The FITS format structure is presented for the GBT tracking local
oscillator (LO1) scan data files. The scan data FITS files are permanently
archived after each observation, and will usually be input to the
aips++ filler, which has the task of combining all scan data FITS
files into an aips++ Measurement Set. This data may then either be
processed further in aips++, or written out in an aips++ supported
FITS format (one of which is single dish FITS).
The LO1 FITS files, produced separately for each LO contains binary
tables describing the commanded LO1 frequencies as a function of time
throughout the scan. This is separated two components separately describing
the effects of Doppler tracking frequency switching.