| PRELIMINARY RESULTS FROM A CLOSED-LOOP ADAPTIVE OPTICS SYSTEM USING A SODIUM LASER GUIDE STAR AT THE MULTIPLE MIRROR TELESCOPE M. Lloyd-Hart, R. Angel, B. Jacobsen, D. Wittman, (2007) | |||||||||||||
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| A 0.5 W beam from a continuous-wave dye laser, tuned to the D 2 resonance of atomic sodium, has been used to generate an artificial guide star by illuminating the mesospheric sodium layer, 90 km above the site of the Multiple Mirror Telescope (MMT). The resonant backscattered light appeared as a source of 1.3 FWHM, equivalent in brightness to a natural star of magnitude 12.5 seen through a standard V filter. This artificial source was used by the MMT adaptive optics system to compensate in real time for atmospherically-induced image motion between the six 1.8 m primary mirrors of the telescope, at correction rates of between 5 and 30 Hz. In related experiments, we have recorded images of the laser return and a coincident natural star using a high-speed CCD speckle camera, in which the six individual beams from the telescope are deliberately separated in the focal plane. From these images we have made the first direct measurements of the ability of the laser guide star to sense correct... | |||||||||||||
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