WISE

Wide-field Infrared Survey Explorer


The Wide-Field Infrared Survey Explorer (WISE) is a NASA-funded infrared-wavelength astronomical space telescope. The Earth-orbiting satellite will carry a 40 cm (16 in) diameter infrared-sensitive telescope, which will be used to survey the entire sky over the course of seven months through images made in the 3 to 25 μm wavelength range (specifically at 3.3, 4.7, 12, and 23 μm). The survey will be at least 500 times more sensitive than the two previous major infrared space survey telescopes, the Infrared Astronomical Satellite (IRAS) and AKARI. WISE is scheduled for rollout to its launch pad at Vandenberg Air Force Base in California on Friday, Nov. 20, 2009, and is scheduled to launch no earlier than 6:09 a.m. PST on Dec. 9, 2009.

The complete mission will create images of 99% of the sky, with at least eight images made of each position on the sky to increase their accuracy. The spacecraft will be placed in a 525 km (326 mi), circular, polar, synchronous orbit for its seven month mission, during which it will take 1.5 million 11-second exposure images. Each image will cover a 47 arcminute field of view.

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.

Science mission
WISE will survey the sky in four wavelengths of the infrared band at a very high sensitivity. Its detector arrays have sensitivity limits of 120, 160, 650, and 2600 µJy at 3.3, 4.7, 12, and 23 microns. This is a factor of a thousand times better sensitivity than the survey completed in 1983 by the IRAS satellite in the 12 and 23 micron bands, and a factor of five hundred thousand 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)

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 (NEO) 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 the 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 lightyear (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.