Editing Great Observatories program (section)

== Great Observatories ==
=== Hubble Space Telescope ===
[[Image:Hubble Space Telescope (27946391011).jpg|thumb|Hubble Space Telescope]]

{{Main|Hubble Space Telescope}}

The history of the Hubble Space Telescope can be traced back to 1946, when the [[astronomer]] [[Lyman Spitzer]] wrote the paper ''Astronomical advantages of an extraterrestrial observatory''.<ref>Spitzer, L., ''REPORT TO PROJECT RAND: Astronomical Advantages of an Extra-Terrestrial Observatory'', reprinted in ''Astronomy Quarterly'' volume 7, p. 131, 1990</ref> Spitzer devoted much of his career to pushing for a space telescope.

The 1966–1972 [[Orbiting Astronomical Observatory]] missions demonstrated the important role space-based observations could play in astronomy. In 1968, NASA developed firm plans for a space-based [[reflecting telescope]] with a 3-meter mirror, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979.<ref>Spitzer, Lyman S (1979), "History of the Space Telescope", ''Quarterly Journal of the Royal Astronomical Society'', v. 20, p. 29</ref> Congress eventually approved funding of US$36 million for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. During the early 1980s, the telescope was named after [[Edwin Hubble]].

Hubble was originally intended to be retrieved and returned to [[Earth]] by the [[Space Shuttle]], but the retrieval plan was later abandoned. On 31 October 2006, [[List of administrators and deputy administrators of NASA|NASA Administrator]] [[Michael D. Griffin]] gave the go-ahead for a final refurbishment mission. The 11-day [[STS-125]] mission by [[Space Shuttle Atlantis|Space Shuttle ''Atlantis'']], launched on 11 May 2009,<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2008/may/HQ_08133_Shuttle_target_dates.html|title=NASA Updates Space Shuttle Target Launch Dates|publisher=NASA|access-date=2008-05-22|archive-date=8 May 2017|archive-url=https://web.archive.org/web/20170508183104/https://www.nasa.gov/home/hqnews/2008/may/HQ_08133_Shuttle_target_dates.html|url-status=dead}}</ref> installed fresh batteries, replaced all gyroscopes, replaced a command computer, fixed several instruments, and installed the [[Wide Field Camera 3]] and the [[Cosmic Origins Spectrograph]].<ref name="Green Light">{{cite news|url=http://www.nbcnews.com/id/15489217|archive-url=https://web.archive.org/web/20131104010540/http://www.nbcnews.com/id/15489217/|url-status=dead|archive-date=4 November 2013|title=NASA gives green light to Hubble rescue|first=Alan|last=Boyle|publisher=NBC News|date=2006-10-31|access-date=2007-01-10}}</ref>

=== Compton Gamma Ray Observatory ===
[[File:CGRO s37-96-010.jpg|thumb|Compton Gamma Ray Observatory]]

{{Main|Compton Gamma Ray Observatory}}

Gamma rays had been examined above the atmosphere by several early space missions. During its [[HEAO Program|High Energy Astronomy Observatory Program]] in 1977, NASA announced plans to build a "great observatory" for [[gamma-ray astronomy]]. The Gamma Ray Observatory (GRO), renamed [[Compton Gamma-Ray Observatory]] (CGRO), was designed to take advantage of the major advances in detector technology during the 1980s. Following 14 years of effort, the CGRO was launched on 5 April 1991.<ref>{{cite web|url=http://heasarc.gsfc.nasa.gov/docs/cgro/epo/brochures/compton/bro5.html|title=Gamma-Ray Astronomy in the Compton Era: The Instruments|access-date=2007-12-07|work=Gamma-Ray Astronomy in the Compton Era|publisher=NASA (GSFC)| archive-url = https://web.archive.org/web/20090224125500/http://heasarc.gsfc.nasa.gov/docs/cgro/epo/brochures/compton/bro5.html | archive-date=2009-02-24| url-status=dead}} {{PD-notice}}</ref> One of the three [[gyroscope]]s on the Compton Gamma Ray Observatory failed in December 1999. Although the observatory was fully functional with two gyroscopes, NASA judged that failure of a second gyroscope would result in inability to control the satellite during its eventual return to Earth due to orbital decay. NASA chose instead to preemptively de-orbit Compton on 4 June 2000.<ref>{{cite web |url=https://spaceflightnow.com/cgrodeorbit/index.html|title=NASA space telescope heads for fiery crash into Pacific|first=William|last=Harwood|publisher=Spaceflight Now|access-date=2020-02-02}}</ref> Parts that survived reentry splashed into the [[Pacific Ocean]].

