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from __future__ import division # confidence high
from stwcs import DEGTORAD, RADTODEG
import numpy as np
from math import sin, sqrt, pow, cos, asin, atan2,pi
import utils
from stsci.tools import fileutil
import logging, time
logger = logging.getLogger(__name__)
class MakeWCS(object):
"""
Recompute basic WCS keywords based on PA_V3 and distortion model.
Notes
-----
- Compute the reference chip WCS:
-- CRVAL: transform the model XREF/YREF to the sky
-- PA_V3 is calculated at the target position and adjusted
for each chip orientation
-- CD: PA_V3 and the model scale are used to cnstruct a CD matrix
- Compute the second chip WCS:
-- CRVAL: - the distance between the zero points of the two
chip models on the sky
-- CD matrix: first order coefficients are added to the components
of this distance and transfered on the sky. The difference
between CRVAL and these vectors is the new CD matrix for each chip.
-- CRPIX: chip's model zero point in pixel space (XREF/YREF)
- Time dependent distortion correction is applied to both chips' V2/V3 values.
"""
tdd_xyref = {1: [2048, 3072], 2:[2048, 1024]}
def updateWCS(cls, ext_wcs, ref_wcs):
"""
recomputes the basic WCS kw
"""
logger.info("\n\tStarting MakeWCS: %s" % time.asctime())
ltvoff, offshift = cls.getOffsets(ext_wcs)
v23_corr = cls.zero_point_corr(ext_wcs)
rv23_corr = cls.zero_point_corr(ref_wcs)
cls.uprefwcs(ext_wcs, ref_wcs, rv23_corr, ltvoff, offshift)
cls.upextwcs(ext_wcs, ref_wcs, v23_corr, rv23_corr, ltvoff, offshift)
kw2update = {'CD1_1': ext_wcs.wcs.cd[0,0],
'CD1_2': ext_wcs.wcs.cd[0,1],
'CD2_1': ext_wcs.wcs.cd[1,0],
'CD2_2': ext_wcs.wcs.cd[1,1],
'CRVAL1': ext_wcs.wcs.crval[0],
'CRVAL2': ext_wcs.wcs.crval[1],
'CRPIX1': ext_wcs.wcs.crpix[0],
'CRPIX2': ext_wcs.wcs.crpix[1],
'IDCTAB': ext_wcs.idctab,
}
return kw2update
updateWCS = classmethod(updateWCS)
def upextwcs(cls, ext_wcs, ref_wcs, v23_corr, rv23_corr, loff, offsh):
"""
updates an extension wcs
"""
ltvoffx, ltvoffy = loff[0], loff[1]
offshiftx, offshifty = offsh[0], offsh[1]
ltv1 = ext_wcs.ltv1
ltv2 = ext_wcs.ltv2
if ltv1 != 0. or ltv2 != 0.:
offsetx = ext_wcs.wcs.crpix[0] - ltv1 - ext_wcs.idcmodel.refpix['XREF']
offsety = ext_wcs.wcs.crpix[1] - ltv2 - ext_wcs.idcmodel.refpix['YREF']
fx,fy = ext_wcs.idcmodel.shift(ext_wcs.idcmodel.cx,ext_wcs.idcmodel.cy,offsetx,offsety)
else:
fx, fy = ext_wcs.idcmodel.cx, ext_wcs.idcmodel.cy
tddscale = (ref_wcs.pscale/fx[1,1])
v2 = ext_wcs.idcmodel.refpix['V2REF'] + v23_corr[0,0] * tddscale
v3 = ext_wcs.idcmodel.refpix['V3REF'] - v23_corr[1,0] * tddscale
v2ref = ref_wcs.idcmodel.refpix['V2REF'] + rv23_corr[0,0] * tddscale
v3ref = ref_wcs.idcmodel.refpix['V3REF'] - rv23_corr[1,0] * tddscale
R_scale = ref_wcs.idcmodel.refpix['PSCALE']/3600.0
off = sqrt((v2-v2ref)**2 + (v3-v3ref)**2)/(R_scale*3600.0)
if v3 == v3ref:
theta=0.0
else:
theta = atan2(ext_wcs.parity[0][0]*(v2-v2ref), ext_wcs.parity[1][1]*(v3-v3ref))
