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Reflector Surface and Holography

An adjustment of the surface panels of the 30m telescope was initiated in the first week of November 1993. It was based on holography observations of the geostationary satellite ITALSAT at 39 GHz. These observations were made at 43 degrees elevation during several night time sessions during the summer months of 1993. They have the advantage over previous observations made at 11 degrees elevation, that no corrections for gravitational deformations are necessary to refer the results to the elevation at which the telescope performance is to be optimised. For the adjustment of the reflector about 500 screws with measured deviations of more than 50 microns had to be moved. Bad weather restricted the working time during the first week of November, and the adjustment was completed on the 7th of December. A very brief (due to bad weather) holography measurement made on the 10th of November (with 72% of the screws adjusted) suggests an improvement of the surface rms error. These results will be verified in a longer holography session.

Robert Lucas
Thu Mar 9 14:51:14 MET 1995