2.1 STIS Overview

Raw STIS data are calibrated through the STScI calstis pipeline. The pipeline unpacks the data bits from individual exposures, combines them into files containing raw, uncalibrated data, and performs image and spectroscopic reduction to produce output files that can be used directly for scientific analysis (see Chapter 3 for a more detailed description of the STIS pipeline). Unlike previous HST pipelines, the STIS pipeline calibrates data from multiple science exposures and any contemporaneously obtained line lamp calibration exposures through the pipeline as a single unit. These multiple associated STIS exposures that are processed through the pipeline as a unit are combined into a single dataset, to allow easy identification and compact storage. See Chapter 5 in the Introduction to the HST Data Handbooks for a general explanation of HST data associations.

To work effectively with your data you will need to understand:

• The nature of the individual files in your dataset. To understand the contents of each file, see Section 2.2.
• The basic format in which the STIS data are stored, the information and nature of the data stored for each observation; see Section 2.3.
• How to use the header keyword information to identify the principal parameters of your observation and to determine the calibration processing steps that were performed on your dataset; see Section 2.4.
• The meanings of the error and data quality arrays, which are propagated through the pipeline for each STIS science observation; see Section 2.5.