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tests/test_field_distortion.py

+import unittest
+
+import numpy as np
+import galsim
+import os
+import sys
+from astropy.table import Table
+from scipy import interpolate
+import pickle
+
+
+class test_field_distortion(unittest.TestCase):
+    def __init__(self, methodName="runTest"):
+        super(test_field_distortion, self).__init__(methodName)
+        self.dataMainPath = os.path.join(
+            os.getenv("UNIT_TEST_DATA_ROOT"), "csst_msc_sim/field_distortion"
+        )
+        self.dataInputPath = os.path.join(self.dataMainPath, "input_catalog")
+        self.fdModelName = "FieldDistModel_v2.0_test.pickle"
+
+    def test_fd_model(self):
+        cat_dir = self.dataInputPath
+        model_dir = self.dataMainPath
+        model_date = "2024-05-08"
+        model_name = self.fdModelName
+        field_distortion_model(
+            cat_dir,
+            model_dir,
+            poly_degree=4,
+            model_date=model_date,
+            model_name=model_name,
+        )
+
+    def test_fd_apply(self):
+        model_name = self.fdModelName
+        model_dir = self.dataMainPath
+        cat_dir = self.dataMainPath
+        field_distortion_apply(
+            model_name, model_dir, cat_dir, ra_cen=60.0, dec_cen=-40.0, img_rot=0.0
+        )
+
+
+def ccdParam():
+    """
+    Basic CCD size and noise parameters.
+    """
+    # CCD size
+    xt, yt = 59516, 49752
+    x0, y0 = 9216, 9232
+    xgap, ygap = (534, 1309), 898
+    xnchip, ynchip = 6, 5
+    ccdSize = xt, yt, x0, y0, xgap, ygap, xnchip, ynchip
+
+    # other parameters
+    readNoise = 5.0  # e/pix
+    darkNoise = 0.02  # e/pix/s
+    pixel_scale = 0.074  # pixel scale
+    gain = 1.0
+    ccdBase = readNoise, darkNoise, pixel_scale, gain
+
+    return ccdSize, ccdBase
+
+
+def chipLim(chip):
+    ccdSize, ccdBase = ccdParam()
+    xt, yt, x0, y0, gx, gy, xnchip, ynchip = ccdSize
+    gx1, gx2 = gx
+
+    rowID = ((chip - 1) % 5) + 1
+    colID = 6 - ((chip - 1) // 5)
+
+    xrem = 2 * (colID - 1) - (xnchip - 1)
+    xcen = (x0 // 2 + gx1 // 2) * xrem
+    if chip <= 5 or chip == 10:
+        xcen = (x0 // 2 + gx1 // 2) * xrem + (gx2 - gx1)
+    if chip >= 26 or chip == 21:
+        xcen = (x0 // 2 + gx1 // 2) * xrem - (gx2 - gx1)
+    nx0 = xcen - x0 // 2 + 1
+    nx1 = xcen + x0 // 2
+
+    yrem = (rowID - 1) - ynchip // 2
+    ycen = (y0 + gy) * yrem
+    ny0 = ycen - y0 // 2 + 1
+    ny1 = ycen + y0 // 2
+
+    return nx0, nx1, ny0, ny1
+
+
+def chip_filter(nchip):
+    """
+    return filter name of a given chip
+    """
+    filtype = ["nuv", "u", "g", "r", "i", "z", "y"]
+
+    # updated configurations
+    # if nchip>24 or nchip<7: raise ValueError("!!! Chip ID: [7,24]")
+    if nchip in [6, 15, 16, 25]:
+        filter_name = "y"
+    if nchip in [11, 20]:
+        filter_name = "z"
+    if nchip in [7, 24]:
+        filter_name = "i"
+    if nchip in [14, 17]:
+        filter_name = "u"
+    if nchip in [9, 22]:
+        filter_name = "r"
+    if nchip in [12, 13, 18, 19]:
+        filter_name = "nuv"
+    if nchip in [8, 23]:
+        filter_name = "g"
+
+    filter_id = filtype.index(filter_name)
+
+    return filter_id, filter_name
+
+
+def skyLim(wcs, x0, x1, y0, y1):
+    """
+    The sky coverage of a single exposure image
+    """
+    r2d = 180.0 / np.pi
+    # xt, yt, x0, y0, gx, gy, xnchip, ynchip = ccdSize()
+    s1 = wcs.toWorld(galsim.PositionD(x0, y0))
+    s2 = wcs.toWorld(galsim.PositionD(x0, y1))
+
+    s3 = wcs.toWorld(galsim.PositionD(x1, y0))
+    s4 = wcs.toWorld(galsim.PositionD(x1, y1))
+    ra = [s1.ra.rad * r2d, s2.ra.rad * r2d, s3.ra.rad * r2d, s4.ra.rad * r2d]
+    dec = [s1.dec.rad * r2d, s2.dec.rad * r2d, s3.dec.rad * r2d, s4.dec.rad * r2d]
