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20.1 Overview
Calibrated STIS data have been processed through the STScI calstis pipeline. The pipeline unpacks the databits from individual exposures, combines them into files containing raw, uncalibrated data, and performs image and spectroscopic reduction on the data to produce output files which can be used directly for scientific analysis (see Chapter 21 for a more detailed description of the STIS pipeline). Unlike previous HST pipelines, the STIS pipeline performs contemporaneous calibrations, processing data from multiple science exposures as well as contemporaneously obtained line lamp calibration exposures through the pipeline as a single unit. These multiple associated STIS exposures which are processed through the pipeline as a unit are combined into a single dataset, to allow easy identification and compact storage. (See Appendix B for a general explanation of HST data associations.)
To work effectively with your data you will need to understand:
- The basic format in which the STIS data are stored, the information and nature of the data stored for each observation-see "STIS File Structures", below.
- The nature of the individual files in your dataset, i.e., what data is stored in what file. Spectroscopic observers looking for the final calibrated product will want first to examine the *_sx2.fits or *_x2d.fits files, which store rectified, flux- and wavelength-calibrated, two-dimensional spectra, in the case of first order long slit data; or to examine the *_sx1_fits or *_x1d.fits files which store background subtracted, aperture extracted, flux- and wavelength-calibrated, one dimensional spectra, for the case of echelle spectroscopy-see "Types of STIS Files" on page 20-6.
- How to use the header keyword information to identify the principal parameters of your observation and to determine the calibration processing steps which were performed on your dataset-see "Headers, Keywords, and Relationship to Phase II" on page 20-9.
- The meanings of the error and data quality arrays, which are propagated through with each STIS science observation-see "Error and Data Quality Arrays" on page 20-13.
- How to use the STIS Paper Products-see page 20-15.
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Last updated: 11/13/97 17:34:12