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Near-Earth Objects Pose Threat, General Says
for Air Force Print News
Washington - Sep 17, 2002
This summer, much of the world watched as India and Pakistan faced-off over the disputed Kashmir region, worried that the showdown could escalate into a nuclear war.
Coincidentally, U.S. early warning satellites detected an explosion in the Earth's atmosphere June 6, at the height of the tension, with an energy release estimated to be 12 kilotons.
Fortunately the detonation, equivalent to the blast that destroyed Hiroshima, occurred over the Mediterranean Sea.
However, if it had occurred at the same latitude a few hours earlier, the result on human affairs might have been much worse, said Brig. Gen. Simon P. Worden, U.S. Space Command's deputy director for operations at Peterson Air Force Base, Colo.
Had the bright flash, accompanied by a damaging shock wave, occurred over India or Pakistan, the resulting panic could have sparked a nuclear war, Worden recently told members of the congressionally mandated Commission on the Future of the
U. S. Aerospace Industry in testimony here.
Although U.S. officials quickly determined that a meteor caused the explosion, neither India nor Pakistan have the sophisticated sensors that can determine the difference between a natural near-Earth object impact and a nuclear detonation, Worden said in written testimony.
This is one of many threats posed by NEOs, especially as more and more nations acquire nuclear weapons, said Worden, who appeared before the commission as a scientist who has studied NEOs and as a space expert familiar with the technologies that can be used to address the NEO threat.
In recent years, the Department of Defense has been working to provide data about asteroid strikes to nations potentially under missile attack and to the scientific community; however, it takes several weeks for the data to be released since much of it is gathered from classified systems.
Worden suggested that a NEO warning center be established that can assess and release this data as soon as possible to all interested parties while ensuring sensitive data is safeguarded.
He recommended to the commission that a natural impact warning clearinghouse could be formed by adding no more than 10 people to current U.S. Space Command early warning centers.
This organization would catalog and provide credible warning information on future NEO impact problems, as well as rapidly provide information on the nature of an impact.
In order for this clearinghouse to provide accurate information, NEOs must first be detected, cataloged and their orbits defined.
Current ground-based systems are already cataloging large kilometer-sized objects but have a difficult time finding smaller NEOs. Most sail by the earth unnoticed until they have passed, he said.
"Just about everyone knows of the 'dinosaur killer' asteroids," Worden said. "These are objects, a few kilometers across, that strike on time scales of tens of millions of years. While the prospect of such strikes grabs people's attention and makes great catastrophe movies, too much focus on these events has been counterproductive. We need to focus our energies on the smaller, more immediate threats."
The smaller strikes, while not exactly commonplace, have occurred on several occasions over the past century, with potentially devastating results, he said.
"An object probably less than 100 meters in diameter struck Tunguska in Siberia in 1908, releasing the energy equivalent to a 10-megaton nuclear blast," Worden said. "In 1996, our satellite sensors detected a burst over Greenland equal to a 100-kiloton yield. Had any of these struck over a populated area, perhaps hundreds of thousands might have perished."
An even worse catastrophe would be an ocean impact near a heavily populated shore by one of these Tunguska-sized objects.
"The resulting tidal wave could inundate shorelines for hundreds of miles and potentially kill millions," Worden explained.
"There are hundreds of thousands of objects this size that come near the Earth," he said. "We know the orbits of just a few. New space-surveillance systems capable of scanning the entire sky every few days are needed. They could enable us to completely catalog and warn of objects (less than 100 meters in diameter)."
According to Worden, this does not mean other groups, in particular the international scientific community, should not continue their independent efforts. But the United States is likely, for the foreseeable future, to have most of the required sensors to do this job. He added that DOD has the discipline and continuity to ensure consistent, long-term focus.
"I believe various aspects related to NEO impacts, including the possibility that an impact would be misidentified as a nuclear attack, are critical national and international security issues," he said. "The focus of NEO mitigation efforts should shift to smaller objects. The near-term threats are much more likely to come from these 'small' objects, and we might be able to divert such objects without (resorting) to nuclear devices."
The National Defense Authorization Act for Fiscal Year 2001 established the Commission on the Future of the U.S. Aerospace Industry. The commission was formed to study the future of the U.S. aerospace industry in the global economy, particularly in relationship to national security, and provide recommendations to the president and Congress.
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Santa Cruz - Sep 11, 2002
Direct measurements of the surface properties and interior structures of asteroids and comets should be fundamental elements of future spacecraft missions to these primitive solar system bodies, according to participants in a scientific workshop held in Arlington, VA, from September 3-6.