UPGRADING THE HAYSTACK RADIO TELESCOPE FOR OPERATION AT 115 GHZ

The Haystack 37-m radio telescope has been upgraded for operation at f requencies up to 115 GHz. A unique deformable subreflector with active actuator control has been developed to correct for gravitational dist ortion effects including astigmatism and deflections associated with t he particular reflector surface. Active thermal compensation of the su rface has also been implemented to correct for both thermal lag effect s and circularly symmetric gravitational deviations. Holographic mappi ng of the antenna surface deviations was achieved using 12-GHz geostat ionary satellite transmissions, which required the use of special tech niques to correct for diffraction and multiple reflection effects invo lving the space-frame radome that covers the antenna. Realignment of t he antenna surface utilized a finite-element structural model to trans late surface deviations to motions of the unusual adjustment mechanism s on the antenna. The currently measured rms surface deviation ( Dec. 23, 1992) is 210 mum. The telescope has been equipped with a two-chann el cryogenically cooled 3-mm SIS receiver, covering the range from 84 to 115 GHz. A new flexible digital spectrometer has been constructed f or spectral line astronomy. Configurations can range from a widest ban dwidth coverage of 160 MHz at 512 lags to 0.66 MHz at 4096 lags. Examp les are given of surface holographic maps and radio measurements of ap erture efficiency, pointing, and other performance parameters.