SAM: a facility GLAO instrument

The SOAR Adaptive Module (SAM) will compensate ground-layer atmospheric turbulence, improving image resolution in the visible over a 3'x3' field and increasing light concentration for spectroscopy. Ground layer compensation will be achieved by means of a UV (355nm) laser guide star (LGS), imaged at a nominal distance of 10km from the telescope, coupled to a Shack-Hartmann wave front sensor (WFS) and a bimorph deformable mirror. Unique features of SAM are: access to a collimated space for filters and ADC, two science foci, built-in turbulence simulator, flexibility to operate at LGS distances of 7 to 14 km as well as with natural guide stars (NGS), a novel APD-based two-arm tip-tilt guider, a laser launch telescope with active control on both pointing and beam transfer. We describe the main features of the design, as well as operational aspects. The goal is to produce a simple and reliable ground layer adaptive optics system. The main AO module is now in the integration and testing stage; the real-time software, the WFS, and the tip-tilt guider prototype have been tested. SAM commissioning in NGS mode is expected in 2009; the LGS mode will be completed in 2010.