Takao Nakagawa

天文学の観測にとって、宇宙に浮かぶ人工衛星からの観測は、地上にある望遠鏡からの観測に比べて、大きなメリットが数多くある。これらのメリットを活かすべく、様々な宇宙天文台が打ち上げられてきた。ただし、そこに搭載される望遠鏡には、ロケットの限られた打ち上げ能力を活かすべく、徹底した軽量化が求めらる一方、ロケット打ち上げという過酷な機械環境に耐えるという、相反する機械的要求がある。本講演では、このような困難にうちかって各種の宇宙天文台を実現してきた活動のうち、特に日本での活動について紹介する。

A two-stage Stirling cooler has been developed and tested for the infrared astronomical satellite ASTRO-F that is planned to be launched by Japanese M-V rocket in 2005. ASTRO-F has a hybrid cryogenic system that is a combination of superfluid liquid helium and two-stage Stirling coolers. The cooler has a new linear-ball-bearing system for the piston-supporting structure in a compressor. The linear-ball-bearing supporting system achieves the piston clearance seal, the long piston-stroke operation and the low frequency operation. The typical cooling power is 0.2W at 20 K and the total input power to the compressor and the cold head is below 90 W. The engineering, the prototype and the flight models of the cooler have been fabricated and evaluated to verify the capability for ASTRO-F. This paper describes the design of the cooler and the results from verification tests including cooler performance test, thermal vacuum test, vibration test and lifetime test.

The first Japanese infrared astronomical satellite ASTRO-F is scheduled to be launched within a few years. ASTRO-F, equipped with a cooled, 67 cm telescope, is going to carry out an allsky survey at 50-200 micron, and also to make detailed observations of selected targets at 2-200 micron. The main purposes of the ASTRO-F mission are to investigate (1) birth and evolution of galaxies at early universe, (2) birth and evolution of stars, and (3) the formation process of planetary systems.

A two-stage Stirling cooler has been developed and tested for the infrared astronomical satellite ASTRO-F that is planned to be launched by Japanese M-V rocket in 2005. ASTRO-F has a hybrid cryogenic system that is a combination of superfluid liquid helium and two-stage Stirling coolers. The cooler has a new linear-ball-bearing system for the piston-supporting structure in a compressor. The linear-ball-bearing supporting system achieves the piston clearance seal, the long piston-stroke operation and the low frequency operation. The typical cooling power is 0.2W at 20 K and the total input power to the compressor and the cold head is below 90 W. The engineering, the prototype and the flight models of the cooler have been fabricated and evaluated to verify the capability for ASTRO-F. This paper describes the design of the cooler and the results from verification tests including cooler performance test, thermal vacuum test, vibration test and lifetime test.