We have developed a 1.2 m submillimeter-wave telescope at the summit of Mt. Fuji to survey emission lines of the neutral carbon atom (CI) toward the Milky Way. A superconductor-insulator-superconductor mixer receiver on the Nasmyth focus is used to observe the 492 GHz band in SSB and the 345 GHz band in DSB simultaneously. The receiver noise temperature is 300 K in SSB and 200 K in DSB for 492 and 345 GHz, respectively. The intermediate frequency frequency is 1.8-2.5 GHz. An acousto-optical spectrometer which has the total bandwidth of 0.9 GHz and 1024 channel outputs has also been developed. The telescope was installed at the summit of Mt. Fuji (alt. 3725 m) in July 1998. It has been remotely operated via a satellite communication system from Tokyo or Nobeyama. Atmospheric opacity at Mt. Fuji was 0.4-1.0 at 492 GHz during 30% of the time and 0.07-0.5 at 345 GHz during 60% of the time from November 1998 to February 1999. The system noise temperature was 1000-3000 K in SSB at 492 GHz and 500-2000 K in DSB at 345 GHz. We observed the CI (3P1-3P0: 492 GHz) and CO (J = 3 - 2: 345 GHz) emission lines from nearby molecular clouds with the beam size of 2′.2 and 3′.1, respectively. We describe the telescope system and report the performance obtained in the 1998 winter.
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