From ESO: “VLT’s New Laser Launchers Arrive at ESO”
22 February 2012
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“Four special telescopes to fire laser beams high into the atmosphere to create artificial stars have been delivered to ESO. These are vital components of the Four Laser Guide Star Facility (4LGSF) for ESO’s Very Large Telescope (VLT) that were developed by the Netherlands Organisation for Applied Scientific Research (TNO).
The 4LGSF is part of the next-generation adaptive optics system that will be installed on the VLT’s 4th Unit Telescope Yepun in 2013. Composed of four powerful 20-watt lasers, it will help the VLT correct the image distortion caused by turbulence in the air.
Telescopes usually collect light coming from the sky and focus it into an instrument. However, the new components send light in the opposite direction. These ‘launchers’, are used to project the lasers into the sky to create brilliant points of light. The laser beams excite a layer of sodium atoms at an altitude of 90 kilometres in the atmosphere and make them glow. These glowing spots act as an artificial guide star which can be positioned at will in the sky, so astronomers are not restricted to observations close to a sufficiently bright natural guide star.”
See the full article here with links to further information.
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ALMA Atacama Large Millimeter/submillimeter Array
ESO, the European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.