GALEX at the pre-launch tests
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{{Short description|NASA UV space telescope of the Explorer program, operated 2003-2013}} |
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{{other uses}} |
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{{About|the ultraviolet space telescope|the neutrino detector|GALLEX|other uses|GALEX (disambiguation)}} |
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{{Infobox space telescope |
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{{Use American English|date=June 2021}} |
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| name = Galaxy Evolution Explorer (GALEX) |
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{{Use dmy dates|date=June 2021}} |
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| image = [[File:Galex.jpg|250px|Artist's impression of GALEX]] |
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{{Infobox spaceflight |
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| caption = Artist's impression of GALEX |
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| name = Galaxy Evolution Explorer |
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| organization = [[NASA]] / [[Jet Propulsion Laboratory|JPL]] / [[California Institute of Technology|Caltech]] |
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| names_list = Explorer-83<br/>SMEX-7 |
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| major_contractors = [[Orbital Sciences Corporation]] |
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| image = GALEX spacecraft model.png |
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| image_caption = GALEX spacecraft |
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| image_size = 300px |
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| orbit_type = Near-circular |
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| mission_type = [[Ultraviolet astronomy]] |
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| height = {{convert|697|km}} |
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| operator = [[NASA]]{{\}}[[Jet Propulsion Laboratory|JPL]] (2003-2012)<br/>[[California Institute of Technology|Caltech]] (2012-2013) |
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| period = |
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| COSPAR_ID = 2003-017A |
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| SATCAT = 27783 |
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| website = https://www.galex.caltech.edu/ |
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| launch_date = 2003-04-28 11:59:54 [[Coordinated Universal Time|UTC]] |
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| mission_duration = 29 months (planned) <ref name="Display"/><br/>{{time interval|28 April 2003|28 June 2013|show=ym|sep=,}} (achieved) <ref name="JPL"/><ref name="Decommission"/> |
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| launch_location = ~ 60 km offshore from<br>[[Cape Canaveral Air Force Station]] |
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| launch_vehicle = [[Lockheed L-1011|L-1011 Stargazer]] / [[Pegasus XL]] |
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| spacecraft = Explorer LXXXIII |
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| mission_length = |
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| spacecraft_type = Galaxy Evolution Explorer |
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| deorbit_date = |
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| spacecraft_bus = [[GeoEye|Orbview 4]] |
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| wavelength = 135 to 280 [[Nanometre|nm]] ([[Ultraviolet]]) |
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| manufacturer = [[Orbital Sciences Corporation]] |
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| mass = {{convert|280|kg}} |
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| launch_mass = {{cvt|280|kg}} |
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| dimensions = {{cvt|1|xx|2.5|m}} |
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| power = 290 [[watt]]s |
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| focal_length = 3 m |
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| launch_date = 28 April 2003, 11:59:57 [[Coordinated Universal Time|UTC]]<ref name="Display"/> |
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| coolant = |
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| launch_rocket = [[Pegasus (rocket)|Pegasus XL]] (F33) |
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| instrument_1_name = |
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| launch_site = [[Cape Canaveral Space Force Station|Cape Canaveral]], ''[[Stargazer (aircraft)|Stargazer]]'' |
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| instrument_1_characteristics = |
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| launch_contractor = [[Orbital Sciences Corporation]] |
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| instrument_2_name = |
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| instrument_2_characteristics = |
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| entered_service = 28 May 2003 <ref name="JPL"/> |
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| instrument_3_name = |
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| deactivated = 28 June 2013, 19:09 UTC <ref name="Decommission"/> |