+
+    return min(ra), max(ra), min(dec), max(dec)
+
+
+def wcsMain(imgRotation=0.0, raCenter=0.0, decCenter=0.0):
+    ccdSize, ccdBase = ccdParam()
+    xsize, ysize, _, _, _, _, _, _ = ccdSize
+    _, _, pixelScale, _ = ccdBase
+    xmcen, ymcen = 0.0, 0.0
+    imrot = imgRotation * galsim.degrees
+    racen = raCenter * galsim.degrees
+    deccen = decCenter * galsim.degrees
+
+    # define the wcs
+    dudx = -np.cos(imrot.rad) * pixelScale
+    dudy = +np.sin(imrot.rad) * pixelScale
+    dvdx = -np.sin(imrot.rad) * pixelScale
+    dvdy = -np.cos(imrot.rad) * pixelScale
+    moscen = galsim.PositionD(x=xmcen, y=ymcen)
+    skyCenter = galsim.CelestialCoord(ra=racen, dec=deccen)
+    affine = galsim.AffineTransform(dudx, dudy, dvdx, dvdy, origin=moscen)
+    wcs = galsim.TanWCS(affine, skyCenter, units=galsim.arcsec)
+
+    return wcs
+
+
+# FD model
+def field_distortion_model(
+    cat_dir,
+    model_dir,
+    poly_degree=4,
+    model_date="2024-05-08",
+    model_name="FieldDistModel_v2.0_test.pickle",
+):
+    # default parameter setup
+    nccd, nwave, npsf = 30, 4, 30 * 30
+
+    # load a CSST-like wcs
+    wcs = wcsMain()
+    cd11, cd12 = wcs.cd[0, 0], wcs.cd[0, 1]
+    cd21, cd22 = wcs.cd[1, 0], wcs.cd[1, 1]
+    xmcen, ymcen = wcs.crpix
+
+    # obtain the interpolation model
+    fdFunList = {}
+    fdFunList["date"] = model_date
+    for iwave in range(1, nwave + 1):
+        # if iwave!=1: continue
+        iwaveKey = "wave%d" % iwave
+
+        # first construct the global interpolation
+        xwList, ywList = [], []
+        xdList, ydList = [], []
+        fdFunList[iwaveKey] = {}
+        for iccd in range(1, nccd + 1):
+            # if iccd!=9: continue
+            iccdKey = "ccd" + str("0%d" % (iccd))[-2:]
+
+            # load PSF data
+            ipsfDatn = cat_dir + "ccd%d_%s.dat" % (iccd, iwaveKey)
+            ipsfDat = Table.read(ipsfDatn, format="ascii")
+            for ipsf in range(1, npsf + 1):
+                # if ipsf!=2: continue
+                xField = ipsfDat["field_x"][ipsf - 1]
+                yField = ipsfDat["field_y"][ipsf - 1]
+
+                # image coordinate with field distortion
+                xImage = 100.0 * (
+                    ipsfDat["image_x"][ipsf - 1] + ipsfDat["centroid_x"][ipsf - 1]
+                )
+                yImage = 100.0 * (
+                    ipsfDat["image_y"][ipsf - 1] + ipsfDat["centroid_y"][ipsf - 1]
+                )
+
+                # image coordinate only with wcs projection
+                xwcs = (cd12 * yField - cd22 * xField) / (
+                    cd12 * cd21 - cd11 * cd22
+                ) + xmcen
+                ywcs = (cd21 * xField - cd11 * yField) / (
+                    cd12 * cd21 - cd11 * cd22
+                ) + ymcen
+
+                xwList += [xwcs]
+                ywList += [ywcs]
+                xdList += [xImage]
+                ydList += [yImage]
+
+        # global interpolation
+        xImageFun = interpolate.SmoothBivariateSpline(
+            xwList, ywList, xdList, kx=poly_degree, ky=poly_degree
+        )
+        yImageFun = interpolate.SmoothBivariateSpline(
+            xwList, ywList, ydList, kx=poly_degree, ky=poly_degree
+        )
+        fdFunList[iwaveKey] = {
+            "xImagePos": xImageFun,
+            "yImagePos": yImageFun,
+            "interpLimit": [
+                np.min(xwList),
+                np.max(xwList),
+                np.min(ywList),
+                np.max(ywList),
+            ],
+        }
+
+        # construct the residual interpolation
+        fdFunList[iwaveKey]["residual"] = {}
+        for iccd in range(1, nccd + 1):
+            # if iccd!=1: continue
+            iccdKey = "ccd" + str("0%d" % (iccd))[-2:]
