ACS

• RAW (*_raw.fits) images.

WFPC2

• Most WFPC2 observing modes have been tested and are supported by Multidrizzle, including area mode and subarray observations.  Full support for WFPC2 is currently in development.
• Multidrizzle is able to accept GEIS and waivered FITS format files as input. However, these files are automatically converted to multi extension FITS format files.  When file conversion occurs, an association file is created containing the names of the new files.  The association file will have the same rootname as the original input with "MDZ_" prepended.  The output file name also has "MDZ_" prepended during the file conversion step (this won't occur in future versions).
• If IVM files are going to be provided as input, they must be formatted as multi-extension FITS files with a separate extension for each chip's IVM array.  Each extension should also have 'EXTNAME' set to 'IVM' as well.
  

• Plate scale differences are taken into account during the sky subtraction step. The 'MDRIZSKY' header value for WFPC2 is taken to be on the WF3 plate scale.

• The single-drizzle step only uses the Static Mask for weighting.  As a result, the regions of each chip edge masked by the WFPC2 pyramid do not get removed.  This goes into creating a median image where those regions are influenced by the noise of those vignetted edges, reducing the effectiveness of the cosmic-ray determination for those areas.  The next version will allow the user to mask out the vignetted edges through the use of the 'bits' parameter if the corresponding '.c1h' data-quality image is present for each input WFPC2 science image.

• MultiDrizzle updates the input images WCS keywords based on the distortion coefficients provided as input.  In addition, MultiDrizzle also updates the input file DQ arrays with the pixels that it identified as cosmic-rays.  WFPC2 GEIS images, though, get converted on input to multi-extension FITS files and ONLY those converted FITS files get updated by MultiDrizzle, not the original input GEIS images.

• Support for STIS imaging is complete at this time.  STIS spectroscopy is not yet supported.
  
• Multidrizzle allows for the use of multi-imset STIS _flt files as input.  These files will be automatically split into separate files prior to processing by Multidrizzle.  The files will be named "rootname_flt_extnX.fits" where X represents the original extension number of the input file.
  

• Since MultiDrizzle and calstis2 both assign the value 8192 to cosmic rays in the DQI file of the input flt image, users may want to run Multidrizzle on basic2d-calibrated flt.fits files not already modified by calstis2 (or by its equivalent, stsdas.hst_calib.stis.ocrreject with crmask=yes).

• MDRIZTAB (_mdz.fits) reference files, which can be used to set parameter values, do not yet exist for STIS. Although the default values in MultiDrizzle were chosen with ACS in mind, they generally work well for STIS. Tests have shown that a slightly relaxed value of 'driz_cr_scale' (1.5 0.7) preserves the peaks of well-centered stars while still providing good cosmic ray rejection.
  

• Until the PA_V3 keyword is automatically included in the header  of STIS science exposures, the spt files should be kept in the working directory for the initial run.  Multidrizzle will then extract the keyword value from the spt files and add it to the primary science headers. The PA_V3 keyword should now be included for all STIS data retrieved from the HST archive as of June 2005.
  

• MultiDrizzle updates the input images WCS keywords based on the distortion coefficients provided as input.  In addition, MultiDrizzle also updates the input file DQ arrays with the pixels that it identified as cosmic-rays.  Associated STIS images, though, get converted on input to multi-extension FITS files, one for each SCI extension named in the ASN file, and ONLY those converted FITS files get updated by MultiDrizzle, not the original input multi-extension file.

• Support for NICMOS imaging is only preliminary at this time.  Full support for NICMOS is under development.
• Multidrizzle only supports processing of NICMOS CAL files and ASN (*_asn.fits and *_asc.fits) tables.

• Until the PA_V3 keyword is automatically included in the header of NICMOS science exposures, it should be read from the primary header of the spt files and added to the primary header of the science exposures manually before running Multidrizzle. The PA_V3 keyword should now be included for all NICMOS data retrieved from the HST archive as of June 2005.