Calstis Version 2.13b was installed in the OTFR pipeline on September 5 2002. It is available for download in the new STSDAS release, Version 3.0 which can be found at the STSDAS Advisories page.

The following OPRs are closed by the release of CALSTIS 2.13b:
OPR 45787: Blaze shift correction in STIS pipeline
OPR 45573: Implement improved STIS NUV DARK scaling algorithm in CALSTIS1
OPR 45390: Implement time-dependent sensitivity algorithm in calstis (6 and 7)
OPR 45340: CALSTIS should produce an sfl file if RPTCORR = PERFORM
OPR 45349: CR rejection in CALSTIS4 must use double precision
OPR 45138: Calstis should not check for low voltage values

Below we give more details on changes that are likely to be noticed by users in their data.

OPR 45787: Blaze shift correction in STIS pipeline:

Sensitivity curves are tabulated versus wavelength, so a shift in wavelength translates into a shift in the sensitivity curve used to convert net count rate into flux. Unfortunately, the sensitivity in an echelle order is not really a strict function of wavelength. There is a more rapidly varying component due to the echelle blaze function, which depends on incidence angle. In practice, this means that the appropriate shift for the sensitivity curve is not exactly equal to the wavelength shift. The shifts in the sensitivity curves shifts were determined to obtain self-consistent fluxes in order overlap intervals. These shifts were fitted as a function of X offset, Y offset, and the time since STIS was installed in HST. The residuals are still significant, but predicted shifts are still an improvement over naive application of the wavelength shift. Predicted shifts are currently available only for primary central wavelengths. NOTE: The _pht file for the FUV-MAMA spectroscopic modes were updated on September 12, 2002. As a result, during the period Sep 5 to Sep 12, 2002, the improved blaze-shift correction was not applied in the pipeline calibrations. The users who have downloaded STIS FUV-MAMA spectroscopic data during this brief interval should download reprocessed data again from the archive.

OPR 45573: Implement improved STIS NUV DARK scaling algorithm in CALSTIS1

Changes in the mean operating temperature of the NUV-MAMA over time causes the dark current to deviate from the simple scaling law currently used in calstis1 (basic2d). The dark subtraction for the NUV-MAMA requires a special, time- and temperature-dependent characterization of the global rate of dark counts, which has been implemented. This correction is distinct from the application of the DRK image, which corrects for the spatial distribution of the dark counts.

OPR 45390: Implement time-dependent sensitivity algorithm in calstis (6 and 7)

The STIS sensitivities are found to change with time. The sensitivity changes can be adequately expressed as a series of linear segments (delta-sensitivity as a function of time) at different wavelengths. This algorithm has been implemented in calstis6/7.

OPR 45340: CALSTIS should produce an sfl file if RPTCORR = PERFORM

When CALSTIS is run on MAMA repeatobs data with RPTCORR = PERFORM, it was producing either an _sx2.fits or _sfl.fits file, depending on whether X2DCORR (or GEOCORR) is PERFORM or OMIT respectively. In either case, only one summed file was produced. CALSTIS is now modified to produce both the _sx2.fits and _sfl.fits files if RPTCORR is PERFORM and X2DCORR or GEOCORR is PERFORM.

OPR 45349: CR rejection in CALSTIS4 must use double precision

When computing the standard deviation of a column of pixel values in a wavecal, for the purposes of rejecting cosmic rays or residual hot pixels, each pixel value is squared using a single precision variable before being added to the double precision sum of squares. In a case where there were only two pixel values, and they were nearly equal, the loss of precision in the squared value resulted in a negative argument to the square root function, which is now fixed.

OPR 45138: Calstis should not check for low voltage values

A function exists in the calstis pipeline to check against low voltages as specified by the SCI header keywords OCBABAV, OCBCDAV, OCBLGCDV, OCBSWALV and OCBRCDLV. This check has been disabled since the requirement for checking these values no longer applies.