Far Ultraviolet Spectroscopic Explorer
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2008-06-22T07:49:07Z
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{{Infobox Space telescope
|name = Far Ultraviolet Spectroscopic Explorer (FUSE)
|image = [[Image:FUSE prelaunch crop.jpg|250px|FUSE in a pre-launch clean room]]
|caption = FUSE in a pre-launch [[clean room]]
|organization = [[Johns Hopkins University|Johns Hopkins]] [[Applied Physics Laboratory|APL]]{{\}}[[NASA]]
|major_contractors =
|alt_names = Explorer 77<br/>MIDEX/FUSE<br/>25791 (NORAD ID)<ref name="nssdc-master"/>
|nssdc_id = 1999-035A<ref name="nssdc-master"/>
|location =
|orbit_type = Circular [[low Earth orbit]]
|height = 746 [[Kilometre|km]] (402.8 [[Nautical mile|nmi]]) to 760 km (410.4 nmi){{lower|0.2em|<ref name="n2yo-25791"/>}}
|period = 99.9 minutes<ref name="n2yo-25791"/>
|velocity =
|accel_gravity =
|launch_date = [[June 24]], [[1999]] at 15:44 [[Coordinated Universal Time|UTC]]<ref name="nssdc-launch"/>
|launch_location = [[Cape Canaveral]]<br/>[[Florida]], [[United States|USA]]<ref name="nssdc-launch"/>
|launch_vehicle = [[Delta II|Delta II 7320]]<ref name="nssdc-launch"/>
|mission_length = Three years (design){{lower|0.2em|<ref name="nssdc-master"/>}}<br/>Eight years (actual){{lower|0.2em|<ref name="sr25334"/>}}
|deorbit_date =
|wavelength = 90.5 to 119.5 [[Nanometre|nm]]<ref name="nssdc-master"/>
|mass = 1400 [[Kilogram|kg]] (3086.5 [[Pound (mass)|lb]])<ref name="nssdc-master"/>
|style = Far [[ultraviolet]]<ref name="nssdc-master"/>
|diameter =
|area =
|focal_length =
|coolant =
|website = http://fuse.pha.jhu.edu/
|as_of = September 2007
|stats_ref = <!--
--><ref name="nssdc-master">{{cite web |url=http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1999-035A |title=NSSDC Master Catalog Display: Spacecraft |work=NASA.gov |date=[[2007-05-18]] |accessdate=2007-09-07}}</ref> <!--
--><ref name="nssdc-launch">{{cite web |url=http://nssdc.gsfc.nasa.gov/nmc/tmp/1999-035A-traj.html |title=NSSDC Master Catalog Display: Spacecraft Launch/Orbital Information |work=NASA.gov |date=[[2007-05-18]] |accessdate=2007-09-07}}</ref> <!--
--><ref name="sr25334">{{cite web |url=http://www.spaceref.com/news/viewsr.html?pid=25334 |title=ROSES-07 Amendment 20: Cancel FUSE Legacy Science Program |work=Spaceref.com |author=NASA HQ |date=[[2007-09-06]] |accessdate=2007-09-07}}</ref> <!--
--><ref name="n2yo-25791">{{cite web |url=http://www.n2yo.com/satellite.php?s=25791 |title=FUSE 1 Satellite details |work=N2YO.com |accessdate=2007-09-07}}</ref>
}}
The '''Far Ultraviolet Spectroscopic Explorer''' ('''FUSE''') is a space-based [[telescope]] operated by the [[Johns Hopkins University]] [[Applied Physics Laboratory]]. ''FUSE'' was launched on a [[Delta II]] rocket on [[June 24]], [[1999]], as a part of [[NASA]]'s [[Origins program]]. ''FUSE'' detected light in the far [[ultraviolet]] portion of the electromagnetic spectrum, between 90.5-119.5 [[nanometre]]s, which is mostly unobservable by other telescopes. Its primary mission was to characterize universal [[deuterium]] in an effort to learn about the stellar processing times of deuterium left over from the [[Big Bang]].
