def test_sun_sync_delta_true_anomaly_non_circular(self):
date = dt.datetime.today().date()
ltan_h = 12
expected_ref_epoch = dt.datetime(date.year, date.month, date.day, 12)
for ta_deg in [-30, 30]:
pred = J2Predictor.sun_synchronous(alt_km=475,
ecc=0.1455,
date=date,
ltan_h=ltan_h,
ta_deg=ta_deg)
self.assertEqual(pred._ta, ta_deg)
self.assertEqual(pred._epoch, expected_ref_epoch)
def test_eclipse_corner_case():
# See https://github.com/satellogic/orbit-predictor/issues/96
start = dt.datetime(2020, 9, 1)
end = dt.datetime(2020, 9, 2)
pred = J2Predictor.sun_synchronous(
alt_km=470.0,
ecc=0.001,
ltan_h=19,
ta_deg=0,
date=start,
)
eclipses = list(pred.eclipses_since(when_utc=start, limit_date=end))
assert len(eclipses) == 16
def test_sun_sync_delta_true_anomaly_has_expected_anomaly_and_epoch(self):
date = dt.datetime.today().date()
ltan_h = 12
expected_ref_epoch = dt.datetime(date.year, date.month, date.day, 12)
for expected_ta_deg in [-30, 0, 30]:
pred = J2Predictor.sun_synchronous(alt_km=800,
ecc=0,
date=date,
ltan_h=ltan_h,
ta_deg=expected_ta_deg)
ta_deg = pred.get_position(
expected_ref_epoch).osculating_elements[5]
self.assertAlmostEqual(ta_deg, expected_ta_deg % 360, places=12)
def test_tca_is_correctly_computed(self):
start = dt.datetime(2020, 5, 9)
end = start + dt.timedelta(days=1)
location = Location(name="loc", latitude_deg=11, longitude_deg=0, elevation_m=0)
predictor = J2Predictor(
sma=475 + 6371, ecc=1.65e-3, inc=53.0, argp=90, raan=0, ta=300, epoch=start,
)
expected_tca = dt.datetime(2020, 5, 9, 9, 19, 15)
passes = list(
predictor.passes_over(
location,
start,
aos_at_dg=0,
max_elevation_gt=0,
limit_date=end,
location_predictor_class=SmartLocationPredictor,
tolerance_s=1e-3,
)
)
self.assertAlmostEqual(passes[1].max_elevation_date, expected_tca, delta=ONE_SECOND)
def test_benchmark_numeric(benchmark):
sma = 6780
ecc = 0.001
inc = 28.5
raan = 67.0
argp = 355.0
ta = 250.0
epoch = dt.datetime(2000, 1, 1, 12, 0)
predictor = J2Predictor(sma, ecc, inc, raan, argp, ta, epoch)
expected_position = np.array(
[2085.9287615146, -6009.5713894563, -2357.3802307070])
expected_velocity = np.array(
[6.4787522759177, 3.2366136616580, -2.5063420188165])
when_utc = epoch + dt.timedelta(hours=3)
position_eci, velocity_eci = benchmark(predictor.propagate_eci,
when_utc=when_utc)
assert_allclose(position_eci, expected_position, rtol=1e-2)
assert_allclose(velocity_eci, expected_velocity, rtol=1e-2)
def test_sun_sync_from_eccentricity_and_inclination(self):
# Vallado 3rd edition, example 11-2
expected_sma = 7346.846
pred = J2Predictor.sun_synchronous(ecc=0.2, inc_deg=98.6)
self.assertAlmostEqual(pred.get_position().osculating_elements[0], expected_sma, places=1)
def test_sun_sync_from_altitude_and_inclination(self):
# Hardcoded from our implementation
expected_ecc = 0.14546153131334466
pred = J2Predictor.sun_synchronous(alt_km=475, inc_deg=97)
self.assertAlmostEqual(pred.get_position().osculating_elements[1], expected_ecc, places=15)
def test_sun_sync_from_altitude_and_eccentricity(self):
# Vallado 3rd edition, example 11-2
expected_inc = 98.6
pred = J2Predictor.sun_synchronous(alt_km=800, ecc=0)
self.assertAlmostEqual(pred.get_position().osculating_elements[2], expected_inc, places=2)
def test_is_sun_sync_detects_almost_sun_sync_orbit():
pred2 = J2Predictor(R_E_KM + 460, 0.001, 97.4, 0, 0, 0, dt.datetime.now())
assert not is_sun_synchronous(pred2)
assert is_sun_synchronous(pred2, rtol=1e-1)
def test_is_sun_sync_returns_false_for_non_sun_sync_orbit():
pred1 = J2Predictor(7000, 0, 0, 0, 0, 0, dt.datetime.now())
assert not is_sun_synchronous(pred1)
def test_repeated_groundtrack_sma(orbits, days, inc_deg, expected_h):
pred = J2Predictor.repeating_ground_track(orbits=orbits, days=days, ecc=0.0, inc_deg=inc_deg)
assert_almost_equal(pred.get_position().osculating_elements[0] - R_E_KM, expected_h, decimal=0)
def non_sun_synchronous():
return J2Predictor(7000, 0, 42, 0, 0, 0, dt.datetime(2020, 2, 26, 0, 0, 0))