Air Weapons: October 19, 2002


If Iraq is attacked, over ten thousand JDAM smart bombs are expected to be used (unless the Iraqis fold early). One rather mysterious problem with this is the possibility that the Iraqis might jam or manipulate the signal the GPS guidance systems JDAM uses. There are several solutions to jamming, but the air force is, justifiably, being quiet about which anti-jamming technology they might use. Manipulating the GPS signal is a more serious problem. Manipulating radar signals goes back to World War II, and the same techniques could be used to make JDAMs believe they are getting a valid signal, when in fact they are getting one that is off just enough to make JDAM miss its target. JDAM has a backup guidance, an inertial guidance system (a gyroscope that does not use any external signal) that is supposed to kick in and replace the GPS guidance if GPS is jammed (and, in effect, receiving no signal. Its not known if the air force has tested its GPS guidance systems when the GPS signal is being manipulated. The Iraqis have plenty of engineers and are known to be capable of playing around with satellite signals. Unless the U.S. has a spy inside of Iraq to let us know what the Iraqis are up to, the initial use of JDAM could be a disaster as many of the bombs go astray because of manipulated GPS signals. There was already an incident last year where several JDAMs mysteriously went astray. All the air force said publicly was that it was probably an operator error (the bomber crew put in the wrong coordinates. But as described, the incident looked like a test of GPS signal manipulation. The U.S. Air Force is known for dealing with dicey technical situations like this, and this time they have a big one.


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