Construction of a 57m hypertelescope in the southern Alps

Abstract

For information-rich direct images at high resolution, hypertelescopes combine light from a sparse array of many subapertures, using pupil densi cation. Among the possible architectures, the Arecibo-like spherical class has xed mirrors arrayed as elements of a common spherical locus, matching approximately the natural curvature of a crater or valley. A focal gondola suspended on the focal sphere, is tracking the primary star image, and several more can be added for independent observations of di erent sources. Since no delay lines are needed, hundred of mirrors can be used for reaching the theoretical information gain with respect to fewer apertures. The aperture size of such instruments may range from 50 to perhaps 1200m at available terrestrial sites. As an example of their broad science capabilities, we have simulated the resolved and spectro-imaging- of an exoplanet transiting across the disk of its parent star, achievable with adaptive optics. Faint cosmological sources may also become observable if a Laser Guide Star can be tted. We describe the current construction and in situ opto-mechanical testing of a 57m hypertelescope, later expandable to 200 with 100 or more sub-apertures. The preliminary operating experience gained in a year, without stellar fringes yet, indicates the likely feasibility of larger versions at suitable sites. Labeyrie et al., (this conference) discuss an "Extremely Large Hypertelescope" (ELHyT) having 1200m sparse aperture and, at similar cost, a larger collection area and higher limiting magnitude than a 40m ELT.