115GHz Radio Telescope with a Low Noise Cooled Receiver

Abstract

In 1975 we made a radio telescope system for interstellar CO spectral survey, which has been used for the observations of molecular clouds and has produced some important resuls. The reciver noise was however much enormous compared with the spectral power of the CO line, so it took too long integration time to survey a large area in the Galaxy. Then we have made our efforts to grade up the telescope system in order to enable efficient observations. Main points of improvements are: 1. A cooled mixer with a GaAs Schottky barrier diode has been developed, which has realized the mixer noise temperature of 500K when cooled down to 77K. 2. A liquid nitrogen cooled receiver for 115GHz signal has been composed, which has given the SSB system noise temperature of 1,200K. 3. A wide-band acousto-optic radio spectrometer has been realized. 4. Automatic observation and efficient data processing have been realized through the introduction of MT and the grade-up of software system. By useing this new telescope system, we are able to observe the molecular cloud more than 200 times as efficiently as the old one.