Orbiting Astronomical Observatory 3

Copernicus or OAO-3 (Orbiting Astronomical Observatory 3), also mentioned as Orbiting Astronomical Observatory-C,^[1][2] was a space telescope intended for ultraviolet and X-ray observation. After its launch, it was named Copernicus to mark the 500th anniversary of the birth of Nicolaus Copernicus in 1473.

Orbiting Astronomical Observatory 3

Orbiting Astronomical Observatory 3 in a clean room before launch.
Names	OAO-3, Copernicus, OAO-C, Orbiting Astronomical Observatory-C, PL-701D
Mission type	Astronomy
Operator	NASA, SERC
COSPAR ID	1972-065A
SATCAT no.	06153
Spacecraft properties
Dry mass	2,204 kilograms (4,859 lb)
Start of mission
Launch date	21 August 1972 (1972-08-21) UTC
Rocket	Atlas SLV-3C Centaur-D
Launch site	Cape Canaveral LC-36B
End of mission
Deactivated	February 1981 (1981-03)
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee altitude	713 kilometres (443 mi)
Apogee altitude	724 kilometres (450 mi)
Inclination	35.0 degrees
Period	99.2 minutes
← OAO-2

Part of the Orbiting Astronomical Observatory program, it was a collaborative effort between NASA and the UK's Science Research Council (currently known as the Science and Engineering Research Council).^[3]

Copernicus collected high-resolution spectra of hundreds of stars, galaxies and planets, remaining in service until February 1981.^[1]

History

At 6:28 a.m. EDT on Aug. 21, 1972, Copernicus lifted off from Complex 36B at Cape Canaveral Air Force Station, Florida.

The OAO-3 satellite, weighing 2,150 kg, was launched on August 21, 1972, by an Atlas SLV-3C from Launch Complex 36, Cape Canaveral, Florida.^[4]

The mission used a new inertial reference unit that was developed by the Massachusetts Institute of Technology.^[5]

Between 1972 and February 1981,^[4] it returned high-resolution spectra of 551 stars along with extensive X-ray observations.^[6] Among the significant discoveries made by Copernicus were the discovery of several long-period pulsars such as X Persei that had rotation times of many minutes instead of the more typical second or less, and confirmation that most of the hydrogen in interstellar gas clouds existed in molecular form.^[5]

Instrumentation

Copernicus carried two instruments:^[5]

• an X-ray detector built by University College London's Mullard Space Science Laboratory;
• an 80 cm UV telescope built by Princeton University under the supervision of Lyman Spitzer.

See also

• Orbiting Astronomical Observatory
• Orbiting Solar Observatory