Orbiting Solar Observatories
  • Series of nine US orbiting observatories mainly meant for solar observation, launched between 1962 and 1975. OSO1 and OSO2 observed mainly solar flares. Confusingly, there were two satellites called OSO3. The first failed to reach orbit but the second was highly successful at observing the Sun in X-ray, ultraviolet, gamma ray and other wavelengths. OSO4 to 8 had similar equipment, although OSO8 made X-ray observations of Milky Way sources as well as of the Sun.

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