The foundation of millimeter wave VLBI station at Kagoshima

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Radio astronomers have developted methods for combining signals from radio telescopes scattered around the globe, creationg an effective aperture thousands km across. This technique, known as very long base line interferometer (VLBI), has elevated astronomical angular resolution measurements to new heights. In Japan, two mm VLBI telescopes have been performing. One in 45 m telescope at Nobeyama (NRO), and the otheris 34 m telescope at Kashima (CRL). Recently, a new mm VLBI telescope was constructed at Mizusawa (Mizusawa Astrogeodynamics Observatory). However, these telescopes are situated in the northern part of Japan. Our project is to construct a new mm VLBI station in the southern part of Japan, creating an effective aperture with the size of Japanese Islands. The 6m telescope was moved from Nobeyama Radio Observatory to Kagoshima. We finished the construction of the antenna and installed a 22 GHz cooled receiver in 1992. Owing to the smallness of this antenna, mm-VLBI observations … More require substantial technical efforts : The system has two distinctive characteristics as compared with current VLBI practice in order to improve thesensitivity. One is the capability of a burst mode operation with a high speed sampller and a large capacity memory. The other is a new bandwidth synthesizer mode operation using both high speed sampler and filters instead of video converters. Optical fiber cables are used for transmission of wide IF band (2GHz) for these new methods.First Kagoshima-Nobeyama-Mizusawa interferometer VLBI experiment was done in 1993 with collaboration from the Nobeyama Radio Observatory, and Mizusawa Observatory. The longest baseline of this network is 1300 km which provides a fringe separation of 2 milliarcsecont at 22 GHz.Recently, we started the monitor VLBI observations of H_2O maser sources in order to detect the apparent motions of masers in months. These data will provide irreplaceable insights into the inner working of interstellar clouds.Also, we are now pushing a plan of 43 GHz VLBI observations and will install a 43 GHz cold receiver in 1995. Less