An internal namespace containing the underlying SGP4 implementation. More...

Classes
struct	elsetrec

Typedefs
typedef struct perturb::sgp4::elsetrec	elsetrec

Enumerations
enum	gravconsttype { wgs72old , wgs72 , wgs84 }

Functions
bool	sgp4init (gravconsttype whichconst, char opsmode, const char satn[5], const double epoch, const double xbstar, const double xndot, const double xnddot, const double xecco, const double xargpo, const double xinclo, const double xmo, const double xno, const double xnodeo, elsetrec &satrec)

bool	sgp4 (elsetrec &satrec, double tsince, double r[3], double v[3])

void	getgravconst (gravconsttype whichconst, double &tumin, double &mus, double &radiusearthkm, double &xke, double &j2, double &j3, double &j4, double &j3oj2)

void	twoline2rv (char longstr1[130], char longstr2[130], char typerun, char typeinput, char opsmode, gravconsttype whichconst, double &startmfe, double &stopmfe, double &deltamin, elsetrec &satrec)

double	gstime_SGP4 (double jdut1)

double	sgn_SGP4 (double x)

double	mag_SGP4 (double x[3])

void	cross_SGP4 (double vec1[3], double vec2[3], double outvec[3])

double	dot_SGP4 (double x[3], double y[3])

double	angle_SGP4 (double vec1[3], double vec2[3])

void	newtonnu_SGP4 (double ecc, double nu, double &e0, double &m)

double	asinh_SGP4 (double xval)

void	rv2coe_SGP4 (double r[3], double v[3], double mus, double &p, double &a, double &ecc, double &incl, double &omega, double &argp, double &nu, double &m, double &arglat, double &truelon, double &lonper)

void	jday_SGP4 (int year, int mon, int day, int hr, int minute, double sec, double &jd, double &jdFrac)

void	days2mdhms_SGP4 (int year, double days, int &mon, int &day, int &hr, int &minute, double &sec)

void	invjday_SGP4 (double jd, double jdFrac, int &year, int &mon, int &day, int &hr, int &minute, double &sec)

Detailed Description

An internal namespace containing the underlying SGP4 implementation.

If you need some deeper functionality, feel free to dig into this. However, the whole goal of this library is to avoid the need to do that. If you find yourself needing some functionality that perturb's interface doesn't offer, please open an issue as others may have similar thoughts / needs.

Function Documentation

◆ angle_SGP4()

double perturb::sgp4::angle_SGP4	(	double	vec1[3],
		double	vec2[3]
	)

                     procedure angle_SGP4

this procedure calculates the angle between two vectors. the output is set to 999999.1 to indicate an undefined value. be sure to check for this at the output phase.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units vec1 - vector number 1 vec2 - vector number 2

outputs : theta - angle between the two vectors -pi to pi

locals : temp - temporary real variable

coupling :

dot dot product of two vectors

◆ asinh_SGP4()

double perturb::sgp4::asinh_SGP4 ( double xval )

                     function asinh_SGP4

this function evaluates the inverse hyperbolic sine function.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units xval - angle value any real

outputs : arcsinh - result any real

locals : none.

coupling :

none.

◆ cross_SGP4()

void perturb::sgp4::cross_SGP4	(	double	vec1[3],
		double	vec2[3],
		double	outvec[3]
	)

                     procedure cross_SGP4

this procedure crosses two vectors.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units vec1 - vector number 1 vec2 - vector number 2

outputs : outvec - vector result of a x b

locals : none.

coupling :

mag magnitude of a vector

◆ days2mdhms_SGP4()

void perturb::sgp4::days2mdhms_SGP4	(	int	year,
		double	days,
		int &	mon,
		int &	day,
		int &	hr,
		int &	minute,
		double &	sec
	)

                     procedure days2mdhms_SGP4

this procedure converts the day of the year, days, to the equivalent month day, hour, minute and second.

algorithm : set up array for the number of days per month find leap year - use 1900 because 2000 is a leap year loop through a temp value while the value is < the days perform int conversions to the correct day and month convert remainder into h m s using type conversions

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units year - year 1900 .. 2100 days - julian day of the year 1.0 .. 366.0

outputs : mon - month 1 .. 12 day - day 1 .. 28,29,30,31 hr - hour 0 .. 23 min - minute 0 .. 59 sec - second 0.0 .. 59.999

locals : dayofyr - day of year temp - temporary extended values inttemp - temporary int value i - index lmonth[13] - int array containing the number of days per month

coupling :

none.

◆ dot_SGP4()

double perturb::sgp4::dot_SGP4	(	double	x[3],
		double	y[3]
	)

                     function dot_SGP4

this function finds the dot product of two vectors.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units vec1 - vector number 1 vec2 - vector number 2

outputs : dot - result

locals : none.

coupling :

none.

