def _get_c2i(support, obstime):
"""
Calculate the Celestial-to-Intermediate rotation matrix.
Uses the coarser grid ``support`` to do the calculation, and interpolates
onto the finer grid ``obstime``.
"""
jd1_tt_support, jd2_tt_support = get_jd12(support, 'tt')
c2i_support = erfa.c2i06a(jd1_tt_support, jd2_tt_support)
c2i = np.empty(obstime.shape + (3, 3))
for dim1 in range(3):
for dim2 in range(3):
c2i[..., dim1, dim2] = np.interp(obstime.mjd, support.mjd, c2i_support[..., dim1, dim2])
return c2i
def gcrs_to_cirs_mat(time):
# celestial-to-intermediate matrix
return erfa.c2i06a(*get_jd12(time, 'tt'))
