No abstract

Abstract.We report the status of ELP-OA (Étoile Laser polychromatique pour l'Optique Adaptative), the full demonstrator which we are building at OHP 1.52m telescope. The goal is to open adaptive optics to the domain of visible wavelengths at large telescopes, which is almost not feasible today because of the tiny isoplanatic patch. ELP-OA relies on the 2-photon excitation of sodium in the mesosphere, through 589 and 569 nm transitions. We use 2 pulsed dye lasers (on loan from CEA) pumped with NdYAGs. The average power at the mesosphere will be 2 × 22W. The twin laser beams are projected to the mesosphere by a 3-aperture interferometer. The backscattered spots in NaI lines at 330, 569 and 589nm are oberved through an adaptive optics at the telescope coudé focus, derived from the ONERA's BOA device. The differential tilt measurement channel is equipped with an EMCCD. We use a correlation algorithm to extract it. From our end to end model we expect tilt Strehl ratios of 35% at 550nm (see Meilard et al in this conference). First lasers launches are planned early 2010, with the full experiment running 2011.