◆ getgravconst()

void perturb::sgp4::getgravconst	(	gravconsttype	whichconst,
		double &	tumin,
		double &	mus,
		double &	radiusearthkm,
		double &	xke,
		double &	j2,
		double &	j3,
		double &	j4,
		double &	j3oj2
	)

                     function getgravconst

this function gets constants for the propagator. note that mu is identified to facilitiate comparisons with newer models. the common useage is wgs72.

author : david vallado 719-573-2600 21 jul 2006

inputs : whichconst - which set of constants to use wgs72old, wgs72, wgs84

outputs : tumin - minutes in one time unit mu - earth gravitational parameter radiusearthkm - radius of the earth in km xke - reciprocal of tumin j2, j3, j4 - un-normalized zonal harmonic values j3oj2 - j3 divided by j2

locals :

coupling : none

references : norad spacetrack report #3

vallado, crawford, hujsak, kelso 2006

◆ gstime_SGP4()

double perturb::sgp4::gstime_SGP4 ( double jdut1 )

                     function gstime_SGP4

this function finds the greenwich sidereal time.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units jdut1 - julian date in ut1 days from 4713 bc

outputs : gstime - greenwich sidereal time 0 to 2pi rad

locals : temp - temporary variable for doubles rad tut1 - julian centuries from the jan 1, 2000 12 h epoch (ut1)

coupling : none

references :

vallado 2013, 187, eq 3-45

◆ invjday_SGP4()

void perturb::sgp4::invjday_SGP4	(	double	jd,
		double	jdfrac,
		int &	year,
		int &	mon,
		int &	day,
		int &	hr,
		int &	minute,
		double &	sec
	)

                     procedure invjday_SGP4

this procedure finds the year, month, day, hour, minute and second given the julian date. tu can be ut1, tdt, tdb, etc.

algorithm : set up starting values find leap year - use 1900 because 2000 is a leap year find the elapsed days through the year in a loop call routine to find each individual value

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units jd - julian date days from 4713 bc jdfrac - julian date fraction into day days from 4713 bc

outputs : year - year 1900 .. 2100 mon - month 1 .. 12 day - day 1 .. 28,29,30,31 hr - hour 0 .. 23 min - minute 0 .. 59 sec - second 0.0 .. 59.999

locals : days - day of year plus fractional portion of a day days tu - julian centuries from 0 h jan 0, 1900 temp - temporary double values leapyrs - number of leap years from 1900

coupling : days2mdhms - finds month, day, hour, minute and second given days and year

references :

vallado 2013, 203, alg 22, ex 3-13

◆ jday_SGP4()

void perturb::sgp4::jday_SGP4	(	int	year,
		int	mon,
		int	day,
		int	hr,
		int	minute,
		double	sec,
		double &	jd,
		double &	jdFrac
	)

                     procedure jday_SGP4

this procedure finds the julian date given the year, month, day, and time. the julian date is defined by each elapsed day since noon, jan 1, 4713 bc.

algorithm : calculate the answer in one step for efficiency

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units year - year 1900 .. 2100 mon - month 1 .. 12 day - day 1 .. 28,29,30,31 hr - universal time hour 0 .. 23 min - universal time min 0 .. 59 sec - universal time sec 0.0 .. 59.999

outputs : jd - julian date days from 4713 bc jdfrac - julian date fraction into day days from 4713 bc

locals : none.

coupling : none.

references :

vallado 2013, 183, alg 14, ex 3-4

◆ mag_SGP4()

double perturb::sgp4::mag_SGP4 ( double x[3] )

                     function mag_SGP4

this procedure finds the magnitude of a vector.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units vec - vector

outputs : mag - answer

locals : none.

coupling :

none.

◆ newtonnu_SGP4()

void perturb::sgp4::newtonnu_SGP4	(	double	ecc,
		double	nu,
		double &	e0,
		double &	m
	)

                     function newtonnu_SGP4

this function solves keplers equation when the true anomaly is known. the mean and eccentric, parabolic, or hyperbolic anomaly is also found. the parabolic limit at 168ø is arbitrary. the hyperbolic anomaly is also limited. the hyperbolic sine is used because it's not double valued.

