def test_tete_quick(self):
# Following copied from intermediate_rotation_transforms.gcrs_to_tete
rbpn = erfa.pnm06a(*get_jd12(self.obstime, 'tt'))
loc_gcrs_frame = get_location_gcrs(
self.loc, self.obstime, tete_to_itrs_mat(self.obstime, rbpn=rbpn),
rbpn)
self.check_obsgeo(loc_gcrs_frame.obsgeoloc, loc_gcrs_frame.obsgeovel)
def get_cip(jd1, jd2):
"""
Find the X, Y coordinates of the CIP and the CIO locator, s.
Parameters
----------
jd1 : float or `np.ndarray`
First part of two part Julian date (TDB)
jd2 : float or `np.ndarray`
Second part of two part Julian date (TDB)
Returns
--------
x : float or `np.ndarray`
x coordinate of the CIP
y : float or `np.ndarray`
y coordinate of the CIP
s : float or `np.ndarray`
CIO locator, s
"""
# classical NPB matrix, IAU 2006/2000A
rpnb = erfa.pnm06a(jd1, jd2)
# CIP X, Y coordinates from array
x, y = erfa.bpn2xy(rpnb)
# CIO locator, s
s = erfa.s06(jd1, jd2, x, y)
return x, y, s
def tete_to_gcrs(tete_coo, gcrs_frame):
# Compute the pn matrix, and then multiply by its transpose.
rbpn = erfa.pnm06a(*get_jd12(tete_coo.obstime, 'tt'))
newrepr = tete_coo.cartesian.transform(matrix_transpose(rbpn))
# We now have a GCRS vector for the input location and obstime.
# Turn it into a GCRS frame instance.
loc_gcrs = get_location_gcrs(tete_coo, rbpn)
gcrs = loc_gcrs.realize_frame(newrepr)
# Finally, do any needed offsets (no-op if same obstime and location)
return gcrs.transform_to(gcrs_frame)
def _apparent_position_in_true_coordinates(skycoord):
"""
Convert Skycoord in GCRS frame into one in which RA and Dec
are defined w.r.t to the true equinox and poles of the Earth
"""
jd1, jd2 = get_jd12(skycoord.obstime, 'tt')
# Classical NPB matrix, IAU 2006/2000A
# (same as in builtin_frames.utils.get_cip).
rbpn = erfa.pnm06a(jd1, jd2)
return SkyCoord(skycoord.frame.realize_frame(
skycoord.cartesian.transform(rbpn)))
def _true_ecliptic_rotation_matrix(equinox):
# This code calls pnm06a from ERFA, which retrieves the precession
# matrix (including frame bias) according to the IAU 2006 model, and
# including the nutation. This family of systems is less popular
# (see https://github.com/astropy/astropy/pull/6508).
jd1, jd2 = get_jd12(equinox, 'tt')
rnpb = erfa.pnm06a(jd1, jd2)
_, nut_obl = erfa.nut06a(jd1, jd2) * u.radian
obl = erfa.obl06(
jd1, jd2
) * u.radian + nut_obl # calculate the true obliquity of the ecliptic
return matrix_product(rotation_matrix(obl, 'x'), rnpb)
def gcrs_to_tete(gcrs_coo, tete_frame):
# Classical NPB matrix, IAU 2006/2000A
# (same as in builtin_frames.utils.get_cip).
rbpn = erfa.pnm06a(*get_jd12(tete_frame.obstime, 'tt'))
# Get GCRS coordinates for the target observer location and time.
loc_gcrs = get_location_gcrs(tete_frame, rbpn)
gcrs_coo2 = gcrs_coo.transform_to(loc_gcrs)
# Now we are relative to the correct observer, do the transform to TETE.
# These rotations are defined at the geocenter, but can be applied to
# topocentric positions as well, assuming rigid Earth. See p57 of
# https://www.usno.navy.mil/USNO/astronomical-applications/publications/Circular_179.pdf
crepr = gcrs_coo2.cartesian.transform(rbpn)
return tete_frame.realize_frame(crepr)
def tete_to_gcrs(tete_coo, gcrs_frame):
# compute the pn matrix, and then multiply by its transpose
jd1, jd2 = get_jd12(tete_coo.obstime, 'tt')
# Classical NPB matrix, IAU 2006/2000A
# (same as in builtin_frames.utils.get_cip).
rbpn = erfa.pnm06a(jd1, jd2)
newrepr = tete_coo.cartesian.transform(matrix_transpose(rbpn))
gcrs = GCRS(newrepr,
obstime=tete_coo.obstime,
obsgeoloc=tete_coo.obsgeoloc,
obsgeovel=tete_coo.obsgeovel)
# now do any needed offsets (no-op if same obstime and 0 pos/vel)
return gcrs.transform_to(gcrs_frame)
def gcrs_to_tete(gcrs_coo, tete_frame):
# first apply GCRS self transform to correct time and observatory position/velocity
gcrs_coo2 = gcrs_coo.transform_to(
GCRS(obstime=tete_frame.obstime,
obsgeoloc=tete_frame.obsgeoloc,
obsgeovel=tete_frame.obsgeovel))
jd1, jd2 = get_jd12(tete_frame.obstime, 'tt')
# Classical NPB matrix, IAU 2006/2000A
# (same as in builtin_frames.utils.get_cip).
rbpn = erfa.pnm06a(jd1, jd2)
# These rotations are defined at the geocenter, but can be applied to
# topocentric positions as well, assuming rigid Earth. See p57 of
# https://www.usno.navy.mil/USNO/astronomical-applications/publications/Circular_179.pdf
crepr = gcrs_coo2.cartesian.transform(rbpn)
return tete_frame.realize_frame(crepr)