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| instrument_3_characteristics = |
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| last_contact = 28 June 2013 |
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| instrument_4_name = |
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| decay_date = 2068 (planned) |
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| instrument_4_characteristics = |
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| website = [http://www.galex.caltech.edu www.galex.caltech.edu] |
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| orbit_reference = [[Geocentric orbit]]<ref name="Trajectory"/> |
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| stats_ref = <ref>{{cite news | author=Justin Ray | title=Mission Status Center: Pegasus Launch Report - GALEX| url=http://spaceflightnow.com/pegasus/galex/status.html | work=Spaceflight Now | date=6 May 2003 | accessdate=2010-03-02}}</ref><ref>{{cite web | author=Jet Propulsion Laboratory | title=GALEX Overview | url=http://www.galex.caltech.edu/about/overview.html | publisher=NASA | date=2010 | accessdate=2010-03-02}}</ref> |
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| orbit_regime = [[Low Earth orbit]] |
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| orbit_periapsis = {{cvt|691|km}} |
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| orbit_apoapsis = {{cvt|697|km}} |
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| orbit_inclination = 29.00° |
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| orbit_period = 98.60 minutes |
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| orbit_rev_number = 85423 |
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| apsis = gee |
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| instruments = Ultraviolet telescope |
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| telescope_type = [[Ritchey–Chrétien telescope|Ritchey–Chrétien]]<ref name="Display"/> |
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| telescope_diameter = {{cvt|50|cm}} |
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| telescope_focal_length = f/6.0 |
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| telescope_wavelength = 135–280 [[Nanometre|nm]] ([[Ultraviolet]]) |
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| insignia = |
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| insignia_caption = |
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| insignia_size = 200px |
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| programme = '''Explorer program''' |
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| previous_mission = [[CHIPS (satellite)|CHIPS]] (Explorer 82) |
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| next_mission = [[Neil Gehrels Swift Observatory]] (Explorer 84) |
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}} |
}} |
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[[File:GALEX Field of View.jpg|thumb|right|250px|GALEX field of view compared to a full Moon]] |
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'''Galaxy Evolution Explorer''' ('''GALEX''' or '''Explorer 83''' or '''SMEX-7''') was a [[NASA]] orbiting space telescope designed to observe the [[universe]] in [[ultraviolet]] [[wavelength]]s to measure the history of [[star formation]] in the universe. In addition to paving the way for future ultraviolet missions, the space telescope allowed astronomers to uncover mysteries about the early universe and how it evolved, as well as better characterize phenomena like [[black hole]]s and [[dark matter]]. The mission was extended three times over a period of 10 years before it was decommissioned in June 2013. GALEX was launched on 28 April 2003 and decommissioned in June 2013.<ref name="Display">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2003-017A|title=Display: GALEX (Explorer 83) 2003-017A |publisher=NASA|date=28 October 2021|access-date=3 December 2021}} {{PD-notice}}</ref> |
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The '''Galaxy Evolution Explorer''' ('''GALEX''') is an [[orbit]]ing [[ultraviolet]] [[space telescope]] launched on April 28, 2003 and operated until early 2012. |
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== |
== Spacecraft == |
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The spacecraft was [[Spacecraft attitude control|three-axis stabilized]], with power coming from four fixed [[solar panel]]s. The [[satellite bus]] is from [[Orbital Sciences Corporation]] based on [[GeoEye|OrbView 4]]. The telescope was a {{cvt|50|cm}} [[Ritchey–Chrétien telescope|Modified Ritchey–Chrétien]] with a rotating [[grism]]. GALEX used the first ever UV light dichroic beam-splitter flown in space to direct [[photon]]s to the [[Ultraviolet|Near UV]] (175–280 nanometers) and Far UV (135–174 nanometers) [[microchannel plate detector]]s. Each of the two detectors has a {{cvt|65|mm}} diameter. The target orbit is {{cvt|670|km}} circular and [[Orbital inclination|inclined]] at 29.00° to the [[equator]]. |
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An airlaunched [[Pegasus (rocket)|Pegasus]] rocket placed the craft into a nearly circular orbit at an [[altitude]] of {{convert|697|km}} and an [[inclination]] to the [[Earth]]'s equator of 29 degrees. |
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== Launch == |
