http://legacy.gsfc.nasa.gov/docs/fcg/common_dict.html
1. Keywords that describe the data or the FITS file itself: TITLE FILENAME FILETYPE ROOTNAME PROGRAM CREATOR CONFIGUR NEXTEND HDUNAME HDUVER HDULEVEL TLMINn TLMAXn TDMINn TDMAXn TDBINn TSORTKEY PROGRAM CREATOR CONFIGUR HDUCLASS HDUDOC HDUVERS HDUCLASn 2. Keywords that describe the observation: SUNANGLE MOONANGL RA DEC RA_NOM DEC_NOM RA_OBJ DEC_OBJ RA_PNT DEC_PNT PA_PNT RA_SCX DEC_SCX RA_SCY DEC_SXY RA_SCZ DEC_SCZ ORIENTAT AIRMASS LATITUDE OBJNAME OBS_ID 3. Keywords that describe the instrument that took the data: OBS_MODE DATAMODE APERTURE DETNAM FILTER FILTERn GRATING GRATINGn SATURATE 4. Keywords that give the date or duration of the observation: TIME-OBS TIME-END DATE-END EXPOSURE EXPTIME TELAPSE ELAPTIME ONTIME LIVETIME 5. Keywords that denote non-standard FITS keyword format conventions: HIERARCH INHERIT CONTINUE 6. File checksum keywords: CHECKSUM DATASUM CHECKVER 7. Hierarchical file grouping keywords: GRPNAME GRPIDn GRPLCn