''FUSE'' resides in a [[low Earth orbit]], approximately 760 [[kilometre|km]] (410 [[nautical mile|nmi]]) in altitude, with an inclination of 25 degrees and just less than a 100 minute orbital period. Its [[Explorer program|Explorer]] designation is ''Explorer 77''.
On [[July 12]], [[2007]], ''FUSE'''s final [[momentum wheel|reaction wheel]], which is required for accurately pointing a spacecraft, failed and efforts to restart it were unsuccessful. An announcement was made on [[September 6]] that because the fine control needed to perform its mission had been lost, the ''FUSE'' mission would be terminated.<ref name="sr25334"/>
== Optical design ==
Although the original specification was to have a [[Wolter telescope |Wolter]]-type grazing incidence telescope,<ref name="ia7-1">{{cite journal |url=http://adsabs.harvard.edu/abs/1994SPIE.2011...34K |title=Optical design of Lyman/FUSE |journal=Instrumentation in Astronomy VII |first=David A. |last=Content |coauthors=et al |month=July |year=1990 |pages=pp. 943–952 |doi=10.1117/12.19157 |volume=1235}}</ref> the final design of the ''FUSE'' telescope comprises four individual mirrors. Each of the four mirrors is a 39-by-35 [[centimetre|cm]] (15.4-by-13.8 [[inch|in]]) off-axis parabola. Two mirror segments are coated with [[silicon carbide]] for reflectivity at the shortest ultraviolet wavelengths, and two mirror segments are coated with [[lithium fluoride]] over [[aluminum]] that reflects better at longer wavelengths. This optimizes performance over the entire spectral range.<ref name="nssdc-master"/>
Each mirror has a corresponding [[astigmatism]]-corrected, [[holography|holographically]]-ruled [[diffraction grating]], each one on a curved substrate so as to produce four 1.65 [[metre|m]] (5.4 [[foot (unit of length)|ft]]) [[Henry Augustus Rowland|Rowland]] circle [[spectrograph]]s. The dispersed ultraviolet light is detected by two [[microchannel plate detector|microchannel plate]] intensified double delay-line detectors, whose surfaces are curved to match the curvature of the focal plane.<ref name="fuse-aas95">{{cite web |url=http://fuse.pha.jhu.edu/papers/technical/aas95/aas95.html |title=The Far Ultraviolet Spectroscopic Explorer Mission |work=JHU.edu |first=D.J. |last=Sahnow |coauthors=et al |date=[[1995-07-03]] |accessdate=2007-09-07}}</ref>
== Science results ==
Over 400 scientific papers have been written using data from ''FUSE'',<ref name="fuse-pub">{{cite web |url=http://fuse.pha.jhu.edu/~awf/fusepubs/JHU/ |title=FUSE Publications |work=JHU.edu |accessdate=2007-09-07}}</ref> with subjects ranging from cool stars to the intergalactic medium. One of the primary science goals of ''FUSE'' was to study the abundance of deuterium, an isotope of [[hydrogen]]. Because of the large number of atomic absorption and emission lines in the far-ultraviolet, ''FUSE'' enabled many studies of galactic, extragalactic and intergalactic chemistry and chemical evolution.
== References ==
{{reflist}}
== External links ==
* [http://fuse.pha.jhu.edu/ ''FUSE'' website] at Johns Hopkins University
* [http://www2.iap.fr/Fuse/ ''FUSE'' website] at Institut d'Astrophysique de Paris
* [http://archive.stsci.edu/fuse ''FUSE'' archive] at Multimission Archive at STScI (MAST)
{{Space telescopes}}
{{Explorer program}}
[[Category:1999 in space exploration]]
[[Category:2007 disestablishments]]
[[Category:Artificial satellites currently orbiting Earth]]
[[Category:Explorer program]]
[[Category:Space telescopes]]
[[Category:Ultraviolet telescopes]]
[[de:Far Ultraviolet Spectroscopic Explorer]]
[[fr:Télescope spatial FUSE]]
[[zh:远紫外分光探测器]]