Calstis version 2.7 was installed in the OTFC pipeline on August 14, 2000. Calstis 2.7 is available for download in the new STSDAS release, Version 2.2, which can be found at the STSDAS Advisories page.
The following OPRs are closed by the release of CALSTIS 2.7:
Below we give more details on changes that are likely to be noticed by users in their data.
The EXPSTART and EXPEND values in the output file written by calstis2 (cosmic ray rejection) are now updated with the minimum and maximum of these keywords in all input image sets, rather than just being copied from the first input imset. The main reason for this change was to improve results when interpolating wavecal shifts over time. (OPR 40830)
The MAMA extension header keyword GLOBRATE gives the counts per second received over the entire detector. This was used by calstis to check for global nonlinearity and to correct for nonlinearity if the count rate is not too high. However, GLOBRATE in the raw file is based on only 0.1 second of exposure, so the statistics are not very good, and the value may not be representative if the target brightness varies during the exposure. Calstis now computes the global count rate, rather than relying on the GLOBRATE keyword in the input file, and GLOBRATE in the output will be updated with the computed value. (OPR 40831)
The dispersion coefficients for prism data are interpreted differently from the coefficients for grating data. The grating dispersion solution gives pixel number as a function of spectral order number and wavelength, while the prism dispersion solution gives wavelength as a function of pixel number. The function is also quite different from that for a grating. Calstis7 (2-D rectification) has been modified to support the prism dispersion solution. Calstis6 (1-D extraction) has not been modified yet. (OPR 41147)
For long-slit data, calstis4 used to find the offset of the wavecal image in the cross-dispersion direction by finding each edge of each occulting bar, and then taking an average. The edge finding didn't always work for bars that were too close to the lower or upper edge of the wavecal image, and when it didn't work the warning message was not very clear. Calstis4 now uses a completely different algorithm, making use of a cross correlation between a template and the wavecal data. The wavecal image is first normalized and inverted, so the values are near one for the occulting bars and near zero elsewhere. (OPR 41150)
Calstis4 finds the offset in the dispersion direction by taking a cross correlation between a template spectrum constructed from the LAMPTAB reference table and the observed wavecal spectrum. The LAMPTAB includes a group of very bright emission lines just redward of the range of wavelengths that cover the wavecal image for observations with G230L. For first-order data, calstis4 is run on the 2-D rectified wavecal, which has a border region of about 88 pixels on each edge. The bright lines are partially within this border region, and calstis4 used to include some of them when constructing the template spectrum and when doing the cross correlation. For G230L these bright lines affected the cross correlation to such an extent that calstis4 failed to find the MSM shift. Calstis4 has been modified to exclude the template spectrum within the border region. (OPR 41563)
Calstis2 uses functions for reading and writing image lines, and the line number argument to these functions was recently changed from one indexing to zero indexing. This change should be completely transparent to users. (OPR 41608)
A new dispersion relation reference table has been delivered that includes one additional coefficient, a term that is cubic in wavelength and spectral order number. Calstis6 and calstis7 have been modified to include this new coefficient. (OPR 41797)