Optical design for Terrestrial Planet Finder

We describe the features of the optical system for the Terrestrial Planet Finder, a space-based, cryogenic (35 K) interferometer for direct detection of Earth-type planets around nearby stars. Interferometric nulling suppresses stellar glare by a factor of several thousand or more, and phase chopping distinguishes planet light from the symmetric background. The mid-infrared (7-20 /spl mu/m) is favorable for detecting planetary emission relative to that from the star, and this spectral region also offers important molecular signatures indicative of key atmospheric gases.