Pentagon officials said they think a Navy missile scored a direct hit on the fuel tank of an errant satellite late Wednesday, eliminating a toxic threat to people on Earth.
"We have a high degree of confidence we got the tank," Marine Gen. James Cartwright said at a Pentagon briefing Thursday morning.
A fireball and a vapor cloud seen after the strike appeared to indicate the toxic hydrazine fuel had been destroyed, he said. The missile that struck the satellite did not carry an explosive warhead.
Cartwright also said the satellite seemed to be reduced to small pieces.
"Thus far, we see nothing larger than a football," he said.
The military was analyzing data from the strike to confirm that the tank was hit and that no larger pieces of debris escaped detection, Cartwright said.
The missile that struck the satellite was launched from the ballistic missile defense cruiser USS Lake Erie from the Pacific Ocean west of Hawaii at 10:26 p.m. ET Wednesday, the general said. It struck the satellite more than 130 miles above it 24 minutes later.
Cartwright said the Navy took its first opportunity to hit the satellite and acted before days of expected bad weather may have prevented a missile launch.
Cartwright said debris from the satellite was burning up in the atmosphere over the Atlantic and Pacific oceans. This process was expected for the next day or so.
The missile didn't carry a warhead, with authorities saying the impact was expected to be sufficient to destroy the fuel tank.
Officials had said the missile would not be fired until the space shuttle Atlantis landed, which it did Wednesday, to ensure debris from the destroyed satellite didn't strike the shuttle.
The attempt cost up to $60 million, according to estimates.
Without intervention, the satellite would have fallen to Earth in early March, officials said. However, since it malfunctioned immediately after being launched in December 2006, it had a full tank -- about 1,000 pounds -- of frozen, toxic hydrazine propellant.
The fuel tank probably would have survived re-entry if the satellite had fallen to Earth on its own. It could have dispersed harmful or even potentially deadly fumes over an area the size of two football fields. Hydrazine is similar to chlorine or ammonia in that it affects the lungs and breathing tissue.
The Chinese military destroyed an aging weather satellite last year, prompting questions about whether the United States is merely flexing its muscle to show an economic and military rival that it can destroy satellites, too.
James Jeffrey, deputy national security adviser, denied such allegations this week. "This is all about trying to reduce the danger to human beings," he said.
But Beijing appears to have doubts.
"China is continuing to closely follow the possible harm caused by the U.S. action to outer space security and relevant countries," Foreign Ministry spokesman Liu Jianchao said Thursday.
"China further requests that the United States ... promptly provide to the international community the necessary information ... so that relevant countries can take precautions."
In January 2007, China used a land-based missile to destroy a 2,200-pound satellite that was orbiting 528 miles above the Earth. The impact left more than 100,000 pieces of debris orbiting the planet, NASA estimated -- 2,600 of them more than 4 inches across. The U.S. agency called the breakup of the Fengyun-C satellite the worst in history.
In 1989, a U.S. fighter jet destroyed an American satellite by firing a modified air-to-air missile into space from an altitude of 80,000 feet. That move adds to evidence the U.S. acted Wednesday strictly to guard against the prospect of a potential disaster, Cartwright said.
The military timed its shootdown attempt so that resulting debris would tumble into the atmosphere and not interfere with other satellites, said Christina Rocca, a U.S. diplomat and expert on disarmament. Her comments were included in an online U.N. report on this month's Conference on Disarmament in Geneva, Switzerland.
The military also timed its efforts to minimize the chances that debris would hit populated areas. But the United States is "prepared to offer assistance to governments to mitigate the consequences of any satellite debris impacts on their territory," according to a report of Rocca's remarks on the Web site of the Geneva office of the United Nations.