Reflections on a cosmic camera
7 November 2001
A camera photographs a telescope mirror, reflecting not one camera but two! The segmented mirror here forms part of one of the detectors for the Pierre Auger Observatory - an international project* to build two giant arrays to monitor the highest energy cosmic rays. The first array is being built in the Sourthern Hemsiphere at Pampa Amarilla near Malargüe in Argentina's Mendoza Province. When complete it will consist of 1600 particle detectors covering an area of 3000 square kilometres, together with telescopes to detect fluoresence in the atmosphere caused by the large showers of high-energy particles produced by the most energetic cosmic rays. On clear, dark moonless nights the telescopes will pick up the glow from the cosmic-ray showers, relecting the light via a segmented mirror onto an array of light-sensitive phototubes - in effect, the telescope's camera. In this image the back of the camera is visible in the lower left corner, but its front can be seen reflected in the mirror. Just to the left of the photographer's reflection some of the hexagonal phototubes are visible - there are 440 for each 30 degree segment! The mirrors, installed in Argentina, were made in the Czech Republic. The fluorescence detector recorded its first showers on 23 May 2001, immediately after switch on.
* The Pierre Auger Observatory - named after Pierre Auger who discovered ultra high energy cosmic ray showers - involves 250 scientists from 19 countries, with spokesmen are from the US and the UK.
Credit: Photo Library of the Pierre Auger Observatory
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