def from_equatorial(equatorial_coo, fixed_frame):
assert equatorial_coo.body == fixed_frame.body
r = equatorial_coo.data.xyz
v = equatorial_coo.data.differentials["s"].d_xyz
ra, dec, W = fixed_frame.rot_elements_at_epoch(equatorial_coo.obstime)
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(
equatorial_coo.body.name, time=equatorial_coo.obstime)
r_trans1 = r - icrs_frame_pos_coord.xyz
r_trans2 = transform_vector(r_trans1, (90 * u.deg + ra), "z")
r_f = transform_vector(r_trans2, (90 * u.deg - dec), "x")
v_trans1 = v - icrs_frame_vel_coord.xyz
v_trans2 = transform_vector(v_trans1, (90 * u.deg + ra), "z")
v_f = transform_vector(v_trans2, (90 * u.deg - dec), "x")
r_f = transform_vector(r_f, W, "z")
v_f = transform_vector(v_f, W, "z")
data = CartesianRepresentation(
r_f, differentials=CartesianDifferential(v_f))
return fixed_frame.realize_frame(data)
def to_equatorial(fixed_coo, equatorial_frame):
# TODO replace w/ something smart (Sun/Earth special cased)
# assert fixed_coo.body == equatorial_frame.body
r = fixed_coo.cartesian.xyz
ra, dec, W = fixed_coo.rot_elements_at_epoch(fixed_coo.obstime)
equatorial_frame._obstime = fixed_coo.obstime
r = transform_vector(r, -W, "z")
r_trans1 = transform_vector(r, -(90 * u.deg - dec), "x")
r_f = transform_vector(r_trans1, -(90 * u.deg + ra), "z")
if fixed_coo.data.differentials:
v = fixed_coo.differentials["s"].d_xyz
v = transform_vector(v, -W, "z")
v_trans1 = transform_vector(v, -(90 * u.deg - dec), "x")
v_f = transform_vector(v_trans1, -(90 * u.deg + ra), "z")
data = CartesianRepresentation(
r_f, differentials=CartesianDifferential(v_f))
else:
data = CartesianRepresentation(r_f)
return equatorial_frame.realize_frame(data)
def to_equatorial(fixed_coo, equatorial_frame):
assert fixed_coo.body == equatorial_frame.body
r = fixed_coo.data.xyz
v = fixed_coo.data.differentials["s"].d_xyz
ra, dec, W = fixed_coo.rot_elements_at_epoch(fixed_coo.obstime)
r = transform_vector(r, -W, "z")
v = transform_vector(v, -W, "z")
r_trans1 = transform_vector(r, -(90 * u.deg - dec), "x")
r_trans2 = transform_vector(r_trans1, -(90 * u.deg + ra), "z")
v_trans1 = transform_vector(v, -(90 * u.deg - dec), "x")
v_trans2 = transform_vector(v_trans1, -(90 * u.deg + ra), "z")
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(
fixed_coo.body.name, time=fixed_coo.obstime)
r_f = icrs_frame_pos_coord.xyz + r_trans2
v_f = icrs_frame_vel_coord.xyz + v_trans2
data = CartesianRepresentation(
r_f, differentials=CartesianDifferential(v_f))
return equatorial_frame.realize_frame(data)
def body_centered_to_icrs(r,
v,
source_body,
epoch=J2000,
rotate_meridian=False):
"""Converts position and velocity body-centered frame to ICRS.
Parameters
----------
r : ~astropy.units.Quantity
Position vector in a body-centered reference frame.
v : ~astropy.units.Quantity
Velocity vector in a body-centered reference frame.
source_body : Body
Source body.
epoch : ~astropy.time.Time, optional
Epoch, default to J2000.
rotate_meridian : bool, optional
Whether to apply the rotation of the meridian too, default to False.
Returns
-------
r, v : tuple (~astropy.units.Quantity)
Position and velocity vectors in ICRS.
"""
ra, dec, W = source_body.rot_elements_at_epoch(epoch)
if rotate_meridian:
r = transform_vector(r, -W, 'z')
v = transform_vector(v, -W, 'z')
r_trans1 = transform_vector(r, -(90 * u.deg - dec), 'x')
r_trans2 = transform_vector(r_trans1, -(90 * u.deg + ra), 'z')
v_trans1 = transform_vector(v, -(90 * u.deg - dec), 'x')
v_trans2 = transform_vector(v_trans1, -(90 * u.deg + ra), 'z')
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(
source_body.name, time=epoch)
r_f = icrs_frame_pos_coord.xyz + r_trans2
v_f = icrs_frame_vel_coord.xyz + v_trans2
return r_f.to(r.unit), v_f.to(v.unit)
def icrs_to_body_centered(r,
v,
target_body,
epoch=J2000,
rotate_meridian=False):
"""Converts position and velocity in ICRS to body-centered frame.