if ref_wcs.idcmodel.refpix['THETA']: theta += ref_wcs.idcmodel.refpix['THETA']*pi/180.0
dX=(off*sin(theta)) + offshiftx
dY=(off*cos(theta)) + offshifty
px = np.array([[dX,dY]])
newcrval = ref_wcs.wcs.p2s(px, 1)['world'][0]
newcrpix = np.array([ext_wcs.idcmodel.refpix['XREF'] + ltvoffx,
ext_wcs.idcmodel.refpix['YREF'] + ltvoffy])
ext_wcs.wcs.crval = newcrval
ext_wcs.wcs.crpix = newcrpix
ext_wcs.wcs.set()
# Create a small vector, in reference image pixel scale
delmat = np.array([[fx[1,1], fy[1,1]], \
[fx[1,0], fy[1,0]]]) / R_scale/3600.
# Account for subarray offset
# Angle of chip relative to chip
if ext_wcs.idcmodel.refpix['THETA']:
dtheta = ext_wcs.idcmodel.refpix['THETA'] - ref_wcs.idcmodel.refpix['THETA']
else:
dtheta = 0.0
rrmat = fileutil.buildRotMatrix(dtheta)
# Rotate the vectors
dxy = np.dot(delmat, rrmat)
wc = ref_wcs.wcs.p2s((px + dxy), 1)['world']
# Calculate the new CDs and convert to degrees
cd11 = utils.diff_angles(wc[0,0],newcrval[0])*cos(newcrval[1]*pi/180.0)
cd12 = utils.diff_angles(wc[1,0],newcrval[0])*cos(newcrval[1]*pi/180.0)
cd21 = utils.diff_angles(wc[0,1],newcrval[1])
cd22 = utils.diff_angles(wc[1,1],newcrval[1])
cd = np.array([[cd11, cd12], [cd21, cd22]])
ext_wcs.wcs.cd = cd
ext_wcs.wcs.set()
upextwcs = classmethod(upextwcs)
def uprefwcs(cls, ext_wcs, ref_wcs, rv23_corr_tdd, loff, offsh):
"""
Updates the reference chip
"""
ltvoffx, ltvoffy = loff[0], loff[1]
offshift = offsh
dec = ref_wcs.wcs.crval[1]
tddscale = (ref_wcs.pscale/ext_wcs.idcmodel.cx[1,1])
rv23 = [ref_wcs.idcmodel.refpix['V2REF'] + (rv23_corr_tdd[0,0] *tddscale),
ref_wcs.idcmodel.refpix['V3REF'] - (rv23_corr_tdd[1,0] * tddscale)]
# Get an approximate reference position on the sky
rref = np.array([[ref_wcs.idcmodel.refpix['XREF']+ltvoffx ,
ref_wcs.idcmodel.refpix['YREF']+ltvoffy]])
crval = ref_wcs.wcs.p2s(rref, 1)['world'][0]
# Convert the PA_V3 orientation to the orientation at the aperture
# This is for the reference chip only - we use this for the
# reference tangent plane definition
# It has the same orientation as the reference chip
pv = troll(ext_wcs.pav3,dec,rv23[0], rv23[1])
# Add the chip rotation angle
if ref_wcs.idcmodel.refpix['THETA']:
pv += ref_wcs.idcmodel.refpix['THETA']
# Set values for the rest of the reference WCS
ref_wcs.wcs.crval = crval
ref_wcs.wcs.crpix = np.array([0.0,0.0])+offsh
parity = ref_wcs.parity
R_scale = ref_wcs.idcmodel.refpix['PSCALE']/3600.0
cd11 = parity[0][0] * cos(pv*pi/180.0)*R_scale
cd12 = parity[0][0] * -sin(pv*pi/180.0)*R_scale
cd21 = parity[1][1] * sin(pv*pi/180.0)*R_scale
cd22 = parity[1][1] * cos(pv*pi/180.0)*R_scale
rcd = np.array([[cd11, cd12], [cd21, cd22]])
ref_wcs.wcs.cd = rcd
ref_wcs.wcs.set()
uprefwcs = classmethod(uprefwcs)
def zero_point_corr(cls,hwcs):
try:
alpha = hwcs.idcmodel.refpix['TDDALPHA']
beta = hwcs.idcmodel.refpix['TDDBETA']
except KeyError:
alpha = 0.0
beta = 0.0
v23_corr = np.array([[0.],[0.]])
