Wide-field Infrared Survey Explorer

Wide-field Infrared Survey Explorer

Artist concept of WISE spacecraft
Names MIDEX/WISE, Explorer 92
Mission type Infrared telescope
Operator NASA / JPL
COSPAR ID 2009-071A
SATCAT № 36119
Website http://www.nasa.gov/wise
Mission duration Planned: 10 months[1]
Elapsed: 6 years, 2 months and 6 days
Spacecraft properties
Bus Ball Aerospace RS-300
Manufacturer Ball Aerospace
Lockheed Martin
Space Dynamics Laboratory
SSG Precision Optronics
Launch mass 661 kg (1,457 lb)[1]
Payload mass 347 kg (765 lb)[1]
Dimensions 2.85 × 2 × 1.73 m (9.4 × 6.6 × 5.7 ft)[1]
Power 551 W[1]
Start of mission
Launch date December 14, 2009, 14:09:33 (2009-12-14UTC14:09:33Z) UTC
Rocket Delta II 7320-10
Launch site Vandenberg SLC-2W
Contractor United Launch Alliance
Orbital parameters
Reference system Sun-synchronous polar
Regime Low Earth
Semi-major axis 6,869.7 km (4,268.6 mi)
Eccentricity 0.000472
Perigee 488.3 km (303.4 mi)
Apogee 494.8 km (307.5 mi)
Inclination 97.5°
Period 94.45 min
RAAN 156.3°
Argument of perigee 103.1°
Mean anomaly 257.05°
Mean motion 15.25°
Velocity 7.6 km/s (4.7 mi/s)
Epoch May 21, 2015, 03:00:06 UTC[2]
Revolution number 30060
Main telescope
Diameter 0.4 m (1.3 ft)[1]
Wavelengths 3.4, 4.6, 12 and 22 microns[1]
Instruments
Four infrared detectors

Wide-field Infrared Survey Explorer (WISE) is a NASA infrared-wavelength astronomical space telescope launched in December 2009,[3][4][5] and placed in hibernation in February 2011 when its transmitter turned off.[6] It was re-activated in 2013.[7] Its observations supported the discovery of the first Y Dwarf and Earth trojan asteroid, tens of thousands of new asteroids, and numerous previously undiscovered star clusters.[6][8][9][10][11][12]

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 40 cm (16 in) diameter infrared telescope in Earth orbit.[13] After its hydrogen coolant depleted, a four-month mission extension called NEOWISE was conducted to search for near-Earth objects such as comets and asteroids using its remaining capability.[14]

The All-Sky data including processed images, source catalogs and raw data, was released to the public on March 14, 2012, and is available at the Infrared Science Archive.[15][16][17][18] In August 2013, NASA announced it would reactivate the WISE telescope for a new three-year mission to search for asteroids that could collide with Earth.[7] 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.

Mission goals

The mission was planned to create infrared images of 99 percent 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 525 km (326 mi), circular, polar, Sun-synchronous orbit for its ten-month mission, during which it has taken 1.5 million images, one every 11 seconds.[19] 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, 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.[20] 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, dim stars such as brown dwarfs, and the most luminous infrared galaxies.

Targets outside the Solar System

Stellar nurseries, which are covered by interstellar dust, are 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.[12] Examples of such embedded star clusters are Camargo 18, Camargo 440, Majaess 101, and Majaess 116.[21][22] In addition, galaxies of the young Universe and interacting galaxies, where star formation is intensive, are bright in infrared. On this wavelength the interstellar gas clouds are also detectable, as well as proto-planetary discs. WISE satellite was expected to find at least 1,000 of those proto-planetary discs.

Targets within the Solar System

WISE was not able to detect Kuiper belt objects, because their temperatures are too low.[23] It was able to detect any objects warmer than 70–100 K. A Neptune-sized object would be detectable out to 700 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.[23]

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.[20]

Spacecraft

Construction of the WISE telescope was divided between Ball Aerospace & Technologies (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 was managed through the Jet Propulsion Laboratory.[14]

The WISE instrument was built by the Space Dynamics Laboratory in Logan, Utah. The WISE spacecraft bus 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 (1,230 lb). 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.

