astroforge.force_models.kepler#

astroforge.force_models.kepler(t, y)[source]#

A built-in force model that computes only the two-body acceleration term. The two body equations of motions are:

\[\ddot{r} = - \frac{GM}{||r||^3} r\]

Parameters:

t (float) – Time, unused. Time must be the first input to this function in order to satisfy the ODE solver API.
y (NDArray[np.float64]) – State vector; should have shape (6, ) with the first three parameters corresponding the 3D position, and the last three parameters corresponding to the 3D velocity of the satellite. Units are km and km/s.

Returns:

ydot – Derivative of the state vector.

Return type:

NDArray[np.float64]