+            # open the ditortion data
+            ipsfDatn = cat_dir + "ccd%d_%s.dat" % (iccd, iwaveKey)
+            ipsfDat = Table.read(ipsfDatn, format="ascii")
+
+            ixwList, iywList = [], []
+            idxList, idyList = [], []
+            for ipsf in range(1, npsf + 1):
+                # if ipsf!=1: continue
+                print(
+                    "^_^ loading: iccd-{:} iwave-{:} ipsf-{:}".format(iccd, iwave, ipsf)
+                )
+                xField = ipsfDat["field_x"][ipsf - 1]
+                yField = ipsfDat["field_y"][ipsf - 1]
+                xImage = 100.0 * (
+                    ipsfDat["image_x"][ipsf - 1] + ipsfDat["centroid_x"][ipsf - 1]
+                )
+                yImage = 100.0 * (
+                    ipsfDat["image_y"][ipsf - 1] + ipsfDat["centroid_y"][ipsf - 1]
+                )
+
+                # image coordinate only with wcs projection
+                xwcs = (cd12 * yField - cd22 * xField) / (
+                    cd12 * cd21 - cd11 * cd22
+                ) + xmcen
+                ywcs = (cd21 * xField - cd11 * yField) / (
+                    cd12 * cd21 - cd11 * cd22
+                ) + ymcen
+
+                ixPred = xImageFun(xwcs, ywcs)[0][0]
+                iyPred = yImageFun(xwcs, ywcs)[0][0]
+                idx = xImage - ixPred
+                idy = yImage - iyPred
+                # print(idx, idy)
+                ixwList += [xwcs]
+                iywList += [ywcs]
+                idxList += [idx]
+                idyList += [idy]
+
+            # interpolation
+            xResFun = interpolate.SmoothBivariateSpline(
+                ixwList, iywList, idxList, kx=poly_degree, ky=poly_degree
+            )
+            yResFun = interpolate.SmoothBivariateSpline(
+                ixwList, iywList, idyList, kx=poly_degree, ky=poly_degree
+            )
+
+            fdFunList[iwaveKey]["residual"][iccdKey] = {
+                "xResidual": xResFun,
+                "yResidual": yResFun,
+                "interpLimit": [
+                    np.min(ixwList),
+                    np.max(ixwList),
+                    np.min(iywList),
+                    np.max(iywList),
+                ],
+            }
+
+    # save the interpolation functions
+    model_name_full = os.path.join(model_dir, model_name)
+    with open(model_name_full, "wb") as out:
+        pickle.dump(fdFunList, out, pickle.HIGHEST_PROTOCOL)
+
+    return
+
+
+def field_distortion_apply(
+    model_name, model_dir, cat_dir, ra_cen=60.0, dec_cen=-40.0, img_rot=0.0
+):
+    # CCD and observation
+    ccdSize, ccdBase = ccdParam()
+    xsize, ysize, xchip, ychip, xgap, ygap, xnchip, ynchip = ccdSize
+    nchip = xnchip * ynchip
+
+    #################################################
+    xmcen, ymcen = 0.0, 0.0
+    #################################################
+
+    badchip = list(range(1, 6)) + list(range(26, 31)) + [10, 21]
+
+    # define the wcs of the image mosaic
+    print(
+        "^_^ Construct the wcs of the entire image mosaic using Gnomonic/TAN projection"
+    )
+    wcs = wcsMain(imgRotation=img_rot, raCenter=ra_cen, decCenter=dec_cen)
+
+    #################################################
+    # load the field distortion model
+    model_name_full = os.path.join(model_dir, model_name)
+    with open(model_name_full, "rb") as f:
+        fdModel = pickle.load(f)
+    #################################################
+
+    raLow, raUp, decLow, decUp = skyLim(
+        wcs, -xsize // 2 + 1, xsize // 2, -ysize // 2 + 1, ysize // 2
+    )
+    dra = (raUp - raLow) * np.cos(dec_cen * np.pi / 180.0)
+    ddec = decUp - decLow
+    print(
+        "    Image pixel size: %d*%d; center: (Ra, Dec)=(%.3f, %.3f)."
