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{{Infobox spaceflight
{{Infobox spaceflight
| name = Orbiting Astronomical Observatory 2
| name = Orbiting Astronomical Observatory 2
| image =
| image = Orbiting Astronomical Observatory 2.jpg
| image_caption = 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.
| image_caption =
| insignia =
| insignia =


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| launch_contractor =
| launch_contractor =


| last_contact = {{end-date|January 1973}}
| disposal_type = Telescope issues
| deactivated = {{end-date|February 1973}}<ref>{{cite web |title=NASA's First Stellar Observatory, OAO 2, Turns 50 |date=11 December 2018 |url=https://www.nasa.gov/feature/goddard/2018/nasa-s-first-stellar-observatory-oao-2-turns-50 |publisher=NASA |access-date=19 March 2023}}</ref>
| decay_date =
| decay_date =


| orbit_epoch = 6 January 1969<ref>{{cite web|url=http://www.planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|accessdate=12 October 2013}}</ref>
| orbit_epoch = 6 January 1969<ref>{{cite web|url=http://www.planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=12 October 2013}}</ref>
| orbit_reference = [[geocentric orbit|Geocentric]]
| orbit_reference = [[geocentric orbit|Geocentric]]
| orbit_regime = [[low Earth orbit|Low Earth]]
| orbit_regime = [[low Earth orbit|Low Earth]]
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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.<ref name=joseph>{{cite book|author=Joseph A. Angelo|title=Spacecraft for Astronomy|url=https://books.google.com/books?id=y8BMepjeciEC&pg=PA20|year=2014|publisher=Infobase Publishing|isbn=978-1-4381-0896-4|page=20}}</ref> An [[Atlas-Centaur]] rocket launched it into a nearly circular {{convert|750|km|adj=on}} altitude Earth orbit.<ref>[http://space.skyrocket.de/doc_sdat/oao-2.htm Gunter – OAO-2]</ref> Data was collected in ultraviolet on many sources including comets, planets, and galaxies.<ref name=joseph/><ref name=o2/> It had two major instrument sets facing in opposite directions; the Smithsonian Astrophysical Observatory (SAO) and the Wisconsin Experiment Package (WEP).<ref name=o2>[http://www.sal.wisc.edu/~meade/OAO/ Orbiting Astronomical Observatory OAO-2]</ref> One discovery was large halos of hydrogen gas around comets,<ref name=o2/> and it also observed [[FH Serpentis|Nova Serpentis]], which was a nova discovered in 1970.<ref name=joseph/>
The '''Orbiting Astronomical Observatory 2''' ('''OAO-2''', nicknamed '''''Stargazer''''') was a space observatory launched on December 7, 1968.<ref name=joseph>[http://books.google.com/books?id=y8BMepjeciEC&pg=PA20&lpg=PA20&dq=stargazer+oao-2&source=bl&ots=_48qTuQ3NN&sig=tbYK9Cxs6AnDsIBT3rwZydykQYg&hl=en&sa=X&ei=TUpYUverJIen4AO5uoCABw&ved=0CEIQ6AEwAw#v=onepage&q=stargazer%20oao-2&f=false Joseph A. Angelo - Spacecraft for Astronomy (2009) - Page 20] (Google Books)</ref>
⚫
An [[Atlas-Centaur]] rocket launched it into a nearly circular {{convert|750|km}} altitude Earth orbit.<ref>[http://space.skyrocket.de/doc_sdat/oao-2.htm Gunter - OAO-2]</ref> Data was collected in ultraviolet on many sources including comets, planets, and galaxies.<ref name=joseph/><ref name=o2/> It had two major instrument sets facing in opposite directions; the Smithsonian Astrophysical Observatory (SAO) and the Wisconsin Experiment Package (WEP).<ref name=o2>[http://www.sal.wisc.edu/~meade/OAO/ Orbiting Astronomical Observatory OAO-2]</ref> One discovery was large halos of hydrogen gas around comets,<ref name=o2/> and it also observed [[Nova Serpentis|FH Serpentis]].<ref name=joseph/>


==Celescope: Smithsonian Astrophysical Observatory==
The Smithsonian Astrophysical Observatory, also called Celescope, had four 12 inch Schwarzschild telescopes that fed into Uvicons.<ref name=sao>[http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1968-110A-01 High-Resolution Telescopes]</ref> Various filters, photocathodes, and electronics aided in collecting data in several ultraviolet light passbands.<ref name=sao/> The experiment was completed in April 1970.<ref name=sao/> By the time it finished about 10 percent of the sky was observed.<ref name=sao/>
{{anchor|Celescope|Smithsonian Astrophysical Observatory|SAO|Uvicon}}
The Smithsonian Astrophysical Observatory, also called Celescope, had four 12 inch (30.5&nbsp;cm) Schwarzschild telescopes that fed into Uvicons.<ref name=sao>[https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1968-110A-01 High-Resolution Telescopes]</ref> The Uvicon was an ultra-violet light detector based on the Westinghouse [[Vidicon]].<ref name="Detector, Uvicon, Celescope">{{Cite news|url=https://airandspace.si.edu/collection-objects/detector-uvicon-celescope-1|title=Detector, Uvicon, Celescope|date=2016-11-24|work=National Air and Space Museum|access-date=2018-01-24|language=en}}</ref> Ultraviolet light was converted into [[electron]]s which were in turn converted to a voltage as those electrons hit the detection area of the tube.<ref>{{cite web |url=https://airandspace.si.edu/collection-objects/detector-uvicon-celescope-1 |title=Detector, Uvicon, Celescope {{!}} National Air and Space Museum |website=airandspace.si.edu |url-status=dead |archive-url=https://web.archive.org/web/20180125015147/https://airandspace.si.edu/collection-objects/detector-uvicon-celescope-1 |archive-date=2018-01-25}} </ref> There has been a Uvicon in the collection of the [[Smithsonian Institution]] since 1973.<ref name="Detector, Uvicon, Celescope"/>


