GALEX

The Galaxy Evolution Explorer (GALEX) was an orbiting ultraviolet space telescope which was launched on April 28, 2003 and operated until early 2012 (decommissioned in June 2013).

This article is about the ultraviolet space telescope. For the neutrino detector, see GALLEX. For other uses, see GALEX (disambiguation).
Galaxy Evolution Explorer
Illustration of GALEX
NamesExplorer-83, SMEX-7
Mission typeUltraviolet astronomy
OperatorNASA / JPL
Caltech
COSPAR ID2003-017A
SATCAT no.27783
Websitehttp://www.galex.caltech.edu/
Mission durationPlanned: 29 months[1]
Final: 10 years, 2 months[2][3]
Spacecraft properties
ManufacturerOrbital Sciences
Launch mass277 kg (611 lb)[4]
Dimensions2.7 × 2.0 m (9 × 6.5 ft)[5]
Power290 W[4]
Start of mission
Launch dateApril 28, 2003, 12:00 (2003-04-28UTC12Z) UTC[6]
RocketPegasus XL
Launch siteStargazer, Cape Canaveral
ContractorOrbital Sciences
Entered serviceMay 28, 2003[2]
End of mission
DisposalDecommissioned
DeactivatedJune 28, 2013, 19:09 (2013-06-28UTC19:10Z) UTC[3]
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Semi-major axis7,065.55 km (4,390.33 mi)
Eccentricity0.0003692
Perigee altitude684.261 km (425.180 mi)
Apogee altitude689.478 km (428.422 mi)
Inclination28.9980°
Period98.4855 minutes
RAAN285.5367°
Argument of perigee215.0418°
Mean anomaly144.9927°
Mean motion14.62146 rev/day
EpochApril 22, 2019 18:10:09 UTC[7]
Revolution no.85423
Main telescope
TypeRitchey–Chrétien[1]
Diameter50 cm (19.7 in)[1]
Wavelengths135–280 nm (Ultraviolet)[1]
 

History

An airlaunched Pegasus rocket placed the craft into a nearly circular orbit at an altitude of 697 kilometres (433 mi) and an inclination to the Earth's equator of 29 degrees.

The first observation was dedicated to the crew of the Space Shuttle Columbia, and was images in the constellation of 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 NASA Mission Control Center.

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.[8]

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. Under this Act, excess research equipment owned by the US government can be transferred to educational institutions and non-profit organizations.[9] In May 2012, GALEX operations were transferred to Caltech.[10]

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.[11]

Science mission
GALEX field of view compared to a full Moon

The telescope 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,[12] the mission will study galaxies and stars across about 10 billion years of cosmic history.

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- 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).

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, Chandra, and Hubble.[13] GOALS stands for Great Observatories All-sky LIRG Survey, and Luminous Infrared Galaxies were studied at the multiple wavelengths allowed by the telescopes.[13]

Specifications

The telescope had a 50 cm diameter aperture primary, in a Richey-Chretien f/6 configuration.[14] It can see light wavelengths from 135 nanometers to 280 nm,[14] with a field of view of 1.2 degrees wide[14] (larger than a full moon). It had gallium-arsenide solar cells which supply nearly 300 watts to the spacecraft.[14]

Pre-launch images
  • GALEX at the pre-launch tests
  • GALEX being mated to a Pegasus XL Rocket
  • GALEX's Pegasus XL being attached to the Lockheed L-1011 Stargazer
  • The L-1011 Stargazer take-off with GALEX attached under-belly

Examples of results
Mira's bow shock and hydrogen gas tail in ultraviolet.
Ultraviolet view of Cygnus Loop

See also

References
  1. "GALEX". National Space Science Data Center. NASA. Retrieved September 14, 2015.
  2. "Mission to Universe: Galaxy Evolution Explorer". NASA. Retrieved September 14, 2015.
  3. "NASA Decommissions Its Galaxy Hunter Spacecraft" (Press release). California Institute of Technology. June 28, 2013. Retrieved September 14, 2015.
  4. "Press Kit: Galaxy Evolution Explorer Launch" (PDF). NASA. April 2003. Retrieved September 14, 2015.
  5. "GALEX Basics". California Institute of Technology. Retrieved September 14, 2015.
  6. "GALEX - Trajectory Details". National Space Science Data Center. NASA. Retrieved September 14, 2015.
  7. "TLE". Retrieved April 23, 2019.
  8. GALEX ends
  9. Stephen Clark (10 February 2011). "NASA, Caltech mull over unique satellite donation". Spaceflight Now. Retrieved 2010-02-17.
  10. Marcus Woo - NASA lends ultraviolet space telescope to Caltech (May 17, 2012) - Phys.org
  11. NASA Decommissions Its Galaxy Hunter Spacecraft
  12. "Cosmic Detectives". The European Space Agency (ESA). 2013-04-02. Retrieved 2013-04-26.
  13. GOALS: The Great Observatories All-Sky LIRG Survey
  14. Encyclopedia Astronautica - GALEX Archived 2008-07-06 at the Wayback Machine

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