#include <time.h>
#include <stdbool.h>

Include dependency graph for predict.h:

Data Structures
struct	predict_orbital_elements_t
	Container for processed TLE data from TLE strings. More...

struct	predict_position
	Predicted orbital values for satellite at a given time. More...

struct	predict_observer_t
	Observation point/ground station (QTH). More...

struct	predict_observation
	Data relevant for a relative observation of an orbit or similar with respect to an observation point. More...

Macros
#define	PREDICT_VERSION_MAJOR 2

#define	PREDICT_VERSION_MINOR 0

#define	PREDICT_VERSION_PATCH 0

#define	PREDICT_VERSION (PREDICT_VERSION_MAJOR * 100 * 100 + PREDICT_VERSION_MINOR * 100 + PREDICT_VERSION_PATCH)

#define	PREDICT_VERSION_STRING "2.0.0"

Typedefs
typedef double	predict_julian_date_t
	The representation of time used by libpredict: The number of days since 31Dec79 00:00:00 UTC. More...

Enumerations
enum	predict_ephemeris { EPHEMERIS_SGP4 = 0, EPHEMERIS_SDP4 = 1, EPHEMERIS_SGP8 = 2, EPHEMERIS_SDP8 = 3 }
	Simplified perturbation models used in modeling the satellite orbits. More...

Functions
int	predict_version_major ()
	Get the major version number of the library. More...

int	predict_version_minor ()
	Get the minor version number of the library. More...

int	predict_version_patch ()
	Get the patch version number of the library. More...

int	predict_version ()
	Get the version number of the library. More...

char *	predict_version_string ()
	Get the version number string of the library. More...

predict_julian_date_t	predict_to_julian (time_t time)
	Convert time_t in UTC to Julian date in UTC. More...

time_t	predict_from_julian (predict_julian_date_t date)
	Convert Julian date in UTC back to a time_t in UTC. More...

predict_orbital_elements_t *	predict_parse_tle (const char tle_line_1, const char tle_line_2)
	Create predict_orbital_elements_t from TLE strings. More...

void	predict_destroy_orbital_elements (predict_orbital_elements_t *orbital_elements)
	Free memory allocated in orbital elements structure. More...

int	predict_orbit (const predict_orbital_elements_t orbital_elements, struct predict_position x, predict_julian_date_t time)
	Main prediction function. More...

bool	predict_is_geosynchronous (const predict_orbital_elements_t *orbital_elements)
	Find whether an orbit is geosynchronous. More...

double	predict_apogee (const predict_orbital_elements_t *x)
	Get apogee of satellite orbit. More...

double	predict_perigee (const predict_orbital_elements_t *x)
	Get perigee of satellite orbit. More...

bool	predict_aos_happens (const predict_orbital_elements_t *x, double latitude)
	Find whether an AOS can ever happen on the given latitude. More...

predict_observer_t *	predict_create_observer (const char *name, double lat, double lon, double alt)
	Create observation point (QTH). More...

void	predict_destroy_observer (predict_observer_t *obs)
	Free observer. More...

void	predict_observe_orbit (const predict_observer_t observer, const struct predict_position orbit, struct predict_observation *obs)
	Find relative position of satellite with respect to an observer. More...

void	predict_observe_moon (const predict_observer_t observer, predict_julian_date_t time, struct predict_observation obs)
	Estimate relative position of the moon. More...

double	predict_moon_ra (predict_julian_date_t time)
	Calculate right ascension of the moon. More...

double	predict_moon_declination (predict_julian_date_t time)
	Calculate declination of the moon. More...

double	predict_moon_gha (predict_julian_date_t time)
	Calculate the greenwich hour angle (longitude) of the moon. More...

void	predict_observe_sun (const predict_observer_t observer, predict_julian_date_t time, struct predict_observation obs)
	Estimate relative position of the sun. More...

double	predict_sun_ra (predict_julian_date_t time)
	Calculate right ascension of the sun. More...

double	predict_sun_declination (predict_julian_date_t time)
	Calculate declination of the sun. More...

double	predict_sun_gha (predict_julian_date_t time)
	Calculate the greenwich hour angle (longitude) of the sun. More...

struct predict_observation	predict_next_aos (const predict_observer_t observer, const predict_orbital_elements_t orbital_elements, predict_julian_date_t start_time)
	Find next acquisition of signal (AOS) of satellite (when the satellite rises above the horizon). More...

struct predict_observation	predict_next_los (const predict_observer_t observer, const predict_orbital_elements_t orbital_elements, predict_julian_date_t start_time)
	Find next loss of signal (LOS) of satellite (when the satellite goes below the horizon). More...

