; CNA_ZSIGCORR: Calculate the amount of signal from sources in a MultiAccum ; zeroth-read image. This is done by computing the amount of signal that ; arrived between the zeroth and first reads, and then scaling that to the ; exposure time of the zeroth read in order to estimate how much signal ; probably came in between the reset and the zeroth read. Note that this ; does not work well if the source flux is so high that it's beginning to ; go non-linear already in either the zeroth or first read. The raw data ; values in the zeroth and first readouts are also differenced with the ; super zero read reference image and checked for saturation in those ; readouts. ; ; Revision history: ; H.Bushouse 25-Jul-1997 Created (Version 3.0) ; H.Bushouse 18-Aug-1997 Modified to use super zero read image in ; NlinData structure (Version 3.0) ; H.Bushouse 11-Sep-1997 Added use of nic.zsthresh to allow user input ; of threshold value (Version 3.0) ; H.Bushouse 28-Oct-1997 Added checks for dummy ref data before ; doing computations (Version 3.0) ; D.Lytle 10-Nov-1997 Corrupted into IDL!! ; H.Bushouse 12-Feb-1998 Added computation of valid zeroth-read value ; for pixels saturated in first read; removed use ; of ZTIME macro, replacing it with new ; nic->sampzero variable; added use of new ; ZEROSIG DQ value; add zsig value to zeroth-read ; input image; changed name from n_zsigcalc to ; n_zsigcorr (Version 3.2) ; H.Bushouse 08-Apr-1998 Added use of new n_pixOK function (Version 3.2) ; I. Barg 10-Jan-2000 Modified structure names (and tag names) to match ; "/iraf/stsdas/lib/hstio.h". ; function cna_zsigcorr, nic, input, mask, nois, dark, nlin, zsig @calnica_common ZTHRESH = 5.0 ; default signal clipping threshold (sigma). ; Arguments: ; nic i: NICMOS info structure ; input i: input images ; mask i: bad pixel mask image ; nois i: read noise image ; dark i: dark current image ; nlin i: non-linearity correction data ; zsig o: zeroth read signal image ; Local variables. ; int i, j ; pixel indexes. ; int nsat0, nsat1 ; number of saturated pixels. ; float zscale ; exposure time scale factor. ; Function definitions. ; int cna_copyGroup (SingleNicmosGroup , SingleNicmosGroup ) ; int cna_asub (SingleNicmosGroup , SingleNicmosGroup ) ; int cna_aor (SingleNicmosGroup , SingleNicmosGroup ) ; int cna_noiscalc (NicInfo , SingleNicmosGroup , SingleNicmosGroup ) ; Initialize counters. nsat0 = 0 nsat1 = 0 ; Set proper threshold value use default if no user input. if (nic.zsthresh eq 0.0) then begin nic.zsthresh = ZTHRESH endif ; Copy first read to zsig image. tempgroup = input.group[nic.ngroups-2] cna_copyGroup, tempgroup, zsig ; If any of the ref data is dummy, zero out the zsig image ; and abort the routine. if (nic.MASK.ref.dummy eq 1 or nic.NOIS.ref.dummy eq 1 or $ nic.DARK.ref.dummy eq 1 or nic.NLIN.ref.dummy eq 1) then begin if (cna_asub (zsig, zsig) ne 0) then return, 8482 print, 'Warning!, ZSIGCALC skipped because ref data is dummy' return, 0 endif ; Subtract the zeroth read from the first read. if (cna_asub (zsig, (input.group[nic.ngroups-1])) ne 0) then return, 8482 ; Mask bad pixels in the zsig image. if (cna_aor (zsig, mask) ne 0) then return, 8482 ; Compute noise in the zsig image. if (cna_noiscalc (nic, nois, zsig) ne 0) then return, 8482 ; Subtract dark current from the zsig image. if (cna_asub (zsig, dark) ne 0) then return, 8482 ; Compute the scale factor to match the zeroth-read exptime. zscale = nic.sampzero / nic.exptime(nic.ngroups-2) ; Get a "good pixel" mask gmask = cna_pixok(zsig.dq.data.data) tempgroup1 = input.group[nic.ngroups-1] tempgroup2 = input.group[nic.ngroups-2] ; Loop over the zsig image. for j = 0, zsig.sci.data.tot_ny-1 do begin for i = 0, zsig.sci.data.tot_nx-1 do begin ; Only look at good pixels. if (gmask(i,j) eq 1) then begin ; Scale pixels with greater than zsthresh*err signal to ; the exposure time of the zeroth read. if (zsig.sci.data.data[i,j] ge nic.zsthresh * $ zsig.err.data.data[i,j]) then begin zsig.sci.data.data[i,j] = zsig.sci.data.data[i,j] * $ zscale zsig.dq.data.data[i,j] = zsig.dq.data.data[i,j] $ or ZEROSIG tempgroup1.dq.data.data[i,j] = $ tempgroup1.dq.data.data[i,j] or ZEROSIG ; Mask out low signal pixels by setting them to zero. endif else zsig.sci.data.data[i,j] = 0.0 ; Flag pixels that are saturated in the zeroth read. if ((tempgroup1.sci.data.data[i,j] - $ nlin.zsci.data.data[i,j]) gt $ nlin.nodes(1).data.data[i,j]) then begin zsig.dq.data.data[i,j] = zsig.dq.data.data[i,j] $ or SATURATED tempgroup1.dq.data.data[i,j] = $ tempgroup1.dq.data.data[i,j] or SATURATED nsat0 = nsat0 + 1 endif ; Flag pixels that are saturated in the first read. if (tempgroup2.sci.data.data[i,j] - $ nlin.zsci.data.data[i,j] gt $ nlin.nodes(1).data.data[i,j]) then begin zsig.dq.data.data[i,j] = zsig.dq.data.data[i,j] $ or SATURATED tempgroup2.dq.data.data[i,j] = $ tempgroup2.dq.data.data[i,j] or SATURATED nsat1 = nsat1 + 1 ; For these pixels, replace the zsig value by ; differencing with the super-zero read image zsig.sci.data.data[i,j] = $ input.group[nic.ngroups-1].sci.data.data[i,j] - $ nlin.zsci.data.data[i,j] endif ; Set flagged pixels to zero in the zsig image. endif else zsig.sci.data.data[i,j] = 0.0 endfor endfor input.group[nic.ngroups-2] = tempgroup2 ; Report the number of saturated pixels detected. print, ' ZSIGCALC detected ',nsat0,' saturated pixels in 0th read' print, ' ZSIGCALC detected ',nsat1,' saturated pixels in 1st read' ; Add zsig image values to zeroth-read image of input data (Vsn 3.2) tempgroup1.sci.data.data = $ tempgroup1.sci.data.data + zsig.sci.data.data input.group[nic.ngroups-1] = tempgroup1 ; Successful return. return, 0 end