Thermal Design of SPICA cryogenic cooling system

This paper presents a thermal design of a cryogenic cooling system for the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), which is an infrared astronomy mission with a 2.5-m telescope. SPICA is a joint space mission between ESA and JAXA and was one of the three candidates for the ESA's Cosmic Vision Medium Class M5 mission. One of the challenging tasks of SPICA is to cool the telescope and all instruments to cryogenic temperature, below 8 K, for highly sensitive, high-resolution observations. Two possible configurations, the vertical and the horizontal ones, were proposed for SPICA, and the vertical configuration was chosen mainly from system points of view. This paper discusses the potential difficulties in thermal design with particular emphasis on the vertical configuration compared to the horizontal configuration. We show the latest thermal design and the steady-state thermal analysis results especially for the vertical configuration.