WASHINGTON – Debris from an obliterated U.S. spy satellite is being tracked over the Pacific and Atlantic oceans but appears to be too small to cause any damage on Earth, a senior military officer said Thursday, just hours after a Navy missile scored a direct hit on the failing satellite.

Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff and an expert on military space technologies, told a Pentagon news conference that officials have a “high degree of confidence” that the missile launched from a Navy cruiser Wednesday night hit exactly where intended.

He estimated there was an 80-90 percent chance that the missile struck the most important target on the satellite – its fuel tank, containing 1,000 pounds of hydrazine, which Pentagon officials say could have posed a health hazard to humans if it had landed in a populated area.

Unlike most spacecraft that fall out of orbit and re-enter the atmosphere, this satellite had an almost full fuel tank because it lost power and became uncontrollable shortly after it reached its initial orbit in December 2006. Cartwright said the hydrazine alone was justification for undertaking the unprecedented effort to use a Navy missile interceptor to attempt to destroy the satellite in orbit.

Cartwright said experts were still watching the debris fields and he could not yet rule out that hazardous material would fall to Earth. But he indicated that this appeared unlikely to pose a problem.

“Thus far we’ve seen nothing larger than a football,” he said, referring to debris spotted by radars and other sensors.

The military concluded that the missile had successfully shattered the satellite because trackers detected a fireball, which seemed to indicate the exploding hydrazine in the tank. Cartwright said it was unlikely that the fireball could have been caused by anything other than the hydrazine. Also, a vapor cloud was detected, further suggesting the destruction of the fuel, Cartwright said.

Debris from the satellite has started re-entry and will continue through Thursday and into Friday, Cartwright said.

The size of the debris is smaller than the Pentagon had forecast and most of the satellite’s intelligence value was likely destroyed, Cartwright said. Though the Pentagon has played down that aspect of the shootdown, analysts had said one of the reasons for the operation was that officials worried that without it, larger chunks of the satellite could fall and be recovered, opening the possibility of secret technology falling into the hands of the Chinese or others.