A series of NASA astronomy satellites operating mainly in the ultraviolet. The first successful mission, OAO-2, was launched in 1968 December. It carried Celescope, a group of four 0.32-m telescopes, plus several other telescopes for ultraviolet observations. The last of the series, OAO-3, was launched in 1972 and was later named the Copernicus satellite.
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1968-110A NASA information page for OAO 2.
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1972-065A NASA information page for OAO 3.
Subjects: Astronomy and Astrophysics.