In Iraq, terrorists using mortars to attack American bases have learned to take advantage of some weaknesses  in the American  Firefinder artillery spotting radar (which is designed to immediately spot and calculate where mortar or artillery shells are coming from, so American artillery can fire back within minutes). The main problem in Iraq is that the American bases are generally on higher ground than the mortars firing at them. The Firefinder needs a line-of-sight to get a good fix on the firing weapons position. Another problem is that if the mortar is too close, Firefinder is much less likely to quickly determine where the fire is coming from. So the enemy mortar teams get as close as they can before they open up. This still makes the mortar teams vulnerable to counterattack by coalition troops, but not the immediate (in a few minutes) artillery fire that Firefinder can make happen under the right conditions. That, however, is not entirely bad, as the terrorists often set up their mortars in residential neighborhoods. This prevents the Americans from using their artillery to fire back, because of the likelihood that there would be many civilian casualties. The biggest danger enemy mortar teams now face are civilians with cell phones, and a willingness to make a call, and collect a reward for reporting where the mortar team is. As a result of the Iraq problems, the army is stopping further upgrades on Firefinder, which was developed thirty years ago, and looking for a new system, a counter-mortar radar, that can deal with the kinds of problems encountered in Iraq.