OAO-2

Orbiting Astronomical Observatory 2

Orbiting Astronomical Observatory 2

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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]

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Celescope: Smithsonian Astrophysical Observatory

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

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

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

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

References

  1. [1]
    "NASA's First Stellar Observatory, OAO 2, Turns 50". NASA. 11 December 2018. Retrieved 19 March 2023.
  2. [2]
    McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 12 October 2013.
  3. [3]
    Joseph A. Angelo (2014). Spacecraft for Astronomy. Infobase Publishing. p. 20. ISBN 978-1-4381-0896-4.
  4. [4]
    Gunter – OAO-2
  5. [5]
    Orbiting Astronomical Observatory OAO-2
  6. [6]
    High-Resolution Telescopes
  7. [7]
    "Detector, Uvicon, Celescope". National Air and Space Museum. 2016-11-24. Retrieved 2018-01-24.
  8. [8]
    "Detector, Uvicon, Celescope | National Air and Space Museum". airandspace.si.edu. Archived from the original on 2018-01-25.
  9. [9]
    Reddy, Francis (11 Dec 2018). "NASA's First Stellar Observatory, OAO 2, Turns 50". NASA.gov. Retrieved 7 January 2023.
  10. [10]
    Wisconsin Experiment Package
  11. [11]
    "OAO-2". Space Based Telescopes. Retrieved 2018-10-25.


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