Earth Gravity Models

class satkit.gravmodel

Earth gravity models available for use

For details, see: http://icgem.gfz-potsdam.de/

property egm96

The “EGM96” gravity model

property itugrace16

the ITU Grace 16 gravity model

property jgm2

The “JGM2” gravity model

property jgm3

The “JGM3” gravity model

This model is used by default in the orbit propagators

satkit.gravity(pos: list[float] | itrfcoord | numpy.typing.ArrayLike[numpy.float], **kwargs)

Return acceleration due to Earth gravity at the input position

Parameters:

pos (list[float] | satkit.itrfcoord | npt.ArrayLike[np.float]) – Position as ITRF coordinate or numpy 3-vector representing ITRF position in meters

Keyword Arguments:

• model (gravmodel) – The gravity model to use. Default is gravmodel.jgm3

• order (int) – The order of the gravity model to use. Default is 6, maximum is 16

Returns:

acceleration in m/s^2 in the International Terrestrial Reference Frame (ITRF)

Return type:

npt.ArrayLike[np.float]

Notes

• For details of calculation, see Chapter 3.2 of: “Satellite Orbits: Models, Methods, Applications”, O. Montenbruck and B. Gill, Springer, 2012.

satkit.gravity_and_partials(pos: itrfcoord | numpy.typing.ArrayLike[numpy.float], **kwargs)

Gravity and partial derivatives of gravity with respect to Cartesian coordinates

Parameters:

pos (itrfcoord | npt.ArrayLike[np.float]) – Position as ITRF coordinate or numpy 3-vector representing ITRF position in meters

Keyword Arguments:

• model (gravmodel) – The gravity model to use. Default is gravmodel.jgm3

• order (int) – The order of the gravity model to use. Default is 6, maximum is 16

Returns:

acceleration in m/s^2 and partial derivative of acceleration with respect to ITRF Cartesian coordinate in m/s^2 / m

Return type:

tuple[npt.ArrayLike[np.float], np.arrayLike[np.float]]

For details of calculation, see Chapter 3.2 of: “Satellite Orbits: Models, Methods, Applications”, O. Montenbruck and B. Gill, Springer, 2012.