Hypertelescopes and Exo-earth Coronagraphy

RESUME Hypertelescopes, or " multi-aperture densified-pupil imaging optical arrays" can provide direct images with full luminosity at arbitrary aperture dilution . They can be equipped with coronagraphic masks for difficult imaging situations such as the search for exo-Earths at infra-red and visible wavelengths . For detecting faint planets, down to 10 relative intensity, multi-stage coronagraphs now appear feasible, both for telescopes and hypertelescopes. A 37-element hypertelescope has been proposed to NASA for TPF. Because the high-resolution image separates the planet's peak from most of the zodiacal and exozodiacal background, sensitivity is gained with respect to planet detection schemes using a beamsplitter for nulling . For resolving continents, and other details such as the "green spots" , of an exo-Earth at 3 parsecs, a second generation hypertelescope will require more than 100 apertures of 3 m, arrayed as a 100 km diluted aperture .