logger.debug("\n\tTDD Zero point correction for chip %s defaulted to: %s" % (hwcs.chip, v23_corr))
return v23_corr
tdd = np.array([[beta, alpha], [alpha, -beta]])
mrotp = fileutil.buildRotMatrix(2.234529)/2048.
xy0 = np.array([[cls.tdd_xyref[hwcs.chip][0]-2048.], [cls.tdd_xyref[hwcs.chip][1]-2048.]])
v23_corr = np.dot(mrotp,np.dot(tdd,xy0)) * 0.05
logger.debug("\n\tTDD Zero point correction for chip %s: %s" % (hwcs.chip, v23_corr))
return v23_corr
zero_point_corr = classmethod(zero_point_corr)
def getOffsets(cls, ext_wcs):
ltv1 = ext_wcs.ltv1
ltv2 = ext_wcs.ltv2
offsetx = ext_wcs.wcs.crpix[0] - ltv1 - ext_wcs.idcmodel.refpix['XREF']
offsety = ext_wcs.wcs.crpix[1] - ltv2 - ext_wcs.idcmodel.refpix['YREF']
shiftx = ext_wcs.idcmodel.refpix['XREF'] + ltv1
shifty = ext_wcs.idcmodel.refpix['YREF'] + ltv2
if ltv1 != 0. or ltv2 != 0.:
ltvoffx = ltv1 + offsetx
ltvoffy = ltv2 + offsety
offshiftx = offsetx + shiftx
offshifty = offsety + shifty
else:
ltvoffx = 0.
ltvoffy = 0.
offshiftx = 0.
offshifty = 0.
ltvoff = np.array([ltvoffx, ltvoffy])
offshift = np.array([offshiftx, offshifty])
return ltvoff, offshift
getOffsets = classmethod(getOffsets)
def troll(roll, dec, v2, v3):
""" Computes the roll angle at the target position based on:
the roll angle at the V1 axis(roll),
the dec of the target(dec), and
the V2/V3 position of the aperture (v2,v3) in arcseconds.
Based on algorithm provided by Colin Cox and used in
Generic Conversion at STScI.
"""
# Convert all angles to radians
_roll = DEGTORAD(roll)
_dec = DEGTORAD(dec)
_v2 = DEGTORAD(v2 / 3600.)
_v3 = DEGTORAD(v3 / 3600.)
# compute components
sin_rho = sqrt((pow(sin(_v2),2)+pow(sin(_v3),2)) - (pow(sin(_v2),2)*pow(sin(_v3),2)))
rho = asin(sin_rho)
beta = asin(sin(_v3)/sin_rho)
if _v2 < 0: beta = pi - beta
gamma = asin(sin(_v2)/sin_rho)
if _v3 < 0: gamma = pi - gamma
A = pi/2. + _roll - beta
B = atan2( sin(A)*cos(_dec), (sin(_dec)*sin_rho - cos(_dec)*cos(rho)*cos(A)))
# compute final value
troll = RADTODEG(pi - (gamma+B))
return troll
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