The Mt. Fuji submillimeter-wave telescope

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 (C-I) 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 ba nd in DSB simultaneously. The receiver noise temperature is 300 K in SSB an d 200 K in DSB for 492 and 345 GHz, respectively. The intermediate frequenc y frequency is 1.8-2.5 GHz. An acousto-optical spectrometer which has the t otal 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 Jul y 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 f rom November 1998 to February 1999. The system noise temperature was 1000-3 000 K in SSB at 492 GHz and 500-2000 K in DSB at 345 GHz. We observed the C I (P-3(1)-P-3(0): 492 GHz) and CO (J=3-2: 345 GHz) emission lines from near by molecular clouds with the beam size of 2.'2 and 3.'1, respectively. We d escribe the telescope system and report the performance obtained in the 199 8 winter. (C) 2000 American Institute of Physics. [S0034-6748(00)04907-8].