NOTE: Due to limited resources, these pages may not have been regularly updated. It is possible that the information provided below and/or in the links given may be outdated or inaccurate. If you come across conflicting information or are confused by the answers given, please contact the STScI helpdesk at: firstname.lastname@example.org.
Q: What are the new *drz.fits files that MAST is delivering?
A: Users requesting WFPC2 data from the MAST archive now receive an additional data product, a quick-look mosaic of the images from all four detectors. The new files, labeled *drz.fits, are produced by the program PyDrizzle. The images are geometricaly corrected and have a plate scale of 0.1" per pixel. (Data sets consisting of a single PC image use the native plate scale of the PC.) Because PyDrizzle is run on each WFPC2 exposure independently, the program cannot perform sub-pixel sampling or cosmic-ray rejection. DRZ files are thus intended as quick-look images, rather than as science data products. DRZ files utilize a multi-extension FITS format, rather than the waiver FITS format of traditional WFPC2 data products.
While most WFPC2 image files are in units of counts (DN), while the units of WFPC2 drizzled images retrieved from MAST are counts per second (DN/s). Always check the value of the header keyword BUNIT to be sure of the units. Note that the keyword PHOTFLAM in the DRZ file is taken from the first extension (usually the PC chip) of the calibrated data file.
Q: Is the pipeline used for reprocessing different from the pipeline used for OTFR?
A: The same pipeline is used for both OTFR and the reprocessing of WFPC2 data.
Q: How do I distinguish between WFITS and MEF files?
A: WFITS files end with "c0f.fits" (u9wj600im_c0f.fits), while MEF format files end with "c0m.fits" (u9wj600im_c0m.fits).
Q: When will the new files be available?
A: The new files will ba available as soon as they are reprocessed. If a user requests a data set that has been reprocessed, the request will be fulfilled from the static archive. Data sets not yet in the static archive will be reprocessed using OTFR as before. With a few exceptions, WFPC2 images are being reprocessed in the order that they were obtained, so it will be a few weeks before the most recent data are available. You can monitor our progress by checking the HST Reprocessing Status page:
Q: How do I retrieve MEF format files from MAST?
A: For data sets in the static archive, MEF files may be requested by entering the desired file extension (c0m) at the bottom of the MAST Retrieval Options page. For data sets not yet in the static archive, only WFITS files are available.
Q: Will STSDAS routines, particularly those in the wfpc package, accept the new MEF files?
A: With few exceptions, the new WFPC2 MEF files may be used with all STSDAS tasks.
Q: Do I need to run STRFITS on MEF files?
A: No. STRFITS will not work with MEF files. Instead, you can run all STSDAS routines directly on MEF files.