An infrared zoom for space applications

In this paper we present the basic concept of an instrument with variable input optics, which takes into account the severe constraints imposed by space applications. Up to now such kind of device has never been proposed for any of the major space infrared instruments. In the infrared spectral region, in fact, the use of lenses can severely affect the efficiency of the system and variable optics, using only mirrors, should be the baseline option. In order to show the possible applications of this optical device we describe in some detail the implementation of two different designs of optical zoom on two infrared instruments having different conceptions and objectives, namely a Fourier non-imaging spectrometer and a grating imaging spectrometer. The use of this instrument in many space experiments could have several interesting applications.