NASA's NEOWISE Completes Scan for Asteroids and Comets

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Whitney Clavin 818-354-4673
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Trent Perrotto 202-358-0321
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trent.j.perrotto@nasa.gov

News release: 2011-031 Feb. 1, 2011

NASA's NEOWISE Completes Scan for Asteroids and Comets

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-031&cid=release_2011-031

PASADENA, Calif. -- NASA's NEOWISE mission has completed its survey of small bodies,
asteroids and comets, in our solar system. The mission's discoveries of previously unknown objects
include 20 comets, more than 33,000 asteroids in the main belt between Mars and Jupiter, and 134
near-Earth objects (NEOs). The NEOs are asteroids and comets with orbits that come within 45
million kilometers (28 million miles) of Earth's path around the sun.

NEOWISE is an enhancement of the Wide-field Infrared Survey Explorer, or WISE, mission that
launched in December 2009. WISE scanned the entire celestial sky in infrared light about 1.5 times. It
captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids
and comets close to Earth.

In early October 2010, after completing its prime science mission, the spacecraft ran out of the frozen
coolant that keeps its instrumentation cold. However, two of its four infrared cameras remained
operational. These two channels were still useful for asteroid hunting, so NASA extended the
NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for
more asteroids and comets, and to finish one complete scan of the main asteroid belt.

"Even just one year of observations from the NEOWISE project has significantly increased our
catalog of data on NEOs and the other small bodies of the solar systems," said Lindley Johnson,
NASA's program executive for the NEO Observation Program.

Now that NEOWISE has successfully completed a full sweep of the main asteroid belt, the WISE
spacecraft will go into hibernation mode and remain in polar orbit around Earth, where it could be
called back into service in the future.

In addition to discovering new asteroids and comets, NEOWISE also confirmed the presence of
objects in the main belt that had already been detected. In just one year, it observed about 153,000
rocky bodies out of approximately 500,000 known objects. Those include the 33,000 that NEOWISE
discovered.

NEOWISE also observed known objects closer and farther to us than the main belt, including roughly
2,000 asteroids that orbit along with Jupiter, hundreds of NEOs and more than 100 comets.

These observations will be key to determining the objects' sizes and compositions. Visible-light data
alone reveal how much sunlight reflects off an asteroid, whereas infrared data is much more directly
related to the object's size. By combining visible and infrared measurements, astronomers also can
learn about the compositions of the rocky bodies -- for example, whether they are solid or crumbly.
The findings will lead to a much-improved picture of the various asteroid populations.

NEOWISE took longer to survey the whole asteroid belt than WISE took to scan the entire sky
because most of the asteroids are moving in the same direction around the sun as the spacecraft
moves while it orbits Earth. The spacecraft field of view had to catch up to, and lap, the movement of
the asteroids in order to see them all.

"You can think of Earth and the asteroids as racehorses moving along in a track," said Amy Mainzer,
the principal investigator of NEOWISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"We're moving along together around the sun, but the main belt asteroids are like horses on the outer
part of the track. They take longer to orbit than us, so we eventually lap them."

NEOWISE data on the asteroid and comet orbits are catalogued at the NASA-funded International
Astronomical Union's Minor Planet Center, a clearinghouse for information about all solar system
bodies at the Smithsonian Astrophysical Observatory in Cambridge, Mass. The science team is
analyzing the infrared observations now and will publish new findings in the coming months.

When combined with WISE observations, NEOWISE data will aid in the discovery of the closest
dim stars, called brown dwarfs. These observations have the potential to reveal a brown dwarf even
closer to us than our closest known star, Proxima Centauri, if such an object does exist. Likewise, if
there is a hidden gas-giant planet in the outer reaches of our solar system, data from WISE and
NEOWISE could detect it.

The first batch of observations from the WISE mission will be available to the public and
astronomical community in April.

"WISE has unearthed a mother lode of amazing sources, and we're having a great time figuring out
their nature," said Edward (Ned) Wright, the principal investigator of WISE at UCLA.

JPL manages WISE for NASA's Science Mission Directorate at the agency's headquarters in
Washington. The mission was competitively selected under NASA's Explorers Program, which
NASA's Goddard Space Flight Center in Greenbelt, Md., manages. The Space Dynamics Laboratory
in Logan, Utah, built the science instrument, and Ball Aerospace & Technologies Corp. of Boulder,
Colo., built the spacecraft. Science operations and data processing take place at the Infrared
Processing and Analysis Center at the California Institute of Technology in Pasadena. JPL manages
NEOWISE for NASA's Planetary Sciences Division. The mission's data processing also takes place at
the Infrared Processing and Analysis Center.

More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu and
http://jpl.nasa.gov/wise .

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