SUMMARY OF SURVEY

The survey uses a 10 meter diameter parabolic antenna to produce a survey of the radio sky at a frequency of 408 MHz. At this frequency the telescope has a beam width of about six degrees. This means that it 'sees' everything within a circle with a radius of three degrees around where it is pointing.

The antenna can move in azimuth and elevation. However, for this survey it is left pointing North or South, depending on the required declination. For the first run it is set to its minimum elevation and left to record noise from the sky for a week. At the end of the week the data is stored on disk and taken away for processing. This gives roughly seven complete scans of the sky for a specific elevation (and consequently declination). The telescope is then set to an elevation 5 degrees higher than previously and left to record sky noise for another week.

Once the whole sky has been scanned from minimum to maximum declination, the procedure is repeated by scanning from maximum to minimum elevation. When this has been completed, quick scans are taken in elevation running from maximum to minimum elevation (as opposed to the scans running in Right Ascension that the rest of the survey consisted of). This way any effects due to the sun and environmental noise can be cancelled out.

A telescope in this mode of use is known as a 'transit telescope' as it only sees sources when they 'transit' the local meridian.