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Hubble Space Telescope
Changes to the STIS Calibration Pipeline in HST MAST Archive

On December 11, 2013 the STIS team delivered an updated Dark Correction Table (TDCTAB) for the NUV-MAMA detector and installed a new STIS calibration software in the HST MAST archive pipeline.

The dark correction table (TDCTAB) provides a new time- and temperature-dependent characterization of the global rate of dark counts. After the last HST servicing mission (SM4, May 2009) it was noticed that the time and temperature dependence of the NUV-MAMA dark rate were significantly different from before SM4.The table has been updated to account for these dependency changes. For a detailed description on the contents and improvements of this reference table see STIS ISR 2013-01.

CalSTIS is the software task used in routine calibration of STIS data by the HST MAST archive during the On-The-Fly-Reprocessing (OTFR) procedure. Previous versions of CalSTIS used IRAF libraries for image and table I/O. In an effort to remove this dependence on IRAF, CalSTIS has been ported to the HSTCAL environment. Users comparing calibrated products from CalSTIS 2.40 (IRAF-dependent) to CalSTIS 3.3 (IRAF-independent) should expect to see differences in the photometric keyword values in exposures taken with the OIII filter. As part of this change the STIS team delivered a new type of reference file to be used when populating such photometric keywords. The STIS Image Photometry Table (IMPHTTAB) is only used for imaging data to estimate the photometric keyword values PHOTZPT, PHOTFLAM, PHOTPLAM and PHOTBW.

The new HSTCAL software includes an interface to CFITSIO, replacing the previous interface to IRAF I/O.