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The [[First light (astronomy)|first observation]] was dedicated to the crew of the [[Space Shuttle Columbia]] and images the sky in the [[constellation]] [[Hercules (astronomy)|Hercules]], taken on May 21, 2003. This region was selected because it had been directly overhead the shuttle at the time of its last contact with the [[Christopher C. Kraft Jr. Mission Control Center|NASA Mission Control Center]]. |
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An air launched [[Northrop Grumman Pegasus|Pegasus]] [[launch vehicle]], launched on 28 April 2003 at 11:59:57 [[Coordinated Universal Time|UTC]], placed the craft into a nearly circular orbit at an [[altitude]] of {{cvt|697|km}} and an [[orbital inclination]] to the Earth's [[equator]] of 29.00°.<ref name="Trajectory">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=2003-017A|title=Trajectory: GALEX (Explorer 83) 2003-017A|publisher=NASA|date=28 October 2021|access-date=3 December 2021}} {{PD-notice}}</ref> |
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== Mission == |
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After its primary mission of 29 months, observation operations were extended to almost 9 years with NASA placing it into standby mode on 7 Feb 2012.<ref>[http://www.universetoday.com/93409/galex-mission-comes-to-an-end/ GALEX ends]</ref> |
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The Galaxy Evolution Explorer (GALEX) which explored the origin and evolution of galaxies, and the origins of stars and heavy elements over the [[redshift]] range of Z between 0 and 2. GALEX conducted an all-sky imaging survey, a deep imaging survey, and a survey of 200 [[Galaxy|galaxies]] nearest to the [[Milky Way]] galaxy. As well, GALEX performed three spectroscopic surveys over the 135–300 [[nanometre]] band. GALEX had a planned 29-month mission, and is a part of the Small Explorer (SMEX) program. |
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The [[First light (astronomy)|first observation]] was dedicated to the crew of the [[Space Shuttle Columbia]], and was images in the [[constellation]] of [[Hercules (astronomy)|Hercules]] taken on 21 May 2003. This region was selected because it had been directly overhead the shuttle at the time of its last contact with the [[Christopher C. Kraft Jr. Mission Control Center|NASA Mission Control Center]], [[Houston]], [[Texas]]. |
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NASA cut off financial support for operations of GALEX in early February 2011 as it was ranked lower than other projects which were seeking a limited supply of funding. The mission's life-cycle cost to NASA was $150.6 million. The [[California Institute of Technology]] negotiated to transfer control of GALEX and its associated ground control equipment to the California Institute of Technology in keeping with the [[Stevenson-Wydler Technology Innovation Act of 1980|Stevenson-Wydler Technology Innovation Act]]. Under this Act, excess research equipment owned by the US government can be transferred to educational institutions and [[Nonprofit organization|non-profit organizations]].<ref>{{cite news | author=Stephen Clark | title=NASA, Caltech mull over unique satellite donation | url=http://www.spaceflightnow.com/news/n1202/10galex/ | work=Spaceflight Now | date=10 February 2011 | accessdate=2010-02-17}}</ref> In May 2012, GALEX operations were transferred to Caltech.<ref name=woo>[http://phys.org/news/2012-05-nasa-ultraviolet-space-telescope-caltech.html Marcus Woo - NASA lends ultraviolet space telescope to Caltech (May 17, 2012) - Phys.org]</ref> |
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After its primary mission of 29 months, observation operations were extended. In 2009, one of its detectors, which observed in far-ultraviolet light, stopped functioning.<ref name="SFN20120210"/> Late in the mission, observations of more intense UV sources were allowed, including the Kepler field.<ref name="SFN20120210"/> |
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A fund-raising effort called GALEX CAUSE is being run to try and complete its All-Sky UV Survey.<ref name=cause>[http://www.galex.caltech.edu/cause/ GALEX - CAUSE]</ref> Its unique ultraviolet observations shed new light on special studies of galaxies, black-holes, supernova, stars, and beyond.<ref name=cause/> |
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Observation operations were extended to almost 9 years, with NASA placing it into standby mode on 7 February 2012.<ref name=UT>[http://www.universetoday.com/93409/galex-mission-comes-to-an-end/ ''GALEX Mission Comes to an End'' 7 February 2012 Universe Today]</ref> NASA cut off financial support for operations of GALEX in early February 2011 as it was ranked lower than other projects which were seeking a limited supply of funding. The mission's life-cycle cost to NASA was US$150.6 million. The [[California Institute of Technology]] (Caltech) negotiated to transfer control of GALEX and its associated ground control equipment to the California Institute of Technology in keeping with the [[Stevenson-Wydler Technology Innovation Act of 1980|Stevenson-Wydler Technology Innovation Act]]. Under this Act, excess research equipment owned by the [[Federal government of the United States|U.S. government]] can be transferred to educational institutions and [[Nonprofit organization|non-profit organizations]].<ref name="SFN20120210">{{cite news|author=Stephen Clark|title=NASA, Caltech mull over unique satellite donation|url=https://www.spaceflightnow.com/news/n1202/10galex/|publisher=Spaceflight Now|date=10 February 2012|access-date=8 June 2021}}</ref> On 17 May 2012, GALEX operations were transferred to Caltech.<ref name="Phys.org">{{cite web|url=https://phys.org/news/2012-05-nasa-ultraviolet-space-telescope-caltech.html|title=NASA lends ultraviolet space telescope to Caltech|publisher=Phys.org|date=17 June 2012|access-date=3 December 2021}}</ref> |
