The Parkes radio telescope modified for rapid receiver changes

This paper describes improvements to the Parkes 64 m radio telescope. It is being upgraded to allow rapid switching between receivers, and to track the best-fitting focus as the elevation angle changes. Carried out under contract on behalf of NASA, the upgrade included installing a low-noise 2.3 GHz receiver for tracking the spacecraft Galileo in 1997. We explain the mechanical and structural aspects of the upgrade, including the need to replace the existing focus cabin with a larger unit, and the effect of the increased weight at the prime focus on the focusing characteristics and reflector accuracy. Finally, we summarize the designs of the feed and receiver to optimize the antenna-efficiency/temperature ratio at 2.3 GHz for the Galileo mission.