Orbiting Solar Observatory

Series of American solar space observatories

The Orbiting Solar Observatory Program was the name of a series of American space telescopes primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully into low Earth orbit by NASA between 1962 and 1975 using Delta rockets. Their primary mission was to observe an 11-year sun spot cycle in UV and X-ray spectra. The initial seven were built by Ball Aerospace, then known as Ball Brothers Research Corporation (BBRC), in Boulder, Colorado. OSO 8 was built by Hughes Space and Communications Company, in Culver City, California.

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