Mt. Fuji submillimeter-wave telescope

The Mt. Fuji submillimeter-wave telescope has been operated since November 1998 to survey neutral atomic carbon (CI) toward the Milky Way. It has a 1.2 m main reflector with a surface accuracy of 10 μm in rms. A dual polarization superconductor-insulator-superconductor (SIS) mixer receiver mounted on the Nasmyth focus receives 810/492/345 GHz bands in DSB simultaneously. An acousto-optical spectrometer (AOS) has 1024 channels for 0.8 GHz bandwidth. The telescope was installed with a helicopter and bulldozers at the summit of Mt. Fuji (alt. 3725 m) in July 1998 after a test operation at Nobeyama for a year. It has been remotely operated via a satellite communication from Tokyo or Nobeyama. Atmospheric opacity at Mt. Fuji was 0.4 - 1.0 at 492 GHz in 30% of time and 0.07 - 0.5 at 345 GHz in 60% of time during winter five months. The system noise temperature was typically 1200 K (SSB) at 492 GHz and 500 K (DSB) at 345 GHz. The beam size was measured to be 2.′2 and 3.′1 at 492 and 345 GHz, respectively. We have conducted a large-scale survey of the CI (492 GHz) and CO (3-2:345 GHz) emission from nearby molecular clouds with a total area of 10 square degrees. We describe the telescope system and report the performance obtained in the 1998 winter.