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Darwin (Esa)Darwin is a proposed European Space Agency (ESA) mission designed to directly detect Earth-like planets orbiting nearby stars, and search for evidence of life on these planets. The launch date will be at or after 2014. The current design envisions six telescopes, each 1.5 meters diameter, flying in formation. In addition, two auxiliary spacecraft would be needed, one to combine the light from the six telescopes and measure the resulting optical signal, and one to handle communications with Earth. As well as studying extrasolar planets, the instrument will probably have a general purpose imaging mode which will produce very high resolution (i.e. milliarcsecond) infrared images, allowing detailed study of a variety of astrophysical processes. The planet search would use a nulling interferometer configuration. In this system, phase shifts would be introduced into the six beams, so that light from the central star would suffer destructive interference and cancel itself out. However, light from any orbiting planets would not cancel out, as the planets are offset slightly from the position of the star. This would allow planets to be detected, despite the much brighter signal from the star. For planet detection, the instrument would operate in an imaging mode. To detect an Earth-like planet would require about 10 hours of observation in total, spread out over several months. Once a planet is detected, a more detailed study of its atmosphere would be made by taking an infrared spectrum of the planet. By analysing this spectrum, the chemistry of the atmosphere could be determined, and this could provide evidence for life on the planet. The interferometric version of NASA's Terrestrial Planet Finder mission is very similar in concept to Darwin, as also has very similar scientific aims. Given this, and the technical difficulties inherent in such a project, it seems unlikely that both instruments will be built; a collaborative project is more likely. External Links Darwin (Space IR Interferometry Project) on the internet
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