Each STSDAS instrument package includes a calibration task (see Table 6.1). Each of these calibration tasks has a single input parameter--the root name of the raw data set to be calibrated--and a single output parameter, the root name of the output calibrated data set. All other parameters that affect the calibration, such as the names of reference files or tables, are specified in the header of the input raw data file. Various tools are available (such as chcalpar in the ctools package) to modify the header keywords. An overview of STSDAS tools that support the general calibration process can be viewed online by typing help ctools opt=sys.
STSDAS Instrument Calibration Tasks
Users at STScI will also find that the most current reference files and tables are available on-line. Reference tables are also available in the Calibration Data Base (CDBS) relations and can be accessed using the
cdbsutil tools in the STSDAS stlocal package. Query tools in cdbsutil create STSDAS tables which can then be manipulated using tasks in the ttools package.
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Editing Headers with chcalpar
The chcalpar task is used to edit calibration header keywords for any HST dataset. The task works by loading keywords from your image into a pset for the instrument used, this pset is then edited with the
eparam editor. When you are done editing keywords, you exit from eparam and are then asked to confirm your changes before the new values are written to your output image. As with all STSDAS tasks, details are found in the online help file (type help chcalpar). A detailed description of chcalpar also appeared in the
Winter 1993 issue of the STSDAS Newsletter (Number 3, page 8), which is obtainable from the STSDAS HotSeat. Reference Files
The calibration tasks use both reference data files (such as flat field images) and reference tables (with values such as a sensitivity constant that is applied to all data values). Copies of the reference files used to calibrate your observation are sometimes included with your data set if you received a tape from STScI. Copies of the reference files and tables can also be obtained from the HST Archive. To use the archive, you will need to request an account on one of the archive hosts and you can also request a copy of the HST Archive Primer to get you started. Requests can be made via e-mail to: archive@stsci.edu