sc_gravity.h File Reference

Spherical harmonic gravity model type and functions. More...

Go to the source code of this file.

Classes
struct	gravity_s
	Structure for storing gravitational properties of a planet, used to compute the gravitational matrix at a location and time. More...

Typedefs
typedef struct gravity_s	gravity_t
	Structure for storing gravitational properties of a planet, used to compute the gravitational matrix at a location and time.

Functions
gravity_t *	init_gravity (int z_harm, int t_harm, int spherical, double p_radius, double mu, const ml_matrix &c_dist, const ml_matrix &s_dist, const ml_matrix &j)
	Allocate and initialize a gravity structure. More...
void	destroy_gravity (gravity_t *gravity)
	Deallocate a gravity structure. More...
ml_matrix	compute_gravity (gravity_t *gravity, const ml_matrix &x_eci, const ml_matrix &m_eci_to_ef)
	Compute the gravity matrix at a location and time. More...
double	total_energy_n_body (const ml_matrix &r, const ml_matrix &v, const ml_matrix &mass)
	Compute the total energy for n bodies. More...
ml_matrix	gravity_n_body (const ml_matrix &r, const ml_matrix &mass, double eps=0)
	Compute the gravity for n bodies. More...
ml_matrix	accel_planet (const ml_matrix &r, ml_matrix &mu, ml_matrix &rho)
	Compute the gravity for n bodies. More...
ml_matrix	accel_planet (const ml_matrix &r, double mu, ml_matrix &rho)
	Compute the gravity for n bodies. More...

Detailed Description

Spherical harmonic gravity model type and functions.

Function Documentation

init_gravity()

gravity_t * init_gravity	(	int	z_harm,
		int	t_harm,
		int	spherical,
		double	p_radius,
		double	mu,
		const ml_matrix &	c_coef,
		const ml_matrix &	s_coef,
		const ml_matrix &	j
	)

Allocate and initialize a gravity structure.

Allocate and initialize a gravity structure.

Parameters

z_harm	Number of zonal harmonics
t_harm	Number of tesseral harmonics
spherical	If non-zero, include the spherical gravity term in the output force
p_radius	Planet equatorial radius
mu	Planet spherical gravity coefficient
s_coef	The sine term coefficients
c_coef	The cosine term coefficients
j	The J coefficients

Returns

A newly allocated gravity structure. This structure should be deallocated using destroy_gravity() when it is no longer needed.

References gravity_s::c_coef, gravity_s::c_dist, gravity_s::l_coef, gravity_s::mu, gravity_s::p_radius, gravity_s::s_coef, gravity_s::s_dist, gravity_s::spherical, gravity_s::t_harm, and gravity_s::z_harm.

destroy_gravity()

void destroy_gravity

(

gravity_t *

gravity

)

Deallocate a gravity structure.

Deallocate a gravity structure.

Parameters

gravity

The gravity structure to be deallocated.

compute_gravity()

ml_matrix compute_gravity	(	gravity_t *	gravity,
		const ml_matrix &	x_eci,
		const ml_matrix &	m_eci_to_ef
	)

Compute the gravity matrix at a location and time.

Parameters

gravity	The gravity structure to use in the computation.
x_eci	The position matrix at which to calculate the gravity.
m_eci_to_ef	Transformation matrix from eci to earth fixed.

Returns

A 3x1 matrix representing the acceleration due to gravity at the specified location and time.

References gravity_s::c_dist, gravity_s::l_coef, gravity_s::mu, gravity_s::p_radius, gravity_s::s_dist, gravity_s::spherical, gravity_s::t_harm, and gravity_s::z_harm.

total_energy_n_body()

double total_energy_n_body	(	const ml_matrix &	r,
		const ml_matrix &	v,
		const ml_matrix &	mass
	)

Compute the total energy for n bodies.

Compute the total energy for n bodies.

Parameters

r	Position vectors [r1 r2 ... rn]
v	Velocity vector [v1 v2 ... vn]
mass	Planet mass [m1, m2, ... mn]

Returns

total energy

gravity_n_body()

ml_matrix gravity_n_body	(	const ml_matrix &	r,
		const ml_matrix &	mass,
		double	eps
	)

Compute the gravity for n bodies.

Compute the gravity for n bodies.

Parameters

r	State vector [r1 r2 ... rn]
mass	Planet mass [m1, m2, ... mn]
eps	Factor to account for being too close to a gravity source

Returns

x dot

accel_planet() [1/2]

ml_matrix accel_planet	(	const ml_matrix &	r,
		ml_matrix &	mu,
		ml_matrix &	rho
	)

Compute the gravity for n bodies.

Compute the gravity for n bodies.

Parameters

r	Vector of the spacecraft from the central body
mu	Planet gravitational parameter(s)
rho	Vector of the perturbing planet(s) from the central body

Referenced by accel_planet(), and gravity_earth::compute_accel().

accel_planet() [2/2]

ml_matrix accel_planet	(	const ml_matrix &	r,
		double	mu,
		ml_matrix &	rho
	)

Compute the gravity for n bodies.

Compute the gravity for n bodies.

Parameters

r	Vector of the spacecraft from the central body
mu	Planet gravitational parameter(s)
rho	Vector of the perturbing planet(s) from the central body

References accel_planet().