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Earth Gravity Models

gravmodel

Earth gravity models available for use

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

jgm3 class-attribute

The "JGM3" gravity model

This model is used by default in the orbit propagators

jgm2 class-attribute

The "JGM2" gravity model

egm96 class-attribute

The "EGM96" gravity model

itugrace16 class-attribute

the ITU Grace 16 gravity model

gravity(pos, **kwargs)

Return acceleration due to Earth gravity at the input position

Parameters:

Name Type Description Default
pos list[float] | itrfcoord | ArrayLike[float]

Position as ITRF coordinate or numpy 3-vector representing ITRF position in meters

 required

Other Parameters:

Name Type Description
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:

Type Description
NDArray[float64]

npt.ArrayLike[np.float]: acceleration in m/s^2 in the International Terrestrial Reference Frame (ITRF)
Notes
  • For details of calculation, see Chapter 3.2 of: "Satellite Orbits: Models, Methods, Applications", O. Montenbruck and B. Gill, Springer, 2012.
Example 
coord = satkit.itrfcoord(latitude_deg=42.44, longitude_deg=-71.15, altitude=0)
accel = satkit.gravity(coord)
print(accel)
# array with acceleration in m/s^2 in ITRF

gravity_and_partials(pos, **kwargs)

Gravity and partial derivatives of gravity with respect to Cartesian coordinates

Parameters:

Name Type Description Default
pos itrfcoord | ArrayLike[float]

Position as ITRF coordinate or numpy 3-vector representing ITRF position in meters

 required

Other Parameters:

Name Type Description
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:

Type Description
tuple[NDArray[float64], NDArray[float64]]

tuple[npt.ArrayLike[np.float], np.arrayLike[np.float]]: acceleration in m/s^2 and partial derivative of acceleration with respect to ITRF Cartesian coordinate in m/s^2 / m

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