HDU classes

Following NASA’s recommendation (see HFWG Recommendation R8), a hierarchical classification is applied to each HDU within DL3 FITS files, using the HDUCLASS and HDUCLASn keywords.

Some useful links from other projects:

The different HDUs defined in the current specifications are listed here:

  • EVENTS : Table containing the event lists. See EVENTS.
  • GTI : Table containing the Good Time Intervals (‘GTIs’) for the event list. See GTI.
  • POINTING : Table containing the pointing direction of the telescopes for a number of time stamps. See POINTING.
  • RESPONSE : Table containing any of the different instrument response function components defined in the specs. See IACT IRFs.

The current HDU class scheme used is the following:

  • HDUCLASS : General identifier of the data format. Recommended value: “GADF” (for “gamma-astro-data-formats”)
  • HDUDOC : Link to the DL3 specifications documentation
  • HDUVERS : Version of the DL3 specification format
  • HDUCLAS1 : General type of HDU, currently: EVENTS, GTI or RESPONSE
  • HDUCLAS2 : In case of RESPONSE type, refers to the IRF components stored within the HDU: EFF_AREA, BKG, EDISP or RPSF
  • HDUCLAS3 : In case of RESPONSE type, refers to the way the IRF component was produced (POINT-LIKE or FULL-ENCLOSURE)
  • HDUCLAS4 : In case of RESPONSE type, refers to the name of the specific format
HDUCLAS1 HDUCLAS2 HDUCLAS3 HDUCLAS4
EVENTS      
GTI      
POINTING      
RESPONSE EFF_AREA POINT-LIKE AEFF_2D
    FULL-ENCLOSURE AEFF_2D
  EDISP POINT-LIKE EDISP_2D
    FULL-ENCLOSURE EDISP_2D
  RPSF FULL-ENCLOSURE PSF_TABLE
      PSF_3GAUSS
      PSF_KING
      PSF_GTPSF
  BKG POINT-LIKE BKG_2D
      BKG_3D
    FULL-ENCLOSURE BKG_2D
      BKG_3D
INDEX OBS    
  HDU