Xile
18-02-2010, 21:46
Wide-Field Infrared Survey Explorer (WISE) is a NASA-funded infrared-wavelength astronomical space telescope launched on 14 December 2009. The Earth-orbiting satellite carries a 40-centimetre (16 in) diameter infrared-sensitive telescope, which will survey the entire sky over the course of six months through images made in the 3 to 25 μm wavelength range. The telescope's image detectors are designed to make the survey at least 1,000 times more sensitive to infrared sky features than the sky surveys of previous major infrared space survey telescopes such as the Infrared Astronomical Satellite (IRAS), AKARI and COBE.
The complete mission will create images of 99% of the sky, with at least eight images made of each position on the sky in order to increase accuracy. The spacecraft will be placed in a 525 km (326 mi), circular, polar, sun-synchronous orbit for its 10 month mission, during which it will take 1.5 million images, one every 11 seconds. Each image will cover a 47 arcminute field of view. Each area of the sky will be scanned 10 times. The image library produced will contain data on the local Solar System, the Milky Way Galaxy, and the more distant universe. Among the objects WISE will study are asteroids, cool, dim stars such as brown dwarfs, and the most luminous infrared galaxies.
Construction of the WISE telescope was divided between Ball Aerospace & Technologies Corp. (spacecraft, operations support), SSG Precision Optronics, Inc. (telescope, optics, scan mirror), DRS and Rockwell (focal planes), Lockheed Martin (cryostat, cooling for the telescope), and Space Dynamics Laboratory (instruments, electronics, and testing). The program is managed through the Jet Propulsion Laboratory.
WISE will also serve as a replacement for the Wide Field Infrared Explorer (WIRE) spacecraft, which failed within hours of reaching orbit in March 1999.
The WISE spacecraft was built by Ball Aerospace and Technologies Corp. in Boulder, Colorado. The spacecraft is derived from the Ball Aerospace RS-300 spacecraft architecture, particularly the NEXTSat spacecraft built for the successful Orbital Express mission launched on March 9, 2007. The flight system has an estimated mass of 560 kg (about 1,175 pounds). The spacecraft is three-axis stabilized, with body-fixed solar arrays. It uses a high-gain antenna in the Ku band to transmit to the ground through the TDRSS geostationary system. Ball also performed the testing and flight system integration.
WISE will survey the sky in four wavelengths of the infrared band, at a very high sensitivity. Its detector arrays have 5-sigma sensitivity limits of 120, 160, 650, and 2600 micro-Jansky (µJy) at 3.3, 4.7, 12, and 23 microns.[4] This is a factor of 1,000 times better sensitivity than the survey completed in 1983 by the IRAS satellite in the 12 and 23 micron bands, and a factor of 500,000 times better than the 1990s survey by the Cosmic Background Explorer (COBE) satellite at 3.3 and 4.7 microns.
* Band 1 – 3.4 microns—broad-band sensitivity to stars and galaxies
* Band 2 – 4.6 microns—detect thermal radiation from the internal heat sources of sub-stellar objects like brown dwarfs
* Band 3 – 12 microns—detect thermal radiation from asteroids
* Band 4 – 22 microns—sensitivity to dust in star-forming regions (material with temperatures of 70–100 Kelvin)
A scaffolding structure built around WISE allowed engineers to freeze its hydrogen coolant
The primary mission lasts ten months: one month for checkout, six months for a full-sky survey, then an additional three months of survey until cryogenic coolant runs out. The partial second survey pass will facilitate the study of changes (e.g. orbital movement) in observed objects.
On November 8, 2007, the House Committee on Science and Technology's Subcommittee on Space and Aeronautics held a hearing to examine the status of NASA's Near-Earth Object (NEO) survey program. The prospect of using WISE was proposed by NASA officials.
NASA officials told Committee staff that NASA plans to use WISE to detect near-Earth objects in addition to performing its science goals. It is projected that WISE could detect 400 NEOs (or roughly 2 percent of the estimated NEO population of interest) within its one-year mission.
