[meteorite-list] NEOWISE Telescope Cooling Off To Find Asteroids Near Earth

[Ron Baalke]

http://www.spaceflightnow.com/news/n1310/09neowise/ 

Orbiting telescope cooling off to find asteroids near Earth
BY STEPHEN CLARK
SPACEFLIGHT NOW
October 9, 2013

Approved for an extended mission in August, NASA has reactivated the orbiting 
NEOWISE mission from hibernation, and the telescope's infrared detectors 
are cooling off to undertake a renewed survey for asteroids coming perilously 
close to Earth, the project's top scientist said Tuesday.
 
The electronic eyes inside the Wide-field Infrared Survey Explorer can 
only detect infrared light from cold asteroids when the detectors are 
chilled to frigid temperatures as low as minus 325 degrees Fahrenheit.

Amy Mainzer, principal investigator of the NEOWISE extended mission, said 
ground controllers have established communications with the WISE spacecraft. 
Engineers pointed the telescope away from Earth toward the cold darkness 
of deep space on Oct. 3, beginning a three-to-four-month chill down.

Since WISE was put in hibernation in 2011, the satellite was pointing 
its 16-inch telescope toward Earth for half of each 300-mile-high orbit, 
warming up the mission's sensitive instrumentation.

"We're now radiatively cooling," Mainzer said Tuesday in a press conference 
at the American Astronomical Society's 45th annual Division for Planetary 
Sciences meeting in Denver. "We expect to basically reverse this process."

Mainzer said it would take several months to reach a stable operating 
temperature of about minus 325 degrees Fahrenheit, with science observations 
due to resume by the beginning of 2014.

NASA awarded the NEOWISE team $5 million annually over the next three 
years to scan the inner solar system for near-Earth objects, including 
rocks which pose a potential hazard to Earth.

"We'll be discovering, we think, about 150 new objects over a three-year 
survey," Mainzer said.

Most of the objects discovered by NEOWISE will be larger than the targets 
proposed for NASA's asteroid retrieval mission concept, which calls for 
the launch of an unmanned probe to capture a small asteroid approximately 
7 meters, or 23 feet, across and tug it back to a stable position near 
the moon.

Astronauts aboard an Orion spacecraft would blast off, perhaps as early 
as 2021, and rendezvous with the asteroid for research and spacewalks 
to gather samples.

Mainzer said the NEOWISE extension is not directly affiliated with the 
asteroid retrieval mission.

The WISE spacecraft was not tailored for asteroid hunting, and the modest 
rocks sought by NASA's asteroid retrieval mission are tough to find, according 
to Mainzer, but it's "quite likely" NEOWISE will find a few.

"These objects are very difficult to get at for a number of reasons," 
Mainzer said. "For one thing, they're just intrinsically very faint."

The smallest rock spotted by NEOWISE three years ago was about 8 meters, 
or 26 feet, in diameter.

"It's clear we have a lot of work to do to characterize the small end 
of the near-Earth object population," Mainzer said.

Ground telescopes and future space-based missions may have a better chance 
of scouring the sky for small asteroids, Mainzer said.

"We are keen to find objects that are the most accessible because we think 
that would support a wide variety of missions," Mainzer said.

NEOWISE's infrared data will also yield key data on the size and reflectivity 
of many more objects, including asteroids already discovered by the telescope's 
first round of observations in 2010 and 2011.

Mainzer said NEOWISE will look at a few thousand near-Earth objects over 
the three-year extended mission.

"It's going to enable quite a lot of science," Mainzer said, adding NEOWISE 
would also be observing nearby brown dwarfs and variable stars in two 
infrared wavelengths - 3.4 and 4.6 microns.

The mission will end in 2017 when the natural shifting of the satellite's 
orbital plane around Earth puts the sun in the telescope's field-of-view.

"By early 2017, we won't be able to keep the sun out of the baffle effectively, 
and that's going to end the mission," Mainzer said.

WISE discovered more than 34,000 asteroids in the main belt between Mars 
and Jupiter, 135 near-Earth objects and 21 comets during its initial observing 
campaign in 2010 and 2011, according to a NASA press release.