def prepare_earth_position_vel(time):
"""
Get barycentric position and velocity, and heliocentric position of Earth
Parameters
-----------
time : `~astropy.time.Time`
time at which to calculate position and velocity of Earth
Returns
--------
earth_pv : `np.ndarray`
Barycentric position and velocity of Earth, in au and au/day
earth_helio : `np.ndarray`
Heliocentric position of Earth in au
"""
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import (get_body_barycentric,
get_body_barycentric_posvel)
# get barycentric position and velocity of earth
earth_p, earth_v = get_body_barycentric_posvel('earth', time)
# get heliocentric position of earth, preparing it for passing to erfa.
sun = get_body_barycentric('sun', time)
earth_heliocentric = (earth_p - sun).get_xyz(xyz_axis=-1).to_value(u.au)
# Also prepare earth_pv for passing to erfa, which wants it as
# a structured dtype.
earth_pv = erfa.pav2pv(
earth_p.get_xyz(xyz_axis=-1).to_value(u.au),
earth_v.get_xyz(xyz_axis=-1).to_value(u.au / u.d))
return earth_pv, earth_heliocentric
def prepare_earth_position_vel(time):
"""
Get barycentric position and velocity, and heliocentric position of Earth
Parameters
-----------
time : `~astropy.time.Time`
time at which to calculate position and velocity of Earth
Returns
--------
earth_pv : `np.ndarray`
Barycentric position and velocity of Earth, in au and au/day
earth_helio : `np.ndarray`
Heliocentric position of Earth in au
"""
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import (get_body_barycentric, get_body_barycentric_posvel)
# get barycentric position and velocity of earth
earth_p, earth_v = get_body_barycentric_posvel('earth', time)
# get heliocentric position of earth, preparing it for passing to erfa.
sun = get_body_barycentric('sun', time)
earth_heliocentric = (earth_p -
sun).get_xyz(xyz_axis=-1).to_value(u.au)
# Also prepare earth_pv for passing to erfa, which wants it as
# a structured dtype.
earth_pv = erfa.pav2pv(
earth_p.get_xyz(xyz_axis=-1).to_value(u.au),
earth_v.get_xyz(xyz_axis=-1).to_value(u.au/u.d))
return earth_pv, earth_heliocentric
def icrs_to_iau76_ecliptic(from_coo, to_frame):
# get barycentric sun coordinate
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = get_body_barycentric("sun", to_frame.obstime)
# now compute the matrix to precess to the right orientation
rmat = _obliquity_only_rotation_matrix()
return rmat, (-bary_sun_pos).transform(rmat)
def ecliptic_to_iau76_icrs(from_coo, to_frame):
# first un-precess from ecliptic to ICRS orientation
rmat = _obliquity_only_rotation_matrix()
# now offset back to barycentric, which is the correct center for ICRS
# get barycentric sun coordinate
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = get_body_barycentric("sun", from_coo.obstime)
return matrix_transpose(rmat), bary_sun_pos
def prepare_earth_position_vel(time):
"""
Get barycentric position and velocity, and heliocentric position of Earth
Parameters
-----------
time : `~astropy.time.Time`
time at which to calculate position and velocity of Earth
Returns
--------
earth_pv : `np.ndarray`
Barycentric position and velocity of Earth, in au and au/day
earth_helio : `np.ndarray`
Heliocentric position of Earth in au
"""
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import (
get_body_barycentric,
get_body_barycentric_posvel,
solar_system_ephemeris,
)
# get barycentric position and velocity of earth
ephemeris = solar_system_ephemeris.get()
# if we are using the builtin erfa based ephemeris,
# we can use the fact that epv00 already provides all we need.
# This avoids calling epv00 twice, once
# in get_body_barycentric_posvel('earth') and once in
# get_body_barycentric('sun')
if ephemeris == 'builtin':
jd1, jd2 = get_jd12(time, 'tdb')
earth_pv_heliocentric, earth_pv = erfa.epv00(jd1, jd2)
earth_heliocentric = earth_pv_heliocentric['p']
# all other ephemeris providers probably don't have a shortcut like this
else:
earth_p, earth_v = get_body_barycentric_posvel('earth', time)
# get heliocentric position of earth, preparing it for passing to erfa.
sun = get_body_barycentric('sun', time)
earth_heliocentric = (earth_p - sun).get_xyz(xyz_axis=-1).to_value(
u.au)
