Earth Gravity Models

class satkit.gravmodel

Earth gravity models available for use

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

egm96() → gravmodel

The “EGM96” gravity model

itugrace16() → gravmodel

the ITU Grace 16 gravity model

jgm2() → gravmodel

The “JGM2” gravity model

jgm3() → gravmodel

The “JGM3” gravity model

This model is used by default in the orbit propagators

satkit.gravity(pos: list[float] | itrfcoord | numpy.typing.ArrayLike, **kwargs) → numpy.typing.NDArray[numpy.float64]

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.NDArray[numpy.float64], **kwargs) → tuple[numpy.typing.NDArray[numpy.float64], numpy.typing.NDArray[numpy.float64]]

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.