Hypertelescopes for direct imaging and coronagraphy

Densified-pupil interferometers. also called hypertelescopes, can provide d irect images usable for general imaging and coronagraphy. Their properties can be deduced from a comparison with blazed diffraction gratings. Ground-b ased versions are considered, in the form of 10 km planar telescope arrays or of 5 km spherical arrays comparable to the Arecibo radio-telescope. Step s are taken for tests at Arecibo. Space versions are proposed for detecting extra-solar planets and, in a second step. for resolving these planets and searching photosynthetic bio-markers. (C) 2001 Academie des sciences/Editi ons scientifiques et medicales Elsevier SAS.