Various filters, [[photocathode]]s, and electronics aided in collecting data in several [[Ultraviolet|ultraviolet light]] [[passband]]s.<ref name=sao/> The detectors showed a gradual loss of sensitivity<ref name="nasa-goddard-feature"></ref> and the experiment was turned off in April 1970.<ref name=sao/> By the time it finished about 10 percent of the sky was observed<ref name=sao/> resulting in a catalog of 5,068 UV stars.<ref name="nasa-goddard-feature"></ref>
⚫
The Wisconsin Experiment Package had eleven different telescopes for ultraviolet observations.<ref name=wep>[http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1968-110A-02 Wisconsin Experiment Package]</ref> For example, there was a photoelectric photometer fed by a 16 inch telescope with a six-position filter wheel.<ref name=wep/> WEP observed over 1200 targets in ultraviolet light before the mission ended in early 1973.<ref name=o2/>


== Wisconsin Experiment Package ==
{{-}}
{{anchor|Wisconsin Experiment Package|WEP}}
⚫
The Wisconsin Experiment Package had seven different telescopes for ultraviolet observations.<ref name=wep>[https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1968-110A-02 Wisconsin Experiment Package]</ref> For example, there was a nebular photoelectric photometer fed by a 16-inch (40.64&nbsp;cm)<!--google convert--> telescope with a six-position filter wheel<ref name=wep/> that unfortunately failed a few weeks after launch.<ref name="nasa-goddard-feature"></ref>

Construction was supervised by [[Arthur Code]] of the [[University of Wisconsin-Madison]]. <ref name="nasa-goddard-feature">{{cite web |last1=Reddy |first1=Francis |title=NASA's First Stellar Observatory, OAO 2, Turns 50 |url=https://www.nasa.gov/feature/goddard/2018/nasa-s-first-stellar-observatory-oao-2-turns-50 |website=NASA.gov |access-date=7 January 2023 |date=11 Dec 2018}}</ref> WEP observed over 1200 targets in ultraviolet light before the mission ended in early 1973.<ref name=o2/>

== 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 [[Extinction_(astronomy)#The_2175-angstrom_feature|the 2175-angstrom bump]], an increase in UV absorption at that wavelength that is still not fully explained.<ref name="nasa-goddard-feature"></ref>

== Spacecraft bus ==
The observatory was built in the shape of an [[octagonal prism]]. It measured about {{convert|10|by|7|ft|abbr=on}} and weighed {{convert|4400|lb|abbr=on}}.<ref>{{Cite web|url=https://draperspacetelescopes.weebly.com/oao-2.html|title=OAO-2|website=Space Based Telescopes|access-date=2018-10-25}}</ref>{{-}}


==See also==
==See also==
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==External links==
==External links==
* [http://adsabs.harvard.edu/abs/1978ApJ...223..185M OAO 2 observations of the Alpha Persei cluster]
* [http://adsabs.harvard.edu/abs/1978ApJ...223..185M OAO 2 observations of the Alpha Persei cluster]
*[http://www.sal.wisc.edu/OAO/ OAO-2 Info and pics]

*[https://www.nasa.gov/feature/goddard/2018/nasa-s-first-stellar-observatory-oao-2-turns-50 50th Anniversary Overview of OAO-2 including video]
{{Space observatories}}
{{Space observatories}}
{{Orbital launches in 1968}}
{{Orbital launches in 1968}}
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[[Category:Spacecraft launched in 1968]]
[[Category:Spacecraft launched in 1968]]



{{observatory-stub}}
{{US-spacecraft-stub}}
{{US-spacecraft-stub}}

Latest revision as of 05:52, 2 October 2023

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 typeAstronomy
OperatorNASA
COSPAR ID1968-110A Edit this at Wikidata
SATCAT no.3597
Spacecraft properties
ManufacturerGrumman
Dry mass2,012 kilograms (4,436 lb)
Start of mission
Launch date7 December 1968, 08:40:09 (1968-12-07UTC08:40:09) UTC
RocketAtlas SLV-3C Centaur-D
Launch siteCape Canaveral LC-36B
End of mission
DisposalTelescope issues
DeactivatedFebruary 1973 (1973-03)[1]
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Perigee altitude768 kilometres (477 mi)
Apogee altitude777 kilometres (483 mi)
Inclination35.0 degrees
Period100.30 minutes
Epoch6 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]

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

External links[edit]


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