+        % (xsize, ysize, ra_cen, dec_cen)
+    )
+    print("    Field of Veiw: %.2f * %.2f deg^2." % (dra, ddec))
+
+    # filters and corresponding bounds in the image mosaic
+    fbound = {}
+    print("    Model the filter distributions in the image mosaic ...")
+    stats = {}
+    for i in range(nchip):
+        chip_id = i + 1
+        if chip_id in badchip:
+            continue
+        cx0, cx1, cy0, cy1 = chipLim(chip_id)
+        chip_bound = galsim.BoundsD(cx0 - 1, cx1 - 1, cy0 - 1, cy1 - 1)
+        chip_filter_id, chip_filt = chip_filter(chip_id)
+        # print "^_^ CHIP %d, Filter %s"%(chip_id,chip_filter)
+        fbound[chip_id] = [chip_filter_id, chip_filt, chip_bound]
+        stats[chip_id] = [0, 0, 0]
+
+    # generate object grid
+    ra_input = np.arange(ra_cen - 1.0, ra_cen + 1.0, 0.00125)
+    dec_input = np.arange(dec_cen - 1.0, dec_cen + 1.0, 0.00125)
+    nobj = len(ra_input) * len(dec_input)
+    crdCat = np.zeros((nobj, 2))
+    cid = 0
+    for id1 in range(len(ra_input)):
+        ira = ra_input[id1]
+        for id2 in range(len(dec_input)):
+            idec = dec_input[id2]
+            crdCat[cid, :] = ira, idec
+            cid += 1
+    print("^_^ Total %d objects are generaged" % nobj)
+
+    # main program
+    for i in range(nchip):
+        # if i not in [6]: continue
+        if i + 1 in badchip:
+            continue
+        filtidk, filtnmk, boundk = fbound[i + 1]
+        idStr = str("0%d" % (i + 1))[-2:]
+
+        ###################################################################
+        # 1) Use global field distortion model: FieldDistModelGlobal_v2.0.pickle
+        ifdModel = fdModel["wave1"]
+        irsModel = fdModel["wave1"]["residual"]["ccd" + idStr]
+        xLowI, xUpI, yLowI, yUpI = ifdModel["interpLimit"]
+        xlLowI, xlUpI, ylLowI, ylUpI = irsModel["interpLimit"]
+
+        # field distortion model along x/y-axis
+        ixfdModel = ifdModel["xImagePos"]
+        iyfdModel = ifdModel["yImagePos"]
+        ixrsModel = irsModel["xResidual"]
+        iyrsModel = irsModel["yResidual"]
+
+        # first-order derivatives of the global field distortion model
+        ifx_dx = ixfdModel.partial_derivative(1, 0)
+        ifx_dy = ixfdModel.partial_derivative(0, 1)
+        ify_dx = iyfdModel.partial_derivative(1, 0)
+        ify_dy = iyfdModel.partial_derivative(0, 1)
+        # first-order derivatives of the residual field distortion model
+        irx_dx = ixrsModel.partial_derivative(1, 0)
+        irx_dy = ixrsModel.partial_derivative(0, 1)
+        iry_dx = iyrsModel.partial_derivative(1, 0)
+        iry_dy = iyrsModel.partial_derivative(0, 1)
+        ###################################################################
+
+        # construct the image mosaic firstly
+        xorigin, yorigin = xmcen - boundk.xmin, ymcen - boundk.ymin
+        print("    Construct the chip mosaic ...")
