Orbiting Astronomical Observatory
The Orbiting Astronomical Observatory (OAO) was a series of four space telescopes launched by the US space agency NASA between 1966 and 1972 . The first high quality recordings in the ultraviolet range of light are made through these telescopes . Although two missions failed, the two successful satellites - OAO-2 and OAO-3 - attracted a great deal of attention among astronomers, ultimately leading to the Hubble Space Telescope , launched in 1990 .
OAO-1
The first mission was equipped with instruments for observing UV light, X-rays and gamma rays . The start on April 8, 1966 was successful, but a power failure caused the mission to be aborted after only three days. The satellite could not be brought under control and its solar cells could not be extended.
The launch took place with an Atlas rocket and an Agena-D upper level .
OAO-2
The mission called Stargazer , started on December 7, 1968, was successful. The telescope had two sets of instruments mounted on opposite ends of the satellite: four 12-inch telescopes, which analyzed the light in different UV bands, and the "Wisconsin Experiment Package", which included eleven different telescopes UV observations included, including a 16-inch telescope with six different filters.
Stargazer led to a number of important discoveries - including that comets are surrounded by huge clouds of hydrogen , and that novas in the UV range increase in brightness while those in the visible range decrease. Stargazer also observed the Nova FH Serpentis .
OAO-2 and the two later missions were again launched with Atlas launch vehicles, but with a Centaur upper stage .
OAO-B
This mission was equipped with a telescope with a diameter of 97 cm and should have observed less luminous objects in the UV range. However, the satellite never went into orbit: when launched on November 30, 1970, the payload fairing did not separate from the Atlas launcher, and the extra weight prevented the satellite from entering orbit. The Centaur rocket stage and telescope were destroyed upon re-entry into the atmosphere.
OAO-3
The mission called Copernicus was launched on August 21, 1972 and proved to be the most fruitful of all. In a collaboration between NASA and the British Science Research Council , an X-ray detector was built, and Princeton University contributed a UV telescope with a diameter of 80 cm.
Copernicus was used until February 1981. Significant discoveries made with this telescope include the slowly rotating pulsars , which take several minutes to complete one revolution.
