The Onsala 20 M Millimeter Wave Radio Telescope

A 20 millimeter wave telescope, enclosed in a 30 m metal space frame radome, has recently been completed and put into operation by Research Laboratory of Electronics. A number of novel features are incorporated in this new, Cassegrainian - type instrument. The main reflector is semi-homologous, which permits operations up to 120 GHz, and probably higher. In order to obtain a maximum aperture efficiency for each elevation the subreflector is (automatically) moveable with five degrees of freedom. The telescope is designed for multifrequency operation in the frequency range 8-120 GHz. Lens shortened feed horns are used in the lowest part of this range. TW-maser amplifiers are used up to about 45 GHz. Above 65, and up to about 120 GHz, resistive mixers (later to be cooled) are presently used. This new telescope, the largest one of its kind, its radiometer systems, and the most important results obtained with the same will be presented and discussed.