WASHINGTON – The military's analysis of the missile strike on a dead U.S. spy satellite has revealed no sign of danger from debris, including no hazard from the satellite's fuel tank, a Pentagon spokesman said Friday.
"As we continue to do the post-strike analysis, [it] continues to give us confidence that the hydrazine tank was ruptured. However, the analysis is still ongoing," spokesman Bryan Whitman said.
U.S. officials have said the main reason they shot down the satellite was because of the potential health hazard to humans in the event the satellite's fuel tank, carrying 1,000 pounds of toxic hydrazine, landed in a populated area.
The satellite lost power shortly after reaching its initial orbit in December 2006, and it was projected to re-enter the atmosphere in the first days of March.
On Wednesday night a Navy cruiser in the Pacific launched a missile at the satellite, and military video of the event indicated that it pulverized the spacecraft.
Whitman said initial indications reported on Thursday that the SM-3 missile hit the fuel tank as planned have been reinforced by further analysis. But he said officials are still not 100 percent certain.
"There has been no new data that has changed our level of confidence in the success of the operation," he said.
Whitman said there were no indications of danger posed by falling debris, some of which already has re-entered the atmosphere.
Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, said on Thursday that they had detected no debris larger than a football, and Whitman said that as of Friday that statement remained true.
"Debris tracking and cataloguing is ongoing," Whitman said. "There is no change to our belief that most of the debris should re-enter within about two weeks."
Whitman also said that teams of experts assembled by the government in advance of the shootdown to be ready in case significant debris fell on U.S. soil might not be used.
"We are in the process of taking a look and standing down some of those consequence-management and recovery teams," he said.
Cartwright said Thursday that officials had a "high degree of confidence" that the tank had been destroyed, but would need a day or two to study debris before knowing for sure.
"We have a bunch of techies that are trying to work their way through the data," he told a Pentagon news conference.
"At the end of the day, what's important to us is what debris is out there that could fall, where is it going to fall, and — if it falls in some area that's populated — getting to it and making sure nobody gets hurt," he said.
Debris from the satellite had started re-entry over the Atlantic and Pacific oceans and re-entry was expected to continue into Friday, Cartwright said.
He gave no further details about where the military had tracked fields of fragments from the satellite, which was described as the size of a school bus and weighing about 5,000 pounds.
Amateur observers on Canada's west coast reported see seeing some two dozen trails of debris in the sky within minutes of the missile hit, while they were watching a lunar eclipse late Wednesday.
Private defense analysts said they didn't expect many, if any, pieces of the debris to turn up.
"I wouldn't want to get hit by one, but the chances are pretty small," analyst John Pike said.
That point also was made last week by critics who said the shootdown was unnecessary because parts of rockets or satellites regularly fall from space, but usually burn up on re-entering the atmosphere. When they don't, they rarely fall where they do any harm.
Even before the missile launch, some international leaders and critics in the scientific community suggested it was a thinly disguised attempt to test an anti-satellite weapon — one that could take out other nations' orbiting communications and spy spacecraft.
They also said the U.S. was worried that allowing the errant satellite to fall itself would mean larger pieces might survive re-entry, opening the possibility that secret technology could wind up in the hands of the Chinese or others.
Cartwright estimated there was an 80 percent to 90 percent chance that the missile struck the fuel tank, containing 1,000 pounds of hydrazine. He showed a video clip of the missile smashing into the satellite and producing a flash of light.
"We have a fireball, and given that there's no fuel [on the tip of the missile], that would indicate that that's a hydrazine fire," he said.
The video showed the three-stage SM-3 missile launching from the USS Lake Erie at 10:26 p.m. EST Wednesday northwest of Hawaii, and of the missile's small "kill vehicle" — a non-explosive device at the tip — maneuvering into the path of the satellite and colliding spectacularly.
Cartwright said the satellite and the kill vehicle collided at a combined speed of 22,000 mph about 130 miles above Earth's surface, and that the collision was confirmed at a space operations center at 10:50 p.m. EST.