The U.S. Department of Defense has purchased 253 Patriot anti-aircraft and anti-missile missiles. The U.S. Army has ten Patriot anti-aircraft missile battalions. Each Patriot battalion has 12-24 launchers (3-6 batteries). Each battery is manned by about a hundred troops, and contains a radar, plus four launchers. A battery can fire two types of Patriot missile. The $3.3 million PAC 3 missile is smaller than the cheaper 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.
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 missile has its own radar, and uses it to track the incoming warhead, and execute a collision course.
The Department of Defense also purchased, along with these missiles, upgrades for Patriot systems used by the UAE (United Arab Emirates) and Taiwan. The Patriot missiles, once manufactured, can be kept in service for decades, via upgrades, refurbishment and regular maintenance.