|Space Telescope Science Institute|
|STIS Data Handbook 6.0 May 2011|
The calstis modules evolve and improve with time, as we understand and characterize more fully the on-orbit performance of STIS. It is possible, even likely, that improvements in the calstis software will improve the calibration of your data. To determine the version of the software used to calibrate your data, note the value of the CAL_VER keyword in the primary header. The following example uses hselect to print the rootname, the optical element, and the version of calstis for all _flt files in the current directory:
Watch the STScI Analysis Newsletters (STANs) or consult the STIS WWW pages for any announcement of enhancements to calstis. A history of the enhancements made to calstis is maintained at:If you are uncertain whether a given enhancement to calstis merits recalibrating your data, contact the Help Desk. Often, it is instructive to re-calibrate (or simply re-request your data from the archive) and to determine empirically whether the revised calibration files or software affect the scientific interpretation of your data. If you need to upgrade your version of the stis package, contact your IRAF system administrator.Since the closeout of STIS in 2006, improvements have been made to the STIS calibration pipeline and the reference files. Below are listed the changes that are most relevant to the users.
• The FUV bad pixel table now has an OPT_ELEM column to allow accurate flagging of the repeller wire shadow on the FUV-MAMA. It is planned to add a similar column to the NUV bad pixel table to flag the vignetted corners of the NUV-MAMA.
• Support has been added for two additional dispersion coefficients, for a total of nine. The two new coefficients are for m3 * λ3 and m2. These are not used in the current reference files. They may be used in the future for echelle data.
• A reference temperature keyword, REF_TEMP, and a slope keyword, DRK_VS_T, have been added to the primary header of the CCD dark reference files. These are used in place of hard-coded values to correct the temperature dependence of the CCD dark rate.
• SC2DCORR - A spurious message "Offset of -1 low-res pixels added in dispersion direction" was written during the echelle scattered light correction. This message pertains to slitless data, and is no longer printed.
• X1D - During the echelle scattered light correction, the background is set to gross - net counts. There was a bug in indexing the gross and net, however, which could result in the net for one spectral order being subtracted from the gross for another order. They are now indexed by spectral order number to prevent this. Note that this error only affected the population of the background vector and did not affect the values of the net or extracted flux vectors.
• OCRREJECT - For the case that more than one file was given as input, the keyword CCDAMP is now compared as part of the mode comparison between the files.
• When wx2d is run, it adds the keyword WX2DCORR = 'COMPLETE' to the output file. If x2d is run on the output of wx2d, x2d does not apply the spectral trace or the offset in the cross-dispersion direction, since these were already done by wx2d.
• Input files (either science or wavecal) sometimes have zero exposure times or images with all zero data values. These are now written to output, but a new keyword IMSET_OK in the science extension header will be set to 'F' to indicate that they are not valid.