One of those things you tend to take for granted on the battlefield is radar coverage of whats going on in the air. But this isnt automatic, and you cant keep an AWACS airborne tactical traffic control radar in the air all the time over a new battlefield. To deal with this problem, the U.S. Air Force has mobile radar units. The AN/TPS-75 Radar System (nicknamed "Tipsy 75") is used in situations where you have to set up a ground radar to keep an eye on the surrounding air space. Eight tons of equipment are carried on half a dozen trucks. In daylight, six troops can set the radar up in 90 minutes. At night, it takes closer to three hours. The rectangular radar dish is eleven feet high and 18.4 feet high. It revolves at about once every nine seconds. The radar can track up to 500 aircraft, and detect them up to 400 kilometers away, at from ground level to 100,000 feet. 

Each Expeditionary Air Control Squadron has about a hundred personnel, who operate and maintain the Tipsy 75 and its associated computers, communications gear and generators. The U.S. Air Force has two dozen mobile Tipsy 75s. When Baghdad airport was captured in 2003, an Air Control Squadron was sent up from Kuwait. The convoy took a lot of fire along the way, losing one airman dead and several wounded. But once they arrived, the radar was set up and the process of turning the airport into a temporary air base proceeded. An Air Control Squadron can be flown in as well, as was the case in Afghanistan. For training, Air Control Squadrons will do things like set up their radar systems for training exercises, or for watching the sky over the Caribbean for drug smugglers.