X-ray Multi mirror Mission (XMM) is an ESA astronomy spacecraft that carries three 13-meter long, 4.5-meter diameter X-ray telescopes. Since earth's atmosphere blocks out all X-rays, only a telescope in space can detect and study celestial X-ray sources. The XMM-Newton mission is helping scientists to solve a number of cosmic mysteries, ranging from the enigmatic black holes to the origins of the universe itself. Observing time on XMM-Newton is made available to the scientific community, that applies for observational periods on a competitive basis.
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 Reaction Wheel Unit