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