Global Positioning System Aided Munition (GAM)
[GBU-36/B & GBU-37/B]]

The B-2's principal mission changed from nuclear to conventional in late 1992 when the Air Force decided to incorporate precision-guided munitions on the bomber. Its operational requirements specify that the B-2 weapon system have low observable characteristics and sufficient range and payload to deliver nuclear or conventional weapons anywhere in the world requiring the blending of conventional and state-of-the-art technologies.

The Block 10 model of the B-2 carried only Mk-84 2,000-lb conventional bombs or B83 nuclear weapons. Block 10 initial capabilities were very limited and consisted only of "participation in a conventional war" by delivering general purpose bombs on soft targets from medium to high altitude. Block 10 aircraft were primarily intended to support training. An IOC was not planned until Block 20 aircraft were tested and delivered. Block 20 B-2s provided additional avionics and weapon capabilities and will be deployable to overseas bases. Delivery of the second operational configuration, Block 20, began on April 1, 1996. Block 20 B-2s provided additional avionics and weapon capabilities. The most significant improvements were the addition of Global Positioning System (GPS) Aided Targeting System/GPS Aided Munition (GATS/GAM) and the availability of Terrain Avoidance/Terrain Following (TA/TF) capability.

The Global Positioning System Aided Munition (GAM) was developed by the Air Force and Northrop Grumman Corporation as an interim precision munition for the B-2. GAM is a tail kit that fits on the 2,000-pound Mk84 general purpose bomb [GBU-36/B], or the 4,500 lb BLU-113 penetrator [GBU-37/B]. GAM uses GPS guidance to more accurately guide to target locations. The munition is to be eventually replaced on the B-2 by the Joint Direct Attack Munition. The GBU-37 was added to the B-2 arsenal in late 1997. This weapon is currently the only all-weather, near-precision "bunker busting " capability available. The GBU-37, which is similar to JDAM, includes a 5,000-lb class warhead and is also guided by a GPS tail kit.

The Global Positioning System (GPS) Aided Target System [GATS] is an all weather B-2 targeting system which reduces Target Location Error (TLE) normally associated with target coordinates. By exploiting the synergistic effects of the B-2's GPS navigation and Synthetic Aperture Radar (SAR) capabilities, which combine the SAR's excellent range and range rate capabilities with accurate GPS Position and velocity information, it provides the GAM highly accurate target location relative to current B-2 position.

Smith Pattern & Tooling, Inc. developed and manufactured the layup tools for the flexible strap on bomb stabilization unit for the Global Positioning System Aided Targeting System / Global Positioning System Aided Munition (GATS/GAM).

Three B-2s were used in a live Global Positioning System-Aided Munition (GAM) drop in a demonstration 08 October 1996 at the Nellis AFB, Nev., range complex. The demonstration showcased the B-2's all-weather, day or night near-precision capability, destroying all 16 targets from an altitude of over 40,000 feet. The GATS (GPS-Aided Targeting System) uses the B-2's GPS navigation system and synthetic aperture radar to provide highly accurate target location information which is then passed to the GAM. This historic drop of the first live GATS/GAM weapons by operational B-2s significantly increases America's ability to strike targets anytime, anywhere and through any weather.

On 29 May 1997 a GBU-37/BLU-113 bomb was dropped from a B-2 over the China Lake Range near Edwards Air Force Base, Calif. This marked the first time the 4,700 pound conventional penetrating weapon was paired with the B-2. The accuracy of the all-weather, day or night guidance system proved equal to the wing's successful GATS/GAM (Global Positioning System-Aided Targeting System and Global Positioning System-Aided Munitions) drops in October 1996. The bomber can carry up to eight of these weapons.

The B-2 achieved initial operational capability on April 1, 1997, with interim aircraft capable of flying nuclear and limited conventional missions. The Air Force demonstrated that interim B-2 aircraft could carry and deliver unguided Mk 84 bombs or the precision-guided Global Positioning System (GPS) aided munition (GAM) in the conventional role or B-83/B-61 nuclear weapons in the nuclear role. Reports of flight tests and demonstrations indicated the GAM to be an effective all-weather weapon in attacking fixed targets with near-precision accuracy.

Boeing delivered the first production model of JDAM to the Air Force on June 24, 1998. The B-2 was able to use JDAM flawlessly in Kososvo, however, because the Congress appropriated funding for the early version, GATS/GAM. Congress accelerated the GATS/GAM program in fiscal year 1993 by over a year, and it was successfully tested in 1996. Thanks to all of this early testing, the B-2 pilots were fully qualified to use JDAM when the Kosovo conflict began.

The GATS/GAM system was developed to meet a B-2 Block 20 precision weapon requirement left unfulfilled by the cancellation of another munition. All GAMs have been delivered to the 509th Bomb Wing, Whiteman AFB MO and are in operational use. Demonstrated accuracy by Air Combat Command aircrews has been under 20 feet.

The New York Times reported on 10 October 2001 that the GBU-28 had been used in combat in Afghanistan as part of Operation Enduring Freedom. Strikes conducted on 09 October, the third day of air operations, reportedly included the first use of the 5,000-pound bomb. Prior to this time the only operational aircraft known to be certified to carry the GBU-28 was the land-based F-15E fighter/bomber. However, there were no reports that the F-15E was participating in the air campaign, and it was reported by CNN beginning on 11 October that the GBU-28 was being delivered from the B-2 stealth bomber. These reports apparently represent a confusion between the laser-guided GBU-28 and the GPS-guided GBU-37 Global Positioning System Aided Munition (GAM). Both of these munitions share the common BLU-113 Penetrator bomb body, but they are delivered from different aircraft and have different guidance systems.

Specifications
Mission	Close air support, air interdiction, counterair, airborne strike, suppression of enemy air defense
Targets	Mobile hard, mobile soft, fixed hard, fixed soft, maritime surface
Service	Air Force
Program status	Operational
First capability	1996
Guidance method	GPS/INS
Range	Greater than 5 nautical miles
Circular error probable	12-18 meters
Quantity	128
Development cost	Munition development cost is included with development of the GPS Aided Targeting System
Production cost	$29.6 million
Total acquisition cost	$29.6 million
Acquisition unit cost	$231,250
Production unit cost	$231,250
Platforms	B-2

References

• GPS Part III - US Direct Attack Munition Programs by Carlo Kopp Australian Aviation, October, 1996