struct predict_observation	predict_at_max_elevation (const predict_observer_t observer, const predict_orbital_elements_t orbital_elements, predict_julian_date_t start_time)
	Find maximum elevation of next or current pass. More...

double	predict_doppler_shift (const struct predict_observation *observation, double downlink_frequency)
	Calculate doppler shift of a given downlink frequency with respect to an observer. More...

double	predict_squint_angle (const predict_observer_t observer, const struct predict_position orbit, double alon, double alat)
	Calculate squint angle for satellite, i.e. More...

double	predict_refraction (double el)
	Calculate refraction angle. More...

double	predict_refraction_ext (double el, double pressure, double temp)
	Calculate refraction angle. More...

double	predict_refraction_from_apparent (double apparent_el)
	Calculate refraction angle from apparent elevation. More...

double	predict_refraction_from_apparent_ext (double apparent_el, double pressure, double temp)
	Calculate refraction angle from apparent elevation. More...

double	predict_refraction_rate (double el, double el_rate)
	Calculate refraction rate of change. More...

double	predict_refraction_rate_ext (double el, double el_rate, double pressure, double temp)
	Calculate refraction rate of change. More...

double	predict_apparent_elevation (double el)
	Calculate apparent elevation from true elevation. More...

double	predict_apparent_elevation_ext (double el, double pressure, double temp)
	Calculate apparent elevation from true elevation. More...

double	predict_apparent_elevation_rate (double el, double el_rate)
	Calculate apparent elevation rate. More...

double	predict_apparent_elevation_rate_ext (double el, double el_rate, double pressure, double temp)
	Calculate apparent elevation rate. More...

Macro Definition Documentation

#define PREDICT_VERSION (PREDICT_VERSION_MAJOR * 100 * 100 + PREDICT_VERSION_MINOR * 100 + PREDICT_VERSION_PATCH)

#define PREDICT_VERSION_MAJOR 2

#define PREDICT_VERSION_MINOR 0

#define PREDICT_VERSION_PATCH 0

#define PREDICT_VERSION_STRING "2.0.0"

Typedef Documentation

typedef double predict_julian_date_t

The representation of time used by libpredict: The number of days since 31Dec79 00:00:00 UTC.

Enumeration Type Documentation

enum predict_ephemeris

Simplified perturbation models used in modeling the satellite orbits.

Enumerator
EPHEMERIS_SGP4
EPHEMERIS_SDP4
EPHEMERIS_SGP8
EPHEMERIS_SDP8

Function Documentation

bool predict_aos_happens	(	const predict_orbital_elements_t *	x,
		double	latitude
	)

Find whether an AOS can ever happen on the given latitude.

Parameters

x	Orbital elements
latitude	Latitude of ground station in radians

Returns: true if AOS can happen, otherwise false

Copyright: GPLv2+

double predict_apogee ( const predict_orbital_elements_t * x )

Get apogee of satellite orbit.

Parameters

x	Orbital elements

Returns: Apogee of orbit

Copyright: GPLv2+

double predict_apparent_elevation ( double el )

Calculate apparent elevation from true elevation.

Parameters

el	True elevation angle (rad).

Returns: Apparent elevation (rad).

double predict_apparent_elevation_ext	(	double	el,
		double	pressure,
		double	temp
	)

Calculate apparent elevation from true elevation.

Corrects for different atmospheric pressures and temperatures.

Parameters

el	True elevation angle (rad).
pressure	Atmospheric pressure (kPa).
temp	Temperature (deg C).

Returns: Apparent elevation (rad).

double predict_apparent_elevation_rate	(	double	el,
		double	el_rate
	)

Calculate apparent elevation rate.

Parameters

el	True elevation angle (rad).
el_rate	Rate of change of true elevation angle (rad/s).

Returns: Rate of change of apparent elevation (rad/s).

double predict_apparent_elevation_rate_ext	(	double	el,
		double	el_rate,
		double	pressure,
		double	temp
	)

Calculate apparent elevation rate.

Corrects for different atmospheric pressures and temperatures.

Parameters

el	True elevation angle (rad).
el_rate	Rate of change of true elevation angle (rad/s).
pressure	Atmospheric pressure (kPa).
temp	Temperature (deg C).

Returns: Rate of change of apparent elevation (rad/s).

struct predict_observation predict_at_max_elevation	(	const predict_observer_t *	observer,
		const predict_orbital_elements_t *	orbital_elements,
		predict_julian_date_t	start_time
	)

Find maximum elevation of next or current pass.

