astroforge.force_models.F_J2

astroforge.force_models.F_J2(z)

Computes the monopole (twobody) acceleration and the J2 perturbing acceleration for Earth.

Parameters:

z (NDArray[np.float64]) – Position in space to compute the monopole and J2 forces, should have shape (3, ) and units of km.

Returns:

acc – Total vector acceleration due to monopole force and J2 perturbing force. The output is a vector with shape (3, ) and is in units of km / s².

Return type:

NDArray[np.float64]

Examples

>>> ra, dec = 11 * np.pi / 6, np.pi / 4
>>> x = af.R_earth + 450.0 * np.array(
        [
                np.cos(dec) * np.cos(ra),
                np.cos(dec) * np.sin(ra),
                np.sin(dec)
        ]
    )
>>> x
array([6653.70459606, 6219.03797423, 6696.33505153])
>>> F_J2(x)
array([-0.00183523, -0.00171534, -0.0018489 ])