Spy satellite poses special challenges for U.S. Navy

By David Morgan - Analysis

WASHINGTON (Reuters) - Shooting down an errant U.S. spy satellite hurtling through space with a tank of toxic fuel presents a challenge for a Navy defence system designed to take out slower, lower-flying ballistic missiles, officials say.

In an operation that could last just minutes from launch to intercept, Navy officials hope a missile fired from a ship and travelling at six times the speed of sound will hit the bus-sized satellite about 140 miles (220 km) above Earth with a nonexplosive "kinetic kill vehicle."

The Aegis ballistic-missile defence system has successfully intercepted incoming missiles in 12 of 14 test flights, according to a Navy document.

That is an 85.7 percent success rate for a system that uses infrared sensors to search for a missile-shaped target heated by its supersonic travel through layers of atmosphere.

But the satellite, which became disabled soon after its 2006 launch, is flying dead in space, generating no heat. It is also moving faster than the missile system's usual target at 5-6.2 miles (8-10 km) per second or up to 22,000 miles (35,000 km) per hour.

At 5,000 pounds