SkyFreq: Sky Frequency of the center of the observing band
For each GBT backend, the observer generally is concerned with placing the frequency of interest in the center of the observing bandwidth. It is the responsibility of the GBT M&C system to track the Sky Frequency (SkyFreq) as the radio signals are up and down converted in the GBT IF chain. At each Intermediate frequency (IF) the M&C system is responsible for computing the corresponding SkyFreq for that IF frequency.
-- GlenLangston - 2009-06-19