October 11, 2007: The U.S. Army is upgrading all ten of its Patriot anti-aircraft missile battalions so they can fire the PAC 3 anti-missile missiles. The $3.3 million PAC 3 missile (PHOTO) is smaller than the anti-aircraft version (PAC 2), thus a Patriot launcher can hold sixteen PAC 3 missiles, versus four PAC 2s. A PAC 2 missile weighs about a ton, a PAC 3 weighs about a third of that. The PAC 3 has a shorter range (about 20 kilometers) versus 70 kilometers for the anti-aircraft version. Each Patriot battalion has 12-24 launchers (3-6 batteries).

The upgrade involves new software, upgrades to the Patriot radar system, and new communications systems that allow for launchers to be placed farther from the radar and launch control equipment. While each Patriot launcher, loaded with PAC 3 missiles, can only defend against ballistic missiles approaching within 20 kilometers, the Patriot radar can detect targets out to a hundred kilometers. Two PAC 3 missiles are fired at each incoming ballistic missile, to increase the probability of a hit. The PAC 3 has its own radar, and uses it to track the incoming warhead, and execute a collision course.

The PAC 3 was used for the first time during the 2003 invasion of Iraq. The Iraqis fired eleven long range missiles at American targets (usually headquarters) and PAC 3 missiles took down eight of them. During the 1991 Gulf War, the larger, anti-aircraft version of the Patriot missile, modified for use against missiles, was used, and knocked down about 70 percent of the missiles the Iraqis fired. There is still some dispute over this, largely because the Iraqis had modified their SCUD missiles to give them longer range. This involved installing larger fuel tanks, resulting in longer missiles. This change in the shape and internal strength of the missiles, caused many to come apart as they plunged earthward. That is, the warhead section broke apart from the fuselage. This reduced the accuracy of the missile, but also provided interceptor missiles with two or more incoming targets. The Patriot missiles would often hit something, but it was difficult to tell if the target hit was the warhead or fuselage. That's one reason why two PAC 3s are fired at each target. In any event, the longer range SCUDs are so inaccurate that, unless they are being fired at a large target (like a city) they are unlikely to hit anything valuable. The Iraqis made the increased range modification during their 1980s war with Iran, when the missiles were fired at the Iranian capital, Tehran. It's still unclear if the Iraqis even knew of the "breaking up on re-entry" problem, not that it mattered. As long as their missile hit somewhere inside Tehran, it was a success.

The U.S. Air Force has also configured Patriot PAC 3 anti-missile missiles to be launched from F-15 fighters. This would enable missiles to be in position, over a wider area, to intercept incoming ballistic missiles. An F-15 can move around a lot faster than the towed launchers that normally carry PAC 3 missiles. The PAC 3 fired from the air can also hit cruise missiles, or ballistic missiles that were just launched, and are still climbing. Work is now underway to adapt the 17 foot long PAC 3 to be launched from the F-16, F-22 and F-35 aircraft as well.