Edison program: designing the next-generation infrared space observatory

Since 1990 the Edison program has studied designs for large, long-lived IR space telescopes incorporating intensive use of radiative cooling supplemented by mechanical refrigeration. This approach, which is now generally accepted as the most likely route to achieving large aperture and long lifetimes, led to proposals to ESA in 1993 and 1994 for a 1.7m observatory telescope operating at < 20 K as a Medium-sized mission and a Cornerstone, respectively. Extension of these ideas and the application of newer technology now indicate that a Cornerstone budget and an Ariane 5 launcher could accommodate mid- to far-IR telescopes of up to perhaps 3m aperture and/or achieve telescope temperatures of a few K--thereby attaining the full long-wavelength performance of cryogenic missions--in robust designs able to maintain their performance levels (i.e. low optics temperatures) for many years. These designs, too, have potential applications as the individual elements of spatial interferometers, for example, for searching for extrasolar terrestrial planets.