Orbiting Astronomical Observatory

The Orbiting Astronomical Observatory (OAO) satellites were a series of four American space observatories launched by NASA between 1966 and 1972,{{Cite web |last=Darling |first=David |title=Orbiting Astronomical Observatory |url=https://www.daviddarling.info/encyclopedia/O/OAO.html |access-date=18 August 2024 |website=www.daviddarling.info}} managed by NASA Chief of Astronomy Nancy Grace Roman. These observatories, including the first successful space telescope, provided the first high-quality observations of many objects in ultraviolet light. Although two OAO missions were failures, the success of the other two increased awareness within the astronomical community of the benefits of space-based observations, and led to the instigation of the Hubble Space Telescope.

OAO-1

The first Orbiting Astronomical Observatory was launched successfully on 8 April 1966, carrying instruments to detect ultraviolet, X-ray and gamma ray emission.{{Cite web |title=OAO 1 |url=https://space.skyrocket.de/doc_sdat/oao-1.htm |access-date=18 August 2024 |website=Gunter's Space Page |language=en}} Before the instruments could be activated, a power failure resulted in the termination of the mission after three days. The spacecraft was out of control, so that the solar panels could not be deployed to recharge the batteries that would supply power to the electrical and electronic equipment on board.

OAO-2 ''Stargazer''

Orbiting Astronomical Observatory 2 (OAO-2, nicknamed Stargazer) was launched on 7 December 1968, and carried 11 ultraviolet telescopes.{{Cite web |title=OAO 2 (Stargazer) |url=https://space.skyrocket.de/doc_sdat/oao-2.htm |access-date=18 August 2024 |website=Gunter's Space Page |language=en}} It observed successfully until January 1973, and contributed to many significant astronomical discoveries. Among these were the discovery that comets are surrounded by enormous haloes of hydrogen, several hundred thousand kilometres across, and observations of novae which found that their UV brightness often increased during the decline in their optical brightness.

OAO-B

OAO-B carried a {{convert|38|inch|cm|abbr=on}} ultraviolet telescope, and should have provided spectra of fainter objects than had previously been observable.{{Cite web |title=OAO B (Goddard) |url=https://space.skyrocket.de/doc_sdat/oao-b.htm |access-date=18 August 2024 |website=Gunter's Space Page |language=en}} The satellite was launched on 30 November 1970 with "the largest space telescope ever launched",{{Cite news |date=1 December 1970 |title=U.S. FAILS TO ORBIT LARGE TELESCOPE |url=https://www.nytimes.com/1970/12/01/archives/us-fails-to-orbit-large-telescope-98million-project-ruined-by.html |access-date=18 August 2024 |work=The New York Times |language=en-US |issn=0362-4331}} but never made it into orbit. The payload fairing did not separate properly during ascent and the excess weight of it prevented the Centaur stage from achieving orbital velocity. The Centaur and OAO reentered the atmosphere and broke up, destroying a $98,500,000 project. The disaster was later traced to a flaw in a $100 explosive bolt that failed to fire.{{Cite news |date=13 January 1971 |title=A Faulty Bolt Is Blamed For Failure of Satellite |url=https://www.nytimes.com/1971/01/13/archives/a-faulty-bolt-is-blamed-for-failure-of-satellite.html |access-date=18 August 2024 |work=The New York Times |language=en-US |issn=0362-4331}}

OAO-3 (Copernicus)

File:Flight spare of OAO-3's X-ray mirror.jpg. It is now held in the collections of the Science Museum, London.]]

OAO-3 was launched on 21 August 1972,{{Cite web |title=OAO 3 (Copernicus) |url=https://space.skyrocket.de/doc_sdat/oao-3.htm |access-date=18 August 2024 |website=Gunter's Space Page |language=en}} and proved to be the most successful of the OAO missions. It was a collaborative effort between NASA and the UK's Science Research Council (currently known as the Science and Engineering Research Council).{{Cite web |title=The Copernicus Satellite |url=https://heasarc.gsfc.nasa.gov/docs/copernicus/copernicus.html |access-date=18 August 2024 |website=heasarc.gsfc.nasa.gov}} After its launch, it was named Copernicus to mark the 500th anniversary of the birth of Nicolaus Copernicus in 1473.

Copernicus operated until February 1981, and returned high resolution spectra of hundreds of stars along with extensive X-ray observations.{{Cite web |title=MAST Copernicus |url=https://archive.stsci.edu/copernicus/ |access-date=18 August 2024 |website=archive.stsci.edu}} 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.{{cite web |last1=Reddy |first1=Francis |date=19 August 2022 |title=50 Years Ago, NASA's Copernicus Set the Bar for Space Astronomy |url=https://www.nasa.gov/feature/goddard/2022/50-years-ago-nasa-s-copernicus-set-the-bar-for-space-astronomy |access-date=7 January 2023 |website=NASA.gov}}

Launches

OAO-1: Atlas-Agena D from Launch Complex 12, Cape Canaveral, Florida
OAO-2, OAO-B and OAO-3: Atlas SLV-3C from Launch Complex 36, Cape Canaveral, Florida

In popular culture

In the first season of the alternate history space drama show For All Mankind, a repair mission to an OAO-like satellite was the original objective of the Apollo 25 mission, with an artist's conception of OAO-1 appearing on the mission's emblem.{{citation needed|date=October 2024}}