Development of 1 K-class mechanical cooler for SPICA Original Research Article

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a future mission to launch a large infrared observatory to the second Sun–Earth Lagrangian liberation point (L2) by H-IIA rocket. A unique feature of its cryogenic system is a warm launch system using radiative cooling and closed-cycle mechanical coolers in orbit to cool its detectors and mirrors down to about 4.5 and 1.7 K. The 1 K-class cooler, which consists of a two-stage Stirling cooler and a Joule–Thomson (JT) cooler with 3He as the working fluid, has been developed for cooling the far infrared detectors to 1.7 K. Designed cooling capacity of the cooler is 10 mW at 1.7 K and the total input power to the cooler is about 180 W without driver electronics. This paper describes the preliminary design and the results from preliminary test of the prototype cooler for the 1 K-class cooler.