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On June 28, 2013 NASA decommissioned GALEX. It is expected that the spacecraft will remain in orbit for at least 65 years before it will re-enter the atmosphere.<ref>[http://www.galex.caltech.edu/newsroom/glx2013-03r.html NASA Decommissions Its Galaxy Hunter Spacecraft]</ref> |
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On 28 June 2013, NASA decommissioned GALEX. It is expected that the spacecraft will remain in orbit until at least 2068 before it will re-enter the atmosphere.<ref name="Decommission">{{cite web |url=http://www.galex.caltech.edu/newsroom/glx2013-03r.html|title=NASA Decommissions Its Galaxy Hunter Spacecraft|publisher=CalTech|date=28 June 2013|access-date=3 December 2021}}</ref><ref name="JPL">{{cite web|url=https://www.jpl.nasa.gov/missions/galaxy-evolution-explorer-galex/|title=Mission to Universe: Galaxy Evolution Explorer|publisher=NASA|access-date=3 December 2021}} {{PD-notice}}</ref> |
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==Science mission== |
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During its initial 29-month mission, which was extended, it made observations in [[ultraviolet]] wavelengths to measure the history of [[star]] formation in the [[universe]] 80 percent of the way back to the [[Big Bang]]. Since scientists believe the Universe to be about 13.8 billion years old,<ref>{{cite web |
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|last = |
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|first = |
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|title = Cosmic Detectives |
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|url=http://www.esa.int/Our_Activities/Space_Science/Cosmic_detectives |
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|authorlink = |
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|work = |
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|publisher = The European Space Agency (ESA) |
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|date = 2013-04-02 |
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|doi = |
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|accessdate = 2013-04-26}} |
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</ref> the mission will study [[galaxy|galaxies]] and stars across about 10 billion years of cosmic history. |
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== Science mission == |
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The [[space observatory|spacecraft's]] mission is to observe hundreds of thousands of [[galaxy|galaxies]], with the goal of determining the distance of each galaxy from Earth and the rate of [[star formation]] in each galaxy. Near- and far-UV emissions as measured by GALEX can indicate the presence of young stars, but may also originate from old stellar populations (e.g. [[sdB stars]]). |
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[[File:GALEX Field of View.jpg|thumb|upright=1.0|left|GALEX field of view compared to a full Moon]] |
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The telescope made observations in ultraviolet wavelengths to measure the history of [[star]] formation in the [[universe]] 80% of the way back to the [[Big Bang]]. Since scientists believe the Universe to be about 13.8 billion years old, the mission studied galaxies and stars across about 10 billion years of cosmic history.<ref>{{cite web |url=http://www.esa.int/Our_Activities/Space_Science/Cosmic_detectives|title=Cosmic Detectives|publisher=European Space Agency (ESA)|date=2013-04-02|access-date=2013-04-26}}</ref> |
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Partnering with the NASA [[Jet Propulsion Laboratory]] (JPL) on the mission are the [[California Institute of Technology]], [[Orbital Sciences Corporation]], [[University of California, Berkeley]], [[Yonsei University]], [[Johns Hopkins University]], [[Columbia University]], and [[Laboratoire d'Astrophysique de Marseille, France]]. |
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The [[space observatory|spacecraft's]] mission was to observe hundreds of thousands of galaxies, with the goal of determining the distance of each galaxy from [[Earth]] and the rate of [[star formation]] in each galaxy. Near-UV (NUV) and Far-UV (FUV) emissions as measured by GALEX can indicate the presence of young stars, but may also originate from old stellar populations (e.g. [[sdB stars]]). |
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The observatory participated in GOALS with Spitzer, Chandra, and Hubble.<ref name=goals>[http://arxiv.org/abs/0904.4498 GOALS: The Great Observatories All-Sky LIRG Survey]</ref> GOALS stands for ''Great Observatories All-sky LIRG Survey'', and [[Luminous Infrared Galaxies]] were studied at the multiple wavelengths allowed by the telescopes.<ref name=goals/> |
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Partnering with the NASA [[Jet Propulsion Laboratory]] (JPL) on the mission were the [[California Institute of Technology]], [[Orbital Sciences Corporation]], [[University of California, Berkeley]], [[Yonsei University]], [[Johns Hopkins University]], [[Columbia University]], and [[Marseille Observatory|Laboratoire d'Astrophysique de Marseille]], [[France]]. |
