kRPC Solar Prime Vector

# Returns Solar Prime Vector (Prime Meridian of the Solar System)
def solar_prime_vector(reference_frame):
    sun = space_center.bodies["Sun"]
    seconds_per_degree = sun.rotational_period / 360
    rotation_offset = np.mod(space_center.ut/seconds_per_degree, 360)
    sun_position = sun.position(reference_frame)
    sun_position2 = sun.surface_position(
        0, 0 - rotation_offset, reference_frame)

    prime_vector = np.asarray(sun_position2) - np.asarray(sun_position)

    return normalize(prime_vector)