Development of mechanical cryocoolers for the Japanese IR space telescope SPICA

The next Japanese infrared space telescope SPICA features a large 3.5-m-diameter primary mirror and an optical bench cooled to 4.5 K with advanced mechanical cryocoolers and effective radiant cooling instead of using a massive and short-lived cryogen system. To obtain a sufficient thermal design margin for the cryogenic system, cryocoolers for 20 K, 4 K, and 1 K have been modified for higher reliability and higher cooling power. The latest results show that all mechanical cryocoolers achieve sufficient cooling capacity for the cooling requirement of the telescope and detectors on the optical bench at the beginning of life. Consequently, the feasibility of the SPICA cryogenic system concept was validated, while attempts to achieve higher reliability, higher cooling capacity and less vibration have continued for stable operations at the end of life.