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HSTCAL Release Notes

HSTCAL Release Notes

The HSTCAL package provides an environment for compiling IRAF tasks written in C without using IRAF at all. The HSTIO image and tables C API has been replicated using CFITSIO. This API was used to compile the ACS calibration code CALACS, WFC3 calibration code CALWF3 and STIS calibration code CALSTIS.


Version 3.1.6 of CALWF3 was installed in Nov 2013 and remains the calibration software that gets used in the archive for pipeline calibrations. It replaced the now outdated STSDAS/IRAF based version (both of which have been removed from STSDAS). This release includes calwf3 related tasks; namely, wf32d, wf3ccd, wf3ir, and wf3rej.

No changes since the last release of HSTCAL with CALWF3.


Version 8.2.0 of CALACS has been included in this release. Changes from previous release include:

  • Fixed HSTIO read/write bug in ACSREJ so file is closed properly before being reopened in a different IO mode
  • Separated PCTECORR from ACSCCD and made it into its own ACSCTE step


This release includes, for the first time, the calibration code for STIS: CALSTIS. This version continues the development of CALSTIS that was previously released under STSDAS.

Version 3.4 (13-November-2013) includes the following changes made since the last public release:

  • In the code for echelle scattered light correction, an image of the PSF of the telescope is read from a reference file. This image covers 0.2 by 0.2 arcseconds and is oversampled. For echelle data, the aperture is usually no larger than this, so the PSF image will be truncated to match the aperture used for an exposure. The code to truncate the PSF did not take into account the case of an aperture that was larger than 0.2 arcsec, however. This has been fixed.
  • Use the mean instead of median when applying the NUV-MAMA dark reference image.
  • A bug was fixed in the background subtraction for the X1D extraction step. Due to roundoff errors, the number of pixels used for the background region was sometimes smaller than intended.
  • For NUV data taken since SM4, the latest calibration developed by C. Cox now gets used to scale the dark reference image. Calstis now opens the TDCTAB and determines which format it is from the columns that are found in the table. The temperature and time correction factor then gets determined by evaluating either Colin's newly calibrated expression or the pre-SM4 expression.
  • When the image I/O interface used by the C versions of the pipeline software was first written, there was code in calstis that opened a file readonly, then opened it again read/write without first closing the file (this was fixed some time ago). The IRAF interface permitted that, but CFITSIO -- which is used in the current (hstcal) version of calstis -- does not. As a workaround, when the openInputImage function in the hstcal version of the image I/O interface was first written a few years ago, it opened the input file read/write. This was highly undesireable, however, because calstis would fail if the user did not have write permission for the input file, so the openInputImage function has now been modified to open the input file readonly. This bug also affected CALACS and CALWF3 where it was corrected as well (noted as "fixing an HSTIO read/write bug").


This package provides all the support necessary for interpreting IMPHTTAB reference files. Use of the IMPHTTAB reference files replaces direct calls to IRAF's synphot package when computing the photometry keywords. The following bugs and enhancements have been implemented since the last release:

  • Fixed a bug in PHOTCORR that crashed when PHOT* value is zero, which is a valid value for SBC blocking filter.
  • Added support for MJD extrapolation. This is actually for STIS Team but would affect other instruments (such as ACS) should they require this feature at some later time.
  • The code was updated to allow acceptence of IMPHTTAB reference files with varying extension numbers. Previously, all HST instrument files had the same number of extensions and they were explicitly read in, but since WFC3 has added extensions for use with the new photometry scaling routine a code update was needed. This update is backwards compatable.