def test_horizons_consistency_with_precision():
"""
A test to compare at high precision against output of JPL horizons.
Tests ephemerides, and conversions from ICRS to GCRS to TETE. We are aiming for
better than 2 milli-arcsecond precision.
We use the Moon since it is nearby, and moves fast in the sky so we are
testing for parallax, proper handling of light deflection and aberration.
"""
# JPL Horizon values for 2020_04_06 00:00 to 23:00 in 1 hour steps
# JPL Horizons has a known offset (frame bias) of 51.02 mas in RA. We correct that here
ra_apparent_horizons = [
170.167332531, 170.560688674, 170.923834838, 171.271663481, 171.620188972, 171.985340827,
172.381766539, 172.821772139, 173.314502650, 173.865422398, 174.476108551, 175.144332386,
175.864375310, 176.627519827, 177.422655853, 178.236955730, 179.056584831, 179.867427392,
180.655815385, 181.409252074, 182.117113814, 182.771311578, 183.366872837, 183.902395443
] * u.deg + 51.02376467 * u.mas
dec_apparent_horizons = [
10.269112037, 10.058820647, 9.837152044, 9.603724551, 9.358956528, 9.104012390, 8.840674927,
8.571162442, 8.297917326, 8.023394488, 7.749873882, 7.479312991, 7.213246666, 6.952732614,
6.698336823, 6.450150213, 6.207828142, 5.970645962, 5.737565957, 5.507313851, 5.278462034,
5.049521497, 4.819038911, 4.585696512
] * u.deg
with solar_system_ephemeris.set('de430'):
loc = EarthLocation.from_geodetic(-67.787260*u.deg, -22.959748*u.deg, 5186*u.m)
times = Time('2020-04-06 00:00') + np.arange(0, 24, 1)*u.hour
astropy = get_body('moon', times, loc)
apparent_frame = TETE(obstime=times, location=loc)
astropy = astropy.transform_to(apparent_frame)
usrepr = UnitSphericalRepresentation(ra_apparent_horizons, dec_apparent_horizons)
horizons = apparent_frame.realize_frame(usrepr)
assert_quantity_allclose(astropy.separation(horizons), 0*u.mas, atol=1.5*u.mas)
def setup(self):
self.t = Time('1980-03-25 00:00')
self.apparent_frame = TETE(obstime=self.t)
# Results returned by JPL Horizons web interface
self.horizons = {
'mercury':
SkyCoord(ra='22h41m47.78s',
dec='-08d29m32.0s',
distance=c * 6.323037 * u.min,
frame=self.apparent_frame),
'moon':
SkyCoord(ra='07h32m02.62s',
dec='+18d34m05.0s',
distance=c * 0.021921 * u.min,
frame=self.apparent_frame),
'jupiter':
SkyCoord(ra='10h17m12.82s',
dec='+12d02m57.0s',
distance=c * 37.694557 * u.min,
frame=self.apparent_frame),
'sun':
SkyCoord(ra='00h16m31.00s',
dec='+01d47m16.9s',
distance=c * 8.294858 * u.min,
frame=self.apparent_frame)
}
def setup(self):
kitt_peak = EarthLocation.from_geodetic(lon=-111.6*u.deg,
lat=31.963333333333342*u.deg,
height=2120*u.m)
self.t = Time('2014-09-25T00:00', location=kitt_peak)
self.apparent_frame = TETE(obstime=self.t, location=kitt_peak)
# Results returned by JPL Horizons web interface
self.horizons = {
'mercury': SkyCoord(ra='13h38m58.50s', dec='-13d34m42.6s',
distance=c*7.699020*u.min, frame=self.apparent_frame),
'moon': SkyCoord(ra='12h33m12.85s', dec='-05d17m54.4s',
distance=c*0.022054*u.min, frame=self.apparent_frame),
'jupiter': SkyCoord(ra='09h09m55.55s', dec='+16d51m57.8s',
distance=c*49.244937*u.min, frame=self.apparent_frame)}
def test_positions_skyfield(tmpdir):
"""
Test positions against those generated by skyfield.
"""
load = Loader(tmpdir)
t = Time('1980-03-25 00:00')
location = None
# skyfield ephemeris
try:
planets = load('de421.bsp')
ts = load.timescale()
except OSError as e:
if os.environ.get('CI', False) and 'timed out' in str(e):
pytest.xfail('Timed out in CI')
else:
raise
mercury, jupiter, moon = planets['mercury'], planets[
'jupiter barycenter'], planets['moon']
earth = planets['earth']
skyfield_t = ts.from_astropy(t)
if location is not None:
earth = earth + Topos(latitude_degrees=location.lat.to_value(u.deg),
longitude_degrees=location.lon.to_value(u.deg),
elevation_m=location.height.to_value(u.m))
skyfield_mercury = earth.at(skyfield_t).observe(mercury).apparent()
skyfield_jupiter = earth.at(skyfield_t).observe(jupiter).apparent()
skyfield_moon = earth.at(skyfield_t).observe(moon).apparent()
if location is not None:
frame = TETE(obstime=t, location=location)
else:
frame = TETE(obstime=t)
ra, dec, dist = skyfield_mercury.radec(epoch='date')
skyfield_mercury = SkyCoord(ra.to(u.deg),
dec.to(u.deg),
distance=dist.to(u.km),
frame=frame)
ra, dec, dist = skyfield_jupiter.radec(epoch='date')
skyfield_jupiter = SkyCoord(ra.to(u.deg),
dec.to(u.deg),
distance=dist.to(u.km),
frame=frame)
ra, dec, dist = skyfield_moon.radec(epoch='date')
skyfield_moon = SkyCoord(ra.to(u.deg),
dec.to(u.deg),
distance=dist.to(u.km),
frame=frame)
# planet positions w.r.t true equator and equinox
moon_astropy = get_moon(t, location, ephemeris='de430').transform_to(frame)
mercury_astropy = get_body('mercury', t, location,
ephemeris='de430').transform_to(frame)
jupiter_astropy = get_body('jupiter', t, location,
ephemeris='de430').transform_to(frame)
assert (moon_astropy.separation(skyfield_moon) <
skyfield_angular_separation_tolerance)
assert (moon_astropy.separation_3d(skyfield_moon) <
skyfield_separation_tolerance)
assert (jupiter_astropy.separation(skyfield_jupiter) <
skyfield_angular_separation_tolerance)
assert (jupiter_astropy.separation_3d(skyfield_jupiter) <
skyfield_separation_tolerance)
assert (mercury_astropy.separation(skyfield_mercury) <
skyfield_angular_separation_tolerance)
assert (mercury_astropy.separation_3d(skyfield_mercury) <
skyfield_separation_tolerance)
planets.close()