Catalina Sky Survey Tops 2005 NEO Discoveries

From Lori Stiles, University Communications, 520-621-1877
Tuesday, January 17, 2006

------------------------------
Contact information listed at the end
------------------------------

When it comes to finding asteroids or comets that swing too close to
home,
the Catalina Sky Survey is currently Earth's best defense.

The Catalina Sky Survey discovered more near-Earth objects (NEOs) than
any
other sky survey in 2005. That includes more NEOs larger than a
kilometer in
diameter, as well as more smaller objects that potentially threaten
Earth.

The University of Arizona's NASA-funded Catalina Sky Survey (CSS) is
directed by Stephen M. Larson of the Lunar and Planetary Laboratory. It
is
among a handful of surveys in NASA's 10-year, congressionally-mandated
Spaceguard program that aims to discover at least 90 percent of the
one-kilometer near-Earth asteroids and comets by the end of 2008. If an
object even a third as large (300 meters) hit Earth, it would explode
with
24 times the energy of the world's largest thermonuclear bomb
explosion, a
58 megaton Soviet bomb exploded in 1961.

CSS astronomers discovered 310 NEOs, or 49 percent of all NEOs
discovered
in 2005. That's a record-breaking number of discoveries for any NEO
survey,
ever.

Of these, 29 objects are at least a kilometer across, and 40 are
classified
"potentially hazardous asteroids," objects large enough and close
enough to
Earth to bear watching. All other Spaceguard surveys found a total 46
potentially hazardous asteroids last year.

"I am elated," Larson said. He credits CSS's success to two
developments.
"We've finished upgrades on all three of our telescopes, so we have
more
sensitive detectors. And we've made a lot of improvements to our
software so
we can now process data much more efficiently."

Seven CSS astronomers operate two telescopes in the Santa Catalina
Mountains north of Tucson, Ariz., and a third telescope, in
collaboration
with the Australian National University, at Siding Spring, Australia.
That
makes CSS the only NEO survey that covers both the northern and
southern
hemispheres.

During the past three years, CSS automated its three manually
controlled
telescopes, developed computer systems capable of processing large
amounts
of data and added three new, large format CCD cameras, all for about
$500,000. Spectral Instruments of Tucson, Ariz., built the cameras,
which
incorporate ImagerLabs CCD chips thinned at the UA Steward Observatory
Imaging Technology Lab headed by Mike Lesser.

The survey is a bargain for taxpayers, the astronomers noted. "We've
done
this survey on the cheap, relative to what other surveys expend," CSS
astronomer Ed Beshore said.

CSS found nearly half the NEOs discovered in 2005 at just one-sixth the
2005 NASA Near-Earth Object Observations Program budget. The CSS team
succeeded at finding about 25 NEOs a month despite a week of downtime
due to
lightning damage last year.

CSS shut down its original survey telescope near Mount Bigelow for a
comprehensive upgrade and overhaul of virtually every telescope and
detector
subsystem in 2000. When the Schmidt telescope resumed routine
observations
in November 2003, it featured 0.7 meter (28 inch) optics, making it the
second largest Schmidt-type telescope in the United States. The
now-automated telescope has a wide-field camera (8 square degree
field-of-view) that images large regions of sky, typically 1,000 square
degrees of sky in a single night. At 8,250-feet, the Schmidt is higher
than
Tucson's air pollution. Pointing up and away from the city's lights, it
can
detect faint objects down to about 20th magnitude, or about 400,000
times
fainter than visible with the naked eye.

Robert H. McNaught and Gordon Garradd of the Siding Spring Survey near
Coonabarabran, New South Wales, began routine surveying in 2004. The
Arizona
and Australian team upgraded the 0.5 meter (20 inch) "Uppsala" Schmidt
telescope with a camera and computer system identical to the CSS
Schmidt in
the northern hemisphere. The Australian astronomers also use a
one-meter
(40-inch) telescope to quickly confirm suspect asteroids detected with
the
Uppsala telescope.

At the same time, CSS upgraded and began using the UA's 1.5 meter (60
inch)
Cassegrain reflector telescope at Steward Observatory's 9,100-foot
Mount
Lemmon site in December 2004. Its narrower (1.3 square degree)
field-of-view
camera images only a sixth the area that the Catalina Schmidt telescope
covers, but it detects fainter objects than the Schmidt telescope does.
The
Mount Lemmon telescope can detect objects more than two million times
fainter than visible with the naked eye.

CSS surveys a region of sky four times over 40 minutes to spot any
close,
fast-moving objects among the fixed background of more distant stars.
"We
observe a region more often than some other surveys because it helps us
cut
down spurious objects that show up and might be misinterpreted as being
real," Larson said.

"Another advantage is that we're set up to do our own follow-up during
the
night," Larson added. "We're as close to a real-time system as you can
get.
We actually see results within an hour after they are taken, and then
our
software analyzes the data to see if an object moves like an NEO. If
so, we
get additional observations that same evening."

The survey requires six high-speed computers running simultaneously to
process the 600 images, or 20 gigabytes of data, taken by each of the
telescopes on a good observing night. That much data would fill nearly
30
CDs.

Survey astronomers report their NEO discoveries to the Minor Planet
Center
at Harvard University, which posts them to a Website called the NEO
Confirmation Page. Amateur astronomers play a critical role by locating
and
further tracking the objects, CSS astronomer Ed Beshore said. Amateur
astronomers provide needed followup observations to help refine an
object's
orbit, allowing the Minor Planet Center to confirm if objects are true
NEOs
or not.

Once an object is designated an NEO, the job isn't finished, however.

"If you don't continue to observe these things, the uncertainties in
their
orbits increase with time," Beshore said. "You have to re-observe them
to
make sure they're where you expect them to be. It's kind of a waste of
taxpayers' money to observe them and then lose them. In addition to
surveying, CSS plans to do a lot of recovery work to make sure that
objects,
once found, aren't lost again. Discovery and followup is sort of our
good-citizen contribution to our planet's well-being."

CSS astronomers are merciless when it comes to squeezing incremental
improvements from the telescopes and computer software, Beshore added.
"We
constantly talk about how to get another 5 percent from the telescope,
how
to cover more sky, how to observe fainter objects, how much more
sensitive
we can make the software, how we can make the software compensate for
all
the false detections we get by making it more sensitive. If you just
ruthlessly attack the problem like that, pretty soon you've got 50
percent
more efficiency in your system."

Continued efforts to improve CSS should pay off in an even better NEO
yield
in 2006.

The four other major NASA-funded NEO surveys include the MIT Lincoln
Labs-Air Force LINEAR project at Soccorro, N.M.; UA's Spacewatch -- the
pioneering NEO survey founded by Tom Gehrels and directed by Robert
McMillan; Lowell Observatory's LONEOS at Flagstaff; and the Jet
Propulsion
Laboratory's NEAT program.

Last year, LINEAR discovered 137 NEOS, of which 22 were at least a
kilometer in diameter and 20 were classified as potentially hazardous
asteroids. Spacewatch discovered 82 NEOs, of which 10 were at least a
kilometer in diameter and 8 were classified as potentially hazardous.
The
same numbers for LONEOS were 42 NEOs, 4 at a kilometer or larger and 10
potentially hazardous; and for NEAT were 38 NEOs, 9 at a kilometer or
larger
and 8 potentially hazardous.

--------------------------------------------------

Contact Information
Stephen M. Larson 520-621-4973
Ed Beshore 520-621-4900

Related Web sites
http://www.lpl.arizona.edu/css/
http://cfa-www.harvard.edu/iau/NEO/ToConfirm.html
http://neo.jpl.nasa.gov/stats/