gravity_earth Class Reference

Earth gravity model. More...

List of all members.

Public Member Functions
	gravity_earth (void)
	Constructor.
void	initialize (char *filename)
	Initialize with a filename.
void	initialize (void)
	Initialize with GEMT1.
ml_matrix	compute_accel (const ml_matrix &r_eci, double julian_date)
	Update the model with the input position in ECI (Earth Centered Inertial) coordinates.
ml_matrix	compute_accel_ef (const ml_matrix &r_ef, double julian_date)
	Update the model with the input position in EF (earth fixed) coordinates.
void	set_order (int n)
	Set the order (See description)
void	set_degree (int n)
	Set the degree (See description)
void	include_moon_accel (void)
	Include the lunar gravitational perturbations.
void	include_sun_accel (void)
	Include the solar gravitational perturbations.
ml_matrix	get_point_accel (void)
	Get the point source acceleration.
ml_matrix	get_tesseral_accel (void)
	Get the tesseral acceleration.
ml_matrix	get_zonal_accel (void)
	Get the zonal acceleration.

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Detailed Description

Gravity model. This uses a table of data passed in from a file. This model supports GEMT1, JGM-2 and JGM-3. The SCControl project copies these models into your Library. You can initialize(filename) or initialize() which automatically gives you GEMT1. If you don't initialize you get a point mass model. There are accessors to set the order and to set the degree. You can include solar and lunar perturbations.

The subscript n is the degree of the model and m is the order. The harmonic terms are classified as zonal, sectorial and tesseral. Terms having m = 0 are zonals and depend only on latitude. Terms have m = n are call sectorials and depend on longitude. Tesseral terms depend on latitude and longitude and are terms where n > m and m != 0

The class outputs the total acceleration and has methods for the point mass, tesseral and zonal harmonic contributions.

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Member Function Documentation

void gravity_earth::initialize

(

void

)

Initialize the model from an ASCII text file.

ml_matrix gravity_earth::compute_accel	(	const ml_matrix &	r_eci,
		double	julian_date
	)

Update the gravitational acceleration given the ECI position vector and the Julian date.

Parameters:

r_eci	ECI position vector
julian_date	Julian day number

References MU_MOON, and MU_SUN.

ml_matrix gravity_earth::compute_accel_ef	(	const ml_matrix &	r_ef,
		double	julian_date
	)

Update the gravitational acceleration given the ECI position vector and the Julian date.

Parameters:

r_ef	EF position vector
julian_date	Julian day number