This paper describes that the feasibility of the next Japanese infrared astronomical SPICA mission is verified in thermal design by numerical analyses and developed technologies. In this advanced cryogenic mission, in order to cool the large primary mirror and focal plane instruments down to 4.5 K for 5 years or longer without cryogen, the mechanical cooling is employed with effective radiant cooling, which compensates the limited cooling capacity of the JT cryocooler for 4.5 K upgraded from that developed for the "JEM/SMILES" mission on the International Space Station. First, thermal design of the telescope is numerically discussed with thermal mathematical models. Some configurations of radiators, shields and solar-array paddles are investigated and compared in technical and mission feasibilities. Next, the development status of the 3He-JT circuit with the Stirling cryocooler for one detector operated at the lowest temperature of 1.7 K is reported. The recent results of experiments give that the breadboard model of the 1.7 K cryocooler successfully exceeds the required cooling capacity of 10mW at 1.7K with small power consumption. Finally, the heat rejection system from those cryocoolers is discussed. As a promising candidate, the loop heat pipe is chosen and suitably designed.

Date Published: 12 October 2004
PDF: 9 pages
Proc. SPIE 5487, Optical, Infrared, and Millimeter Space Telescopes, (12 October 2004); doi: 10.1117/12.551173

Published in SPIE Proceedings Vol. 5487:
Optical, Infrared, and Millimeter Space Telescopes
John C. Mather, Editor(s)