an Entity references as follows:
A radar picket is a radar-equipped station, ship, submarine, aircraft, or vehicle used to increase the radar detection range around a nation or military (including naval) force to protect it from surprise attack, typically air attack, or from criminal activities such as smuggling. By definition a radar picket must be some distance removed from the anticipated targets to be capable of providing early warning. Often several detached radar units would be placed to encircle a target to provide increased cover in all directions; another approach is to position units to form a barrier line.