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Tim Butterley |
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Slope Detection and Ranging (SLODAR) is a crossed-beams atmospheric turbulence profiling technique in which the strength and altitude of turbulence is retrieved from the cross-correlation of wavefront slopes from a Shack-Hartmann wavefront sensor observing two stars. When implemented on a small telescope the technique is suitable for monitoring the turbulence profile at an astronomical site, providing information that is essential for predicting the performance of an adaptive optics system. The first small-telescope SLODAR was field-tested at CTIO in December 2004 before being installed at Paranal. Since then, it and two other similar systems have collected ground layer turbulence data at Paranal, Mauna Kea, SAAO and La Palma. I will describe the development of these instruments and summarize their key results. I will go on to present details of the first fully robotic SLODAR system which was commissioned at Paranal in March 2011. |