Binary Image

The holography FITS file contains a binary image which represents the data acquired by the holography backend for the purpose of assisting in the determination of GBT surface features.

The header keywords for the binary image is as follows:

XTENSION= 'BINTABLE'           / binary table extension
BITPIX  =                    8 / 8-bit bytes
NAXIS   =                    2 / 2-dimensional binary table
NAXIS1  =                   60 / width of table in bytes
NAXIS2  =                   99 / number of rows in table
PCOUNT  =                    0 / size of special data area
GCOUNT  =                    1 / one data group (required keyword)
TFIELDS =                    8 / number of fields in each row
TTYPE1  = 'DMJD    '           / label for field   1
TFORM1  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT1  = 'd       '           / physical unit of field
TTYPE2  = 'IFFLAG  '           / label for field   2
TFORM2  = '1J      '           / data format of field: 4-byte INTEGER
TUNIT2  = 'CODE    '           / physical unit of field
TTYPE3  = 'TESTxTEST'          / label for field   3
TFORM3  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT3  = 'COUNTS  '           / physical unit of field
TTYPE4  = 'QTESTxQTEST'        / label for field   4
More?[Yes]
TFORM4  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT4  = 'COUNTS  '           / physical unit of field
TTYPE5  = 'REFxREF '           / label for field   5
TFORM5  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT5  = 'COUNTS  '           / physical unit of field
TTYPE6  = 'TESTxQTEST'         / label for field   6
TFORM6  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT6  = 'COUNTS  '           / physical unit of field
TTYPE7  = 'TESTxREF'           / label for field   7
TFORM7  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT7  = 'COUNTS  '           / physical unit of field
TTYPE8  = 'REFxQTEST'          / label for field   8
TFORM8  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT8  = 'COUNTS  '           / physical unit of field
EXTNAME = 'DATA    '           / name of this binary table extension
SCAN    =                   34 / Scan number
UTDATE  =                54544 / MJD start of integration
UTCSTART=   3.600000000000E+00 / start time in sec since midnight
BACKEND = 'Holo    '           / Holography Receiver
END

       DMJD                  IFFLAG                 TESTxTEST
        d                     CODE                   COUNTS
5.454400004166667E+04          1                1.000000000000000E+00
     QTESTxQTEST             REFxREF                TESTxQTEST
       COUNTS                COUNTS                  COUNTS
1.000000000000000E+01   1.000000000000000E+02   1.000000000000000E+03
     TESTxREF                REFxQTEST
      COUNTS                 COUNTS
1.000000000000000E+04   1.000000000000000E+05

The columns are described below:

DMJD is the time-stamp in modified Julian days and fractions of a day of the end of integration. (TBD)

IFFLAG is a flag which if non-zero, indicates the data in the associated row is invalid, contaminated by RFI, or for some other reason is questionable. This flag is currently always zero. (Unimplemented.)

The columns TESTxTEST, QTESTxQTEST, REFxREF, TESTxQTEST, TESTxREF, REFxQTEST represent the magnitudes of the cross-correlations of the signals in the column name. (e.g. TESTxREF is the cross-correlation of the test signal with the reference signal.) Each of these columns is in terms of counts, which are unitless.

It is questionable of whether or not the keyword values of SCAN, UTDATE, UTCSTART and BACKEND are useful in the data table, since by default there will always only be one binary table per scan. I leave this as an item for discussion.