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==Specifications== |
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The telescope has a 50 cm diameter aperture primary, in a Richey-Chretien f/6 configuration.<ref name=astro>[http://www.astronautix.com/craft/galex.htm Encyclopedia Astronautica - GALEX]</ref> It can see light wavelengths from 135 nanometers to 280 nm,<ref name=astro/> with a field of view of 1.2 degrees wide<ref name=astro/> (larger than a full moon). It has gallium-arsenide solar cells which supply nearly 300 watts to the spacecraft.<ref name=astro/> |
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The observatory participated in GOALS with [[Spitzer Space Telescope]], [[Chandra X-ray Observatory]], and [[Hubble Space Telescope]].<ref name=goals>[https://arxiv.org/abs/0904.4498 GOALS: The Great Observatories All-Sky LIRG Survey]</ref> GOALS stands for ''Great Observatories All-sky LIRG Survey'', and [[Luminous Infrared Galaxies]] were studied at the multiple wavelengths allowed by the telescopes.<ref name=goals/> |
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==Pre-launch images== |
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{{Gallery|lines=3|width=150 |
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|File:Galex PIA04264.jpg|GALEX at the pre-launch tests |
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|File:GALEX Pegasus.jpg|GALEX being mated to a [[Pegasus XL]] Rocket |
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|File:GALEXRollout.jpg|GALEX's [[Pegasus XL]] being attached to the [[Lockheed Martin|Lockheed]] [[Lockheed L-1011 TriStar|L-1011]] ''[[Stargazer (aircraft)|Stargazer]]'' |
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|File:GALEXLaunch.jpg|The L-1011 ''Stargazer'' take-off with GALEX attached under-belly <!-- |
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|File:A-Mira-Full down sampled and cropped.jpg|An image of [[Mira]]'s bow shock and tail of hydrogen gas.--> |
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}} |
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== Science objectives == |
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==Examples== |
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The primary objective of the Galaxy Evolution Explorer was to learn what factors trigger star formation inside galaxies; how quickly stars form, evolve and die; and how heavy chemical elements form in stars. Additional goals include:<ref name="galex-presskit">{{cite web|url=http://www.jpl.nasa.gov/news/press_kits/galex.pdf|title=Galaxy Evolution Explorer Launch|publisher=NASA|date=April 2003|access-date=3 December 2021}} {{PD-notice}}</ref> |
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<!--{{wide image|A-Mira-Full down sampled and cropped.jpg|1500px|align-cap=center|[[Mira]]'s bow shock and hydrogen gas tail in ultraviolet.}}--> |
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[[File:A-Mira-Full down sampled and cropped.jpg|thumb|699px|center|<center>[[Mira]]'s bow shock and hydrogen gas tail in ultraviolet.</center>]] |
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{{-}} |
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* Determining how fast stars are forming inside each galaxy |
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[[File:Ultraviolet image of the Cygnus Loop Nebula crop.jpg|thumb|center|420px|<Center>Ultraviolet view of [[Cygnus loop]]</center>]] |
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* Determining when and how the stars we see today formed |
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{{-}} |
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* Creating the first map of the ultraviolet universe |
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* Helping scientists find and understand ultraviolet bright quasars. These objects can serve as background sources for the Hubble Space Telescope and FUSE as it probes the gases from which galaxies form stars |
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To accomplish its objectives, the Galaxy Evolution Explorer will conduct eight surveys, grouped into two broad categories – a local universe investigation and a star formation history investigation. The local universe investigation includes the following four surveys:<ref name="galex-presskit"/> |
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==See also== |
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* All-sky imaging survey – will look at the entire sky and develop a comprehensive catalogue of ultraviolet galaxy images, useful to map the distribution of star formation within the local universe |
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* Nearby galaxy survey – will study about 150 nearby galaxies that are familiar to scientists to understand how stars formed in individual galaxies |
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* Wide-field spectroscopic survey – will analyze the light wavelengths of galaxies in a wide swath of the sky |
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* Medium spectroscopic survey – will examine the light properties of galaxies within a narrower portion of the sky |
