GBU-15

The GBU-15 bomb is an unpowered, glide weapon used to destroy high value enemy targets. It is designed to be used with F-15E and F-111F aircraft. While laser guided munitions can be pointed at a laser dot and directed through a doorway, the GBU-15 can be guided real-time by the 'Wizzo' to land precisely on the door's knob. In other words, the miss distance is not measureable when the weapon system officer is in the loop.

The GBU-15 provides the capability for accurate (automatic or manual) guided delivery of a MK-84 bomb at increased ranges. The GBU-15's effective standoff range is greater than that of laser-guided munitions, since the GBU-15 does not need to have acquired the target before it is released. The weapon is remotely controlled by a datalink system, and the weapon systems operator locates the target area and the specific aimpoint by observing the video transmitted from the weapon. The weapon's midcourse flight path can be adjusted either automatically or manually. Weapon video is either electro-optical (TV camera) or infrared, and generated in the nose of the weapon.

The weapon consists of consisting of various interchangeable guidance, fusing, and control systems designed to meet specific mission requirements, that are attached to either an MK-84 or BLU-109 penetrating warhead. Each weapon has five components -- a forward guidance section, warhead adapter section, control module, airfoil components and a weapon data link.

The guidance section is attached to the nose of the weapon and contains either a television guidance system for daytime or an imaging infrared system for night or limited, adverse weather operations. A data link in the tail section sends guidance updates to the control aircraft that enables the weapon systems operator to guide the bomb by remote control to its target.

An external electrical conduit extends the length of the warhead which attaches the guidance adapter and control unit. The conduit carries electrical signals between the guidance and control sections. The umbilical receptacle passes guidance and control data between cockpit control systems of the launching aircraft and the weapon prior to launch.

The rear control section consists of four wings are in an "X"-like arrangement with trailing edge flap control surfaces for flight maneuvering. The control module contains the autopilot, which collects steering data from the guidance section and converts the information into signals that move the wing control surfaces to change the weapon's flight path.

The GBU-15 may be used in direct or indirect attack. In a direct attack, the pilot selects a target before launch, locks the weapon guidance system onto it and launches the weapon. The weapon automatically guides itself to the target, enabling the pilot to leave the area. In an indirect attack, the weapon is guided by remote control after launch. The pilot releases the weapon and, via remote control, searches for the target. Once the target is acquired, the weapon can be locked to the target or manually guided via the date-link system. This highly maneuverable weapon has a low-to-medium altitude delivery capability with high accuracy. It also has a standoff capability.

During Desert Storm, all 71 GBU-15 modular glide bombs used were dropped from F-111F aircraft. Most notably, GBU-15s were the munitions used for destroying the oil manifolds on the storage tanks to stop oil from spilling into the Gulf. These GBU-15s sealed flaming oil pipeline manifolds sabotaged by Saddam Hussein's troops.

The Air Force Development Test Center, Eglin Air Force Base, Fla., began developing the GBU-15 in 1974. It was a product improvement of the early guided bombs used during the Southeast Asia conflict. Flight testing of the weapon began in 1975. The GBU-15 with television guidance, completed full-scale operational test and evaluation in November 1983. In February 1985, initial operational test and evaluation was completed on the imaging infrared guidance seeker.

In December 1987, the program management responsibility for the GBU-15 weapon system transferred from the Air Force Systems Command to the Air Force Logistics Command. The commands merged to become the Air Force Materiel Command in 1992.

EGBU-15 Enhanced Guided Bomb Unit-15 (EGBU-15)

The EGBU-15 promises to add to the standoff range and firepower of the Boeing F-15E, the only U.S. fighter qualified to carry the weapon. The upgrade gives the weapon an all-weather capability it previously did not possess. The GPS navigation equipment is bolted inside the main body of the munition so the existing daytime television guidance and nighttime imaging infrared systems can remain in place. The EGBU-15 can be guided to the target by GPS alone, or the aircrew can take control and remotely guide the weapon to the target.

The EGBU-15 promises to add to the standoff range and firepower of the Boeing F-15E, the only U.S. fighter qualified to carry the weapon. The upgrade gives the weapon an all-weather capability it previously did not possess. The GPS navigation equipment is bolted inside the main body of the munition so the existing daytime television guidance and nighttime imaging infrared systems can remain in place. The EGBU-15 can be guided to the target by GPS alone, or the aircrew can take control and remotely guide the weapon to the target.

On 23 April 1999, the Chief of Staff of the Air Force gave direction to provide the GBU-15 air-to-surface weapon with Global Positioning System, or GPS, guidance giving it an all-weather capability. In early May 1999 contracts were signed with Applied Sciences Engineering International of Niceville FL and Raytheon Defense Systems of Tucson AZ. The two contractors' concepts were different but proven and compatible with the F-15E. The total quick reaction program including these two contracts and all government costs total $7 million for the first phase of additional GPS guidance to the GBU-15. An unreleased quantity of the enhanced weapon were delivered to combat units by 01 July 1999. During the second phase, the best concepts of both contractors will be adopted. They will then work as a team to upgrade an additional 1,200 to 1,500 GBU-15s, which is expected to cost approximately $50 million.

Air Force Association officials selected Precision Strike Systems Program Office members at Eglin AFB with its Citation of Honor, one of the highest national awards the association offers. The SPO development integrated product team's response to urgent combat needs during Operation ALLIED FORCE (Kosovo) earned them the award. Officials said the team helped quickly replenish the Air Force's overall adverse weather precision munitions inventory OAF sorties reduced.

