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PORT Binary Table Extension

The Spectrometer 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.''

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  =                   43 / 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 =                    9 / 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  = 'ATTENSET'           / label for field   3
TFORM3  = '1E      '           / data format of field: 4-byte REAL
TUNIT3  = 'dBm     '           / physical unit of field
TTYPE4  = 'MEASPWR '           / label for field   4
TFORM4  = '1E      '           / data format of field: 4-byte REAL
TUNIT4  = 'V       '           / physical unit of field
TTYPE5  = 'RATIO   '           / label for field   5
TFORM5  = '1E      '           / data format of field: 4-byte REAL
TUNIT5  = 'none    '           / physical unit of field
TTYPE6  = 'LEVEL   '           / label for field   6
TFORM6  = '1J      '           / data format of field: 4-byte INTEGER
TUNIT6  = 'COUNT   '           / physical unit of field
TTYPE7  = 'SPEED   '           / label for field   7
TFORM7  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT7  = 'Hz      '           / physical unit of field
TTYPE8  = 'BANDWDTH'           / label for field   8
TFORM8  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT8  = 'Hz      '           / physical unit of field
TTYPE9  = 'FSTART  '           / label for field   9
TFORM9  = '1D      '           / data format of field: 8-byte DOUBLE
TUNIT9  = 'Hz      '           / physical unit of field
EXTNAME = 'PORT    '           / name of this binary table extension
COMMENT   Channel Frequency Formula:
COMMENT   12.5 and 200 MHz BANDWDTH: F = FSTART + BANDWDTH * (N - 1)/NLAGS
COMMENT   50 and 800 MHz BANDWDTH: F = FSTART - BANDWDTH * (N - 1)/NLAGS
END
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PORT Binary Tables Extension: Data (complete)
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      BANK     PORT       ATTENSET        MEASPWR          RATIO        LEVEL
        1A       1I             1E             1E             1E           1J
     INDEX    INDEX            dBm              V           none        COUNT
1        A        9   1.500000E+01   4.882812E-03   0.000000E+00            9
2        A       13   1.500000E+01   4.882812E-03   0.000000E+00            9

                SPEED             BANDWDTH               FSTART
                   1D                   1D                   1D
                   Hz                   Hz                   Hz
1  1.000000000000E+08   5.000000000000E+07   1.000000000000E+08
2  1.000000000000E+08   5.000000000000E+07   1.000000000000E+08
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The columns BANK and PORT identify an IF input into the Spectrometer and uniquely defines a row in the table.

The columns ATTENSET, MEASPWR and RATIO are associated with the total power at the port as defined by the associated attenuator setting in the Converter Rack, the resultant measured power at the Analog Filter Rack and the ratio of zero to non-zero duty cycle counts in the Spectrometer.

The column LEVEL identifies either 3 or 9 level sampling mode.

The column speed specifies either 100,000,000 or 1,600,000,000 Hz sampling speed.

The columns BANDWDTH and FSTART describe the port's frequency width; and starting frequencies as generated by the A/Ds. The center frequency for each channel may be computed using the ``Channel Frequency Formula'' as described in the comments.



Bob Garwood
2011-07-25