STSDAS v3.1 RELEASE SUMMARY



The primary changes incorporated in this release are:

1) PyDrizzle (v4.4) has had many changes and enhancements. These include: 
   - Rigorous WCS fitting algorithms to accurately handle shift and 
     rotation determinations for all declinations. When using HST guide 
     stars and ACS, the accuracy is generally better than 0.1 pixel.
   - New Python methods to simplify processing by changing parameters 
     without having to start over.
   - Use of intermediate GEIS format files to avoid IRAF FITS kernel 
     problems. This also speeds processing.
   - Support for ICDTAB format for the distortion model for ACS.
   - Velocity aberration correction.
   - Improvements for handling WFPC2 data.
   - Support for single chip processing.
2) Updates to drizzle, blot, traxy, and tranback, and a new task:
   wcs2dr.
3) CALACS 4.3a which has the following changes:
   - Addition of BIASLEV keywords to the header to report the bias 
     levels computed by CALACS. 
   - Previously chip 2 of WFC observations was using the incorrect 
     ccdbias values from the CCDTAB; this has been fixed.
   - Previously associations with one or more exposure with EXPTIME=0 
     were not properly processed. This has been corrected.
   - Removal of sky background before applying scale noise parameter
     instead of after; this fixes some problems with cosmic ray
     rejection, particularly with regard to halos around cosmic-ray
     cleaned pixels.
   - Problems with handling RPT-OBS associations have been fixed.
4) CALSTIS has been updated:
   - Correction for charge transfer efficiency.
   - Correction for a problem with DOPPCORR for FUV data.
   - Removal of sky background before applying scale noise parameter
     instead of after; this fixes some problems with cosmic-ray
     rejection.
   - Improved algorithm for determining location in the cross
     dispersion direction.
   - Fix for uninitialized memory problem.
5) Added STISNOISE task to remove pattern noise from spectra.
6) WFPC package tasks work with appropriately formatted FITS file (alas 
   not the format obtained from the HST archive). See full release notes 
   or package level help for details.
7) New task TEPOCH for handling time format conversions for table 
   columns.

The Science Software Branch is engaged in an effort to move to having
most of its software development done in Python. This release of
STSDAS/TABLES (v3.1) has tasks that require our command language
for IRAF called PyRAF (see pyraf.stsci.edu).

PyRAF 1.1 is being released at the same time as STSDAS/TABLES v3.1.

New packages or tasks:

hst_calib.stis.stisnoise (requires PyRAF)
         .doppinfo
         .synphot.modeinfo
toolbox.tools.tepoch

Packages or tasks that have seen significant changes include:

analysis.dither.pydrizzle
               .blot
               .buildasn
               .drizzle
               .tranxy
               .tranback
               .wcs2dr
hst_calib.acs.calacs
         .stis.calstis
              .odelaytime
              .tastis
         .wfpc

Packages or tasks that have had minor enhancements or bug fixes include:

hst_calib.ctools.ckwstis3
                .ckwstis4
         .nicmos.calnica
                .calnicb
                .mosdisplay
         .paperprod
         .stis.inttag 
         .synphot
toolbox.headers.iminfo
       .imgtools.addmasks
                .imcalc
                .mstools.mscombine


Parameter files that have changed (new parameters or new default values,
excluding parameters indicating version number changes):

analysis/dither/pydrizzle.par- 'fillvlaue' added
                             - 'section' added
                             - 'single' added
                             - 'clean' comment changed
                             - 'kernel' added lanczos3 option
                blot.par     - 'interpol' added sinc option
                updateasn.par- 'mode' added
hst_calib/ctools/ckwstis3.par- 'tdctab' added
                 chwstis4.par- 'tdstab' added
                               'tdctab' added