The U.S. Air Force has tested a new MP-RTIP AESA radar, that does the same job as the E-8 JSTARS ground radar aircraft AESA, but can be mounted in the RQ-4 Global Hawk UAV. The air force had planned to build a replacement for the E-8, the E-10, but that has been cancelled because of the high cost. Meanwhile, an updated AESA (Active Electronically Scanned Array) radar for JSTARS enables them to spot smaller, man sized, objects.
AESA type radars have been around a long time, popular mainly for their ability deal with lots of targets simultaneously, and produce a more accurate picture of what is out there. AESA radar consists of thousands of tiny radars that can be independently aimed in different directions. An AESA radar made the JSTARS aircraft possible, as it enabled it to locate vehicles moving on the ground. The smaller MP-RTIP radar for the RQ-4 can also spot smaller objects on the ground.
As a result of an RQ-4 UAV equipped with AESA, the air force has a choice between extending the life of the E-8 aircraft, or replacing them with the UAVs. Currently, the E-8 fleet is being equipped with new JT8D-219 engines. The new engines are not only 10 percent more powerful, but more reliable and easier to maintain. There are also upgrades inside the aircraft, replacing a lot of 1980s era electronics with modern gear.
All this is so the E-8 can serve for another 60 years. That would see some of these aircraft retiring after 70 years of service. Since the E8 is based on the Boeing 707 airliner (a 1950s design), this would result in that aircraft type still being in the air more than a century after it first entered service. But putting the new MP-RTIP AESA radar on the RQ-4, the air force has a cheaper aircraft to buy, and is cheaper to operate (all the human operators stay on the ground, back in the United States).
Initially designed at the end of the Cold War to track NATO and Soviet armed forces in the dreaded (but ultimately avoided) World War III, E-8 JSTARS first saw action during the 1991 Gulf War, and proved very useful. For the last six years, JSTARS has proved remarkably effective in Iraq. E-8s have flown about 20,000 hours a year over Iraq. That means that, two-thirds of the time over Iraq, a JSTARS aircraft was in the air. One or two JSTARS have been stationed in the region since 2003. No one will say, officially, exactly what the JSTARS is doing, but whatever it is, it's been doing a lot of it for a long time. From 2003-6, E8s averaged about a hundred hours a week over Iraq.
JSTARS has proved to be remarkably flexible. It is known that the E-8 radar has been used to track where the terrorists go after an attack on American troops. Many of the attacks take place in sparely populated places, and at night. JSTARS can track vehicles on the ground over a wide area. For example, a single JSTARS can cover all of central Iraq, although its ground radar can only zoom in on a smaller area for useful information. The JSTARS radar has two modes; wide area (showing a 25 by 20 kilometer area) and detailed (4,000 by 5,000 meters). The radar can see out to several hundred kilometers and each screen full of information could be saved and brought back later to compare to another view (to see what has moved).
Operators can track movement of ground units, or individual vehicles, over a wide area. Operators can also use the detail mode to pick out specific details of what's going on down there, like tracking the movement of vehicles fleeing the scene of an ambush. JSTARS is real good at picking up trucks moving along highways on flat terrain. JSTARS can stay up there for over 12 hours at a time, and two or more JSTARS can operate in shifts to provide 24/7 coverage. The RQ-4 can stay in the air more than 24 hours at a time, providing the same persistence as the E-8, and more cheaply.
JSTARS has been used to monitor the Syrian and Iranian borders for smugglers. Some stuff comes across the borders in trucks, but much still arrives on the back of animals, which JSTARS cannot track. But tracking the movement of vehicles in western Iraq, in the middle of night, has proved useful. When the JSTARS crew (of 18 equipment and surveillance specialists) spots something, they can alert combat troops on the ground to take a closer look.
JSTARS can also send its data to computer terminals on the ground, in army brigade or division headquarters. The new JSTARS radar can spot smaller targets, although the air force won't say if this includes horses or camels, loaded with weapons, crossing the Syrian or Iranian border. The E-8s have been in Afghanistan since 2002, and more of these aircraft are headed there, as operations in Iraq wind down.
The air force has 17 JSTARs in service, each costing about $366 million each. RQ-4s, equipped with a similar radar, cost less than half as much. The U.S. Navy is also interested in this kind of RQ-4, as the new AESA radar is also very good at watching a seascape, especially along coasts where small boats can be a potential terrorist threat.