Design and Development of a 20K Stirling-Cycle Cooler for FIRST

Abstract

The Far Infra-Red Space Telescope (FIRST) is the 4th Cornerstone mission of the European Space Agency (ESA) ‘Horizon 2000’ space science programme and is designed to offer observational opportunities in the last poorly explored parts of the electromagnetic spectrum, the sub-millimetre and far infra-red. The cryogenic sub-system required for instrument cooling is based upon the use of mechanical coolers to achieve cooling of shields at approximately 65K, 20K and 4K. A further cooler capable of cooling to O.IK is to be provided by the scientific instrument.

This paper describes the design and development of a two stage Stirling cycle cooler to meet the 20K requirements of the FIRST mission. This cooler is used both as a stand alone cooler and as a pre-cooler for a closed cycle Joule-Thomson 4K Cooler.

A cooler of this type has previously been development by RAL and subject to a pre- qualification test programme by MMS under ESA contract, but the criticality of the cryogenic cooling sub-system to the mission is such that ESA have identified the need to prove and qualify the cooler against the FIRST specific requirements before the start of the spacecraft development.

The environmental and performance requirements of the cooler are challenging and the FIRST 20K Cooler includes many features to enhance performance over previous designs.

In making changes due regard has been taken of the need to maintain the heritage gained on other MMS coolers and the cooler has been designed with a high degree of modularity with respect to other MMS Stirling coolers that are in batch manufacture.

In addition to the design of the cooler, this paper describes the design verification process required to ensure that all of the FIRST requirements have been addressed.