The Orbiting Astronomical Observatory 2 (OAO-2, nicknamed Stargazer) was the first successful space telescope (first space telescope being OAO-1, which failed to operate once in orbit), launched on December 7, 1968.[2] An Atlas-Centaur rocket launched it into a nearly circular 750-kilometre (470 mi) altitude Earth orbit.[3] Data was collected in ultraviolet on many sources including comets, planets, and galaxies.[2][4] It had two major instrument sets facing in opposite directions; the Smithsonian Astrophysical Observatory (SAO) and the Wisconsin Experiment Package (WEP).[4] One discovery was large halos of hydrogen gas around comets,[4] and it also observed Nova Serpentis, which was a nova discovered in 1970.[2]

Orbiting Astronomical Observatory 2

Technicians in a clean room at NASA’s Kennedy Space Center in Cape Canaveral, Florida, check out the Orbiting Astronomical Observatory 2 before the mission’s Dec. 7, 1968, launch.
Mission type	Astronomy
Operator	NASA
COSPAR ID	1968-110A
SATCAT no.	3597
Spacecraft properties
Manufacturer	Grumman
Dry mass	2,012 kilograms (4,436 lb)
Start of mission
Launch date	7 December 1968, 08:40:09 (1968-12-07UTC08:40:09) UTC
Rocket	Atlas SLV-3C Centaur-D
Launch site	Cape Canaveral LC-36B
End of mission
Last contact	January 1973 (1973-02)
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee altitude	768 kilometres (477 mi)
Apogee altitude	777 kilometres (483 mi)
Inclination	35.0 degrees
Period	100.30 minutes
Epoch	6 January 1969[1]

Celescope: Smithsonian Astrophysical Observatory

The Smithsonian Astrophysical Observatory, also called Celescope, had four 12 inch (30.5 cm) Schwarzschild telescopes that fed into Uvicons.[5] Various filters, photocathodes, and electronics aided in collecting data in several ultraviolet light passbands.[5] The experiment was completed in April 1970.[5] By the time it finished about 10 percent of the sky was observed.[5] The Uvicon was an ultra-violet light detector based on the Westinghouse Vidicon.[6] Ultraviolet light was converted into electrons which were in-turn converted to a voltage as those electrons hit the detection area of the tube.[7] There has been a Uvicon in the collection of the Smithsonian Institution since 1973.[6]

Wisconsin Experiment Package

The Wisconsin Experiment Package had eleven different telescopes for ultraviolet observations.[8] For example, there was a photoelectric photometer fed by a 16-inch (40.64 cm) telescope with a six-position filter wheel.[8] WEP observed over 1200 targets in ultraviolet light before the mission ended in early 1973.[4]

Spacecraft bus

The observatory was built in the shape of an octagonal prism. It measured about 10 by 7 ft (3.0 by 2.1 m) and weighed 4,400 lb (2,000 kg).[9]

See also

• Orbiting Astronomical Observatory
• Orbiting Solar Observatory

References

External links

• OAO 2 observations of the Alpha Persei cluster
• OAO-2 Info and pics
• 50th Anniversary Overview of OAO-2 including video

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