SIMPLE  =                    T / HDU 0==========================================
BITPIX  =                    8 / Number of bits per data pixel
NAXIS   =                    0 / Number of data axes
EXTEND  =                    T / FITS dataset may include extensions
COMMENT
COMMENT                        / Configuration control--------------------------
COMMENT
ORIGIN  = 'ASC     '
CREATOR = 'xxx - Version 0.0'
CHECKSUM= '0000000000000000'   / ASCII encoded HDU checksum
DATASUM = '         0'         / Data unit checksum written in ASCII
COMMENT
COMMENT                        / Time information block-------------------------
COMMENT
DATE    = '1998-01-01T00:00:00'  / Date and time of file creation (UTC)
DATE-OBS= '1998-01-01T00:00:00'  / TT, with clock correction if CLOCKAPP
DATE-END= '1998-01-01T00:00:00'  / TT, with clock correction if CLOCKAPP
TIMESYS = 'TT      '           / AXAF time will be TT (Terrestrial Time)
CLOCKAPP=                    T / Clock correction applied (if false)
TIMEZERO=                  0.0 / Clock correction (if not zero)
TIMEUNIT= 's       '
MJDREF  =                50814 / 1998-01-01T00:00:00 (TT) expressed in MJD (TT)
TSTART  =                  0.0 / As in the "TIME" column: raw space craft clock;
TSTOP   =                  0.0 /   add TIMEZERO and MJDREF for absolute TT
COMMENT
COMMENT                        / Observation information block------------------
COMMENT
OBS_ID  = 'xxxxxxxxxxxxxxx'    / Whatever the convention is ...
MISSION = 'AXAF    '           / Mission is AXAF
TELESCOP= 'AXAF    '           / Telescope is AXAF
INSTRUME= 'ACIS    '           / HRC, ACIS, EPHIN, S/C subsystems
END