moon_normal_vector

ssapy.compute.moon_normal_vector(t)

Calculate the normal vector to the Moon’s orbital plane at a given time.

This function computes the normal vector to the Moon’s orbital plane by taking the cross product of the Moon’s position vectors at two different times: the given time t and one week later. The resulting vector is normalized to provide the direction of the orbital plane’s normal.

Parameters:

tTime

The time at which to calculate the normal vector to the Moon’s orbital plane.

Returns:

numpy.ndarray

A 3-element array representing the normal vector to the Moon’s orbital plane at the given time. The vector is normalized to have a unit length.

Notes:

• The function assumes a circular orbit for the Moon and uses a time step of one week (604800 seconds) to calculate the normal vector.

• The normal vector is perpendicular to the plane defined by the Moon’s position vectors at the given time and one week later.

Example usage:

>>> t = Time("2024-01-01")
>>> normal_vector = moon_normal_vector(t)
>>> normal_vector
array([-0.093,  0.014,  0.995])