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Functions
void	sun2000 (int iyr, int iday, double sec, float sun[3], float *rs)

void	nutate (double t, double xls, double gs, double xlm, double omega, double dpsi, double eps)

void	gha2000 (int iyr, double day, double *gha)

void	ephparms (double t, double xls, double gs, double xlm, double omega)

Function Documentation

◆ ephparms()

void ephparms	(	double	t,
		double *	xls,
		double *	gs,
		double *	xlm,
		double *	omega
	)

This subroutine computes ephemeris parameters used by other Mission Operations routines: the solar mean longitude and mean anomaly, and the lunar mean longitude and mean ascending node. It uses the model referenced in The Astronomical Almanac for 1984, Section S (Supplement) and documented and documented in "Exact closed-form geolocation algorithm for Earth survey sensors", by F.S. Patt and W.W. Gregg, Int. Journal of Remote Sensing, 1993. These parameters are used to compute the solar longitude and the nutation in longitude and obliquity.

Parameters

t	Time in days since January 1, 2000 at 12 hours UT
xls	Mean solar longitude (degrees)
gs	Mean solar anomaly (degrees)
xlm	Mean lunar longitude (degrees)
omega	Ascending node of mean lunar orbit (degrees)

Definition at line 3 of file ephparms.c.

◆ gha2000()

void gha2000	(	int	iyr,
		double	day,
		double *	gha
	)

This subroutine computes the Greenwich hour angle in degrees for the input time. It uses the model referenced in The Astronomical Almanac for 1984, Section S (Supplement) and documented in "Exact closed-form geolocation algorithm for Earth survey sensors", by F.S. Patt and W.W. Gregg, Int. Journal of Remote Sensing, 1993. It includes the correction to mean sideral time for nutation as well as precession. Subprograms referenced:

JD Computes Julian day from calendar date EPHPARMS Computes mean solar longitude and anomaly and mean lunar lontitude and ascending node NUTATE Compute nutation corrections to lontitude and obliquity

   Program written by:     Frederick S. Patt
                           General Sciences Corporation
                           November 2, 1992

Parameters

iyr	Year (four digits)
day	Day (time of day as fraction)
gha	reenwich hour angle (degrees)

Definition at line 5 of file gha2000.c.

◆ nutate()

void nutate	(	double	t,
		double	xls,
		double	gs,
		double	xlm,
		double	omega,
		double *	dpsi,
		double *	eps
	)

This subroutine computes the nutation in longitude and the obliquity of the ecliptic corrected for nutation. It uses the model referenced in The Astronomical Almanac for 1984, Section S (Supplement) and documented in "Exact closed-form geolocation algorithm for Earth survey sensors", by F.S. Patt and W.W. Gregg, Int. Journal of Remote Sensing, 1993. These parameters are used to compute the apparent time correction to the Greenwich Hour Angle and for the calculation of the geocentric Sun vector. The input ephemeris parameters are computed using subroutine ephparms. Terms are included to 0.1 arcsecond. Program written by: Frederick S. Patt General Sciences Corporation October 21, 1992.

Parameters

t	Time in days since January 1, 2000 at 12 hours UT
xls	Mean solar longitude (degrees)
gs	Mean solar anomaly (degrees)
xlm	Mean lunar longitude (degrees)
omega	Ascending node of mean lunar orbit (degrees)
dpsi	Nutation in longitude (degrees)
eps	Obliquity of the Ecliptic (degrees) (includes nutation in obliquity)

Definition at line 7 of file nutate.c.

◆ sun2000()

void sun2000	(	int	iyr,
		int	iday,
		double	sec,
		float	sun[3],
		float *	rs
	)

This subroutine computes the Sun vector in geocentric inertial (equatorial) coodinates. It uses the model referenced in The Astronomical Almanac for 1984, Section S (Supplement) and documented in "Exact closed-form geolocation algorithm for Earth survey sensors", by F.S. Patt and W.W. Gregg, Int. Journal of Remote Sensing, 1993. The accuracy of the Sun vector is approximately 0.1 Subprograms referenced: JD Computes Julian day from calendar date EPHPARMS Computes mean solar longitude and anomaly and mean lunar lontitude and ascending node NUTATE Compute nutation corrections to lontitude and obliquityc Coded by: Frederick S. Patt, GSC, November 2, 1992 Modified to include Earth constants subroutine by W. Gregg, May 11, 1993. arcminute.

Parameters

iyr	Year, four digits (i.e, 1993)
iday	Day of year (1-366)
sec	Seconds of day
sun	Unit Sun vector in geocentric inertial coordinates of date
rs	Magnitude of the Sun vector (AU)

arcseconds

Definition at line 8 of file sun2000.c.

Functions

Function Documentation

◆ ephparms()

◆ gha2000()

◆ nutate()

◆ sun2000()