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The star formation history investigation will take information gathered by the local universe investigation and apply it to more distant galaxies by looking further back in time. It includes the following four surveys:<ref name="galex-presskit"/> |
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* Deep imaging survey – will look at a portion of the sky to study the distribution of star formation in the deep universe |
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* Deep spectroscopic survey – will look for the most distant galaxies |
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* Ultra-deep imaging survey – will look as deep as possible at a very small portion of the sky |
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* Medium imaging survey – will study star formation in galaxies beyond our local cosmic neighborhood, but not as deep as the deep imaging survey |
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== Telescope specifications == |
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The telescope had a {{cvt|50|cm}} diameter aperture primary, in a [[Ritchey–Chrétien telescope]] f/6.0 configuration. It can see light wavelengths from 135 nanometres to 280-nm, with a field of view of 1.2° wide (larger than a full Moon). It had [[gallium arsenide]] (GaAs) [[solar cell]]s which supply nearly 300 [[watt]]s to the spacecraft.<ref name=astro>[http://www.astronautix.com/craft/galex.htm Encyclopedia Astronautica – GALEX] {{webarchive|url=https://web.archive.org/web/20080706050843/http://astronautix.com/craft/galex.htm|date=2008-07-06}}</ref> |
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== Experiment == |
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=== Ultraviolet telescope === |
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GALEX carries a single f/6.0, Ritchey–Chrétien telescope, with a {{cvt|50|cm}} diameter primary, and a {{cvt|22|cm}} secondary mirror. Beam-splitters direct the Near UV (NUV) and Far UV (FUV) components to separate photoelectric detectors of diameter {{cvt|6.5|cm}}. In each, the photoelectrons are multiplied by a microchannel plate, and detected by the anode grid. The grid enables determination of the exact position of [[electron]] impact, by the time delay of each pulse at the two ends. The telescope has a [[field of view]] (FoV) of 1.2°, and a resolution of five [[Minute and second of arc|arcseconds]], and enables either imaging or spectral composition of a single star/galaxy, by a rotatable wheel containing a clear window and a [[grism]] (a cross between a grating and a prism).<ref name="Experiment1">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=2003-017A-01|title=Experiment: Ultraviolet Telescope|publisher=NASA|date=28 October 2021|access-date=3 December 2021}} {{PD-notice}}</ref> |
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== Pre-launch images == |
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{{Gallery|width=200 |
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|File:Galex PIA04264.jpg|GALEX at the pre-launch tests |
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|File:GALEX Pegasus.jpg|GALEX being mated to a [[Pegasus XL]] launch vehicle |
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|File:GALEXRollout.jpg|GALEX's Pegasus XL being attached to the [[Lockheed Martin|Lockheed]] [[Lockheed L-1011 TriStar|L-1011]] ''[[Stargazer (aircraft)|Stargazer]]'' |
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|File:GALEXLaunch.jpg|The L-1011 ''Stargazer'' take-off with GALEX attached under-belly |
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}} |
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== See also == |
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{{Portal|Spaceflight}} |
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* {{annotated link|Explorer program}} |
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* [[Ultraviolet astronomy]] |
* [[Ultraviolet astronomy]] |
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* [[ |
* [[GALEX Arecibo SDSS Survey]] |
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* [[Arecibo Observatory]] |
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* [[Galaxy And Mass Assembly survey]], with GALEX participation |
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==References== |
== References == |
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{{ |
{{Reflist}} |
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==External links== |
== External links == |
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{{Commons category|GALEX}} |
{{Commons category|GALEX}} |
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*[http://www.galex.caltech.edu GALEX |
* [http://www.galex.caltech.edu GALEX website] by the [[California Institute of Technology]] |
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*[ |
* [https://www.jpl.nasa.gov/missions/galaxy-evolution-explorer-galex GALEX website] by the [[Jet Propulsion Laboratory]] |
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* [http://galex.stsci.edu GALEX data archive] by the [[Space Telescope Science Institute|STScI]]{{\}}MAST |
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*[http://starrymirror.com/teenagegalaxiesnov17.htm GALEX Detects "Teenage" Galaxies] |
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* [http://galex.stsci.edu/GalexView/ GALEXView Search Tool] by the STScI{{\}}MAST |
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*[http://www.nasa.gov/centers/jpl/missions/galex.html JPL GALEX description] |
