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Smart Missile Ready for Action

May 2008
By Henry S. Kenyon

The high-speed anti-radiation missile (HARM) destruction of enemy air defense attack module (HDAM) is a precision attack weapon designed to assault heavily defended and time-sensitive targets from beyond visual range. A modification of the existing HARM platform, the new missile includes digital navigation and guidance systems and software improvements to enhance its accuracy.
Modified weapon offers fast response to a range of threats.

A missile upgrade kit will allow U.S. Air Force and Navy aircraft to attack mobile targets precisely while limiting collateral damage. Applied to a combat-proven high-speed missile, the modifications permit pilots to select specific areas to attack and to designate restricted zones within a target area. The enhancements allow the military to convert a relatively specialized radar-seeking missile into a multipurpose attack weapon.

Combat missions in urban areas are challenging for U.S. and allied warfighters. Experience from operations against Serbian forces in Kosovo and Iraqi forces during the Gulf War highlighted the need for a fast, yet precise, weapon capable of striking time-sensitive targets. Many targets such as radars and anti-aircraft weapons often were deliberately positioned near civilian facilities such as schools and hospitals. A fast, precision weapon capable of hitting a range of targets without incurring civilian casualties would enhance tactical operations in urban areas.

A joint development effort between the Air Force and the Raytheon Company, TucsonArizona, led to the high-speed anti-radiation missile (HARM) destruction of enemy air defense attack module (HDAM) upgrade kit, which converts existing missiles into programmable precision weapons. HDAM is built on the successful AGM-88 HARM platform developed in the 1970s as a joint U.S. Air Force/U.S. Navy program. According to Jeff Wadsworth, Raytheon’s HARM/ HDAM program director, some 22,000 HARM missiles have been produced since the early 1980s. The missile is carried on Navy and Marine Corps F/A-18s and EA-6Bs and on U.S. Air Force F-16Cs. The AGM-88C is the latest HARM version in use today.

HARM is an anti-radiation missile designed to home in on and destroy enemy radar installations and transmitters. In contrast, the HDAM upgrade allows the missile to be more flexible in its choice of targets. Although the destruction of enemy air defenses remains an important role for HDAM, the missile can attack any target that is time critical, such as mobile surface-to-surface missile launchers and non-radiating threats.

Until the development of HDAM, HARM upgrades mainly focused on the weapon’s seeker and software. The HDAM upgrade modifies the missile’s control section and software. The upgrade kit replaces the missile’s mechanical gyroscopes with a navigation unit consisting of high-precision fiber optic gyroscopes, an internal global positioning system receiver and an inertial measurement unit. Data from these devices is fused to create a navigation solution for the weapon. The upgrade also adds a microprocessor to the missile’s control section, allowing it to merge targeting solutions from the navigation and seeker systems. “You get a significant improvement in the probability of kill against advanced threats,” says Wadsworth.

A key feature of the upgrades is the ability to control and select targets. In a situation with restricted rules of engagement, an HDAM can be ordered to attack a specific area, or it can be told to target a region containing preset “no go” areas. For example, the missile could be designated to attack targets on one side of a road while avoiding civilian buildings such as hospitals directly across the road. This system can be used to limit collateral damage, or it can be focused on a specific area posing a threat to attack aircraft.

Targeting data can be loaded into the missile either before a mission or in flight. Wadsworth recommends loading data before a mission to reduce pilot workloads. But in the case of a multi-seat aircraft, the weapons officer may use some of the weapon’s more advanced features to acquire targets in flight. Operators can program in areas of responsibility to ensure that the missile only impacts a designated area. Other features include the ability to set zones of exclusion and missile impact zones for limiting impact to a specific area.

Up to four geographic specificity software packages containing a geographic region can be stored in an HDAM’s memory. Each portion of these areas can contain up to 25 zones of exclusion. After targeting information is loaded into an aircraft, its weapons officer can decide where the mission, and the missiles, will or will not go. Wadsworth says that this capability is already integrated on Air Force F-16s.

The HDAM kits allow U.S. and allied warplanes to attack targets based on their geographic locations. Unlike HARM, which only focuses on a target’s radar emissions, HDAM can target both geographic coordinates and emissions. In a radiation-tracking mode, if an enemy system should stop emitting while a missile is in flight, HDAM can automatically attack a preloaded alternate target. Operators also can select the missile’s warhead to explode on impact or at a specified height above the target. The HDAM’s 150-pound warhead is an area blast/fragmentation warhead designed to explode on impact or in close proximity to its target. “It can do quite a bit of damage. It does quite a bit more if you precisely control where it goes when you set it off,” he says.

The modifications package turns the HARM/HDAM into a precision supersonic strike weapon. Wadsworth adds that HDAM is the only U.S. supersonic air-to-ground weapon that he is aware of. “If you know where the target is, and it’s time-critical, then you can fly very quickly and make the kill,” he maintains.

Wadsworth notes that not all missiles are supersonic. HARM was designed as a non-line-of-sight, standoff weapon built to attack surface-to-air missile (SAM) sites outside of their effective range. HARM was developed from Air Force and Navy experience in Vietnam where aircraft had to attack anti-aircraft missile batteries with guns and bombs. “That’s a little closer than you want to be,” he shares.

The HDAM can be launched from U.S. Air Force F-16s and U.S. Navy and Marine Corps F/A-18 fighter jets. The weapon can be programmed to enable U.S. forces to hit targets in urban areas while avoiding unnecessary collateral damage.
The HDAM modification allows warplanes to engage a variety of mobile and other time-critical targets. In its anti-radiation homing mode, HARM can attack moving targets such as naval vessels. HDAM improves this capability because of its digital- and satellite-based navigational capabilities. “HDAM can exploit that information to make a better attack on a moving ship, a stationary SAM or a threat that is using more sophisticated tactics or countermeasures,” he says.

Raytheon engineers have not modified the missile’s datalinks. But Wadsworth notes that customers can request additional improvements to HDAM. These potential modifications could include changes to the seeker or the missile’s engine or the warhead. However, he notes that the basic HDAM kit already provides an effective capability.

HDAM was developed as part of a cooperative research and development agreement with the Air Force. Raytheon provided the upgrade kits and installed them, but the service planned and carried out the test missions and provided the aircraft and pilots and conducted the tests, Wadsworth says.

The Air Force has successfully fired three HDAMs at test targets. These launches were preceded by a series of firings during HDAM’s precursor program, which developed the precision navigation package used in the kit. Wadsworth explains that the hardware in these earlier tests was similar, but not identical to, HDAM. Adding that it is not a proof-of-concept prototype, he is sanguine about the missile’s future procurement by the Air Force.

The HDAM program is in the Air Force’s fiscal year 2008 and fiscal year 2009 unfunded requirements list. Raytheon also is investing some of its own resources to begin immediate production should the government decide to acquire the missile. However, Wadsworth cautions, any production and acquisition discussions are tentative until funding is approved.

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