Chapter 91 - New generation of cooled infrared space telescopes

Abstract

This chapter reviews a new generation of cooled infrared space telescopes. Observations at mid and far infrared wavelengths require cold space telescopes, the detectors have to be cooled to temperatures 0.1 K < T < 7 K. The first generation of small infrared space telescopes was launched into geocentric orbits and completely cooled with liquid helium. The next generation has much larger telescope mirrors launched warm. Locating these satellites on an earth trailing orbit or in the Lagrange Point 2 (L2), allows stable thermal conditions and radiation cooling of the telescope mirrors down to 40 K. The new infrared missions will address fundamental questions, like the search for the first light in the universe as well as for earth-like planets around other stars. The next generation of space telescopes will be launched with warm instruments, too. After passive cool down, they are further cooled by heat-switch connection to an onboard coolant or by mechanical coolers. Temperatures in the mK range will be achieved by sorption, dilution, and demagnetization coolers. The increase of the telescopes' size from 0.6 m of the first generation to several meters of the new generation was based on light-weight mirrors and actively controlled surfaces of the largest ones.