[meteorite-list] Astronomers Take Search for Earth-Threatening Space Rocks to Southern Skies

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:11 2004
Message-ID: <200404061927.MAA15826_at_zagami.jpl.nasa.gov>

http://uanews.org/cgi-bin/WebObjects/UANews.woa/4/wa/SRStoryDetails?ArticleID=8916

ASTRONOMERS TAKE SEARCH FOR EARTH-THREATENING SPACE ROCKS TO SOUTHERN SKIES
>From Lori Stiles, UA News Services, 520-621-1877
April 6, 2004

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Contact Information
Stephen M. Larson 520-621-4973 slarson_at_lpl.arizona.edu
Robert H. McNaught 02-6842-6260 rmn_at_mso.anu.edu.au
Gordon Garradd 02-6769-1603 gordon_at_mso.anu.edu.au

ANU media contacts:
Tim Winkler tim.winkler_at_anu.edu.au
Vince Ford 02-6125-0261 vince_at_mso.anu.edu.au

Related Web sites
http://msowww.anu.edu.au/~rmn/index.htm
http://www.lpl.arizona.edu/css/

Discovery images
http://msowww.anu.edu.au/~gordon/Uppsala/2004FH29.gif
http://msowww.anu.edu.au/~gordon/Uppsala/2004FJ29.gif
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The hunt for space rocks on a collision course with Earth has so far been
pretty much limited to the Northern Hemisphere.

But last week astronomers took the search for Earth-threatening asteroids to
southern skies.

Astronomers using a refurbished telescope at the Australian National
University's Siding Spring Observatory discovered their first two near-Earth
asteroids (NEAs) on March 29. NEAs are asteroids that pass near the Earth
and may pose a threat of collision.

Siding Spring Survey (SSS) astronomer Gordon Garradd detected a roughly
100-meter (about 300-foot) diameter asteroid and 300-meter (about
1,000-foot) diameter asteroid in images he obtained with the 0.5-meter
(20-inch) Uppsala Schmidt telescope.

SSS partner Robert H. McNaught confirmed both discoveries in images he took
with the Siding Spring 1-meter (40-inch) that same night.

The 100-meter asteroid, designated 2004 FH29, makes a complete orbit around
the sun every 2.13 years. It missed Earth by 3 million kilometers (1.9
million miles), or 8 times the Earth-to-moon distance, yesterday, traveling
at 10 km per second (22,000 mph) relative to Earth.

The 300-meter asteroid, designated 2004 FJ29, orbits the sun about every 46
weeks. It came within 20 million kilometers (12 million miles), or within 52
lunar distances of Earth, last Tuesday, March 30, traveling at 18 km per
second (40,000 mph) relative to Earth.

Neither object poses a direct threat of colliding with Earth.

Had the asteroids not missed, damage from their impacts would have depended
on what kind of rock they're made of. The 100-meter object likely would
mostly burn up in Earth's atmosphere in an airblast equivalent to 10
megatons of TNT, comparable to the 1908 explosion above the Tunguska River
valley in Siberia, McNaught said. The 300-meter rocky asteroid likely would
reach Earth's surface, dumping the equivalent of 1,400 megatons of TNT
energy into Earth's atmosphere, he added. That's comparable to 200
Tunguskas, or 24 times the largest thermonuclear bomb explosion, a 58
megaton Soviet bomb exploded in 1961.

The new survey is a joint collaboration between the University of Arizona
Lunar and Planetary Laboratory and ANU's Research School of Astronomy and
Astrophysics. It is funded by NASA's Near-Earth Object Observation Program,
a 10-year effort to discover and track at least 90 percent of the one
kilometer (six-tenths of a mile) or larger NEOs with the potential to become
impact hazards.

When astronomers detect what they suspect is an NEA, they immediately must
take additional images to confirm their discovery, McNaught said. Surveys
often have to suspend their NEA searches and spend observing time confirming
NEAs, or they risk losing them altogether because follow-up observations
were made too late, he added.

The SSS plan is to use the 1-meter (40-inch) telescope for part of the month
to quickly confirm suspect asteroids detected with the Uppsala, freeing the
smaller telescope to continue it searches.

"Our confirmation strategy worked beautifully on our first try," McNaught
said.

The Uppsala Schmidt telescope was built in the 1950s for Uppsala Observatory
in Sweden. It was sited at Stromlo as the Uppsala Southern Station to make
wide field photographs of the southern sky. Increasing light pollution from
Canberra led to its relocation to Siding Spring, near Coonabarabran in New
South Wales, in the late 1982. Despite its high quality optics, the
telescope drifted into disuse because it used photographic film rather than
modern electronic detectors and had to be operated manually.

In 1999, McNaught and Stephen M. Larson of UAšs Lunar and Planetary
Laboratory joined in an effort to refurbish and upgrade the Uppsala
telescope. Larson had similarly just overhauled a manually operated,
photographic wide-field Schmidt telescope in the Santa Catalina Mountains
north of Tucson for his Catalina Sky Survey (CSS), part of the NASA-funded
program to spot and track asteroids headed toward Earth.

The SSS builds on telescope control, detector technology and software
developed for the CSS in Tucson. During the upgrade, the Uppsala was
completely reconditioned, and fitted with computer control, a large format
(16 megapixel) solid state detector array, and extensive support computers
and software that detects objects moving against background stars.

Larson said his reaction to the SSS milestone was "one of relief, since it
took several years to make the telescope and facility modifications. Now the
real work begins."

Larson and Catalina Sky Survey team member Ed Beshore worked on
commissioning the Uppsala telescope during the past few months.
Commissioning a telescope is like commissioning a ship: You have to get all
the parts working and working together, and adjust things so they perform as
expected.

"We actually achieved 'first light' last summer, with good images from the
start," Larson said.

McNaught and Garradd will operate SSS about 20 nights each month. They
suspend operations when the week around full moon brightens the sky, making
faint object detection difficult.

The Catalina telescope, which Larson and his team upgraded again in May
2000, features new optics that give it a 69 centimeter (27-inch) aperture
and a new, more sensitive camera. In addition to Larson and Beshore, Eric
Christensen, Rik Hill, David McLean, and Serena Howard operate CSS.

Both CSS and SSS telescopes can detect objects as faint as 20th magnitude,
close to sky background level generated by scattered city light and auroral
glow that brightens Earth's upper atmosphere.
Received on Tue 06 Apr 2004 03:26:57 PM PDT