Optical design and testing of a fast, large aperture, infrared space telescope

An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minimum aperture 2.5 m with an F/1.2 primary and wavelength coverage from 2 to as least 40 microns, and possibly to 100 microns. Compactness, low thermal emission from the optics and structure, diffraction limited imaging at 2 microns, and sensitivity to misalignment aberrations and manufacturing errors were the main considerations for this study. Ray tracing results are presented showing the characteristics of the various designs considered. A preliminary investigation of stray light properties is also given. Special emphasis has been placed on the testing of such a fast primary, and optical systems using a lateral shearing interferometer are described for testing both the primary and the primary/secondary combination.