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 ------------------------------------------------------------------------------- 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 ------------------------------------------------------------------------------- PORT Binary Tables Extension: Data (complete) ------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------
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.