NEOWISE, the Near-Earth Object Wide-field Infrared Survey Explorer, is a space telescope that detects, tracks and characterizes moving solar system objects, including near-Earth asteroids. It surveys the sky in infrared, which makes it particularly well-suited to observing very dark asteroids that do not reflect much visible light.
Originally launched as WISE in 2009, the telescope and its 4 infrared detectors were kept chilled inside a tank with frozen hydrogen-filled walls to prevent WISE from detecting its own heat. It scanned the sky for the nearest and coolest stars, the most luminous galaxies in the universe, and asteroids.
The spacecraft's hydrogen supply ran out as expected in 2010, rendering 2 of its detectors useless. After a 30-month hibernation, NASA reactivated the spacecraft as NEOWISE in 2013. The mission implemented a new data processing pipeline that was designed to work best on solar system objects that have detectable motion. NEOWISE is expected to operate until atmospheric drag shifts its orbit to the point where it will be unable to make observations without sunlight or reflected Earth light entering the telescope.
WISE science goals and results
- To find the nearest and coolest stars
- To find the most luminous galaxies in the universe
- To find and study asteroids in our solar system
- To better understand the evolution of planets, stars and galaxies
During its primary mission, WISE scanned the entire sky twice in infrared, snapping pictures of three-quarters of a billion objects. By February 2011, at the end of the primary mission and 4-month NEOWISE Post-Cryogenic Mission, the space telescope had detected more than 157,000 moving solar system objects that included at least 584 near-Earth objects, roughly 2,000 Jupiter Trojans, 18 Centaurs and scattered-disk objects, and about 120 comets. WISE also detected a handful of irregular satellites of Jupiter and Saturn, including Iapetus and Phoebe, as well as cometary dust trails and dust bands in the zodiacal cloud.
NEOWISE science goals and results
The overall goal of NEOWISE is to detect, track and characterize near-Earth asteroids. The goal of the 3-year primary mission, which started in December 2013, was to observe the entire sky 6 times using the telescope's remaining 2 infrared detectors.
The extended mission's current goals are:
- Expand on the NEOWISE survey of Near-Earth Objects at mid-infrared wavelengths using WISE W1 and W2 channels
- Obtain physical characterization (including diameters and albedos) of these NEOs and the several thousand other small bodies detected by NEOWISE
As of mid-April 2019, NEOWISE has made over 800,000 infrared observations of approximately 34,000 different solar system objects.
NEOWISE principal investigator: Amy Mainzer, JPL
Key NEOWISE discoveries
Launch mass: 673.6 kilograms
Bus and science instrument mass: 661 kilograms
Dimensions: 2.85 meters along telescope axis, 2 meters wide on solar panel axis, 1.7 meters deep.
Power: NEOWISE's fixed solar arrays can provide up to 551 watts of power; on average the spacecraft consumes 301 watts.
Cooling: WISE's cyrostat cooling system, which surrounds the telescope and its infrared detectors, used a primary and secondary frozen hydrogen tank to chill the telescope's two longer-wavelength detectors to less than 8 Kelvin. The hydrogen supply was expected to last 10 months, and lasted until roughly 10-and-a-half months after launch.
Orbit: WISE was launched into a 525-kilometer, circular, sun-synchronous polar orbit with an inclination of 97.5 degrees. Over time, atmospheric drag has caused it to drift into what is now a 481 x 487-kilometer orbit with an inclination of 97.4 degrees.
The orbit allows the spacecraft to stay in sunlight continuously, with its solar arrays face-on to the Sun while the telescope points perpendicular into space. As the spacecraft continues to drift, it will eventually be unable to observe without sunlight or reflected Earth light entering the telescope, which will end the mission.
Launch vehicle: Delta II 7320-10 from Vandenberg Air Force Base
NEOWISE is equipped with a 40-centimeter-diameter telescope. Light from the telescope is routed to 4, 1-megapixel infrared detectors tuned to distinct wavelengths: 3.4, 4.6, 12, and 22 μm (designated W1, W2, W3, W4, respectively). After the telescope's frozen hydrogen supply ran out, only the shorter-wavelength 3.4 and 4.6 μm detectors remained usable.
WISE’s 1-million-pixel detectors were a vast improvement over the 1983 Infrared Astronomical Satellite’s 62-pixel detectors. The James Webb Space Telescope will improve on WISE with 4-million-pixel detectors in the 0.6 to 5 μm range, and 1-million pixel-detectors up to 28 μm.
- 11 April 2019: NASA releases fifth year of NEOWISE data
- January 2019: The spacecraft's orbit has remained stable for longer than expected thanks to low solar activity over the past 3 years, which has minimized atmospheric drag
- 2018: NEOWISE continues to receive mission extensions
- June 2017: NEOWISE mission approved through the end of 2017
- January 2017: NEOWISE funding set to expire in 3 months
- 23 December 2013: NEOWISE begins 3-year mission
- 3 October 2013: NEOWISE brought out of hibernation
- 21 August 2013: NASA announces NEOWISE 3-year mission, spacecraft orbit expected to degrade by 2017
- Early to mid-2013: NASA considers waking NEOWISE to assist with its Asteroid Initiative, initially to help find targets for the now-defunct Asteroid Redirect Mission. It was eventually funded by the Planetary Science Division's Near-Earth Objects Observation Program.
- 17 February 2011: NEOWISE put into hibernation
- 1 February 2011: NEOWISE Post-Cryogenic Mission completes a survey of the inner edge of the main asteroid belt
- Around October 2010: 4-month NEOWISE Post-Cryogenic Mission begins
- 30 September 2010: WISE primary cryogenic hydrogen tank depleted, ending mission
- 5 August 2010: WISE secondary cryogenic hydrogen tank depleted
- Mid-July 2010: WISE sky survey completed
- 14 January 2010: WISE sky survey begins
- 14 December 2009: WISE launches