Design and implementation of an error-compensating subreflector for the NRAO 12-m radio telescope

Describes the measurement of the surface shape of the primary reflector of the NRAO 12-m radio telescope and the use of the measurements to machine the shape of a secondary mirror to compensate for the primary reflector errors. The method known as holography was used with the 38.04-GHz transmitter on the geosynchronous Lincoln Experimental Satellite to map the main reflector. The machining of the secondary compensated for the errors in the primary shape, and as a result, at 345 GHz, the axial gain of the instrument was increased by about 50% and the antenna pattern correspondingly improved. >