Observations
On April 7-8, 2004 GBT project checkout observations were performed using
the Ku-Band receiver. Serveral scans to identify RFI in the Ku-Band
nominal receiver bandpass were made as part of these observations. The
spectrometer was used for these observations. The spectrometer was setup
to provide 800 MHz instantaneous bandwidth in two separate side-by-side
bandpasses. The frequency were shifted and observations repeated in
order to cover the entire receiver bandpass. The center frequencies used
were 12.4, 13.1, 13.8, 14.5, 14.3 and 15.0 GHz.
Horizon scans were taken where the GBT was moved from 0 degrees azimuth to
360 degrees azimuth at a constant elevation of 20 degrees. The telescope
was slewed at 30 degrees per minute in azimuth and a 3 second integration
time was used. The scans were made so that data at all frequencies within
the receiver bandpass could be obtained.
Elevations scans were taken were the GBT was moved between 10 degrees and
80 degrees elevation at three different azimuths. These were
180, 245, and 350 degrees azimuth. Data were only taken for the bandpasses
centered on 12.4 and 13.1 GHz since no apparent RFI was present in the other
bands (see below).
Several integrations within each scan that appeared to have no RFI were
used to remove an interpolated "baseline" from the data. This allows
us to easily visulize were the RFI is present. I have not attempted to
calibrate the data.