def get_planet_angular_sep(body: str,
ra: float,
dec: float,
time=None,
observer_position: str = 'earth') -> float:
"""Get angular separation between planet ``body`` and target ``ra``, ``dec``.
Valid values for the ``observer_position`` argument are:
- 'earth' (default, approximate, fastest)
- 'chandra' (reasonably accurate fast, requires fetching ephemeris)
- 'chandra-horizons' (most accurate, slow, requires internet access)
:param body: str
Body name (lower case planet name)
:param ra: float
RA in degrees
:param dec: float
Dec in degrees
:param time: CxoTime-compatible object
Time or times of observation
:param observer_position: str
Observer position ('earth', 'chandra', or 'chandra-horizons')
:returns: angular separation (deg)
"""
from agasc import sphere_dist
if not isinstance(time, CxoTime):
time = CxoTime(time)
if observer_position == 'earth':
eci = get_planet_eci(body, time)
body_ra, body_dec = eci_to_radec(eci)
elif observer_position == 'chandra':
eci = get_planet_chandra(body, time)
body_ra, body_dec = eci_to_radec(eci)
elif observer_position == 'chandra-horizons':
if time.shape == ():
time = CxoTime([time, time + 1000 * u.s])
is_scalar = True
else:
is_scalar = False
pos = get_planet_chandra_horizons(body,
time[0],
time[1],
n_times=len(time))
body_ra = pos['ra']
body_dec = pos['dec']
if is_scalar:
body_ra = body_ra[0]
body_dec = body_dec[0]
else:
raise ValueError(f'{observer_position} is not an allowed value: '
f'("earth", "chandra", or "chandra-horizons")')
sep = sphere_dist(ra, dec, body_ra, body_dec)
return sep
def test_eci_to_radec():
eci = np.array([0.92541658, 0.16317591, 0.34202014])
ra, dec = eci_to_radec(eci)
assert np.allclose(ra, 9.9999999129952908)
assert np.allclose(dec, 19.999999794004037)
assert isinstance(ra, np.float64)
assert isinstance(dec, np.float64)
def test_venus_position2():
# *******************************************************************************
# Target body name: Venus (299) {source: CHANDRA_MERGED}
# Center body name: Chandra Observatory (spacecraft) (-151) {source: CHANDRA_MERGED}
# Center-site name: BODYCENTRIC
# *******************************************************************************
# Start time : A.D. 2020-Jan-01 00:00:00.0000 UT
# Stop time : A.D. 2020-Jun-01 00:00:00.0000 UT
# Step-size : 21600 minutes
# *******************************************************************************
txt = """
date ra dec
2020-01-01T00:00 21:08:43.02 -18:22:41.8
2020-01-16T00:00 22:19:56.31 -12:03:15.4
2020-01-31T00:00 23:26:25.34 -04:40:18.3
2020-02-15T00:00 00:29:55.07 +03:09:41.1
2020-03-01T00:00 01:31:42.96 +10:46:02.6
2020-03-16T00:00 02:32:52.02 +17:25:28.9
2020-03-31T00:00 03:32:39.01 +22:40:58.7
2020-04-15T00:00 04:26:52.03 +26:10:57.3
2020-04-30T00:00 05:07:55.28 +27:38:30.8
2020-05-15T00:00 05:22:08.73 +27:05:38.1
2020-05-30T00:00 04:59:36.37 +24:14:26.9
"""
dat = ascii.read(txt)
date = CxoTime(dat['date'])
sc = SkyCoord(dat['ra'], dat['dec'], unit=(u.hr, u.deg))
eci = get_planet_chandra('venus', date)
ra, dec = eci_to_radec(eci)
dist = sphere_dist(ra, dec, sc.ra.to_value(u.deg), sc.dec.to_value(u.deg)) * 3600
