The Boeing E-3A airborne warning and control system (AWACS) is like the binoculars of a fighter formation. By emitting a 3GHz electromagnetic pulse, the E-3A's Northrop Grumman APY-2 radar can spot an inbound fighter at 30,000ft as far as 430nm away. But what if the fighter is stealthy, which means partly that its designed to scatter radar waves in any direction except back to the source? That is the whole idea behind electromagnetic stealth -- a capability almost monopolized by US forces until very recently. The appearance of the Sukhoi PAK-FA and the Chengdu J-20 within the past 20 months is a warning. To detect the most dangerous targets, E-3A soon may need help.A new concept for addressing precisely this problem appeared late last week. In a 19 October solicitation notice, the US Air Force Research Laboratory asked radar companies if they could develop a new electromagnetic trick. Technically, it's called bistatic target detection. It basically means one aircraft -- in this case, the E-3A -- emits the radar pulse, and the returns are detected by radar receivers operating passively on one or more other aircraft. So the stealthy target scatters the radar waves in different directions, but it still can't hide.
The AFRL wants to demonstrate a bistatic radar system for AWACS using an unmanned air vehicle with a very unique radar antenna. The E-3A operates a giant 24ft by 5ft planar array antenna installed on top of the aircraft like a flying saucer. The AFRL, however, wants the UAV radar receivers to be integrated into the load-bearing structure of the aircraft. It's a concept that's been in development for many years, and it's called Sensorcraft (see picture of AFRL wind tunnel model above). The AFRL solicitation could be a prelude to full-scale development of such a new UAV. On the other hand, it's possible the conformal antenna could be integrated into an existing UAV, such as the Northrop Grumman X-47 or the General Atomics Aeronautical Systems Inc Avenger.
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