The FITS format structure is presented for the GBT Antenna Control
Unit (ACU) 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 main content of the ACU FITS file is a binary table containing
a stream of the actual (indicated) telescope positions sampled at
10Hz through-out the scan.