DESIGN AND IMPLEMENTATION OF AN ERROR-COMPENSATING SUBREFLECTOR FOR THE NRAO 12-M RADIO TELESCOPE

This paper describes the measurement of the surface shape of the prima ry reflector of the NRAO 12-m radio telescope and the use of the measu rements to machine the shape of a secondary mirror to compensate for t he primary reflector errors. The method known as holography was used w ith the 38.04-GHz transmitter on-board the geosynchronous Lincoln Expe rimental Satellite to map the main reflector. The machining of the sec ondary compensated for the errors in the primary shape, and as a resul t, at 345 GHz, the axial gain of the instrument was increased by about 50% and the antenna pattern correspondingly improved.