The MIM-104 Patriot missile is a surface-to-air missile which is used against aircraft and missiles at all altitudes. PATRIOT is the acronym for Phased Array Tracking Radar to Intercept Of Target. (A more far-fetched abbreviation is Protection Against Threats, Real, Imagined, Or Theorized.) It was designed by Raytheon as an anti-aircraft missile, but its primary role today is ballistic missile defense. Each battery costs about $1 billion, and a single missile can cost several million dollars. A single battery has 8 launchers and can launch up to 16 missiles.
As a mobile system, it takes about 25 minutes to set up once it reaches the launch site. By contrast, the Russian S-400 takes 5 minutes.
In 1976, the Armys SAM-D (Surface-to-Air Missile, Development) program was renamed the PATRIOT program. The tests at the White Sands Missile Range were successful, and the Patriot was deployed in 1984. Although it served for a while as an anti-aircraft system, it was upgraded in 1984 and changed to an anti-ballistic missile weapon.