Background

All GBT scan data FITS files should conform to the standards specified in the GBT Software Project Note 4.0, ``Device and Log FITS Files for the GBT.'' A bank of the spectrometer is created by combining the output lag data from one or more of the quadrants of the spectrometer. Each quadrant can produce up to 8 correlations simultaneously. Four GBT Spectrometer binary table extensions will be produced for each bank of the spectrometer used for the observations: PORT, SAMPLER, STATE, ACT_STATE and DATA, and these tables will be placed in a single scan data FITS file for each scan. Since one spectrometer FITS file will be created for each bank, a constraint on each bank output is that all correlations for a given bank will have the same number of lags. Different banks may produce correlations with different numbers of lags.

In the current version of the design (FITSVER 1.2) the Spectrometer Manager will not perform any FFTs, and so only correlation functions will be written to file, using the third column in the DATA table. This fact is indicated by the keyword/value pair FFT = F in the primary header. If in the future, we support fourier transforms and other data processing in the Spectrometer Manager, the structure definition for the FITS file will need to be modified accordingly.