/** \brief Calculate satellite visibility.
* \param sat The satellite structure.
* \param qth The QTH
* \param jul_utc The time at which the visibility should be calculated.
* \return The visiblity code.
*
*/
sat_vis_t
get_sat_vis (sat_t *sat, qth_t *qth, gdouble jul_utc)
{
gboolean sat_sun_status;
gdouble sun_el;
gdouble threshold;
gdouble eclipse_depth;
sat_vis_t vis = SAT_VIS_NONE;
vector_t zero_vector = {0,0,0,0};
geodetic_t obs_geodetic;
/* Solar ECI position vector */
vector_t solar_vector=zero_vector;
/* Solar observed az and el vector */
obs_set_t solar_set;
/* FIXME: could be passed as parameter */
obs_geodetic.lon = qth->lon * de2ra;
obs_geodetic.lat = qth->lat * de2ra;
obs_geodetic.alt = qth->alt / 1000.0;
obs_geodetic.theta = 0;
Calculate_Solar_Position (jul_utc, &solar_vector);
Calculate_Obs (jul_utc, &solar_vector, &zero_vector, &obs_geodetic, &solar_set);
if (Sat_Eclipsed (&sat->pos, &solar_vector, &eclipse_depth)) {
/* satellite is eclipsed */
sat_sun_status = FALSE;
}
else {
/* satellite in sunlight => may be visible */
sat_sun_status = TRUE;
}
if (sat_sun_status) {
sun_el = Degrees (solar_set.el);
/* FIXME */
/* threshold = (gdouble) sat_cfg_get_int (SAT_CFG_INT_PRED_TWILIGHT_THLD); */
threshold = (gdouble) -6;
if (sun_el <= threshold && sat->el >= 0.0)
vis = SAT_VIS_VISIBLE;
else
vis = SAT_VIS_DAYLIGHT;
}
else
vis = SAT_VIS_ECLIPSED;
return vis;
}
/* Main program */
int
main(void)
{
/* TLE source file */
char tle_file[] = "./rax.txt";
/* Observer's geodetic co-ordinates. */
/* Lat North, Lon East in rads, Alt in km */
geodetic_t obs_geodetic = {0.7368, -1.4615, 0.251, 0.0};
/* Two-line Orbital Elements for the satellite */
tle_t tle ;
/* Zero vector for initializations */
vector_t zero_vector = {0,0,0,0};
/* Satellite position and velocity vectors */
vector_t vel = zero_vector;
vector_t pos = zero_vector;
/* Satellite Az, El, Range, Range rate */
vector_t obs_set;
/* Solar ECI position vector */
vector_t solar_vector = zero_vector;
/* Solar observed azi and ele vector */
vector_t solar_set;
/* Calendar date and time (UTC) */
struct tm utc;
/* Satellite's predicted geodetic position */
geodetic_t sat_geodetic;
double
tsince, /* Time since epoch (in minutes) */
jul_epoch, /* Julian date of epoch */
jul_utc, /* Julian UTC date */
eclipse_depth = 0, /* Depth of satellite eclipse */
/* Satellite's observed position, range, range rate */
sat_azi, sat_ele, sat_range, sat_range_rate,
/* Satellites geodetic position and velocity */
sat_lat, sat_lon, sat_alt, sat_vel,
/* Solar azimuth and elevation */
sun_azi, sun_ele;
/* Used for storing function return codes */
int flg;
char
ephem[5], /* Ephemeris in use string */
sat_status[12]; /* Satellite eclipse status */
/* Input one (first!) TLE set from file */
flg = Input_Tle_Set(tle_file, &tle);
/* Abort if file open fails */
if( flg == -1 )
{
printf(" File open failed - Exiting!\n");
exit(-1);
}
/* Print satellite name and TLE read status */
printf(" %s: ", tle.sat_name);
if( flg == -2 )
{
printf("TLE set bad - Exiting!\n");
exit(-2);
}
else
printf("TLE set good - Happy Tracking!\n");
/* Printout of tle set data for tests if needed */
/* printf("\n %s %s %i %i %i\n"
" %14f %10f %8f %8f\n"
