FACTBOX: High-tech system to try to intercept satellite

(Reuters) - President George W. Bush has ordered the Navy to try to shoot down a defunct U.S. spy satellite that could leak deadly toxic gas if its fuel tank reaches the Earth's atmosphere intact.

Here is how the United States will try to destroy it:

- Two U.S. Navy ships have been deployed in the Pacific armed with anti-ballistic missile systems to target the bus-sized satellite. A third ship will help collect data as part of the task force.

- The ships use "Aegis" combat systems with powerful computers and radar to detect and track the satellite as it rises above the horizon. The Aegis system, built by Lockheed Martin Corp, provides target data to a ship-based interceptor known as a Standard Missile-3.

- Upon command from the ship's crew, the SM-3 missile, built by Raytheon Co., boosts from its launcher and establishes radio communication with the ship.

- Using in-flight communications, the three-stage missile guides itself to the predicted interception point. After being propelled into space, the missile's third stage pitches over to eject its nosecone, exposing the so-called Kinetic Warhead.

- Roughly 30 seconds before the scheduled intercept, the warhead separates from the third stage and scans for the target using heat-seeking infrared homing technology.

- The warhead closes on the satellite using tiny onboard thruster rockets at about eight kilometers per second, roughly the same speed as the satellite.

- The warhead is designed to zero in on the fuel tank for maximum destruction. The stated goal is to pulverize it so its toxic fuel will burn up without harming anyone on earth.

- The impact of the collision on the target is roughly the equivalent of a 10-ton truck traveling at 600 miles per hour.

(Reporting by Jim Wolf in Washington; editing by David Wiessler)