=== Chandra X-ray Observatory ===
[[File:Chandra_artist_illustration.jpg|thumb|Chandra X-ray Observatory]]

{{Main|Chandra X-ray Observatory}}

In 1976 the [[Chandra X-ray Observatory]] (called AXAF at the time) was proposed to NASA by [[Riccardo Giacconi]] and [[Harvey Tananbaum]]. Preliminary work began the following year at [[Marshall Space Flight Center]] (MSFC) and the [[Smithsonian Astrophysical Observatory]] (SAO). In the meantime, in 1978, NASA launched the first imaging X-ray telescope, [[Einstein Observatory]] (HEAO-2), into orbit. Work continued on the Chandra project through the 1980s and 1990s. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments.  Chandra's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point. This eliminated the possibility of improvement or repair by the [[Space Shuttle program|Space Shuttle]] but put the observatory above the Earth's [[Van Allen radiation belt|radiation belts]] for most of its orbit.

=== Spitzer Space Telescope ===
[[File:SIRTF_downlink.jpg|thumb|Spitzer points its high-gain antenna towards the Earth.]]

{{Main|Spitzer Space Telescope}}

By the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of [[atmosphere of Earth]]. Most of the early concepts, envisioned repeated flights aboard the NASA Space Shuttle. This approach was developed in an era when the Shuttle program was presumed to be capable of supporting weekly flights of up to 30 days duration. In 1979, a National Research Council of the [[United States National Academy of Sciences|National Academy of Sciences]] report, ''A Strategy for Space Astronomy and Astrophysics for the 1980s'', identified a ''Shuttle Infrared Telescope Facility'' (SIRTF) as "one of two major astrophysics facilities [to be developed] for [[Spacelab]]," a Shuttle-borne platform.

The launch of the [[Infrared Astronomical Satellite]], an Explorer-class satellite designed to conduct the first [[infrared]] survey of the sky led to anticipation of an instrument using new infrared detector technology. By September 1983, NASA was considering the "possibility of a long duration [free-flyer] SIRTF mission". The 1985 [[STS-51-F|Spacelab-2]] flight aboard [[STS-51-F]] confirmed the Shuttle environment was not well suited to an onboard infrared telescope, and a free-flying design was better. The first word of the name was changed from ''Shuttle'' so it would be called the Space Infrared Telescope Facility.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/spitzer/infrared/index.html|title=Studying the Universe in Infrared|access-date=2007-12-08|last=Watanabe|first=Susan|date=2007-11-22|publisher=NASA|archive-date=7 July 2019|archive-url=https://web.archive.org/web/20190707072050/https://www.nasa.gov/mission_pages/spitzer/infrared/index.html|url-status=dead}} {{PD-notice}}</ref><ref>{{cite web|last=Kwok|first=Johnny|title=Finding a Way: The Spitzer Space Telescope Story|work=Academy Sharing Knowledge|publisher=NASA|date=Fall 2006 |url=http://appel.nasa.gov/ask/issues/25/25s_finding.php|access-date =2007-12-09|url-status=dead|archive-url=https://web.archive.org/web/20070908000438/http://appel.nasa.gov/ask/issues/25/25s_finding.php|archive-date=2007-09-08}} {{PD-notice}}</ref>

Spitzer was the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to be so launched, but after the [[STS-51L|''Challenger'' disaster]], the [[Centaur (rocket stage)|Centaur]] [[Liquid hydrogen|LH2]]/[[Liquid oxygen|LOX]] [[Multistage rocket|upper stage]] that would have been required to push it into a [[heliocentric orbit]] was banned from Shuttle use. [[Titan (rocket family)|Titan]] and [[Atlas (rocket family)|Atlas]] launch vehicles were canceled for cost reasons. After redesign and lightening, it was launched in 2003 by a [[Delta II]] [[launch vehicle]] instead. It was called the [[Spitzer Space Telescope|Space Infrared Telescope Facility]] (SIRTF) before launch. The telescope was deactivated when operations ended on 30 January 2020.