AN ANALYSIS OF 50mK AND 300mK CRYOGENIC ENVIRONMENTS FOR FUTURE ESA SCIENCE MISSIONS

Abstract

A number of future European Space Agency (ESA), science missions may require detector cooling to sub-Kelvin temperatures. One such mission is the X-ray Evolving Universe Spectroscopy (XEUS), mission, which is a candidate for the ESA Cosmic Vision 2015-2025 plan, following XMM-Newton and Chandra. The Detector Spacecraft model payload comprises a passively cooled wide-field camera at 200K, and one of two narrowfield instruments at 300mK and 50mK. As with several other science missions, the required lifetime is at least 5 years, with a 10 year goal, necessitating the use of long-life closed cycle cooling systems. Under contract to ESA, Astrium has worked with the Mullard Space Science Laboratory (MSSL), Rutherford Appleton Laboratory (RAL), and CEA-SBT, to propose a payload accommodation design for XEUS capable of meeting the demanding requirements. Our baseline consists of a two stage Adiabatic Demagnetization Refrigerator (ADR), at 50mK, and a helium sorption cooler at 300mK. Each system will be pre-cooled by a closed cycle J-T system, similar to Planck, at 2.5K or 4K, which itself will be precooled by a two-stage Stirling cycle cooler, at 17K or 18K. This paper describes the mission, and discusses the cryogenic architectures in depth.