author : david vallado 719-573-2600 27 may 2002

revisions vallado - fix small 24 sep 2002

inputs description range / units ecc - eccentricity 0.0 to nu - true anomaly -2pi to 2pi rad

outputs : e0 - eccentric anomaly 0.0 to 2pi rad 153.02 ø m - mean anomaly 0.0 to 2pi rad 151.7425 ø

locals : e1 - eccentric anomaly, next value rad sine - sine of e cose - cosine of e ktr - index

coupling : asinh - arc hyperbolic sine

references :

vallado 2013, 77, alg 5

◆ rv2coe_SGP4()

void perturb::sgp4::rv2coe_SGP4	(	double	r[3],
		double	v[3],
		double	mus,
		double &	p,
		double &	a,
		double &	ecc,
		double &	incl,
		double &	omega,
		double &	argp,
		double &	nu,
		double &	m,
		double &	arglat,
		double &	truelon,
		double &	lonper
	)

                     function rv2coe_SGP4

this function finds the classical orbital elements given the geocentric equatorial position and velocity vectors.

author : david vallado 719-573-2600 21 jun 2002

revisions vallado - fix special cases 5 sep 2002 vallado - delete extra check in inclination code 16 oct 2002 vallado - add constant file use 29 jun 2003 vallado - add mu 2 apr 2007

inputs description range / units r - ijk position vector km v - ijk velocity vector km / s mu - gravitational parameter km3 / s2

outputs : p - semilatus rectum km a - semimajor axis km ecc - eccentricity incl - inclination 0.0 to pi rad omega - right ascension of ascending node 0.0 to 2pi rad argp - argument of perigee 0.0 to 2pi rad nu - true anomaly 0.0 to 2pi rad m - mean anomaly 0.0 to 2pi rad arglat - argument of latitude (ci) 0.0 to 2pi rad truelon - true longitude (ce) 0.0 to 2pi rad lonper - longitude of periapsis (ee) 0.0 to 2pi rad

locals : hbar - angular momentum h vector km2 / s ebar - eccentricity e vector nbar - line of nodes n vector c1 - v**2 - u/r rdotv - r dot v hk - hk unit vector sme - specfic mechanical energy km2 / s2 i - index e - eccentric, parabolic, hyperbolic anomaly rad temp - temporary variable typeorbit - type of orbit ee, ei, ce, ci

coupling : mag - magnitude of a vector cross - cross product of two vectors angle - find the angle between two vectors newtonnu - find the mean anomaly

references :

vallado 2013, 113, alg 9, ex 2-5

◆ sgp4()

bool perturb::sgp4::sgp4	(	elsetrec &	satrec,
		double	tsince,
		double	r[3],
		double	v[3]
	)

                       procedure sgp4

this procedure is the sgp4 prediction model from space command. this is an updated and combined version of sgp4 and sdp4, which were originally published separately in spacetrack report #3. this version follows the methodology from the aiaa paper (2006) describing the history and development of the code.

author : david vallado 719-573-2600 28 jun 2005

inputs : satrec - initialised structure from sgp4init() call. tsince - time since epoch (minutes)

outputs : r - position vector km v - velocity km/sec return code - non-zero on error. 1 - mean elements, ecc >= 1.0 or ecc < -0.001 or a < 0.95 er 2 - mean motion less than 0.0 3 - pert elements, ecc < 0.0 or ecc > 1.0 4 - semi-latus rectum < 0.0 5 - epoch elements are sub-orbital 6 - satellite has decayed

locals : am - axnl, aynl - betal - cosim , sinim , cosomm , sinomm , cnod , snod , cos2u , sin2u , coseo1 , sineo1 , cosi , sini , cosip , sinip , cosisq , cossu , sinsu , cosu , sinu delm - delomg - dndt - eccm - emsq - ecose - el2 - eo1 - eccp - esine - argpm - argpp - omgadf -c pl - r - rtemsq - rdotl - rl - rvdot - rvdotl - su - t2 , t3 , t4 , tc tem5, temp , temp1 , temp2 , tempa , tempe , templ u , ux , uy , uz , vx , vy , vz inclm - inclination mm - mean anomaly nm - mean motion nodem - right asc of ascending node xinc - xincp - xl - xlm - mp - xmdf - xmx - xmy - nodedf - xnode - nodep - np -

coupling : getgravconst- no longer used. Variables are conatined within satrec dpper dpspace

references : hoots, roehrich, norad spacetrack report #3 1980 hoots, norad spacetrack report #6 1986 hoots, schumacher and glover 2004

vallado, crawford, hujsak, kelso 2006

◆ sgp4init()

bool perturb::sgp4::sgp4init	(	gravconsttype	whichconst,
		char	opsmode,
		const char	satn[5],
		const double	epoch,
		const double	xbstar,
		const double	xndot,
		const double	xnddot,
		const double	xecco,
		const double	xargpo,
		const double	xinclo,
		const double	xmo,
		const double	xno_kozai,
		const double	xnodeo,
		elsetrec &	satrec
	)

                       procedure sgp4init

this procedure initializes variables for sgp4.