Parameters

observer	Ground station
orbital_elements	Orbital elements of satellite
start_time	Search time. If elevation is negative, max elevation is sought from the start_time and on. If elevation is positive, max elevation is searched for within the current pass

Returns: Observed properties at maximum elevation

predict_observer_t* predict_create_observer	(	const char *	name,
		double	lat,
		double	lon,
		double	alt
	)

Create observation point (QTH).

Parameters

name	Name of observation point
lat	Latitude in radians (easting/northing)
lon	Longitude in radians (easting/northing)
alt	Altitude in meters

Returns: Allocated observation point

void predict_destroy_observer ( predict_observer_t * obs )

Free observer.

Parameters

obs	Observer to be freed.

void predict_destroy_orbital_elements ( predict_orbital_elements_t * orbital_elements )

Free memory allocated in orbital elements structure.

Parameters

orbital_elements Orbit to free

double predict_doppler_shift	(	const struct predict_observation *	observation,
		double	downlink_frequency
	)

Calculate doppler shift of a given downlink frequency with respect to an observer.

Parameters

observation	Observation of a satellite orbit
downlink_frequency	Downlink frequency of the satellite

Returns: The frequency difference from the original frequency

Copyright: GPLv2+

time_t predict_from_julian ( predict_julian_date_t date )

Convert Julian date in UTC back to a time_t in UTC.

Parameters

date	Julian date in UTC

Returns: Time in UTC

bool predict_is_geosynchronous ( const predict_orbital_elements_t * orbital_elements )

Find whether an orbit is geosynchronous.

This function uses the definition of geosynchronous orbits found in "Classification of geosynchronous objects", Issue 17, 28 March 2015, from the European Space Agency:

Eccentricity smaller than 0.2
Mean motion between 0.9 and 1.1
Inclination lower than 70 degrees

The function is mainly used internally for avoiding long iteration loops in functions like predict_at_max_elevation() and predict_next_aos(). The wider definition of a geosynchronous orbits is appropriate here. The definition of a geostationary satellite would be stricter, but is not considered here.

Parameters

orbital_elements Orbital elements

Returns: true if orbit is geosynchronous, false otherwise

double predict_moon_declination ( predict_julian_date_t time )

Calculate declination of the moon.

Parameters

time Time

Returns: Declination in radians

double predict_moon_gha ( predict_julian_date_t time )

Calculate the greenwich hour angle (longitude) of the moon.

Parameters

time Time

Returns: GHA in radians

Copyright: GPLv2+

double predict_moon_ra ( predict_julian_date_t time )

Calculate right ascension of the moon.

Parameters

time Time

Returns: RA in radians

struct predict_observation predict_next_aos	(	const predict_observer_t *	observer,
		const predict_orbital_elements_t *	orbital_elements,
		predict_julian_date_t	start_time
	)

Find next acquisition of signal (AOS) of satellite (when the satellite rises above the horizon).

Ignores previous AOS of current pass if the satellite is in range at the start time.

Parameters

observer	Point of observation
orbital_elements	Orbital elements
start_time	Start time for AOS search

Returns: Observation of the AOS

Copyright: GPLv2+

struct predict_observation predict_next_los	(	const predict_observer_t *	observer,
		const predict_orbital_elements_t *	orbital_elements,
		predict_julian_date_t	start_time
	)

Find next loss of signal (LOS) of satellite (when the satellite goes below the horizon).

Finds LOS of the current pass if the satellite currently is in range, finds LOS of next pass if not.

Parameters

observer	Point of observation
orbital_elements	Orbital elements
start_time	Start time for LOS search

Returns: Observation of the LOS

Copyright: GPLv2+

void predict_observe_moon	(	const predict_observer_t *	observer,
		predict_julian_date_t	time,
		struct predict_observation *	obs
	)

Estimate relative position of the moon.

Parameters

observer	Point of observation
time	Time of observation
obs	Return object for position of the moon relative to the observer

Copyright: GPLv2+

void predict_observe_orbit	(	const predict_observer_t *	observer,
		const struct predict_position *	orbit,
		struct predict_observation *	obs
	)

Find relative position of satellite with respect to an observer.

Calculates range, azimuth, elevation and relative velocity.

Parameters

observer	Point of observation
orbit	Satellite orbit
obs	Return of object for position of the satellite relative to the observer.

Copyright: GPLv2+

void predict_observe_sun	(	const predict_observer_t *	observer,
		predict_julian_date_t	time,
		struct predict_observation *	obs
	)

Estimate relative position of the sun.

Parameters

observer	Point of observation
time	Time of observation
obs	Return object for position of the sun relative to the observer

Copyright: GPLv2+

int predict_orbit	(	const predict_orbital_elements_t *	orbital_elements,
		struct predict_position *	x,
		predict_julian_date_t	time
	)

Main prediction function.

