PORT Binary Table Extension

The VEGAS FITS keywords for the PORT table conforms to the definition for common FITS headers as described in GBT Software Project Note 4.0 ``Device and Log FITS Files for the GBT.''

The PORT table for VEGAS will always contain 2 rows.

PORT Binary Tables Extension: Header
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XTENSION= 'BINTABLE'           / binary table extension
BITPIX  =                    8 / 8-bit bytes
NAXIS   =                    2 / 2-dimensional binary table
NAXIS1  =                   12 / width of table in bytes
NAXIS2  =                    2 / number of rows in table
PCOUNT  =                    0 / size of special data area
GCOUNT  =                    1 / one data group (required keyword)
TFIELDS =                    4 / number of fields in each row
TTYPE1  = 'BANK    '           / label for field   1
TFORM1  = '1A      '           / data format of field: ASCII Character
TUNIT1  = 'INDEX   '           / physical unit of field
TTYPE2  = 'PORT    '           / label for field   2
TFORM2  = '1I      '           / data format of field: 2-byte INTEGER
TUNIT2  = 'INDEX   '           / physical unit of field
TTYPE3  = 'MEASPWR '           / label for field   3
TFORM3  = '1E      '           / data format of field: 4-byte REAL
TUNIT3  = 'dBm     '           / physical unit of field
TTYPE4  = 'T_N_SW  '           / label for field   4
TFORM4  = '5A      '           / data format of field: 5 ASCII Characters
EXTNAME = 'PORT    '           / name of this binary table extension
END
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PORT Binary Tables Extension: Data (complete)
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      BANK     PORT       MEASPWR  T_N_SW
        1A       1I            1E      5A
     INDEX    INDEX           dBm
1        A        1 -1.973621E+00    TONE
2        A        2 -2.048295E+00    TONE

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The PORT columns are:

BANK This is itentical to the BANK keyword value in the primary HDU. It is included here as a column with a constant value to keep this FITS file format as similar to that found in the original GBT Spectrometer as possible.

PORT When used with BANK this identifies a unique row in the IF FITS for this scan and backend (VEGAS) associate with each input to this instrument.

MEASPWR The average measured power in the spectrometer for that port derived from the ADC histogram just prior to the start of the scan.

T_N_SW The TONE/NOISE switch value. This will be either 'TONE' or 'NOISE'.