File and Table Structures

Reference data, like most other HST data, is stored as FITS files. FITS with extensions for the newer instruments, or "waiver" FITS for the legacy Instruments and WFPC2. The FITS files for reference data contain information in the form of tables or images.

For a detailed discussion of understanding and working with these file types, see Chapter 2 of the on-line HST Data Handbook.

Each operational reference file past or present has a unique name. The file name root has the format YMDHHMMSI where:

  
      Y  denotes the year (1->Z, 1981=1)
      M  denotes the month (1->C, January = 1)
      D  denotes the day of the month (1->V)
      HH denotes the hour (00->23)
      MM denotes the minutes (00->59)
      S  denotes seconds/2 (0->T)
      I  denotes the instrument 
          (j=ACS, n=NICMOS, u=WFPC2, o=STIS, f=FGS,
           v=HSP, w=WFPC, x=FOC, y=FOS, z=GHRS, m=multiple)
 

The file name extension which is defined by file type is appended to the unique root.
Example: p9e1544dj_drk.fits is an ACS file (last character in the rootname is j=>ACS); it is a dark file (drk), named on 14 September 2005 at 15 hours 44 minutes 26 seconds (p9e1544d).

For the detailed specifications of calibration reference data, see document ICD-47 (PDF).

• Active instruments' reference files and calibration history
• Legacy instruments' reference file information