TTYPE1  = 'SPEC_NUM'           / Spectrum Number
TFORM1  = '1I      '           / format of field
TTYPE2  = 'CHANNEL   '         / Channel number                                                                              
TFORM2  = 'nI      '          / data format of field
TUNIT2  = 'chan    '           / physical unit of field
TTYPE3  = 'COUNTS   '          / Total count in channel
TFORM3  = 'nJ      '          / data format of field
TUNIT3  = 'count    '          / physical unit of field
1CDLT3  = 1                    / Pixel increment along CTYP axis
1CDPX3  = 1                    / reference pixel of the CTYP axis
1CRVL3  = 0                    / Value of the CTYP axis reference pixel
1CUNI3  = 'chan     '          / Unit of the pixel along the CTYP axis
TTYPE4  = 'EXPOSURE '          / Exposure in spectra
TFORM4  = '1E       '          / data format of field
TUNIT4  = 's        '          / physical unit of field
TTYPE5  = 'BACKFILE  '         / Associated background
TFORM5  = '40A      '          / data format of field  
TTYPE6  = 'QUALITY  '          / data quality
TFORM6  = 'I        '          / data format of field
TTYPE7  = 'TIME     '          / Start time of the spectra
TFORM7  = '1D       '          / data format of field
TUNIT7  = 's        '          / physical unit of field
TTYPE8  = 'ENDTIME  '          / Stop time of the spectra
TFORM8  = '1D       '          / data format of field
TUNIT8  = 's        '          / physical unit of field
EXTNAME = 'SPECTRUM '          / Extension Name
HDUCLASS= 'OGIP     '          / Format conforms to OGIP/GSFC standards
HDUCLAS1= 'SPECTRUM '          / First class level
HDUCLAS2= 'TOTAL    '          / Second class level
HDUCLAS3= 'COUNT    '          / Third class level
HDUCLAS4= 'TYPEII   '          / Indicate PHA TYPE II file format
HDUVERS = '1.2.0    '          / Version of format (OGIP memo OGIP-92-007)
HDUVERS1= '1.2.0    '          / Obsolete included for back compatibility
AREASCAL= 1.000000E+00         / area scaling factor
BACKSCAL= 1.000000E+00         / background file scaling factor
CORRFILE= 'none     '          / associated scaling file
CORRSCAL= 1.000000E+00         / correction file scaling factor
RESPFILE= 'none     '          / associated redist matrix filename
ANCRFILE= 'none     '          / associated ancillary response filename
PHAVERS = '1992a    '          / obsolete
DETCHANS= -99                   / total number possible channels
CHANTYPE= 'PHA'                 / channel type (PHA, PI etc)
POISSERR=                    T / Poissonian errors to be assumed
STAT_ERR= 0                    / no statistical error specified
SYS_ERR = 0                    / no systematic error specified
GROUPING= 0                    / no grouping of the data has been defined
TELESCOP= 'BURSTCUBE'          / Telescope mission name
INSTRUME= 'string'             / Instrument name
DATAMODE= 'string'           / Data mode
OBJECT  = 'string'             / Object name
RA_OBJ  = -99.0                / R.A. Object
DEC_OBJ = -99.0                / Dec Object
POSFLAG = -99                  / Position FLAG 1=good 0=best effort -1=false
EQUINOX = 2000                 / Equinox
RADECSYS= 'FK5'                / Coordinates Systems
OBS_ID  = 'yymmdd'             / Observation ID
MJDREFI =                59215 / MJD reference day 01 Jan 2021 00:00:00
MJDREFF =  0.00080074074074074 / MJD reference (fraction of day)
TIMEREF = 'LOCAL   '           / Reference Frame
TASSIGN = 'SATELLITE'          / Time assigned
TIMESYS = 'TT      '           / Time system
TIMEUNIT= 's       '           / Time unit for timing header keywords
CLOCKAPP=                    F / If clock corrections are applied (T/F)
TRIGGER = 0                    / Trigger number
TRIGTIME= 0.0                  / Trigger Time sec since 01 Jan 2021 00:00:00
TRIGUTC = 'isodate'            / TIME of Trigger time in UTC
DATE-OBS= 'isodate'            / Start Date
DATE-END= 'isodate'            / Stop Date
TSTART  = 0.0                  / Start Time
TSTOP   = 0.0                  / Stop Time
CREATOR = 'string'             / Software that create 1st the file
PROCVER = 'string'             / Processing version
CALDBVER= 'string'             / CALDB version
SEQPNUM = 1                    / Number of times the dataset has been processed
ORIGIN  = 'GSFC    '           / Origin of the fits file
DATE    = 'isodate'            / File creation date
CHECKSUM= 'string'             / data unit checksum updated date
DATASUM = 'string'             / HDU checksum updated date