author : david vallado 719-573-2600 28 jun 2005

inputs : opsmode - mode of operation afspc or improved 'a', 'i' whichconst - which set of constants to use 72, 84 satn - satellite number bstar - sgp4 type drag coefficient kg/m2er ecco - eccentricity epoch - epoch time in days from jan 0, 1950. 0 hr argpo - argument of perigee (output if ds) inclo - inclination mo - mean anomaly (output if ds) no - mean motion nodeo - right ascension of ascending node

outputs : satrec - common values for subsequent calls return code - non-zero on error. 1 - mean elements, ecc >= 1.0 or ecc < -0.001 or a < 0.95 er 2 - mean motion less than 0.0 3 - pert elements, ecc < 0.0 or ecc > 1.0 4 - semi-latus rectum < 0.0 5 - epoch elements are sub-orbital 6 - satellite has decayed

locals : cnodm , snodm , cosim , sinim , cosomm , sinomm cc1sq , cc2 , cc3 coef , coef1 cosio4 - day - dndt - em - eccentricity emsq - eccentricity squared eeta - etasq - gam - argpm - argument of perigee nodem - inclm - inclination mm - mean anomaly nm - mean motion perige - perigee pinvsq - psisq - qzms24 - rtemsq - s1, s2, s3, s4, s5, s6, s7 - sfour - ss1, ss2, ss3, ss4, ss5, ss6, ss7 - sz1, sz2, sz3 sz11, sz12, sz13, sz21, sz22, sz23, sz31, sz32, sz33 - tc - temp - temp1, temp2, temp3 - tsi - xpidot - xhdot1 - z1, z2, z3 - z11, z12, z13, z21, z22, z23, z31, z32, z33 -

coupling : getgravconst- initl - dscom - dpper - dsinit - sgp4 -

references : hoots, roehrich, norad spacetrack report #3 1980 hoots, norad spacetrack report #6 1986 hoots, schumacher and glover 2004

vallado, crawford, hujsak, kelso 2006

◆ twoline2rv()

void perturb::sgp4::twoline2rv	(	char	longstr1[130],
		char	longstr2[130],
		char	typerun,
		char	typeinput,
		char	opsmode,
		gravconsttype	whichconst,
		double &	startmfe,
		double &	stopmfe,
		double &	deltamin,
		elsetrec &	satrec
	)

                     function twoline2rv

this function converts the two line element set character string data to variables and initializes the sgp4 variables. several intermediate varaibles and quantities are determined. note that the result is a structure so multiple satellites can be processed simaltaneously without having to reinitialize. the verification mode is an important option that permits quick checks of any changes to the underlying technical theory. this option works using a modified tle file in which the start, stop, and delta time values are included at the end of the second line of data. this only works with the verification mode. the catalog mode simply propagates from -1440 to 1440 min from epoch and is useful when performing entire catalog runs.

author : david vallado 719-573-2600 1 mar 2001

inputs : longstr1 - first line of the tle longstr2 - second line of the tle typerun - type of run verification 'v', catalog 'c', manual 'm' typeinput - type of manual input mfe 'm', epoch 'e', dayofyr 'd' opsmode - mode of operation afspc or improved 'a', 'i' whichconst - which set of constants to use 72, 84

outputs : satrec - structure containing all the sgp4 satellite information

coupling : getgravconst- days2mdhms - conversion of days to month, day, hour, minute, second jday - convert day month year hour minute second into julian date sgp4init - initialize the sgp4 variables

references : norad spacetrack report #3

Classes

Typedefs

Enumerations

Functions

Detailed Description

Function Documentation

◆ angle_SGP4()

dot dot product of two vectors

◆ asinh_SGP4()

none.

◆ cross_SGP4()

mag magnitude of a vector

◆ days2mdhms_SGP4()

none.

◆ dot_SGP4()

none.

◆ getgravconst()

vallado, crawford, hujsak, kelso 2006

◆ gstime_SGP4()

vallado 2013, 187, eq 3-45

◆ invjday_SGP4()

vallado 2013, 203, alg 22, ex 3-13

◆ jday_SGP4()

vallado 2013, 183, alg 14, ex 3-4

◆ mag_SGP4()

none.

◆ newtonnu_SGP4()

vallado 2013, 77, alg 5

◆ rv2coe_SGP4()

vallado 2013, 113, alg 9, ex 2-5

◆ sgp4()

vallado, crawford, hujsak, kelso 2006

◆ sgp4init()

vallado, crawford, hujsak, kelso 2006

◆ twoline2rv()

vallado, crawford, hujsak, kelso 2006