Portal:Astronomy/Picture/18 August 2005
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![](http://upload.wikimedia.org/wikipedia/commons/7/74/OAO-3_in_the_clean_room.jpg)
The Orbiting Astronomical Observatory satellites were a series of four space observatories launched by NASA between 1966 and 1972. The OAO program demonstrated the viability of space-based observatories and paved the way for the development of the Hubble Space Telescope. This image shows OAO-3 being prepared for launch in a clean room.