+        fimage = galsim.ImageF(xchip, ychip)
+        fimage.setOrigin(boundk.xmin, boundk.ymin)
+
+        fimage.wcs = wcs
+        raLow, raUp, decLow, decUp = skyLim(
+            wcs, boundk.xmin, boundk.xmax, boundk.ymin, boundk.ymax
+        )
+        dra = (raUp - raLow) * np.cos(dec_cen * np.pi / 180.0)
+        ddec = decUp - decLow
+        print("    Image coverage: %.2f * %.2f arcmin^2." % (dra * 60.0, ddec * 60.0))
+        # enlarge the sky coverage in order to catch the galaxies at the chip edge
+        raLow -= 0.2 / 60.0
+        decLow -= 0.2 / 60.0
+        raUp += 0.2 / 60.0
+        decUp += 0.2 / 60.0
+        print(
+            "    Range: RA=[%.4f, %.4f]; DEC=[%.4f, %.4f]"
+            % (raLow, raUp, decLow, decUp)
+        )
+
+        # generate the galaxy and star images
+        catxxn = os.path.join(
+            cat_dir, "csst_mainfocus_field_distortion_ccd%s_%s.cat" % (idStr, filtnmk)
+        )
+        hdrxx = "#id_obj id_chip filter ra_true dec_ture x_image_ture y_image_ture x_image y_image g1_fd g2_fd\n"
+        fmtxx = "%8d %3d %4s %12.6f %12.6f %13.6f %13.6f %13.6f %13.6f %9.5f %9.5f\n"
+        catxx = open(catxxn, "w")
+        catxx.write(hdrxx)
+        oidxx = 0
+        for k in range(nobj):
+            # if k != 0: continue
+            # input galaxy parameters
+            rak = crdCat[k, 0]
+            deck = crdCat[k, 1]
+
+            # reject objects out of the image
+            if (rak - raLow) * (rak - raUp) > 0.0 or (deck - decLow) * (
+                deck - decUp
+            ) > 0.0:
+                continue
+
+            world_pos = galsim.CelestialCoord(
+                ra=rak * galsim.degrees, dec=deck * galsim.degrees
+            )
+            image_pos = fimage.wcs.toImage(world_pos)
+            xk_true = image_pos.x
+            yk_true = image_pos.y
+
+            #################################################################
+            # field distortion
+            if (xLowI - xk_true) * (xUpI - xk_true) > 0 or (yLowI - yk_true) * (
+                yUpI - yk_true
+            ) > 0:
+                continue
+            xk = ixfdModel(xk_true, yk_true)[0][0]
+            yk = iyfdModel(xk_true, yk_true)[0][0]
+
+            # global offset correction
+            if (xlLowI - xk) * (xlUpI - xk) > 0 or (ylLowI - yk) * (ylUpI - yk) > 0:
+                continue
+            dxk = ixrsModel(xk, yk)[0][0]
+            dyk = iyrsModel(xk, yk)[0][0]
+            xk = xk + dxk
+            yk = yk + dyk
+
+            # field distortion induced ellipticity
+            ix_dx = ifx_dx(xk, yk) + irx_dx(xk, yk)
+            ix_dy = ifx_dy(xk, yk) + irx_dy(xk, yk)
+            iy_dx = ify_dx(xk, yk) + iry_dx(xk, yk)
+            iy_dy = ify_dy(xk, yk) + iry_dy(xk, yk)
+
+            g1k_fd = 0.0 + (iy_dy - ix_dx) / (iy_dy + ix_dx)
+            g2k_fd = 0.0 - (iy_dx + ix_dy) / (iy_dy + ix_dx)
+            #################################################################
+            dxk_true, dyk_true = xk_true - xmcen, yk_true - ymcen
+            xLock_true, yLock_true = dxk_true + xorigin + 1.0, dyk_true + yorigin + 1.0
+
+            dxk, dyk = xk - xmcen, yk - ymcen
+            xLock, yLock = dxk + xorigin + 1.0, dyk + yorigin + 1.0
+
+            if (xLock_true < 0) or (xLock_true > xchip):
+                continue
+            if (yLock_true < 0) or (yLock_true > ychip):
+                continue
+            if (xLock < 0) or (xLock > xchip):
+                continue
+            if (yLock < 0) or (yLock > ychip):
+                continue
+            linexx = fmtxx % (
+                k + 1,
+                i + 1,
+                filtnmk.lower(),
+                rak,
+                deck,
+                xLock_true,
+                yLock_true,
+                xLock,
+                yLock,
+                g1k_fd[0][0],
+                g2k_fd[0][0],
+            )
+            catxx.write(linexx)
+
+        catxx.close()
+
+    return
+
+
+if __name__ == "__main__":
+    unittest.main()