Wide Field Infrared Explorer

Summary

Wide Field Infrared Explorer
Wide Field Infrared Explorer module.jpg
Wide Field Infrared Explorer spacecraft
NamesWIRE
Small Explorer / WIRE
Explorer-75
SMEX-5
SMEX / WIRE
Mission typeInfrared astronomy
OperatorNASA / GSFC
Bowie State University (BSOCC)
COSPAR ID1999-011A
SATCAT no.25646
Websitehttp://www.ipac.caltech.edu/wire/
Mission duration4 months (planned)
1y, 4m, 10d (achieved) [1]
Spacecraft properties
SpacecraftWIRE
Spacecraft typeExplorer
ManufacturerSpace Dynamics Laboratory (SDL)
Launch mass250 kg (550 lb)
Power160 watts
Start of mission
Launch date5 March 1999, 02:56 UTC
RocketPegasus XL
Launch siteStargazer, Vandenberg Air Force Base
ContractorOrbital Sciences Corporation (OSC)
Entered serviceFailed on orbit
End of mission
DisposalDecommissioned
Deactivated30 September 2000
Decay date10 May 2011, 07:00 UTC
Orbital parameters
Reference systemGeocentric orbit [2]
RegimeSun-synchronous orbit
Perigee altitude470 km (290 mi)
Apogee altitude540 km (340 mi)
Inclination97°
Main telescope
TypeRitchey–Chrétien [2]
Diameter30 cm (12 in)
Resolution20-23 arcsec
← TRACE
RHESSI →
 

The Wide Field Infrared Explorer (WIRE) was a satellite launched on 5 March 1999, on the Pegasus XL rocket into polar orbit between 409 and 426 km (254 and 265 mi) above the Earth's surface. WIRE was intended to be a four-month infrared survey of the entire sky at 21-27 µm and 9-15 µm, specifically focusing on starburst galaxies and luminous protogalaxies.

The science team was based at the Infrared Processing and Analysis Center (IPAC) in Pasadena, California. Flight operations, integration, and testing were from Goddard Space Flight Center in Maryland. The telescope was built by Space Dynamics Laboratory in Utah. Premature ejection of the spacecraft aperture cover led to depletion of the solid hydrogen shortly after launch, ending the primary science mission. The onboard star tracker remained functional, and has been used for long-term precision photometric monitoring of bright stars in support of an asteroseismology program. WIRE reentered atmosphere of Earth on 10 May 2011 (around 07:00 UTC).[3]

Science

The Wide-field Infrared Explorer (WIRE) was a two-color, solid hydrogen-cooled, infrared imaging telescope designed to study starburst galaxies and to search for protogalaxies. The science goals of WIRE were to: 1) determine what fraction of the luminosity of the universe at a redshift of >0.5 is due to starburst galaxies; 2) assess how fast and in what ways starburst galaxies evolve; and, 3) examine whether luminous protogalaxies are common at redshifts <3. In order to accomplish these goals, WIRE was to conduct a four month survey at 12 and 25 µm over an area of between ten and several hundred square degrees of the sky.[4]

WIRE telescope

The WIRE telescope itself had an entrace aperture of 30 cm and a 32 x 32 arc-minute field of view. It was of a Ritchey–Chrétien telescope design with no moving parts and no reimaging optics. Shortly after launch, while the spacecraft was still tumbling early after orbit insertion, the telescope cover came off prematurely. This resulted in the exposure of the cryogenic materials to light, warming them at a high rate causing outgassing and increasing the rate of spin of the spacecraft beyond the ability of the reaction wheels to slow it. Although ground controllers began work to decrease the excess spin of the spacecraft, they were not able to do so in time to prevent the total loss of the frozen hydrogen used to cool the primary science instrument. Attempts to recover control of the spacecraft were successful, though as a result of the coolant loss no science data were obtainable.[4]

Mission

A design flaw in the spacecraft control electronics caused the telescope dust cover to eject prematurely in its first few hours on-orbit, exposing the telescope to the Earth. In normal operations, the telescope would avoid pointing at the Earth as well as the Sun because the heat load was too high for the cryogenic cooling. At this early stage in the mission, the telescope was deliberately pointed at the Earth for safety under the assumption that the dust cover was present. The influx of power into the telescope caused the solid hydrogen cryostat to boil off all of its cryogen. The cryostat was designed to non-propulsively vent small amounts of gaseous hydrogen as the instruments were cooled. However, due to the unexpected heating, the vent began expelling gas at rates orders of magnitude higher than designed. The over-active vent acted as an uncontrolled, off-axis thruster. Eventually, the attitude control system was unable to counter the thrust of the cryostat vent, and the spacecraft began to spin. By the time the hydrogen supply was exhausted, the spacecraft was spinning as fast as 60 rpm. As the thrust finally abated, spacecraft engineers were able to re-establish attitude control. However, with the cryogen gone, the science instrument was no longer functional and the original science mission ended.

In order to salvage some functionality from the US$73 million spacecraft, operations were redirected after the failure of the cryogenic system to an alternate science mission using the undamaged onboard star tracker for long-term monitoring of bright stars in support of an asteroseismology program. This technique aims to measure oscillations in nearby stars to probe their structure. While the star tracker has poor spatial resolution, having been designed primarily for a wide field of view and detection of the brightest stars, it is above the atmosphere and thus avoids scintillation, enabling high-precision photometry. As a secondary experiment, one solar array includes a section with reflectors, to test a concentrator system.[5]

The original science goals of WIRE may finally be achieved by the Wide-field Infrared Survey Explorer (WISE) mission which was successfully launched into orbit on 14 December 2009, and began observations on 14 January 2010.

See also

  • IRAS – Infrared space observatory
  • WISE – NASA infrared-wavelength space telescope
  • Spitzer Space Telescope – Infrared space telescope
  • JWST – Planned space observatory

References

  1. ^ Laher, Russ (16 January 2004). "Complete WIRE Star-Camera Observation History". Infrared Processing and Analysis Center (IPAC). Retrieved 15 March 2021.
  2. ^ a b "The WIRE Instrument". Infrared Processing and Analysis Center (IPAC). 3 September 1997. Retrieved 3 September 2015.
  3. ^ Shupe, Dave; Laher, Russ; Mabry, Joe; Barlow, Tom (28 April 2006). "Wide Field Infrared Explorer (WIRE)". Infrared Processing and Analysis Center (IPAC). Retrieved 22 November 2008.
  4. ^ a b "WIRE 1999-011A". NASA. 10 February 2021. Retrieved 15 March 2021. This article incorporates text from this source, which is in the public domain.
  5. ^ Sanders, Robert (27 July 1999). "UCB Astronomer Salvages Disabled NASA Satellite for Stellar Research". University of California, Berkeley. Retrieved 15 March 2021.

External links

  • Wide Field Infrared Explorer by the California Institute of Technology