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