Edison: a new direction for infrared space astronomy

Previous designs for infrared space observatories assumed that the best method of cooling these systems was a single large tank of liquid helium. Although effective, as demonstrated by the IRAS and, soon, the ISO missions, this technique produces limited lifetime, small telescope aperture, and inflexibility in optical design. More modern spacecraft designs, including the Japanese IRIS and European Edison concepts, instead adopt multiple cooling strategies: radiative, cryogenic, and/or mechanical. This alternative philosophy permits each technique to be applied to the most appropriate task, taking advantage of strengths of each technology and minimizing weaknesses. In this paper we give a brief history of the development of some cooling technologies, emphasizing the advantages of the designs adopted for a pair of possible future infrared space missions, IRIS and Edison. We also briefly discuss negative aspects of the IRAS legacy in infrared spacecraft design and we speculate on what types of missions might follow IRIS and Edison.