Integration, tests and laboratory performance of SAXO, the VLT-SPHERE extreme AO system


C. Petit(1), T. Fusco(1), J.-F. Sauvage(1), A. Sevin(2), M. Suarez(3), J. Charton(4), P. Baudoz(2), J .-L. Beuzit(4), T. Buey(2), K. Dohlen(5), P. Feautrier(4), E. Fedrigo(3), B. Fleuzry(1), J.-L. Gach(5), N. Hubin(3), M. Kasper(3), D. Mouillet(4), D. Perret(2), P. Puget(4), J.-C. Sinquin(6), C. Soenke(3), F. Wildi(7)


(1) ONERA, (2) LESIA / Observatoire de Paris, (3) ESO, (4) IPAG / Observatoire de Grenoble, (5) LAM / Observatoire de Marseille, (6) CILAS, (7) Observatoire de Genève


Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also one of the most challenging areas in modern astronomy due to the very large contrast between the host star and the planet at very small angular separations. SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe) is a second-generation instrument for the ESO VLT dedicated to this scientific objective. It combines an extreme adaptive optics system, various coronagraphic devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetry capabilities in the visible and near-infrared spectral ranges.

The extreme AO system, SAXO, is the heart of the SPHERE system, providing to the scientific instruments a flat wavefront corrected from all the atmospheric turbulence and internal defects. We will present a status of SAXO assembly integration and performance. The main requirements and system characteristics will be recalled, then each sub system will be individually presented and fully characterized and finally the full AO loop performance will be quantified. It will be demonstrated that SAXO will meet its challenging requirements (more than 90% of SR in H band with a residual jitter lower than 3 milli-arcseconds for average observation conditions on the VLT). Thanks to a coronagraphic analysis of the AO residuals, a detailed comparison between actual and simulated residual intensity profiles will be provided and will help to adjust the expected performance of the SPHERE system on sky, knowing that its first light is foreseen for mid 2012.

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