PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY PHILIPPE PLAILLY / SCIENCE PHOTO LIBRARY
HESS gamma ray telescope mirror tests. Technicians testing mirrors on a telescope in the HESS (High Energy Stereoscopic System) array, located in Namibia. This array uses four of these Imaging Atmospheric Cherenkov Telescopes (IACTs), which detect the flashes of Cherenkov radiation produced as high-energy gamma rays and cosmic rays hit the Earth's atmosphere. The HESS array is used to investigate gamma ray sources such as supernova remnants and pulsars. The telescopes use hundreds of mirrors (round), each 60 centimetres in diameter and made of aluminised glass with a silica coating. The mirrors must meet a high reflectivity standard The HESS array has been operational since December 2003. Photographed in January 2006.
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