Predict satellite orbit at given time.

Parameters

orbital_elements	Orbital elements
x	Predicted orbit
time	Julian day in UTC

Returns: 0 if everything went fine

Copyright: GPLv2+

predict_orbital_elements_t* predict_parse_tle	(	const char *	tle_line_1,
		const char *	tle_line_2
	)

Create predict_orbital_elements_t from TLE strings.

Parameters

tle_line_1	First line of NORAD two-line element set string
tle_line_2	Second line of NORAD two-line element set string

Returns: Processed TLE parameters

Copyright: GPLv2+

double predict_perigee ( const predict_orbital_elements_t * x )

Get perigee of satellite orbit.

Parameters

x	Orbital elements

Returns: Perigee of orbit

Copyright: GPLv2+

double predict_refraction ( double el )

Calculate refraction angle.

This function assumes atmospheric pressure of 101.0kPa and temperature 10deg celsius.

Parameters

el	True elevation angle (rad).

Returns: Refraction angle (rad).

double predict_refraction_ext	(	double	el,
		double	pressure,
		double	temp
	)

Calculate refraction angle.

Corrects for different atmospheric pressure and temperature.

Parameters

el	True elevation angle in rads.
pressure	Atmospheric pressure in kPa.
temp	Temperature in deg celsius.

Returns: Refraction angle (rad).

double predict_refraction_from_apparent ( double apparent_el )

Calculate refraction angle from apparent elevation.

This function assumes atmospheric pressure of 101.0kPa and temperature 10deg celsius.

Parameters

apparent_el Apparent elevation angle (rad).

Returns: Refraction angle (rad).

double predict_refraction_from_apparent_ext	(	double	apparent_el,
		double	pressure,
		double	temp
	)

Calculate refraction angle from apparent elevation.

Corrects for different atmospheric pressure and temperature.

Parameters

apparent_el	Apparent elevation angle (rad).
pressure	Atmospheric pressure in kPa.
temp	Temperature in deg celsius.

Returns: Refraction angle (rad).

double predict_refraction_rate	(	double	el,
		double	el_rate
	)

Calculate refraction rate of change.

Parameters

el	True elevation angle (rad).
el_rate	Rate of change of true elevation angle (rad/s).

Returns: Refraction rate of change (rad/s).

double predict_refraction_rate_ext	(	double	el,
		double	el_rate,
		double	pressure,
		double	temp
	)

Calculate refraction rate of change.

Corrects for different atmospheric pressure and temerature.

Parameters

el	True elevation angle (rad).
el_rate	Rate of change of true elevation angle (rad/s).
pressure	Atmospheric pressure in kPa.
temp	Temperature in deg celsius.

Returns: Apparent elevation (rad).

double predict_squint_angle	(	const predict_observer_t *	observer,
		const struct predict_position *	orbit,
		double	alon,
		double	alat
	)

Calculate squint angle for satellite, i.e.

angle between the satellite antenna and the QTH antenna.

Parameters

observer	Point of observation
orbit	Current state of satellite orbit
alon	Attitude longitude in radians (describes orientation of the satellite at apogee)
alat	Attidue latitude in radians (see above)

Returns: Squint angle in radians. Will output nan if the satellite is not an SDP4 satellite

Copyright: GPLv2+

double predict_sun_declination ( predict_julian_date_t time )

Calculate declination of the sun.

Parameters

observer	Point of observation
time	Time of observation

Returns: Declination in radians

double predict_sun_gha ( predict_julian_date_t time )

Calculate the greenwich hour angle (longitude) of the sun.

Parameters

time Time

Returns: GHA in radians

Copyright: GPLv2+

double predict_sun_ra ( predict_julian_date_t time )

Calculate right ascension of the sun.

Parameters

observer	Point of observation
time	Time of observation

Returns: RA in radians

predict_julian_date_t predict_to_julian ( time_t time )

Convert time_t in UTC to Julian date in UTC.

Parameters

time	Time in UTC

Returns: Julian day in UTC

int predict_version ( )

Get the version number of the library.

Returns: 2 digit major, 2 digit minor, 2 digit patch decimal version number

int predict_version_major ( )

Get the major version number of the library.

Returns: Major version number

int predict_version_minor ( )

Get the minor version number of the library.

Returns: Minor version number

int predict_version_patch ( )

Get the patch version number of the library.

Returns: Patch version number

char* predict_version_string ( )

Get the version number string of the library.

Returns: Version number string ("major.minor.patch")

Data Structures

Macros

Typedefs

Enumerations

Functions

Macro Definition Documentation

Typedef Documentation

Enumeration Type Documentation

Function Documentation