Ground Layer Adaptive Optics and advancements in Laser Tomography at the 6.5m MMT telescope

In this paper, we report the performance achieved by the multi laser guide star (LGS) implemented at the 6.5 m MMT telescope operating in Ground Layer Adaptive Optics mode. The system uses five range-gated and dynamically refocused Rayleigh laser beacons to sense the atmospheric wavefront aberration. Corrections are then applied to the wavefront using the 336-actuator adaptive secondary mirror of the telescope. So far, the system has demonstrated successful control of ground-layer aberration over a field of view substantially wider than is delivered by conventional adaptive optics. We report a reduction in the width of the on-axis point-spread function from 1.07" to <0.2" in H band. Finally, we also describe the status of the development of least-squares Laser Tomography AO mode for the MMT laser system. In this case the reconstructor is obtained using simultaneous measurements of the wavefronts from the LGS and an additional natural guide star.