JDAM (Joint Direct Attack Munition)
The Joint Direct Attack Munition (JDAM) is a satellite-guided "smart" bomb capable of accurate and high-precision strikes in any weather. JDAM munitions have found increasing use in military missions and the use of precision bombs exceeded 80 percent in the U.S.-led Operation Iraqi Freedom conducted in 2003. Because of their high degree of accuracy, JDAM munitions can also be used to selectively strike at intelligence-related targets, and in the Iraq campaign, they were used to strike at military and intelligence (e.g. leadership targets) that Saddam Hussein's forces had placed or attempted to conceal in or near civilian areas.
JDAM munitions also found wide use in the NATO air campaign against the Federal Republic of Yugoslavia in 1999 and in the 2001 U.S.-led Operation Enduring Freedom against the Taliban regime and al-Qaeda forces hiding in Afghanistan. As of April 2003, U.S. B-1, B-2, B-52, F-16 and F/A-18 bombers and fighter/strike aircraft were capable of carrying JDAM munitions.
JDAM munitions are intended to provide accurate delivery of general purpose bombs in adverse weather conditions. Although not quite as accurate as laser-guided munitions, JDAM offer high precision—but at a far lower cost than laser-guided munitions. JDAMs are dumb bombs converted to smart bombs by the supplemental addition of fixed aerodynamic surfaces (mid-body strakes and tail fins) and a guidance package that allows inertial navigational guidance of the bomb following release. Targeting is maintained via continuously updated global positioning satellite (GPS) data that steers the bomb to the target. Under normal conditions, JDAMs can determine location and strike within 10 yards of an intended target. Because they rely on GPS signals, JDAMs can be used even under cloudy conditions, or when the sky is obscured by smoke.
Jamming equipment that can scramble or block GPS signals has limited effectiveness against JDAM munitions because the tracking sequence is progressive (i.e., the jamming is not effective until the bomb is almost on target) and software corrections allow the bombs to revert to inertial navigation if the GPS signal is blocked or obscured. In general, Iraqi forces using Russian-made jamming equipment found little success in reducing JDAM precision. Although detailed assessments were not yet complete as of May 2003, Iraqi attempts at jamming JDAMs—intended for precision strikes at military targets hidden near civilian areas—may have accounted for some unintended civilian casualties.
Other significant JDAM misses include the accidental bombing of the Chinese embassy by a JDAM released by a U.S. B-2 bomber over Belgrade in May 1999. The bombing killed three Chinese citizens. That targeting error was not a result of jamming but was attributed to a software error that relied on outdated maps.
█ FURTHER READING:
Federation of American Scientists. Military Analysis Network. Joint Direct Attack Munition (JDAM) GBU-29, GBU-30, GBU-31, GBU-32. September 18, 2002. < http://www.fas.org/man/dod-101/sys/smart/jdam.htm > (April 15, 2003).