Wide-field Infrared Survey Explorer

Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy space telescope in the Explorers Program launched in December 2009.. . . WISE discovered thousands of minor planets and numerous star clusters. Its observations also supported the discovery of the first Y-type brown dwarf and Earth trojan asteroid. ... . WISE performed an all-sky astronomical survey with images in 3.4, 4.6, 12 and 22 μm wavelength range bands, over ten months using a diameter infrared telescope in Earth orbit..

After its solid hydrogen coolant depleted, it was placed in hibernation mode in February 2011. In 2013, NASA reactivated the WISE telescope to search for near-Earth objects (NEO), such as comets and asteroids, that could collide with Earth.

The reactivation mission was called Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE). As of August 2023, NEOWISE was 40% through the 20th coverage of the full sky.

Science operations and data processing for WISE and NEOWISE take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, California. The WISE All-Sky (WISEA) data, including processed images, source catalogs and raw data, was released to the public on 14 March 2012, and is available at the Infrared Science Archive.. . .

The NEOWISE mission was originally expected to end in early 2025 with the satellite reentering the atmosphere some time after.. However, the NEOWISE mission concluded its science survey on 31 July 2024 with the satellite expected to reenter Earth's atmosphere later the same year (2 November 2024). This decision was made due to increased solar activity hastening the decay of its orbit and the lack of an onboard propulsion system for orbital maintenance. The onboard transmitter was turned off on 8 August, marking the formal decommissioning of the spacecraft.

Mission goals The mission was planned to create infrared 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 was placed in a , circular, polar, Sun-synchronous orbit for its ten-month mission, during which it has taken 1.5 million images, one every 11 seconds. The satellite orbited above the terminator, its telescope pointing always to the opposite direction to the Earth, except for pointing towards the Moon, which was avoided, and its solar cells towards the Sun. Each image covers a 47 arcminute field of view (FoV), which means a 6 arcsecond resolution. Each area of the sky was scanned at least 10 times at the equator; the poles were scanned at theoretically every revolution due to the overlapping of the images. The produced image library contains data on the local Solar System, the Milky Way, and the more distant Universe. Among the objects WISE studied are asteroids, cool and dim stars such as brown dwarfs, and the most luminous infrared galaxies.

Targets within the Solar System WISE was not able to detect Kuiper belt objects, because their temperatures are too low. Pluto is the only Kuiper belt object that was detected. It was able to detect any objects warmer than 70–100 K. A Neptune-sized object would be detectable out to 700 Astronomical unit (AU), a Jupiter mass object out to 1 light year (63,000 AU), where it would still be within the Sun's zone of gravitational control. A larger object of 2–3 Jupiter masses would be visible at a distance of up to 7–10 light years.

At the time of planning, it was estimated that WISE would detect about 300,000 main-belt asteroids, of which approximately 100,000 will be new, and some 700 Near-Earth objects (NEO) including about 300 undiscovered. That translates to about 1000 new main-belt asteroids per day, and 1–3 NEOs per day. The peak of magnitude distribution for NEOs will be about 21–22 V. WISE would detect each typical Solar System object 10–12 times over about 36 hours in intervals of 3 hours.

Targets outside the Solar System Star formation, a process where visible light is normally obscured by interstellar dust, is detectable in infrared, since at this wavelength electromagnetic radiation can penetrate the dust. Infrared measurements from the WISE astronomical survey have been particularly effective at unveiling previously undiscovered star clusters. Examples of such embedded star clusters are Camargo 18, Camargo 440, Majaess 101, and Majaess 116. In addition, galaxies of the young Universe and interacting galaxies, where star formation is intensive, are bright in infrared. At infrared wavelengths, interstellar gas clouds are also detectable, as well as proto-planetary discs. The WISE satellite was expected to find at least 1,000 proto-planetary discs.

Spacecraft The WISE satellite bus was built by Ball Aerospace & Technologies in Boulder, Colorado. The spacecraft was derived from the Ball Aerospace & Technologies RS-300 spacecraft architecture, particularly the NEXTSat spacecraft built for the successful Orbital Express mission launched on 9 March 2007. The flight system had an estimated mass of . The spacecraft was three-axis stabilized, with body-fixed solar arrays. It used a high-gain antenna in the Ku-band to transmit to the ground through the Tracking and Data Relay Satellite System (TDRSS) geostationary system. Ball also performed the testing and flight system integration.

Telescope

Construction of the WISE telescope was divided between Ball Aerospace & Technologies (spacecraft, operations support), SSG Precision Optronics, Inc. (telescope, optics, scan mirror), DRS Technologies and Rockwell International (focal planes), Lockheed Martin (cryostat, cooling for the telescope), and Space Dynamics Laboratory (instruments, electronics, and testing). The program was managed through the Jet Propulsion Laboratory.

The WISE instrument was built by the Space Dynamics Laboratory in Logan, Utah.

