Earth gravity model. More...

#include <sc_gravity_earth.h>

Public Member Functions
	gravity_earth (void)
	Constructor.

void	initialize (char *filename)
	Initialize with a filename.

void	initialize (void)
	Initialize with GEMT1. More...

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. More...

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. More...

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.

Detailed Description

Earth 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(char * 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.

Member Function Documentation

◆ initialize()

void gravity_earth::initialize ( void )

Initialize with GEMT1.

Initialize the model from an ASCII text file.

◆ compute_accel()

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

Update the model with the input position in ECI (Earth Centered Inertial) coordinates.

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 accel_planet(), jd_to_jcent(), moon_vector(), MU_MOON, MU_SUN, sun_vector(), and true_earth().

◆ compute_accel_ef()

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

Update the model with the input position in EF (earth fixed) coordinates.