def __getCIPandCIOlocator(self,epoch: datetime.datetime):
"""
Gets Celestial Intermediate Pole at epoch
:param epoch:
:return: X , Y of CIP
"""
# Gets x,y coords of Celestial Intermediate Pole (CIP) and CIO locator s
# CIO = Celestial Intermediate Origin
# Both in GCRS
mjd = pySat.pySatTime.UTC2MJD(epoch)
Xcio, Ycio, Scio = erfa.xys06a(2400000.5, mjd)
return Xcio, Ycio, Scio
def gcrs2irts_matrix_b(t, eop):
"""
Ref: http://www.iausofa.org/sofa_pn_c.pdf
Purpose:
This function calculates the cartesian transformation matrix for transforming GCRS to ITRS or vice versa
:param eop:
eop is a dataframe containing the Earth Orientation Parameters as per IAU definitions
:param t:
t is a datetime object or a list of datetime objects with the UTC times for the transformation matrix to be
calculated for
:return:
matrix is a [3,3] numpy array or list of arrays used for transforming GCRS to ITRS or vice versa at the
specified times; ITRS = matrix @ GCRS
"""
if not (isinstance(t, Iterable)):
t = [t]
matrix = []
for ti in t:
year = ti.year
month = ti.month
day = ti.day
hour = ti.hour
minute = ti.minute
second = ti.second
# TT (MJD). */
djmjd0, date = erfa.cal2jd(iy=year, im=month, id=day)
# jd = djmjd0 + date
day_frac = (60.0 * (60.0 * hour + minute) + second) / DAYSEC
utc = date + day_frac
Dat = erfa.dat(year, month, day, day_frac)
tai = utc + Dat / DAYSEC
tt = tai + 32.184 / DAYSEC
# UT1. */
dut1 = eop["UT1-UTC"][date] * (
1 - day_frac) + eop["UT1-UTC"][date + 1] * day_frac
tut = day_frac + dut1 / DAYSEC
# ut1 = date + tut
# CIP and CIO, IAU 2006/2000A. */
x, y, s = erfa.xys06a(djmjd0, tt)
# X, Y offsets
dx06 = (eop["dX"][date] *
(1 - day_frac) + eop["dX"][date + 1] * day_frac) * DAS2R
dy06 = (eop["dY"][date] *
(1 - day_frac) + eop["dY"][date + 1] * day_frac) * DAS2R
# Add CIP corrections. */
x = x + dx06
y = y + dy06
# GCRS to CIRS matrix. */
rc2i = erfa.c2ixys(x, y, s)
# Earth rotation angle. */
era = erfa.era00(djmjd0 + date, tut)
# Form celestial-terrestrial matrix (no polar motion yet). */
rc2ti = erfa.cr(rc2i)
rc2ti = eraRZ(era, rc2ti)
#rc2ti = erfa.rz(era, rc2ti)
# Polar motion matrix (TIRS->ITRS, IERS 2003). */
xp = (eop["x"][date] *
(1 - day_frac) + eop["x"][date + 1] * day_frac) * DAS2R
yp = (eop["y"][date] *
(1 - day_frac) + eop["y"][date + 1] * day_frac) * DAS2R
rpom = erfa.pom00(xp, yp, erfa.sp00(djmjd0, tt))
# Form celestial-terrestrial matrix (including polar motion). */
rc2it = erfa.rxr(rpom, rc2ti)
matrix.append(rc2it)
if len(matrix) == 1:
matrix = matrix[0]
return matrix