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*[http:// |
* [http://wikisky.org/?object=M31&img_source=GALEX GALEX Ultraviolet Sky Survey]at[[Wikisky.org]] |
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*[http://galex.stsci.edu/GalexView GALEXView Search Tool at MAST] |
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*[http://wikisky.org/?object=M31&img_source=GALEX GALEX on-line sky survey on WikiSky] |
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{{Explorer program}} |
{{Explorer program}} |
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{{Space observatories}} |
{{Space observatories}} |
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{{Jet Propulsion Laboratory}} |
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{{Orbital launches in 2003}} |
{{Orbital launches in 2003}} |
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[[Category:Satellites orbiting Earth]] |
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{{Use American English|date=January 2014}} |
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[[Category:Explorers Program]] |
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[[Category:Space telescopes]] |
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{{DEFAULTSORT:Galex}} |
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[[Category:Artificial satellites orbiting Earth]] |
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[[Category:Explorers program (NASA)]] |
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[[Category:Space observatories]] |
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[[Category:Ultraviolet telescopes]] |
[[Category:Ultraviolet telescopes]] |
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[[Category:Spacecraft launched in 2003]] |
[[Category:Spacecraft launched in 2003]] |
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[[Category:Spacecraft launched by Pegasus rockets]] |
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GALEX spacecraft
| |
| Names | Explorer-83 SMEX-7 |
|---|---|
| Mission type | Ultraviolet astronomy |
| Operator | NASA / JPL (2003-2012) Caltech (2012-2013) |
| COSPAR ID | 2003-017A  |
| SATCAT no. | 27783 |
| Website | https://www.galex.caltech.edu/ |
| Mission duration | 29 months (planned) [1] 10 years, 2 months (achieved) [2][3] |
| Spacecraft properties | |
| Spacecraft | Explorer LXXXIII |
| Spacecraft type | Galaxy Evolution Explorer |
| Bus | Orbview 4 |
| Manufacturer | Orbital Sciences Corporation |
| Launch mass | 280 kg (620 lb) |
| Dimensions | 1 × 2.5 m (3 ft 3 in × 8 ft 2 in) |
| Power | 290 watts |
| Start of mission | |
| Launch date | 28 April 2003, 11:59:57 UTC[1] |
| Rocket | Pegasus XL (F33) |
| Launch site | Cape Canaveral, Stargazer |
| Contractor | Orbital Sciences Corporation |
| Entered service | 28 May 2003 [2] |
| End of mission | |
| Deactivated | 28 June 2013, 19:09 UTC [3] |
| Last contact | 28 June 2013 |
| Decay date | 2068 (planned) |
| Orbital parameters | |
| Reference system | Geocentric orbit[4] |
| Regime | Low Earth orbit |
| Perigee altitude | 691 km (429 mi) |
| Apogee altitude | 697 km (433 mi) |
| Inclination | 29.00° |
| Period | 98.60 minutes |
| Revolution no. | 85423 |
| Main telescope | |
| Type | Ritchey–Chrétien[1] |
| Diameter | 50 cm (20 in) |
| Focal length | f/6.0 |
| Wavelengths | 135–280 nm (Ultraviolet) |
| Instruments | |
| Ultraviolet telescope | |
Explorer program
← CHIPS (Explorer 82)
Neil Gehrels Swift Observatory (Explorer 84) →
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Galaxy Evolution Explorer (GALEXorExplorer 83orSMEX-7) was a NASA orbiting space telescope designed to observe the universeinultraviolet wavelengths to measure the history of star formation in the universe. In addition to paving the way for future ultraviolet missions, the space telescope allowed astronomers to uncover mysteries about the early universe and how it evolved, as well as better characterize phenomena like black holes and dark matter. The mission was extended three times over a period of 10 years before it was decommissioned in June 2013. GALEX was launched on 28 April 2003 and decommissioned in June 2013.[1]
The spacecraft was three-axis stabilized, with power coming from four fixed solar panels. The satellite bus is from Orbital Sciences Corporation based on OrbView 4. The telescope was a 50 cm (20 in) Modified Ritchey–Chrétien with a rotating grism. GALEX used the first ever UV light dichroic beam-splitter flown in space to direct photons to the Near UV (175–280 nanometers) and Far UV (135–174 nanometers) microchannel plate detectors. Each of the two detectors has a 65 mm (2.6 in) diameter. The target orbit is 670 km (420 mi) circular and inclined at 29.00° to the equator.
An air launched Pegasus launch vehicle, launched on 28 April 2003 at 11:59:57 UTC, placed the craft into a nearly circular orbit at an altitude of 697 km (433 mi) and an orbital inclination to the Earth's equator of 29.00°.[4]
The Galaxy Evolution Explorer (GALEX) which explored the origin and evolution of galaxies, and the origins of stars and heavy elements over the redshift range of Z between 0 and 2. GALEX conducted an all-sky imaging survey, a deep imaging survey, and a survey of 200 galaxies nearest to the Milky Way galaxy. As well, GALEX performed three spectroscopic surveys over the 135–300 nanometre band. GALEX had a planned 29-month mission, and is a part of the Small Explorer (SMEX) program.
