, "arg %d: '%s'\n", (int)i, argv[i]);
dummy_main( argc, argv);
fprintf( lock_file, "dummy_main called\n");
free( buff);
printf( "On-line Sat_eph compiled " __DATE__ " " __TIME__ " UTC-5h\n");
printf( "See <a href='https://www.github.com/Bill-Gray/sat_code'>"
"https://www.github.com/Bill-Gray/sat_code</a> for source code\n");
printf( "</pre> </body> </html>");
return( 0);
}
#endif