Calstis Version 2.14c was installed in the OTFR in February 2003. It is not yet available for download in STSDAS.

The following OPRs are closed by the release of CALSTIS 2.14c:

47041: CALSTIS1 needs EXPSTART for DOPPCORR
46954: Calstis should correctly locate geocoronal emission lines
46850: Correct the use of scalense in STIS cosmic ray rejection
46279: Background Smoothing in STIS Spectroscopic Data

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

47041: CALSTIS1 needs EXPSTART for DOPPCORR

In the spring of 2002, CALSTIS1 (basic2d) was modified to include a time dependence for the NUV dark correction. The call to get the exposure start time (EXPSTART) was inadvertently moved from the section for Doppler correction to the section for NUV dark correction. The value of EXPSTART was not gotten, and therefore retained its default value of zero, for all FUV MAMA exposures and also for NUV if the dark correction was omitted. This resulted in a phase error in the computation of the Doppler shift during the exposure, and the flat field correction would not be as effective.

46954: Calstis should correctly locate geocoronal emission lines

The recently added background smoothing algorithm in calstis failed when processing prism data that includes the Ly alpha and 1300 A geocoronal lines. The failure was tracked down to a failure in locating the lines in the input image due to the use of an incorrect dispersion solution.

46850: Correct the use of scalense in STIS cosmic ray rejection

The scalense (scale noise) parameter in the cosmic ray rejection parameters table (and the ocrreject task parameter) is part of the noise model, intended to prevent rejection of the cores of point sources when the individual CR-split exposures are not perfectly aligned. It was being applied to pixel values that include the sky background, however, which is not the correct implementation of the noise model. For large values of scalense and sky level, this resulted in reduced sensitivity to cosmic rays.

46279: Background Smoothing in STIS Spectroscopic Data

For low signal spectroscopic data, the background noise level can be as large as the signal. In such a case, it is useful to smooth the background since such a smoothing can decrease the background noise level, and hence improve the quality of the results. CALSTIS used to smooth the background in the spatial direction alone. A new algorithm adds to this the possibility to smooth the background along the dispersion direction. It uses a procedure developed by the STIS IDT.