# Also prepare earth_pv for passing to erfa, which wants it as
# a structured dtype.
earth_pv = pav2pv(
earth_p.get_xyz(xyz_axis=-1).to_value(u.au),
earth_v.get_xyz(xyz_axis=-1).to_value(u.au / u.d))
return earth_pv, earth_heliocentric
def icrs_to_true_helioecliptic(from_coo, to_frame):
if not u.m.is_equivalent(from_coo.cartesian.x.unit):
raise UnitsError(_NEED_ORIGIN_HINT.format(from_coo.__class__.__name__))
# get barycentric sun coordinate
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = get_body_barycentric('sun', to_frame.obstime)
# now compute the matrix to precess to the right orientation
rmat = _true_ecliptic_rotation_matrix(to_frame.equinox)
return rmat, (-bary_sun_pos).transform(rmat)
def true_helioecliptic_to_icrs(from_coo, to_frame):
if not u.m.is_equivalent(from_coo.cartesian.x.unit):
raise UnitsError(_NEED_ORIGIN_HINT.format(from_coo.__class__.__name__))
# first un-precess from ecliptic to ICRS orientation
rmat = _true_ecliptic_rotation_matrix(from_coo.equinox)
# now offset back to barycentric, which is the correct center for ICRS
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
# get barycentric sun coordinate
bary_sun_pos = get_body_barycentric('sun', from_coo.obstime)
return matrix_transpose(rmat), bary_sun_pos
def icrs_to_helioecliptic(from_coo, to_frame):
if not u.m.is_equivalent(from_coo.cartesian.x.unit):
raise UnitsError(_NEED_ORIGIN_HINT.format(from_coo.__class__.__name__))
# get barycentric sun coordinate
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = get_body_barycentric('sun', to_frame.obstime)
# offset to heliocentric
heliocart = from_coo.cartesian - bary_sun_pos
# now compute the matrix to precess to the right orientation
rmat = _ecliptic_rotation_matrix(to_frame.equinox)
newrepr = heliocart.transform(rmat)
return to_frame.realize_frame(newrepr)
def icrs_to_hcrs(icrs_coo, hcrs_frame):
# this is just an origin translation so without a distance it cannot go ahead
if isinstance(icrs_coo.data, UnitSphericalRepresentation):
raise u.UnitsError(_NEED_ORIGIN_HINT.format(icrs_coo.__class__.__name__))
if icrs_coo.data.differentials:
from astropy.coordinates.solar_system import get_body_barycentric_posvel
bary_sun_pos, bary_sun_vel = get_body_barycentric_posvel('sun',
hcrs_frame.obstime)
bary_sun_pos = -bary_sun_pos.with_differentials(-bary_sun_vel)
else:
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = -get_body_barycentric('sun', hcrs_frame.obstime)
bary_sun_vel = None
return None, bary_sun_pos
def hcrs_to_icrs(hcrs_coo, icrs_frame):
# this is just an origin translation so without a distance it cannot go ahead
if isinstance(hcrs_coo.data, UnitSphericalRepresentation):
raise u.UnitsError(_NEED_ORIGIN_HINT.format(hcrs_coo.__class__.__name__))
if hcrs_coo.data.differentials:
from astropy.coordinates.solar_system import get_body_barycentric_posvel
bary_sun_pos, bary_sun_vel = get_body_barycentric_posvel('sun',
hcrs_coo.obstime)
bary_sun_vel = bary_sun_vel.represent_as(CartesianDifferential)
bary_sun_pos = bary_sun_pos.with_differentials(bary_sun_vel)
else:
from astropy.coordinates.solar_system import get_body_barycentric
bary_sun_pos = get_body_barycentric('sun', hcrs_coo.obstime)
bary_sun_vel = None
return None, bary_sun_pos
def helioecliptic_to_icrs(from_coo, to_frame):
if not u.m.is_equivalent(from_coo.cartesian.x.unit):
raise UnitsError(_NEED_ORIGIN_HINT.format(from_coo.__class__.__name__))
# first un-precess from ecliptic to ICRS orientation
rmat = _ecliptic_rotation_matrix(from_coo.equinox)
intermed_repr = from_coo.cartesian.transform(matrix_transpose(rmat))
# now offset back to barycentric, which is the correct center for ICRS
# this goes here to avoid circular import errors
from astropy.coordinates.solar_system import get_body_barycentric
# get barycentric sun coordinate
bary_sun_pos = get_body_barycentric('sun', from_coo.obstime)
newrepr = intermed_repr + bary_sun_pos
return to_frame.realize_frame(newrepr)
def get_offset_sun_from_barycenter(time,
include_velocity=False,
reverse=False):
"""
Returns the offset of the Sun center from the solar-system barycenter (SSB).
Parameters
----------
time : `~astropy.time.Time`
Time at which to calculate the offset
include_velocity : `bool`
If ``True``, attach the velocity as a differential. Defaults to ``False``.
reverse : `bool`
If ``True``, return the offset of the barycenter from the Sun. Defaults to ``False``.
Returns
-------
`~astropy.coordinates.CartesianRepresentation`
The offset
"""
if include_velocity:
# Import here to avoid a circular import
from astropy.coordinates.solar_system import get_body_barycentric_posvel
offset_pos, offset_vel = get_body_barycentric_posvel('sun', time)
if reverse:
offset_pos, offset_vel = -offset_pos, -offset_vel
offset_vel = offset_vel.represent_as(CartesianDifferential)
offset_pos = offset_pos.with_differentials(offset_vel)
else:
# Import here to avoid a circular import
from astropy.coordinates.solar_system import get_body_barycentric
offset_pos = get_body_barycentric('sun', time)
if reverse:
offset_pos = -offset_pos
return offset_pos
def test_barycentric_pos_posvel_same():
# Check that the two routines give identical results.
ep1 = get_body_barycentric('earth', Time('2016-03-20T12:30:00'))
ep2, _ = get_body_barycentric_posvel('earth', Time('2016-03-20T12:30:00'))
assert np.all(ep1.xyz == ep2.xyz)
def test_barycentric_pos_posvel_same():
# Check that the two routines give identical results.
ep1 = get_body_barycentric('earth', Time('2016-03-20T12:30:00'))
ep2, _ = get_body_barycentric_posvel('earth', Time('2016-03-20T12:30:00'))
assert np.all(ep1.xyz == ep2.xyz)
