def test_rotating_vector_into_frame(): et_seconds = 259056665.1855896 ts = load.timescale() t = ts.tdb_jd(T0 + et_seconds / 3600. / 24.0) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) # Example from "moon_080317.tf" (the raw vector is taken from a # tweaked version of the script in the file that uses "J2000"): vector = ICRF( np.array([ 2.4798273371071659e+05, -2.6189996683651494e+05, -1.2455830876097400e+05 ]) / AU_KM) vector.t = t meter = 1e-3 frame = pc.build_frame_named('MOON_PA_DE421') result = vector.frame_xyz(frame) assert max(abs(result.km - [379908.634, 33385.003, -12516.8859])) < meter relative_frame = pc.build_frame_named('MOON_ME_DE421') result = vector.frame_xyz(relative_frame) assert max(abs(result.km - [379892.825, 33510.118, -12661.5278])) < meter
def test_unloaded_bpc(): pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) try: pc.build_frame_named('MOON_PA_DE421') except LookupError as e: assert str(e) == ('you have not yet loaded a binary PCK file' ' that has a segment for frame 31006')
def test_frame_alias(): pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) f1 = pc.build_frame_named('MOON_PA_DE421') f2 = pc.build_frame_named('MOON_PA') ts = load.timescale() t = ts.tdb_jd(T0) assert (f1.rotation_at(t) == f2.rotation_at(t)).all()
def test_observing_earth_from_location_on_moon_with_time_vector(): # See the above test for a more thorough blow-by-blow test of this # complete operation. Here, we simply run through it quickly and # test only the end result, to see if the operation more thoroughly # tested above will also work when given a time vector. ts = load.timescale() t = ts.utc(2019, 12, [13, 14]) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') pt = pc.build_latlon_degrees(frame, 26.3, 313.2) eph = load('de421.bsp') astrometric = (eph['moon'] + pt).at(t).observe(eph['earth']) apparent = astrometric.apparent() alt, az, distance = apparent.altaz() want = (42.0019, 40.7411), (114.9380, 116.3859) pair = alt.degrees, az.degrees arcsecond = 1.0 / 3600.0 assert abs(np.array(want) - pair).max() < 12 * arcsecond
def moon_subsolar_point(t): eph = load('de421.bsp') sun = eph['sun'] moon = eph['moon'] pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') place = moon + pc.build_latlon_degrees(frame, 90.0, 180.0) sunpos = place.at(t).observe(sun).apparent() lat, lon, dist = sunpos.altaz() return lat.degrees, wrap180(lon.degrees), dist.km
def run(): rospy.init_node('sun_seeker_node', anonymous=True) rospy.Subscriber('/clock', Clock, sim_time_callback) pub = rospy.Publisher('/sun_seeker/vector', Vector3, queue_size=1) rate = rospy.Rate(0.1) eph = load('de421.bsp') sun = eph['sun'] moon = eph['moon'] path = os.path.realpath(__file__) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') place = moon + pc.build_latlon_degrees(frame, -86.79430, -21.18640) sun_angle_msg = Vector3() while not rospy.is_shutdown(): dt = datetime.fromtimestamp(sim_time) dt_utc = dt.replace(tzinfo=pytz.UTC) ts = load.timescale() t = ts.from_datetime(dt_utc) sunpos = place.at(t).observe(sun).apparent() alt, az, distance = sunpos.altaz() sun_angle_msg.x = 0.0 sun_angle_msg.y = alt.degrees sun_angle_msg.z = az.degrees if rospy.get_time() - last_msg_time < msg_timeout: rospy.loginfo('Publishing vector: x = {0:.3f}, y = {1:.3f}, z = {2:.3f}'.format(sun_angle_msg.x, sun_angle_msg.y, sun_angle_msg.z)) pub.publish(sun_angle_msg) else: rospy.logwarn('Timeout {0:.1f} seconds: Is /clock publishing?'.format(msg_timeout)) rate.sleep()
def test_using_elevation_to_locate_center_of_moon(): # Test the `elevation_m` parameter by using it to offset a Moon # surface location back to the Moon's center. ts = load.timescale() t = ts.utc(2020, 4, 23) eph = load('de421.bsp') a1 = eph['moon'].at(t) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') place = pc.build_latlon_degrees(frame, 26.3, 313.2, -1737400) a2 = (eph['moon'] + place).at(t) mm = 1e-3 assert max(abs(a1.position.m - a2.position.m)) < mm
def test_horizons_position_of_latitude_longitude_on_moon(): # This test against HORIZON is low-precision, with agreement only # within about 100m. This is a symptom of the fact that here we are # using the recent high-accuracy MOON_ME frame, while HORIZONS says # it is using the old "IAU_MOON". Alas, the NAIF presentation # `23_lunar-earth_pck-fk.pdf` says that the worse-case agreement # between the frames is 155m and is on average only 76m, so our low # agreement here is reasonable. # # See the file `horizons/moon-from-moon-topos` for the HORIZONS # result this test compares against. ts = load.timescale() t = ts.tdb_jd(2458827.5) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') assert frame.center == 301 pt = pc.build_latlon_degrees(frame, 26.3, -46.8) assert pt.center == 301 geometric = pt.at(t) assert geometric.center == 301 # Note that the sign of these two vectors is flipped, since HORIZONS # measured the other direction, from the surface to the center. want = -1.043588965592271E-05, -3.340834944508400E-06, 3.848560523814720E-06 meter = 1.0 / AU_M assert abs(geometric.position.au - want).max() < 101 * meter want = 3.480953228580460E-07, -2.173626424774260E-06, -9.429610667799021E-07 assert abs(geometric.velocity.au_per_d - want).max() < 1.6e-10
