def test_orbit_representation():
ss = Orbit.circular(
Earth, 600 * u.km, 20 * u.deg, epoch=Time("2018-09-08 09:04:00", scale="tdb")
)
expected_str = "6978 x 6978 km x 20.0 deg (GCRS) orbit around Earth (\u2641) at epoch 2018-09-08 09:04:00.000 (TDB)"
assert str(ss) == repr(ss) == expected_str
def test_pqw_for_circular_equatorial_orbit():
ss = Orbit.circular(Earth, 600 * u.km)
expected_p = [1, 0, 0] * u.one
expected_q = [0, 1, 0] * u.one
expected_w = [0, 0, 1] * u.one
p, q, w = ss.pqw()
assert_allclose(p, expected_p)
assert_allclose(q, expected_q)
assert_allclose(w, expected_w)
def test_geosync_has_proper_period():
expected_period = 1436 * u.min
ss = Orbit.circular(Earth, alt=42164 * u.km - Earth.R)
assert_quantity_allclose(ss.period, expected_period, rtol=1e-4)
def test_circular_has_proper_semimajor_axis():
alt = 500 * u.km
attractor = Earth
expected_a = Earth.R + alt
ss = Orbit.circular(attractor, alt)
assert ss.a == expected_a
def test_circular_raises_error_if_negative_altitude():
with pytest.raises(ValueError) as excinfo:
Orbit.circular(Earth,
-1 * u.m,
epoch=Time(0.0, format="jd", scale="tdb"))
assert "Altitude of an orbit cannot be negative." in excinfo.exconly()
def test_geosync_has_proper_period():
expected_period = 1436 * u.min
ss = Orbit.circular(Earth, alt=42164 * u.km - Earth.R)
assert_quantity_allclose(ss.period, expected_period, rtol=1e-4)
def test_circular_has_proper_semimajor_axis():
alt = 500 * u.km
attractor = Earth
expected_a = Earth.R + alt
ss = Orbit.circular(attractor, alt)
assert ss.a == expected_a
