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15-08-2007
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Sensing the atmosphere above La Palma

Submitter: Ton Schoenmaker
Description: After successful first light of the 20 W laser of the Beam Launch Telescope in May, the team of GLAS (Ground-Layer Adaptive optics System) has succeeded in imaging the returned back-scattered light of the projected artificial star. The movie shows the recorded images on the detector of the Wave Front Sensor. The images were taken with a low-spec test camera and the spots were not fully focussed yet. The frame rate was about 30 Hz with an exposure time of 30 ms. The Beam Launch Telescope was focussed at an altitude of about 14.5 km with a 600 meter range depth set by an optical shutter. The images show the pupil of 4.2 meter mirror (including the central shadow of the secondary mirror) of the William Herschel Telescope with an 8x8 matrix of sub-pupil images. The information in the Shack-Hartmann spots makes it possible to correct the wavefront errors induced by the atmosphere above La Palma. The optics of the Beam Launch Telescope and the Laser Guide Star Wavefront Sensor was designed and (partly) manufactured by ASTRON.
Copyright: Isaac Newton Group of Telescopes, La Palma
 
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