def test_observing_earth_from_location_on_moon(): ts = load.timescale() t = ts.utc(2019, 12, 13) pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_text(load('pck00008.tpc')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_ME_DE421') assert frame.center == 301 pt = pc.build_latlon_degrees(frame, 26.3, 313.2) assert pt.center == 301 eph = load('de421.bsp') astrometric = (eph['moon'] + pt).at(t).observe(eph['earth']) # See the file `horizons/earth-from-moon-topos` for the HORIZONS # source of the following `want` values. ra, dec, distance = astrometric.radec() want = 270.2590484, -22.8079717 arcsecond = 1.0 / 3600.0 assert abs(ra._degrees - want[0]) < 0.03 * arcsecond assert abs(dec.degrees - want[1]) < 0.03 * arcsecond # See the file `horizons/earth-from-moon-topos` for the HORIZONS # source of these angles. TODO: Investigate how we descended from # the brilliant sub-arcsecond precision of the previous result to a # mere 12 arcseconds of agreement. apparent = astrometric.apparent() alt, az, distance = apparent.altaz() want = 42.0019, 114.9380 pair = alt.degrees, az.degrees assert abs(np.array(want) - pair).max() < 12 * arcsecond
def test_frame_rotation_matrices(): # To produce the following matrices: # # import numpy as np # import spiceypy as spice # from skyfield.constants import DAY_S # spice.furnsh('moon_080317.tf') # spice.furnsh('moon_pa_de421_1900-2050.bpc') # g = np.vectorize(repr) # print(g(spice.pxform('J2000', 'MOON_PA', (tdb - T0) * DAY_S))) # print(g(spice.sxform('J2000', 'MOON_PA', (tdb - T0) * DAY_S)[3:6,:3])) ts = load.timescale() pc = PlanetaryConstants() pc.read_text(load('moon_080317.tf')) pc.read_binary(load('moon_pa_de421_1900-2050.bpc')) frame = pc.build_frame_named('MOON_PA_DE421') assert frame._matrix is None # pure segment, with no rotation applied # First, a moment when the angle W is nearly zero radians, so all of # its precision is available to the trigonometry. tdb = T0 - 11150 desired_rotation = [ [0.9994150897380264, 0.032310270603926675, 0.011203785852719871], [-0.034157426811763446, 0.9272642685944782, 0.37284614304233643], [0.0016578894811167893, -0.3730107540024127, 0.9278255379116378], ] desired_rate = [ [ -9.091699265305538e-08, 2.4682369763316187e-06, 9.920226874449144e-07 ], [ -2.660127501349402e-06, -8.620891007588608e-08, -2.930074158824601e-08 ], [ 4.245963144600506e-10, -5.067878765502927e-10, -2.045010122720299e-10 ], ] R = frame.rotation_at(ts.tdb_jd(tdb)) assert (R == desired_rotation).all() # Boom. R2, Rv = frame.rotation_and_rate_at(ts.tdb_jd(tdb)) assert (R == R2).all() if IS_32_BIT: assert abs(Rv - desired_rate).max() < 3e-26 else: assert (Rv == desired_rate).all() # Boom. # Second, a moment when the angle W is more than 2500 radians. tdb = T0 desired_rotation = [ [0.7840447406961362, 0.5582359944893811, 0.2713787372716964], [-0.6203032939745002, 0.7203957219351799, 0.31024800934393754], [-0.02230847532023746, -0.41158544468183367, 0.9110981032001678], ] desired_rate = [ [ -1.6512401259577911e-06, 1.9173507906460613e-06, 8.265640603882371e-07 ], [ -2.0870970217531474e-06, -1.4860137438942676e-06, -7.223743806558455e-07 ], [ -5.817943897465853e-10, -4.4636767256698343e-10, -2.1589045361778893e-10 ], ] R = frame.rotation_at(ts.tdb_jd(tdb)) delta = abs(R - desired_rotation) assert (delta < 2e-13).all() # a few digits are lost in large W radians? R2, Rv = frame.rotation_and_rate_at(ts.tdb_jd(tdb)) assert (R == R2).all() assert abs(Rv - desired_rate).max() < 4e-19 # About 13 digits precision. # Finally, a frame which is defined by a constant rotation of # another frame. tdb = T0 - 11150 desired_rotation = [ [0.9994268420493244, 0.03186286343877705, 0.011434392191818011], [-0.03382833397374688, 0.9272754001640859, 0.37284846261060917], [0.0012771890522186643, -0.37302156798771835, 0.927821792481783], ] desired_rate = [ [ -9.004087820606406e-08, 2.4682648578114788e-06, 9.920321321295625e-07 ], [ -2.660157295439155e-06, -8.539614878340816e-08, -2.8974080519384074e-08 ], [ 4.550211407392054e-10, -1.4469992803332584e-09, -5.823780954758093e-10 ], ] frame = pc.build_frame_named('MOON_ME_DE421') R = frame.rotation_at(ts.tdb_jd(tdb)) delta = abs(R - desired_rotation) if IS_32_BIT: assert abs(R - desired_rotation).max() < 2e-16 else: assert (R == desired_rotation).all() R2, Rv = frame.rotation_and_rate_at(ts.tdb_jd(tdb)) assert (R == R2).all() if IS_32_BIT: assert abs(Rv - desired_rate).max() < 2e-23 else: assert (Rv == desired_rate).all()