" %8f %8f %9f %8f %8f %12f\n",
tle.sat_name, tle.idesg, tle.catnr, tle.elset, tle.revnum,
tle.epoch, tle.xndt2o, tle.xndd6o, tle.bstar,
tle.xincl, tle.xnodeo, tle.eo, tle.omegao, tle.xmo, tle.xno);
*/
/** !Clear all flags! **/
/* Before calling a different ephemeris */
/* or changing the TLE set, flow control */
/* flags must be cleared in main(). */
ClearFlag(ALL_FLAGS);
/** Select ephemeris type **/
/* Will set or clear the DEEP_SPACE_EPHEM_FLAG */
/* depending on the TLE parameters of the satellite. */
/* It will also pre-process tle members for the */
/* ephemeris functions SGP4 or SDP4 so this function */
/* must be called each time a new tle set is used */
select_ephemeris(&tle);
do /* Loop */
{
/* Get UTC calendar and convert to Julian */
UTC_Calendar_Now(&utc);
jul_utc = Julian_Date(&utc);
/* Convert satellite's epoch time to Julian */
/* and calculate time since epoch in minutes */
jul_epoch = Julian_Date_of_Epoch(tle.epoch);
tsince = (jul_utc - jul_epoch) * xmnpda;
/* Copy the ephemeris type in use to ephem string */
if( isFlagSet(DEEP_SPACE_EPHEM_FLAG) )
strcpy(ephem,"SDP4");
else
strcpy(ephem,"SGP4");
/* Call NORAD routines according to deep-space flag */
if( isFlagSet(DEEP_SPACE_EPHEM_FLAG) )
SDP4(tsince, &tle, &pos, &vel);
else
SGP4(tsince, &tle, &pos, &vel);
/* Scale position and velocity vectors to km and km/sec */
Convert_Sat_State( &pos, &vel );
/* Calculate velocity of satellite */
Magnitude( &vel );
sat_vel = vel.w;
/** All angles in rads. Distance in km. Velocity in km/s **/
/* Calculate satellite Azi, Ele, Range and Range-rate */
Calculate_Obs(jul_utc, &pos, &vel, &obs_geodetic, &obs_set);
/* Calculate satellite Lat North, Lon East and Alt. */
Calculate_LatLonAlt(jul_utc, &pos, &sat_geodetic);
/* Calculate solar position and satellite eclipse depth */
/* Also set or clear the satellite eclipsed flag accordingly */
Calculate_Solar_Position(jul_utc, &solar_vector);
Calculate_Obs(jul_utc,&solar_vector,&zero_vector,&obs_geodetic,&solar_set);
if( Sat_Eclipsed(&pos, &solar_vector, &eclipse_depth) )
SetFlag( SAT_ECLIPSED_FLAG );
else
ClearFlag( SAT_ECLIPSED_FLAG );
/* Copy a satellite eclipse status string in sat_status */
if( isFlagSet( SAT_ECLIPSED_FLAG ) )
strcpy( sat_status, "Eclipsed" );
else
strcpy( sat_status, "In Sunlight" );
/* Convert and print satellite and solar data */
sat_azi = Degrees(obs_set.x);
sat_ele = Degrees(obs_set.y);
sat_range = obs_set.z;
sat_range_rate = obs_set.w;
sat_lat = Degrees(sat_geodetic.lat);
sat_lon = Degrees(sat_geodetic.lon);
sat_alt = sat_geodetic.alt;
sun_azi = Degrees(solar_set.x);
sun_ele = Degrees(solar_set.y);
printf("\n Date: %02d/%02d/%04d UTC: %02d:%02d:%02d Ephemeris: %s"
"\n Azi=%6.1f Ele=%6.1f Range=%8.1f Range Rate=%6.2f"
"\n Lat=%6.1f Lon=%6.1f Alt=%8.1f Vel=%8.3f"
"\n Stellite Status: %s - Depth: %2.3f"
"\n Sun Azi=%6.1f Sun Ele=%6.1f\n",
utc.tm_mday, utc.tm_mon, utc.tm_year,
utc.tm_hour, utc.tm_min, utc.tm_sec, ephem,
sat_azi, sat_ele, sat_range, sat_range_rate,
sat_lat, sat_lon, sat_alt, sat_vel,
sat_status, eclipse_depth,
sun_azi, sun_ele);
sleep(1);
} /* End of do */
while( 1 ); /* This stops Compaq ccc 'unreachcode' warning! */
return(0);
} /* End of main() */
