The radar antenna scans the sky looking for incoming targets. Once it finds a target, it scans it more intensely and communicates with the ECS. The goal of the scan is to determine the speed and heading of the target and also to identify it as a friend or a foe. When the operator or computer decides that it has an incoming foe, the ECS calculates an initial heading for the Patriot missile. It chooses the Patriot missile it will launch, downloads the initial guidance information to that missile and launches it
The ECS
The ECS van is the command center of the Patriot missile battery. The ECS contains stations for three operators as well as the computers that control the battery. The radar antenna and all of the launchers in the battery connect to the ECS, and Patriot missiles in flight also communicate with the ECS.
Inside the van there are two radar consoles. Operators can see the status of all of the targets that the system is currently tracking. Operators can let the system run in fully automatic mode, or they can intervene to select or deselect targets. There is also a communication station that allows the battery to communicate with other batteries or with the command center for the region.