NASA’s OAO (Orbiting Astronomical Observatory) program was a series of four satellites that launched between 1966 and 1972, two of which were successful. These missions included OAO 2 (Stargazer) and OAO 3 (Copernicus), the direct ancestors of Hubble, Chandra, Swift, and many other astronomy satellites.

past Mission


Space telescope

First Launch

April 8, 1966



last launch

Aug. 21, 1972

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OAO artist's concept
An artist's concept of OAO 2, nicknamed Stargazer, in orbit around Earth.
Credit: NASA
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