3.1 HST Data Files
The HST data calibration pipeline (HSTCAL; https://github.com/spacetelescope/hstcal) automatically processes and calibrates all the data received from HST and assembles them into a form suitable for most scientific analyses. Data from ACS, COS, NICMOS, STIS, WFC3, and WFPC2 are made available to observers as files in Multi-Extension FITS (MEF) format. For first generation instruments (FGS, FOC, FOS, GHRS, HSP, and WF/PC-1), data are stored in a format called "waivered" FITS. These waivered FITS files have only a single extension, therefore files containing data from multiple cameras must be stored as a three-dimensional data cube. For example, the four WFPC2 CCDs, each having a size of 800 x 800 pixels, would be stored in a waivered FITS file as a 800 x 800 x 4 pixel data cube, while in MEF format as four FITS extensions each containing a 800 x 800 pixel image.
WFPC2 data are stored in MAST as both MEF and waivered FITS files. Selecting the "minimum recommended products" will return the waivered FITS format files with suffixes c0f and c1f. Users may also retrieve the MEF format files by unchecking the "minimum recommended products" option and selecting explicitly the c0m and c1m suffixes.
Table 3.1: HST Instrument File Formats
| Instrument | Status | Format from MAST |
|---|---|---|
| ACS | active | MEF |
| COS | active | MEF |
| FGS | active | waivered FITS |
| FOC | decommissioned SM3B | waivered FITS |
| FOS | decommissioned SM2 | waivered FITS |
| GHRS | decommissioned SM2 | waivered FITS |
| HSP | decommissioned SM1 | waivered FITS |
| NICMOS | decommissioned SM4 | MEF |
| STIS | active | MEF |
| WFC3 | active | MEF |
| WFPC2 | decommissioned SM4 | waivered FITS & MEF |
| WF/PC-1 | decommissioned SM1 | waivered FITS |
The remainder of this chapter describes FITS file formats in more detail.
Throughout this document, references to FITS files will always mean HST Multi-Extension FITS format files. References to waivered FITS files will always be explicitly stated.