Note
The PHOTCORR changes apply to all CALACS data. The destriping and CTE changes apply only to full frame WFC data.
PHOTCORR is now performed using tables of precomputed values instead of calls to synphot. The correct table for a given image must be specified in the IMPHTTAB header keyword in order for CALACS to perform the PHOTCORR step.
If you would like to not perform the PHOTCORR step the PHOTCORR keyword may be set to OMIT.
Data taken after SM-4 is put through a new BLEVCORR step that both subtracts the bias level and removes stripes introduced by new hardware installed during SM-4. Based on an algorithm developed by Jay Anderson.
If the PCTECORR keyword is set to PERFORM in an image header (WFC full frame only) then a CTE correction algorithm is applied. It is applied at the end of the ACSCCD series, after bias level and bias image subtraction, but before combination of CR-SPLIT images and before dark and flat corrections.
Because the CTE correction is applied before dark correction it is necessary to use a CTE corrected dark on CTE corrected products. This file must be specified in the CDRKFILE header keyword.
Parameters characterizing CTE are stored in a table that must be pointed to by the PCTETAB header keyword.
When run with CTE correction CALACS will produce two sets of products, one that has had CTE trails removed and another that has not had the trails removed.