Parameters
----------
r : ~astropy.units.Quantity
Position vector in ICRS.
v : ~astropy.units.Quantity
Velocity vector in ICRS.
target_body : Body
Target body.
epoch : ~astropy.time.Time, optional
Epoch, default to J2000.
rotate_meridian : bool, optional
Whether to apply the rotation of the meridian too, default to False.
Returns
-------
r, v : tuple (~astropy.units.Quantity)
Position and velocity vectors in a body-centered reference frame.
"""
ra, dec, W = target_body.rot_elements_at_epoch(epoch)
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(
target_body.name, time=epoch)
r_trans1 = r - icrs_frame_pos_coord.xyz
r_trans2 = transform_vector(r_trans1, (90 * u.deg + ra), 'z')
r_f = transform_vector(r_trans2, (90 * u.deg - dec), 'x')
v_trans1 = v - icrs_frame_vel_coord.xyz
v_trans2 = transform_vector(v_trans1, (90 * u.deg + ra), 'z')
v_f = transform_vector(v_trans2, (90 * u.deg - dec), 'x')
if rotate_meridian:
r_f = transform_vector(r_f, W, 'z')
v_f = transform_vector(v_f, W, 'z')
return r_f.to(r.unit), v_f.to(v.unit)
def body_centered_to_icrs(r, v, source_body, epoch=J2000, rotate_meridian=False):
"""Converts position and velocity body-centered frame to ICRS.
Parameters
----------
r : ~astropy.units.Quantity
Position vector in a body-centered reference frame.
v : ~astropy.units.Quantity
Velocity vector in a body-centered reference frame.
source_body : Body
Source body.
epoch : ~astropy.time.Time, optional
Epoch, default to J2000.
rotate_meridian : bool, optional
Whether to apply the rotation of the meridian too, default to False.
Returns
-------
r, v : tuple (~astropy.units.Quantity)
Position and velocity vectors in ICRS.
"""
ra, dec, W = source_body.rot_elements_at_epoch(epoch)
if rotate_meridian:
r = transform_vector(r, -W, 'z')
v = transform_vector(v, -W, 'z')
r_trans1 = transform_vector(r, -(90 * u.deg - dec), 'x')
r_trans2 = transform_vector(r_trans1, -(90 * u.deg + ra), 'z')
v_trans1 = transform_vector(v, -(90 * u.deg - dec), 'x')
v_trans2 = transform_vector(v_trans1, -(90 * u.deg + ra), 'z')
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(source_body.name, time=epoch)
r_f = icrs_frame_pos_coord.xyz + r_trans2
v_f = icrs_frame_vel_coord.xyz + v_trans2
return r_f.to(r.unit), v_f.to(v.unit)
def icrs_to_body_centered(r, v, target_body, epoch=J2000, rotate_meridian=False):
"""Converts position and velocity in ICRS to body-centered frame.
Parameters
----------
r : ~astropy.units.Quantity
Position vector in ICRS.
v : ~astropy.units.Quantity
Velocity vector in ICRS.
target_body : Body
Target body.
epoch : ~astropy.time.Time, optional
Epoch, default to J2000.
rotate_meridian : bool, optional
Whether to apply the rotation of the meridian too, default to False.
Returns
-------
r, v : tuple (~astropy.units.Quantity)
Position and velocity vectors in a body-centered reference frame.
"""
ra, dec, W = target_body.rot_elements_at_epoch(epoch)
icrs_frame_pos_coord, icrs_frame_vel_coord = get_body_barycentric_posvel(target_body.name, time=epoch)
r_trans1 = r - icrs_frame_pos_coord.xyz
r_trans2 = transform_vector(r_trans1, (90 * u.deg + ra), 'z')
r_f = transform_vector(r_trans2, (90 * u.deg - dec), 'x')
v_trans1 = v - icrs_frame_vel_coord.xyz
v_trans2 = transform_vector(v_trans1, (90 * u.deg + ra), 'z')
v_f = transform_vector(v_trans2, (90 * u.deg - dec), 'x')
if rotate_meridian:
r_f = transform_vector(r_f, W, 'z')
v_f = transform_vector(v_f, W, 'z')
return r_f.to(r.unit), v_f.to(v.unit)