A quasi-three-stage space-qualified passive radiator system for cooling a detector array to −150°C

Abstract

The necessity for cooling to temperatures less than −100°C has become increasingly common as the sensitivity of detectors used in space has improved. This temperature range is outside the reach of a single radiator, so active coolers or more complex multiple radiator systems are needed. This paper discusses the advantages of using a multiple passive radiator system and explains the rationale behind the design of such a radiator system. To show how a multiple radiator system can be used in practice, the experience gained from producing the radiator system for the EPIC MOS camera head on the XMM spacecraft. This radiator subsystem consists of three conical radiators, forming a quasi-three-stage radiator system, which is completely removable from the camera head. The significant advantages of using conical radiators are explained, and the detailed thermal model and testing of this radiator system are presented. The validity of this design was demonstrated during a thermal balance test of the full camera head that achieved a charge coupled device (CCD) temperature of −150°C. Finally, the sensitivity of the radiator design to degradation of the thermal finishes and the ways in which the radiator system could have been optimized are discussed.