def tete_to_itrs_mat(time):
# compute the polar motion p-matrix
xp, yp = get_polar_motion(time)
sp = erfa.sp00(*get_jd12(time, 'tt'))
pmmat = erfa.pom00(xp, yp, sp)
# now determine the greenwich apparent siderial time for the input obstime
# we use the 2006A model for consistency with RBPN matrix use in GCRS <-> TETE
ujd1, ujd2 = get_jd12(time, 'ut1')
jd1, jd2 = get_jd12(time, 'tt')
gast = erfa.gst06a(ujd1, ujd2, jd1, jd2)
# c2tcio expects a GCRS->CIRS matrix, but we just set that to an I-matrix
# because we're already in CIRS equivalent frame
return erfa.c2tcio(np.eye(3), gast, pmmat)
def tete_to_itrs_mat(time, rbpn=None):
"""Compute the polar motion p-matrix at the given time.
If the nutation-precession matrix is already known, it should be passed in,
as this is by far the most expensive calculation.
"""
xp, yp = get_polar_motion(time)
sp = erfa.sp00(*get_jd12(time, 'tt'))
pmmat = erfa.pom00(xp, yp, sp)
# now determine the greenwich apparent siderial time for the input obstime
# we use the 2006A model for consistency with RBPN matrix use in GCRS <-> TETE
ujd1, ujd2 = get_jd12(time, 'ut1')
jd1, jd2 = get_jd12(time, 'tt')
if rbpn is None:
# erfa.gst06a calls pnm06a to calculate rbpn and then gst06. Use it in
# favour of getting rbpn with erfa.pnm06a to avoid a possibly large array.
gast = erfa.gst06a(ujd1, ujd2, jd1, jd2)
else:
gast = erfa.gst06(ujd1, ujd2, jd1, jd2, rbpn)
# c2tcio expects a GCRS->CIRS matrix, but we just set that to an I-matrix
# because we're already in CIRS equivalent frame
return erfa.c2tcio(np.eye(3), gast, pmmat)