WISE will not be able to detect Kuiper belt objects, as their temperature is too low. It will be able to detect any objects with an internal heat source: a Neptune-sized object would be detectable out to 700 AU, a Jupiter-mass object out to one light year (63,000 AU), where it would still be within the Sun's zone of gravitational control. A small brown dwarf of 2–3 Jupiter masses would be visible at a distance of up to two to three parsecs.
Wide-field Infrared Survey Explorer (http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer)
The complete mission will create images of 99% of the sky, with at least eight images made of each position on the sky in order to increase accuracy. The spacecraft will be placed in a 525 km (326 mi), circular, polar, sun-synchronous orbit for its 10 month mission, during which it will take 1.5 million images, one every 11 seconds. Each image will cover a 47 arcminute field of view. Each area of the sky will be scanned 10 times. The image library produced will contain data on the local Solar System, the Milky Way Galaxy, and the more distant universe. Among the objects WISE will study are asteroids, cool, dim stars such as brown dwarfs, and the most luminous infrared galaxies.
Construction of the WISE telescope was divided between Ball Aerospace & Technologies Corp. (spacecraft, operations support), SSG Precision Optronics, Inc. (telescope, optics, scan mirror), DRS and Rockwell (focal planes), Lockheed Martin (cryostat, cooling for the telescope), and Space Dynamics Laboratory (instruments, electronics, and testing). The program is managed through the Jet Propulsion Laboratory.
WISE will also serve as a replacement for the Wide Field Infrared Explorer (WIRE) spacecraft, which failed within hours of reaching orbit in March 1999.
The WISE spacecraft was built by Ball Aerospace and Technologies Corp. in Boulder, Colorado. The spacecraft is derived from the Ball Aerospace RS-300 spacecraft architecture, particularly the NEXTSat spacecraft built for the successful Orbital Express mission launched on March 9, 2007. The flight system has an estimated mass of 560 kg (about 1,175 pounds). The spacecraft is three-axis stabilized, with body-fixed solar arrays. It uses a high-gain antenna in the Ku band to transmit to the ground through the TDRSS geostationary system. Ball also performed the testing and flight system integration.
WISE will survey the sky in four wavelengths of the infrared band, at a very high sensitivity. Its detector arrays have 5-sigma sensitivity limits of 120, 160, 650, and 2600 micro-Jansky (µJy) at 3.3, 4.7, 12, and 23 microns.[4] This is a factor of 1,000 times better sensitivity than the survey completed in 1983 by the IRAS satellite in the 12 and 23 micron bands, and a factor of 500,000 times better than the 1990s survey by the Cosmic Background Explorer (COBE) satellite at 3.3 and 4.7 microns.
* Band 1 – 3.4 microns—broad-band sensitivity to stars and galaxies
* Band 2 – 4.6 microns—detect thermal radiation from the internal heat sources of sub-stellar objects like brown dwarfs
* Band 3 – 12 microns—detect thermal radiation from asteroids
* Band 4 – 22 microns—sensitivity to dust in star-forming regions (material with temperatures of 70–100 Kelvin)
A scaffolding structure built around WISE allowed engineers to freeze its hydrogen coolant
The primary mission lasts ten months: one month for checkout, six months for a full-sky survey, then an additional three months of survey until cryogenic coolant runs out. The partial second survey pass will facilitate the study of changes (e.g. orbital movement) in observed objects.
On November 8, 2007, the House Committee on Science and Technology's Subcommittee on Space and Aeronautics held a hearing to examine the status of NASA's Near-Earth Object (NEO) survey program. The prospect of using WISE was proposed by NASA officials.
NASA officials told Committee staff that NASA plans to use WISE to detect near-Earth objects in addition to performing its science goals. It is projected that WISE could detect 400 NEOs (or roughly 2 percent of the estimated NEO population of interest) within its one-year mission.
WISE will not be able to detect Kuiper belt objects, as their temperature is too low. It will be able to detect any objects with an internal heat source: a Neptune-sized object would be detectable out to 700 AU, a Jupiter-mass object out to one light year (63,000 AU), where it would still be within the Sun's zone of gravitational control. A small brown dwarf of 2–3 Jupiter masses would be visible at a distance of up to two to three parsecs.
Wide-field Infrared Survey Explorer (http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer)