Far Ultraviolet Spectroscopic Explorer

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Far Ultraviolet Spectroscopic Explorer

(FUSE) A space observatory launched June 1999 as part of NASA's long-term Origins Program. It was developed for NASA by Johns Hopkins University, Baltimore, USA, in collaboration with the space agencies of Canada and France. It was placed into a circular orbit with an altitude of 775 kilometers. The science instrument carried aboard the FUSE spacecraft was the Integrated FUSE spectrograph (IFS), in which ultraviolet light was focused by four mirror segments and dispersed by four corresponding curved gratings allowing the achievement of very high spectral resolution over the operating range of approximately 90–120 nm. An electronic guide camera called the Fine Error Sensor (FES), functioning in the visible part of the spectrum down to the 14th magnitude, provided visual confirmation of where the IFS was being pointed. Computers controlled the targeting mechanism.

FUSE complemented other NASA observatories, revealing new information about the structure and chemical makeup of the Universe. It calculated the ratio of deuterium and the heavier elements to hydrogen in the Universe, and examined other aspects of the chemistry of interstellar and intergalactic space. Among its many discoveries, the satellite detected the immense ‘cobweb’ of helium that has pervaded space since soon after the Big Bang; it confirmed the haloes of hot gas surrounding the Milky Way Galaxy and the neighboring Magellanic Clouds; and it investigated supernova remnants and regions of star formation. In August 2001 it discovered what may be a cloud of millions of comets around the young star Beta Pictoris. Much closer to home, it observed molecular hydrogen in the atmosphere of Mars (a hitherto undetected phenomenon) and discovered molecular nitrogen outside the Solar System for the first time. Although FUSE was originally intended to run for about three years, it received a software upgrade in July 2003 and was still in operation at the beginning of 2005.

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