Orbiting Astronomical Observatory 2
Names | OAO-A2, OAO2 |
---|---|
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 | UTC
Rocket | Atlas SLV-3C Centaur-D |
Launch site | Cape Canaveral LC-36B |
End of mission | |
Disposal | Telescope issues |
Deactivated | February 1973[1] |
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[2] |
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.[3] An Atlas-Centaur rocket launched it into a nearly circular 750-kilometre (470 mi) altitude Earth orbit.[4] Data was collected in ultraviolet on many sources including comets, planets, and galaxies.[3][5] It had two major instrument sets facing in opposite directions; the Smithsonian Astrophysical Observatory (SAO) and the Wisconsin Experiment Package (WEP).[5] One discovery was large halos of hydrogen gas around comets,[5] and it also observed Nova Serpentis, which was a nova discovered in 1970.[3]
Celescope: Smithsonian Astrophysical Observatory
[edit]The Smithsonian Astrophysical Observatory, also called Celescope, had four 12 inch (30.5 cm) Schwarzschild telescopes that fed into Uvicons.[6] The Uvicon was an ultra-violet light detector based on the Westinghouse Vidicon.[7] Ultraviolet light was converted into electrons which were in turn converted to a voltage as those electrons hit the detection area of the tube.[8] There has been a Uvicon in the collection of the Smithsonian Institution since 1973.[7]
Various filters, photocathodes, and electronics aided in collecting data in several ultraviolet light passbands.[6] The detectors showed a gradual loss of sensitivity[9] and the experiment was turned off in April 1970.[6] By the time it finished about 10 percent of the sky was observed[6] resulting in a catalog of 5,068 UV stars.[9]
Wisconsin Experiment Package
[edit]The Wisconsin Experiment Package had seven different telescopes for ultraviolet observations.[10] For example, there was a nebular photoelectric photometer fed by a 16-inch (40.64 cm) telescope with a six-position filter wheel[10] that unfortunately failed a few weeks after launch.[9]
Construction was supervised by Arthur Code of the University of Wisconsin-Madison. [9] WEP observed over 1200 targets in ultraviolet light before the mission ended in early 1973.[5]
Discoveries
[edit]In addition to the Celescope's catalog of UV stars, the WEP observed comet Tago-Sato-Kosaka and found it to be surrounded by a cloud of hydrogen, confirming that the comet was largely made up of water, and detected the 2175-angstrom bump, an increase in UV absorption at that wavelength that is still not fully explained.[9]
Spacecraft bus
[edit]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).[11]
See also
[edit]References
[edit]- ^ "NASA's First Stellar Observatory, OAO 2, Turns 50". NASA. 11 December 2018. Retrieved 19 March 2023.
- ^ McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 12 October 2013.
- ^ a b c Joseph A. Angelo (2014). Spacecraft for Astronomy. Infobase Publishing. p. 20. ISBN 978-1-4381-0896-4.
- ^ Gunter – OAO-2
- ^ a b c d Orbiting Astronomical Observatory OAO-2
- ^ a b c d High-Resolution Telescopes
- ^ a b "Detector, Uvicon, Celescope". National Air and Space Museum. 2016-11-24. Retrieved 2018-01-24.
- ^ "Detector, Uvicon, Celescope | National Air and Space Museum". airandspace.si.edu. Archived from the original on 2018-01-25.
- ^ a b c d e Reddy, Francis (11 Dec 2018). "NASA's First Stellar Observatory, OAO 2, Turns 50". NASA.gov. Retrieved 7 January 2023.
- ^ a b Wisconsin Experiment Package
- ^ "OAO-2". Space Based Telescopes. Retrieved 2018-10-25.
External links
[edit]- OAO 2 observations of the Alpha Persei cluster
- OAO-2 Info and pics
- 50th Anniversary Overview of OAO-2 including video