Hubble Space Telescope (HST)

Most sophisticated optical observatory ever placed into orbit around Earth. Because it is above Earth's obscuring atmosphere, it can obtain images much brighter, clearer, and more detailed than ground-based telescopes can. Named for Edwin Hubble, it was built under NASA supervision and deployed on a 1990 space-shuttle mission. The reflector telescope's mirror optics gather light from celestial objects and direct it to an array of cameras and spectrographs (see spectroscopy). A defect in the primary mirror initially caused it to produce fuzzy images; in 1993 another shuttle mission corrected this and other problems. Subsequent missions to the HST have been for maintenance, repairs, and instrument upgrades.

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