assert np.all(dist < 4.0)
def test_vectorized_eci_to_radec():
eci = np.array([[0.92541658, 0.16317591, 0.34202014],
[0.9248273, -0.16307201, 0.34365969]])
ra, dec = eci_to_radec(eci)
assert np.allclose(ra[0], 9.9999999129952908)
assert np.allclose(ra[1], 349.9999997287627)
assert np.allclose(dec[0], 19.999999794004037)
assert np.allclose(dec[1], 20.099999743270516)
assert isinstance(ra, np.ndarray)
assert isinstance(dec, np.ndarray)
def test_planet_positions_array():
bary = get_planet_barycentric('saturn', ['2020:324:11:44:00', '2020:324:11:44:01'])
assert bary.shape == (2, 3)
eci = get_planet_eci('saturn', ['2020:324:11:44:00', '2020:324:11:44:01'])
assert eci.shape == (2, 3)
eci = get_planet_chandra('saturn', ['2020:324:11:44:00', '2020:324:11:44:01'])
assert eci.shape == (2, 3)
ra, dec = eci_to_radec(eci)
# Value from JPL Horizons (Saturn from Chandra Observatory -151)
ra2, dec2 = 299.27358333, -21.07644444
assert np.all(sphere_dist(ra, dec, ra2, dec2) * 3600 < 1.0)
def test_venus_position1():
"""Obsid 18695 starcat at 2017:010:05:07:20.875, approx obs star 0510z"""
# Output from JPL Horizons for Venus from Chandra
date = CxoTime('2017-01-10T05:10')
sc = SkyCoord('22:36:02.59', '-09:39:07.2', unit=(u.hr, u.deg))
q_att = [-0.54137601, 0.17071483, -0.10344611, 0.81674192]
eci = get_planet_chandra('venus', date)
ra, dec = eci_to_radec(eci)
yag, zag = radec_to_yagzag(ra, dec, q_att)
# Confirm yag value is on "left side" of CCD, opposite all stars in 18695
assert np.isclose(yag, 210.20, rtol=0, atol=0.01)
assert np.isclose(zag, 69.45, rtol=0, atol=0.01)
dist = sphere_dist(ra, dec, sc.ra.to_value(u.deg), sc.dec.to_value(u.deg)) * 3600
assert np.all(dist < 4.0)
def test_planet_positions():
# Test basic functionality and include regression values (not an independent
# functional test)
bary = get_planet_barycentric('saturn', '2020:324:11:44:00')
assert np.allclose(bary, [7.92469846e+08, -1.15786689e+09, -5.12388561e+08])
eci = get_planet_eci('saturn', '2020:324:11:44:00')
assert np.allclose(eci, [7.13565053e+08, -1.27291136e+09, -5.62273593e+08])
eci = get_planet_chandra('saturn', '2020:324:11:44')
assert np.allclose(eci, [7.13516810e+08, -1.27285190e+09, -5.62368753e+08])
# Independent functional test to compare with JPL Horizons (Saturn from
# Chandra Observatory -151)
ra, dec = eci_to_radec(eci)
ra2, dec2 = 299.27358333, -21.07644444
assert sphere_dist(ra, dec, ra2, dec2) * 3600 < 1.0
def test_radec_eci_multidim(shape):
"""Test radec_to_eci and eci_to_radec for multidimensional inputs"""
ras = np.linspace(0., 359., 24)
decs = np.linspace(-90., 90., 24)
ras_nd = ras.reshape(shape)
decs_nd = decs.reshape(shape)
# First do everything as scalars
ecis_list = [
radec_to_eci(ra, dec) for ra, dec in zip(ras.tolist(), decs.tolist())
]
ecis_nd_from_list = np.array(ecis_list).reshape(shape + (3, ))
ecis = radec_to_eci(ras_nd, decs_nd)
assert ecis.shape == shape + (3, )
assert np.allclose(ecis, ecis_nd_from_list)
ras_rt, decs_rt = eci_to_radec(ecis)
assert ras_rt.shape == shape
assert decs_rt.shape == shape
assert np.allclose(ras_rt, ras_nd)
assert np.allclose(decs_rt, decs_nd)