A turn-key total power radiometer for atmospheric research

A novel 7 channel total power radiometer has been developed for atmospheric research. The radiometer has channels at 20.6 GHz, 31.5 GHz, 150 GHz and 4 channels about 183.3 GHz. It is contained within a weatherproof enclosure and temperature stabilised to better than .002 degC/min. Calibration is achieved using internal hot and cold loads. The cold load uses liquid nitrogen to achieve a low temperature reference and has a minimum operating time of three hours. The antenna views the scene through a radome and can scan ±45° from boresight. Major features of the radiometer are its use of subharmonic mixers for the high frequency channels and its use of a quasi-optical feed system for reflector illumination and channel demultiplexing. The antenna beams are defined by the feed system allowing the use of a plane reflector for scene and calibration target observation