Mission

WISE surveyed the sky in four wavelengths of the infrared band, at a very high sensitivity. Its design specified as goals that the full sky atlas of stacked images it produced have 5-sigma sensitivity limits of 120, 160, 650, and 2600 microjanskies (μJy) at 3.3, 4.7, 12, and 23 μm (aka microns). WISE achieved at least 68, 98, 860, and 5400 μJy; 5 sigma sensitivity at 3.4, 4.6, 12, and 22 μm for the WISE All-Sky data release. 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 μm 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 μm. On the other hand, IRAS could also observe 60 and 100 μm wavelengths.

Band 1 – 3.4 μm (micrometre) – broad-band sensitivity to stars and galaxies Band 2 – 4.6 μm – detect thermal radiation from the internal heat sources of sub-stellar objects like brown dwarfs Band 3 – 12 μm – detect thermal radiation from asteroids Band 4 – 22 μm – sensitivity to dust in star-forming regions (material with temperatures of 70–100 kelvins)

The primary mission lasted 10 months: one month for checkout, six months for a full-sky survey, then an additional three months of survey until the cryogenic coolant (which kept the instruments at 17 K) ran out. The partial second survey pass facilitated the study of changes (e.g. orbital movement) in observed objects.

Congressional hearing – November 2007 On 8 November 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 planned to use WISE to detect near-Earth objects in addition to performing its science goals. It was projected that WISE could detect 400 NEOs (or roughly 2% of the estimated NEO population of interest) within its one-year mission.

Results By October 2010, over 33,500 new asteroids and comets were discovered, and nearly 154,000 Solar System objects had been observed by WISE.

Discovery of an ultra-cool brown dwarf, WISEPC J045853.90+643451.9, about 10~30 light years away from Earth, was announced in late 2010 based on early data. In July 2011, it was announced that WISE had discovered the first Earth trojan asteroid, . Also, the third-closest star system, Luhman 16.

As of May 2018, WISE / NEOWISE had also discovered 290 near-Earth objects and comets (see section below).

Project milestones The WISE mission is led by Edward L. Wright of the University of California, Los Angeles. The mission has a long history under Wright's efforts and was first funded by NASA in 1999 as a candidate for a NASA Medium-class Explorer (MIDEX) mission under the name Next Generation Sky Survey (NGSS). The history of the program from 1999 to date is briefly summarized as follows: January 1999 – NGSS is one of five missions selected for a Phase A study, with an expected selection in late 1999 of two of these five missions for construction and launch, one in 2003 and another in 2004. Mission cost is estimated at US$139 million at this time. March 1999 – WIRE infrared telescope spacecraft fails within hours of reaching orbit. October 1999 – Winners of MIDEX study are awarded, and NGSS is not selected. October 2001 – NGSS proposal is re-submitted to NASA as a MIDEX mission. April 2002 – NGSS proposal is accepted by the NASA Explorer office to proceed as one of four MIDEX programs for a Pre-Phase A study. December 2002 – NGSS changes its name to Wide-field Infrared Survey Explorer (WISE). March 2003 – NASA releases a press release announcing WISE has been selected for an Extended Phase-A study, leading to a decision in 2004 on whether to proceed with the development of the mission. April 2003 – Ball Aerospace & Technologies is selected as the spacecraft provider for the WISE mission. April 2004 – WISE is selected as NASA's next MIDEX mission. WISE's cost is estimated at US$208 million at this time. November 2004 – NASA selects the Space Dynamics Laboratory at Utah State University to build the telescope for WISE. October 2006 – WISE is confirmed for development by NASA and authorized to proceed with development. Mission cost at this time is estimated to be US$300 million.

14 December 2009 – WISE successfully launched from Vandenberg Air Force Base, California. 29 December 2009 – WISE successfully jettisoned instrument cover. 6 January 2010 – WISE first light image released. 14 January 2010 – WISE begins its regular four wavelength survey scheduled for nine months duration. It is expected to cover 99% of the sky with overlapping images in the first 6 months and continuing with a second pass until the hydrogen coolant is exhausted about three months later. 25 January 2010 – WISE detects a never-before-seen near Earth asteroid, designated 2010 AB78. 11 February 2010 – WISE detects a previously unknown comet, designated P/2010 B2 (WISE). 25 February 2010 – WISE website reports it has surveyed over 25% of the sky to a depth of 7 overlapping image frames. 10 April 2010 – WISE website reports it has surveyed over 50% of the sky to a depth of 7 overlapping image frames. 26 May 2010 – WISE website reports it has surveyed over 75% of the sky to a depth of 7 overlapping image frames. 16 July 2010 – Press release announces that 100% sky coverage will be completed on 17 July 2010. About half of the sky will be mapped again before the instrument's block of solid hydrogen coolant sublimes and is exhausted. October 2010 – WISE hydrogen coolant runs out. Start of NASA Planetary Division funded NEOWISE mission. January 2011 – Entire sky surveyed to an image density of at least 16+ frames (i.e. second scan of sky completed).

Hibernation