- ARLINGTON, Va. (UPI) -- Celestial
objects crossing Earth's orbit threaten society in ways far more realistic
than the doomsday scenarios Hollywood portrays in films such as "Armageddon,"
an Air Force general said Thursday.
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- The most immediate threat is from smaller objects hitting
the atmosphere and exploding, said Brig. Gen. Pete Worden, vice director
of operations at Air Force Space Command.
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- Military sensors detect many such explosions annually.
About 30 of the yearly impacts are large enough to equal the blast of at
least 1,000 tons of dynamite, he told the Workshop on Scientific Requirements
for Mitigation of Hazardous Comets and Asteroids.
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- "(Some of these) release between 3 and 10 kilotons
(of energy), roughly comparable to the Hiroshima bomb," Worden said.
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- "This is significant because we're seeing a proliferation
of nuclear weapons, and (these blasts) are in the class of those weapons."
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- One such impact occurred over the Mediterranean Sea this
past June, Worden said, when new nuclear powers India and Pakistan were
ready to wage war over the disputed Kashmir region.
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- If the 20-kiloton blast had occurred over Southwest Asia,
it might have triggered a nuclear exchange before the U.S. government or
other agencies with sophisticated sensors could have announced the true
cause, he said.
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- The U.S. military wants to work more closely with scientific
groups for rapid dissemination of data on such near-Earth objects, Worden
said. The Department of Defense is developing a NEO information clearinghouse
and warning center as part of the existing missile warning and space object
tracking complex in Cheyenne Mountain, Colo., he said.
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- Meteor storms, a more energetic form of events such as
the annual Leonid and Perseid meteor showers, also present a real hazard,
Worden said. The showers are caused by a trail of dust and small debris
left by comets, and storms occur when the trail is particularly dense.
An extremely strong storm is capable of damaging satellites, especially
the very valuable Global Positioning System, he said.
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- Improved space surveillance is the key to spotting and
possibly avoiding such hazards, and military sensors play a role here,
he said.
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- The current generation of digital camera-like sensors
could scan the entire sky in about a week, he said, and systems under development
in Canada and the United States might be able to do the same job in only
hours.
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- If larger objects are detected approaching the planet,
it should be possible to determine their basic composition with radar,
said Wlodek Kofman of the Laboratoire Planetologie in Grenoble, France.
Measuring the scattering of a radar signal from fractures and other discontinuities
in a meteor or comet would help show the difference between a solid object,
a "rubble pile" of smaller pieces or other possibilities, Kofman
told the workshop.
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- Knowing an object's make-up could be vital in picking
the proper method for redirecting it. A small rocket motor that would easily
divert a solid body, for example, might break up a rubble pile into a cloud
of objects headed for Earth.
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- As for diverting the "planet killers" Hollywood
focuses on, researchers should focus on rockets and other methods far more
conventional than the screenwriter's choice of a nuclear weapon, Worden
said.
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- The most important thing for researchers to do is work
out a command and control structure for determining issues such as who
sounds the alarm and who would pay for a diversion scheme, he said.
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- The NEO threat is real enough that researchers have to
fight the "giggle factor" that arises when policy leaders first
hear about the issue, he said. Scientists should arm themselves with as
broad a spectrum of information as possible on realistic threats before
trying to educate the public or lawmakers, he said.
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- The workshop, sponsored by NASA, the University of Maryland,
the National Optical Astronomy Observatories and several companies, seeks
to increase understanding of NEOs to find effective ways of diverting or
disrupting any objects that could threaten the planet. The group expects
to publish a recommended timeline of research necessary to meet that goal
by 2030.
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- Copyright © 2002 United Press International. All
rights reserved.
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