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Measurements of 220 GHz atmospheric opacity on Mt. Fuji with a radiometer/radome system |
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| Authors: | Yutaro Sekimoto Hiroshige Yoshida Tomoya Hirota Yasushi Takano Eri Furuyama Satoshi Yamamoto Shuji Saito Hiroyuki Ozeki Junji Inatani Masatoshi Ohishi Apostle G. Cardiasmenos Samuel L. Hensel |
| Affiliation: | 1. Department of Physics, School of Science, University of Tokyo, 113, Japan 2. Research Center for the Early Universe, School of Science, University of Tokyo, Japan 3. Institute for Molecular Science, 444, Okazaki, Japan 4. Nobeyama Radio Observatory, 384-13, Nagano, Japan 5. Electronic Space Systems Corporation, 01742, MA, USA |
| Abstract: | We measured atmospheric opacity at 220 GHz at the summit of Mt. Fuji (alt. 3776 m) about one year in order to explore a feasibility of submillimeter-wave astronomical observations. For this purpose, a 220 GHz radiometer system enclosed in a radome (51×51×62 cm3) has been developed. The 220 GHz opacity was lower than 0.06 for a significant fraction (～ 45 %) of time from November 1994 to March 1995. Diurnal variation of the opacity at the summit of Mt. Fuji is so small that continuous observation at submillimeter-wave is possible through day and night. Yearly variation of the opacity is studied from water vapor pressure data measured at the weather station for the past 3 years. To prevent accumulation of ice and snow on the Gore-Tex membrane in the radome, the outer membrane was supplied with a thermal flux of 0.63 kW m?2 and the adjacent metal radome surfaces were supplied with a flux of ～0.9 kW m?2. We evaluate from the 220 GHz transmission data that this heat flux is sufficient to keep the membrane on the radome free of ice and snow during 83 % of the time in 5 winter months. The summit of Mt. Fuji appears to be a promising site for submillimeter-wave observations. |
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