Gen. Michael Ryan, Air Force chief of staff, directed a two-phased, quick reaction capability program to provide the GBU-15 weapon system with an adverse weather capability. The Eglin team was tasked to deliver 100 weapons within 45 days followed by an additional 1,200 weapons delivered within 12 months. The team integrated Global Positioning System and Inertial Navigation Systems for autonomous navigation. The Phase II effort also extended the capability to include the BLU-109 penetrator mission while retaining the 2,000-pound MK 84 blast fragmentation warhead.

The resulting Enhanced GBU-15 has a nominal standoff range of 15 nautical miles, the ability to lock-on after launch mode and high precision against critical targets. If the EGBU-15 gets dropped into clouds, it can guide to its target with global positioning and hit the target with a certain error of probability. And if it breaks through the clouds, the crew can take over, guiding it with extreme precision, with little or no error, using TV guidance. And that precision can be critical for certain types of targets. The weapon can carry two different loads, an Mk-84 blast fragmentation warhead for surface targets, or the BLU-109 penetration warhead, which can destroy hardened targets and count the floors it penetrates before exploding.

The EGBU-15 program provided for all data and assets necessary for fielding, supportability training and full F-15E integration. A program of this magnitude, providing it runs smoothly with no programmatic issues, normally takes a minimum of 36 months to complete at a cost of several hundred million dollars. The Development IPT aggressively accepted, industriously worked and very successfully completed this monumental task. The EGBU-15's quick reaction capability is estimated to have saved the taxpayer more than $200 million when compared to similar endeavors of a conventional program's structure and length.

The EGBU-15 IPT's extraordinary, yeoman efforts resulted in delivering both Phase I, a $7 million effort, and Phase II, a $53.5 million effort of operational weapons ahead of schedule and within budget. EGBU-15 weapon costs have been substantially reduced with a price tag of only $28,000 per weapon, very inexpensive compared to the procurement costs of today's weapon.

Phase II, which included refining cockpit software to include time and distance information, as well as font size and color adjustments, and testing four more weapons, went exceptionally well. So well in fact that, before the Phase II test and evaluation was complete, teams were sent out to upgrade GBU-15 systems already at different geographic field locations.

On December 21, 1999 Raytheon Systems Company, Tucson, Ariz., was awarded a $46,299,152 modification to a firm-fixed-price contract, F08626-99-C-0251-P00003, to provide for 1,206 EGBU-15 air-to-ground guided munitions applicable to the F-15 aircraft, 41 weapon control units, 12 load crew trainer modification kits, and associated engineering support, training, and spares. Expected contract completion date is Oct. 31, 2000.

The Precision Strike Systems Program Office (WMG), Contracting Directorate (WMGK), Air Armament Center (AAC), Eglin AFB, Florida awarded a sole source contract to Raytheon Systems Company, P.O. Box 11337, Tucson, AZ 85734-1337 to procure nine GPS Aided Inertial Navigation System (GAINS) Units, nomenclature AQU-21/A, stock number 5895-01-476-3912, part number 2229710-100 to support approximately 1,300 tactical Enhanced GBU-15 weapon systems as inventory spare GAINS units.

Inertial Terrain-Aided Guidance (ITAG)

The Inertial Terrain-Aided Guidance (ITAG) system is an adverse weather, precision guidance system for the GBU-15. It replaces the guidance system for this weapon. ITAG is an inertial navigator who uses updates from a radar altimeter correlated with terrain elevation maps. GPS is used to initialize the inertial navigator prior to weapon release. ITAG, being developed by Sandia National Laboratory, gives Joint Force Commanders the capability to accurately deliver weapons against NBC targets during a wide range of adverse weather conditions. The ITAG kit "straps on" to 2000-pound class conventional bombs to make a precision-guided weapon, and it will make it possible to plan attacks to take advantage of local weather conditions which may be favorable to minimizing the dispersal of released NBC agents. The ITAG uses GPS-initialized inertial navigation which is augmented by a terrain-reading, all-weather, high-altitude, precision radar altimeter. The real-time onboard navigation computer correlates radar altimeter data with previously acquired digitized, three-dimensional synthetic aperture radar terrain maps stored on board the weapon. Unlike current laser-guided bombs which can only be employed in clear air-mass conditions, the ITAG is able to achieve 3-meter circular error probable (CEP) accuracy in adverse weather.

Sandia conducted two drop tests of the Inertial Terrain-Aided Guidance (ITAG) system as part of the Defense Threat Reduction Agency's Counterproliferation Advanced Concept Technology Demonstration. ITAG is an adverse-weather precision radar guidance system suitable for use on a conventional penetrator weapon. ITAG took the form of an upgrade to a GBU-15 (2000 lb class) weapon. It includes the Sandia-developed High Altitude Doppler beam sharpened Radar Altimeter and associated batch-recursive terrain-referenced navigation algorithm.

References

• AN/AXQ-14 Data Link System
• GBU-15 gets all-weather capability Leading Edge SEPTEMBER 1999 -- The Precision Strike Systems Program Office has been tasked to equip the GBU-15 air-to-surface weapon with Global Positioning System, or GPS, guidance giving it an all-weather capability.

• Counterproliferation ACTD (CP ACTD)