The term 'TARS' is an acronym for 'Tethered Aerostat Radar System'. It is a type of radar system that uses a tethered aerostat, or a large balloon filled with helium, to lift a radar antenna into the air. The antenna is then used to detect aircraft and other objects in the sky. The radar system is often used in conjunction with other radar systems, such as ground-based radar, to provide a more comprehensive view of the airspace. The use of a tethered aerostat also allows for the radar system to be deployed quickly and easily, making it a popular choice for military and civilian applications.