Mission: The Patriot is the Army's mobile surface-to-air missile defense system. It is the only guided system that can shoot down incoming missiles. Since the mid-1960s, the system has evolved to defend against aircraft and cruise missiles, and more recently against short-range ballistic missiles, such as Scuds. The system has undergone a $3 billion overhaul since the 1991 Persian Gulf War and the PAC-3 system, designed for greater coverage and lethality, was delivered to the Army in September of 2001. Unlike earlier versions of the Patriot missile, which use an explosive warhead to destroy its target, the PAC-3 missile collides with its target in mid-air at extremely high speed, destroying the target and neutralizing its payload.

Features: The heart of the Patriot system is a weapons control computer that tracks and targets incoming missiles via radar. In the rush to bring the Patriot 2 to battle in 1991, there were numerous updates to the operating software. The basic firing unit, called a battery, consists of a phased array radar, an engagement control station, computers, power generating equipment, and launchers that can hold 16 of the smaller PAC-3 missiles at a time - four in each canister. Larger missiles used with the system are limited to one per canister. There are about 90 soldiers assigned to a battery, but three soldiers in the engagement control station are the only personnel required to operate the battery in combat. The PAC-3's active radar and closed-loop guidance allow for a greater number of interceptors to be controlled than in the earlier Patriots.

Background: The Patriot system was first used in combat during the 1991 Gulf War, during which 158 PAC-2 missiles were launched to intercept Iraqi Scud missiles. A software problem has been cited in the PAC-2's failure to intercept an incoming scud that killed 28 Americans at an Army barracks in Saudi Arabia on Feb. 26, 1991.

MIT professor Ted Postol has told CBS News that his studies indicate the Patriots did not shoot down a single Scud during the Gulf War. The Defense Department claimed they were nearly 100 percent on target, but later revised that number down to about 70 percent. Both sides agree that the PAC-3, which has not yet seen combat, vastly improves on the previous model's computer and radar systems. An Army spending plan approved by Congress calls for the total inventory of PAC-3 missiles to eventually be set at 1,159. They are being produced at a rate of about 100 per year.

General Characteristics (PAC-3):
Length: 17 ft. (5.2 m.)
Diameter: 10 in. (25 cm.)
Wingspan: 20 in. (50 cm.)
Fins: four delta shaped fins
Launch Weight: 688 lbs. (312 kg.)
Propulsion: Single-stage solid propellant rocket motor with special attitude-control mechanism for in-flight maneuvering
Guidance: Inertial/Active millimeter-wave radar terminal homing
Warhead: hit-to-kill + lethality enhancer 160 lb. (73 kg.) HE blast/fragmentation with proximity fuze
Max speed: Mach 5
Max range: 9 mi. (15 km.)
Launcher: Mobile trainable semi-trailer
Manufacturer: Raytheon Company Missile Systems Division is the prime contractor for the Patriot system. The Martin Marietta Corporation is a principal subcontractor and assembles the missiles in Orlando, Fla.