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Orbiting Astronomical Observatories (OAO)


OAO-2 launch

Orbiting Astronautical Observatory
Credits - NASA

Map of Copernicus observations

Credits - NASA

The Orbiting Astronomical Observatories (OAO-1, -2, and -3) were a series of early astronomical satellites launched by the National Aeronautics and Space Administration from 1966 through 1972. Its objectives were to provide astronomical data in the ultraviolet (UV) and x-ray wavelengths.


OAO-1 was successfully launched on April 8, 1966, from Cape Canaveral, but it suffered a battery malfunction and failed 1-1/2 hours into the mission.


OAO-2 was successfully launched on December 7, 1968. It carried 11 telescopes, and performed x-ray, UV, and infrared (IR) observations of stars until February 1973. Its instruments detected a supernova in May 1972, as well as the first UV radiation from the center of the Andromeda Galaxy. It was the heaviest satellite orbited up to that time.


OAO-B, on November 30, 1970, failed to achieve Earth orbit, and fell into the Atlantic.


OAO-3 was successfully launched on August 21, 1972, and was later named Copernicus. It returned data until early 1981 on the birth, death, and life cycles of stars. OAO-3 was a collaborative effort between the United States and Great Britain. The main experiment on board was the 450-kilogram Princeton Experiments Package that included an 80-cm UV telescope, the largest telescope up to that time. It also carried an x-ray astronomy experiment sponsored by the University College of London that studied stellar x-ray sources and x-ray absorption in interstellar space. OAO-3 was used primarily in the study of UV radiation from interstellar gas and dust and from stars near the edges of the Milky Way.