Mission

Comet C/2007 Q3 (Siding Spring) in infrared by WISE
A scaffolding structure built around WISE allows engineers access while its hydrogen coolant is being frozen

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 micrometers (aka microns).[24] WISE achieved at least 68, 98, 860, and 5400 µJy 5-sigma sensitivity at 3.4, 4.6, 12, and 22 micrometers for the WISE All-Sky data release.[25] 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 micrometers (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 micrometers.[24] On the other hand, IRAS could also observe 60 and 100 micron wavelengths.[26]

The primary mission lasted ten months: one month for checkout, six months for a full-sky survey, then an additional three months of survey until 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.[27]

Congressional hearing

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.[28]

NASA officials told Committee staff that NASA plans 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 percent 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 were observed by WISE.[29]

Discovery of an ultra-cool brown dwarf, WISEPC J045853.90+643451.9, about 10 to 30 light years away from Earth, was announced in late 2010 based on early data.[30] In July 2011 it was announced that WISE had discovered the first Earth trojan asteroid, 2010 TK7.[31] Also, the third-closest star system, Luhman 16.

As of August 2015, WISE/NEOWISE has also discovered 211[32] near-Earth objects and comets (see also section NEOWISE below).

Project milestones

The WISE Mission is led by Dr. 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:

Comet C/2013 A1 Siding Spring - four different images against background stars (NEOWISE; July 28, 2014).

History

This first light image is a false color infrared image of the sky in the direction of the Carina constellation.

Launch

The launch of the Delta II rocket carrying the WISE spacecraft was originally scheduled for December 11, 2009. This attempt was scrubbed to correct a problem with a booster rocket steering engine. The launch was then rescheduled for December 14, 2009.[44] The second attempt launched on time at 14:09:33 UTC (06:09 local PST) from Vandenberg Air Force Base in California. The rocket successfully placed the WISE spacecraft into the planned polar orbit at an altitude of 326 miles (525 km) above the Earth.[5]

WISE avoided the problem that affected Wide Field Infrared Explorer (WIRE), which failed within hours of reaching orbit in March 1999.[45] In addition, WISE was 1,000 times more sensitive than prior surveys such as IRAS, AKARI, and COBE's DIRBE.[24]

"Cold" mission

A month-long checkout after launch found all spacecraft systems functioning normally and both the low- and high-rate data links to the operations center working properly. The instrument cover was successfully jettisoned on December 29, 2009.[46] A first light image was released on January 6, 2010: an eight-second exposure in the Carina constellation showing infrared light in false color from three of WISE's four wavelength bands: Blue, green and red corresponding to 3.4, 4.6, and 12 micrometers, respectively.[47] On January 14, 2010, the WISE mission started its official sky survey.[48] The WISE group's bid for continued funding for an extended "warm mission" scored low by a NASA review board, in part because of a lack of outside groups publishing on WISE Data. Such a mission would have allowed use of the 3.4 and 4.6 micrometers detectors after the last of cryo-coolant had been exhausted, with the goal of completing a second sky survey to detect additional objects and obtain parallax data on putative brown dwarf stars. NASA extended the mission in October 2010 to search for near-Earth objects.[14]

By October 2010, over 33,500 new asteroids and comets were discovered, and over 154,000 Solar System objects were observed by WISE.[29] While active it found dozens of previously unknown asteroids every day.[49] In total, it captured more than 2.7 million images during its primary mission.[50]

NEOWISE

Number of NEOs detected by various surveys:
      LINEAR       NEAT       Spacewatch       LONEOS       CSS
      Pan-STARRS       NEOWISE       other
Some of the comets discovered during NEOWISE

In October 2010, NASA extended the mission by one month with a program called Near-Earth Object WISE (NEOWISE).[14] Due to its success, the program was extended a further three months.[6] The focus was to look for asteroids and comets close to Earth orbit, using the remaining post-cryogenic detection capability (two of four detectors on WISE work without cryogen).[14] In February 2011, NASA announced that NEOWISE had discovered many new objects in the Solar System, including twenty comets.[51] During its primary and extended missions, the spacecraft delivered characterizations of 158,000 minor planets, including more than 35,000 newly discovered objects.[52][53] The spacecraft was put into hibernation on February 1, 2011.[6] In September 2013, it was reactivated and assigned to assist NASA's efforts to identify the population of potentially hazardous near-Earth objects.[54] Few objects smaller than 100 meters in diameter were detected by NEOWISE's automated detection software known as WISE Moving Object Processing Software (WMOPS).[55] The software requires five or more detections.[55] The average albedo of asteroids larger than 100 meters discovered by NEOWISE is 0.14.[55]

