def get_beta(self, when_utc=None):
"""Gets angle between orbital plane and Sun direction (beta) at given time, in degrees."""
if when_utc is None:
when_utc = dt.datetime.utcnow()
# Here we calculate the complementary angle of beta,
# because we use the normal vector of the orbital plane
beta_comp = angle_between(get_sun(when_utc),
self.get_normal_vector(when_utc))
# We subtract from 90 degrees to return the real beta angle
return 90 - beta_comp
def test_get_sun_matches_expected_result_within_precision(
when_utc, expected_eci):
eci = get_sun(when_utc)
assert angle_between(eci, expected_eci) < 1.0 # Claimed precision
assert angle_between(eci, expected_eci) < 0.5 # Actual precision