The first observation was dedicated to the crew of the Space Shuttle Columbia, and was images in the constellationofHercules taken on 21 May 2003. This region was selected because it had been directly overhead the shuttle at the time of its last contact with the NASA Mission Control Center, Houston, Texas.
After its primary mission of 29 months, observation operations were extended. In 2009, one of its detectors, which observed in far-ultraviolet light, stopped functioning.[5] Late in the mission, observations of more intense UV sources were allowed, including the Kepler field.[5]
Observation operations were extended to almost 9 years, with NASA placing it into standby mode on 7 February 2012.[6] NASA cut off financial support for operations of GALEX in early February 2011 as it was ranked lower than other projects which were seeking a limited supply of funding. The mission's life-cycle cost to NASA was US$150.6 million. The California Institute of Technology (Caltech) negotiated to transfer control of GALEX and its associated ground control equipment to the California Institute of Technology in keeping with the Stevenson-Wydler Technology Innovation Act. Under this Act, excess research equipment owned by the U.S. government can be transferred to educational institutions and non-profit organizations.[5] On 17 May 2012, GALEX operations were transferred to Caltech.[7]
On 28 June 2013, NASA decommissioned GALEX. It is expected that the spacecraft will remain in orbit until at least 2068 before it will re-enter the atmosphere.[3][2]
The telescope made observations in ultraviolet wavelengths to measure the history of star formation in the universe 80% of the way back to the Big Bang. Since scientists believe the Universe to be about 13.8 billion years old, the mission studied galaxies and stars across about 10 billion years of cosmic history.[8]
The spacecraft's mission was to observe hundreds of thousands of galaxies, with the goal of determining the distance of each galaxy from Earth and the rate of star formation in each galaxy. Near-UV (NUV) and Far-UV (FUV) emissions as measured by GALEX can indicate the presence of young stars, but may also originate from old stellar populations (e.g. sdB stars).
Partnering with the NASA Jet Propulsion Laboratory (JPL) on the mission were the California Institute of Technology, Orbital Sciences Corporation, University of California, Berkeley, Yonsei University, Johns Hopkins University, Columbia University, and Laboratoire d'Astrophysique de Marseille, France.
The observatory participated in GOALS with Spitzer Space Telescope, Chandra X-ray Observatory, and Hubble Space Telescope.[9] GOALS stands for Great Observatories All-sky LIRG Survey, and Luminous Infrared Galaxies were studied at the multiple wavelengths allowed by the telescopes.[9]
The primary objective of the Galaxy Evolution Explorer was to learn what factors trigger star formation inside galaxies; how quickly stars form, evolve and die; and how heavy chemical elements form in stars. Additional goals include:[10]
To accomplish its objectives, the Galaxy Evolution Explorer will conduct eight surveys, grouped into two broad categories – a local universe investigation and a star formation history investigation. The local universe investigation includes the following four surveys:[10]
The star formation history investigation will take information gathered by the local universe investigation and apply it to more distant galaxies by looking further back in time. It includes the following four surveys:[10]
The telescope had a 50 cm (20 in) diameter aperture primary, in a Ritchey–Chrétien telescope f/6.0 configuration. It can see light wavelengths from 135 nanometres to 280-nm, with a field of view of 1.2° wide (larger than a full Moon). It had gallium arsenide (GaAs) solar cells which supply nearly 300 watts to the spacecraft.[11]
GALEX carries a single f/6.0, Ritchey–Chrétien telescope, with a 50 cm (20 in) diameter primary, and a 22 cm (8.7 in) secondary mirror. Beam-splitters direct the Near UV (NUV) and Far UV (FUV) components to separate photoelectric detectors of diameter 6.5 cm (2.6 in). In each, the photoelectrons are multiplied by a microchannel plate, and detected by the anode grid. The grid enables determination of the exact position of electron impact, by the time delay of each pulse at the two ends. The telescope has a field of view (FoV) of 1.2°, and a resolution of five arcseconds, and enables either imaging or spectral composition of a single star/galaxy, by a rotatable wheel containing a clear window and a grism (a cross between a grating and a prism).[12]
This article incorporates text from this source, which is in the public domain.
This article incorporates text from this source, which is in the public domain.
This article incorporates text from this source, which is in the public domain.
This article incorporates text from this source, which is in the public domain.
This article incorporates text from this source, which is in the public domain.
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