As of January 2016, WISE/NEOWISE statistics lists a total of 230 near-Earth objects (NEOs) discovered by the spacecraft:[32]

Of the 205 near-Earth asteroids (NEAs), 40 of them are considered potentially hazardous asteroids (PHAs), a subset of the much larger family of NEOs, but particularly more likely to hit Earth and cause significant destruction.[32] NEOs can be divided into NECs (comets only) and NEAs (asteroids only), and further into subcategories such as Atira or Apohele asteroids, Aten asteroids, Apollo asteroids, Amor asteroids and the potentially hazardous asteroids (PHAs).[56]

Data releases

On April 14, 2011, a preliminary release of WISE data was made public, covering 57 percent of the sky observed by the spacecraft.[57] On March 14, 2012, a new atlas and catalog of the entire infrared sky as imaged by WISE was released to the astronomic community.[38] On July 31, 2012 NEOWISE Post-Cryo Preliminary Data was released.[6] A release called AllWISE, combining all data, was approved.[6]

Recommissioning

On August 21, 2013, NASA announced it would recommission WISE with a new mission to search for asteroids with orbits that could potentially lead to a collision with Earth. Additionally, it will search for asteroids that a robotic spacecraft could potentially intercept and redirect to orbit the Moon. The new mission began in September and is scheduled to last three years.[7] With all coolant long used up, NASA brought the temperature of the craft down from its previous 200 K to the necessary 75 K by having the telescope stare into deep space for a while. This caused most of the built up heat to radiate away. The spacecraft's instruments were then re-calibrated and the new mission commenced.[50]

NASA said it hopes to discover 150 previously unknown target asteroids, known as near-Earth objects. The agency hopes to also learn more about the size and shape of 2,000 known asteroids.[50] It will cost an estimated $5 million per year. The new mission was due in part to calls for NASA to step up asteroid detection after the previously undetected Chelyabinsk meteor exploded over Russia in February 2013.[7]

Brown dwarf table

WISE-discovered brown dwarfs within 20 light-years include:

Object ly Spectral
type
Constellation Right
ascension
Declination
Luhman 16 6.6 L8 + T1 Vela 10h 49m 15.57s −53° 19 06
WISE 0855−0714 7.1 Y Hydra
WISE 1506+7027 11 T6 Ursa Minor 15h 06m 49.89s 70° 27 36.23
WISE 0350−5658 12 Y1 Reticulum 03h 50m 00.32s −56° 58 30.2
WISE 1741+2553 18 T9 Hercules 17h 41m 24.22s 25° 53 18.96
WISE 0359−5401 19 Y0 Reticulum 03h 59m 34.06s −54° 01 54.6

Before the discovery of Luhman 16 in 2013, WISE 1506+7027 at a distance of 11.1+2.3
−1.3
light-years was suspected to be closest brown dwarf on the list of nearest stars.[58]

Selected discoveries

Examples of the WISE mission's numbered minor planet discoveries include:

  • 241527 Edwardwright
  • (241528) 2010 CA10
  • 241529 Roccutri
  • 243516 Marklarsen
  • (243526) 2010 DY28
  • (243529) 2010 DO50
  • (243546) 2010 JH61
  • (246837) 2010 CR51

  • (246841) 2010 DR58
  • (246842) 2010 EZ5
  • (246861) 2010 KC18
  • (249514) 2010 CZ44
  • (249515) 2010 CF48
  • (249516) 2010 CV60
  • (249519) 2010 CA130
  • (249521) 2010 CU212

  • (249522) 2010 DP15
  • (249523) 2010 DO53
  • (249530) 2010 GJ92
  • (249539) 2010 HY7
  • (249540) 2010 HX14
  • (249541) 2010 HR25
  • (249542) 2010 HS37
  • (249543) 2010 HA40

  • (249544) 2010 HQ44
  • (249545) 2010 HB45
  • (249546) 2010 HE47
  • (249547) 2010 HZ83
  • (249553) 2010 JV136
  • (249556) 2010 KX29

Gallery

Full sky views by WISE

Selected images by WISE

Map with nearby WISE stars

Nearby stars with WISE discoveries

See also

References

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