Directed infrared counter measures (DIRCM) technologies, such as Rafael Armament’s Britening and BAE Systems’ Matador systems, are proposed for use against the terrorist threat of Raytheon’s FIM-92 Stinger or Russian-made SA-7, SA-16 and SA-18 Man Portable Air Defense shoulder launched missile systems.

Congressional representatives, including Sen. Charles E. Schumer, D-N.Y, and Rep. Steve Israel, D-N.Y., advocate the use of DIRCM for protecting commercial aircraft from attack by man portable air defense systems (MANPADS) with heat-seeking capability.

The proposed DIRCM system contains three main components:

• Missile warning sensor suite
• Data processor
• Gimbaled turret, which houses the laser jamming system, whose main task is to confuse the incoming missile seeker using a concentrated beam of photonic radiation

This system is housed in a conformal pod mounted in the aft ventral section of the aircraft’s fuselage.

Terrorist threat: Dynamic, methodical and adaptive
Terrorists rely upon simple off-the-shelf technologies to effect complex enterprises with maximum potential for destruction and disruption. Terrorists could circumvent DIRCM defense technologies by using alternative methods of anti-aircraft attack. DIRCM does not present the total solution to the critical problem of providing safety and security for commercial airline passengers.

There are two terrorist scenarios that can defeat the use of DIRCM, and should be considered:
• Rocket-propelled grenade
• Alternative missile guidance technologies, such as a two-stage high-powered model rocket equipped with radio frequency or global positioning system technology

These two scenarios are by no means the only methods at the disposal of terrorists for countering DIRCM, however, they represent plausible ways of defeating this technology.

Rocket-propelled grenade
Terrorists may use a point and shoot weapon, namely the rocket propelled grenade (RPG). When launched as the aircraft is approaching the runway for landing, the RPG can prove extremely lethal.

Even though the maximum range of the RPG is 1,000 feet, as opposed to the 26,000 feet of the FIM-92 Stinger, this weapon is relatively inexpensive, easy to hide and operate, and since it does not function on infrared technology, it is immune to DIRCM. Also, the RPG can be obtained easily on the black market in vast numbers, making identification or tracking of a particular unit virtually impossible.

The DIRCM pod must be physically secured and protected at all times while the aircraft is grounded, for maintenance or other reasons. A translucent coating, which is difficult to detect visually even at close proximity, can be applied with an aerosol dispenser over the transparent housing that protects the jamming laser optics, thus rendering the DIRCM system ineffective or inoperable. Furthermore, atmospheric disturbances caused by adverse weather conditions, such as fog, not severe enough to ground the aircraft will decrease the effectiveness of the jamming laser radiant beam, inadvertently aiding in the success of a shoulder-launched missile attack.

Alternative missile guidance technologies: Two-stage high-powered model rocket
It is feasible that terrorists may use a two-stage high-powered model rocket, readily available to sport rocketry enthusiasts, equipped with radio frequency (RF) or global positioning system (GPS) guidance technology, instead of the infrared technology, which DIRCM is designed to defeat.

Radio or GPS beacons, in the form of cellular phones or portable radios, hidden in the cargo bay of the aircraft will act as transceivers guiding the model rocket straight to its target. The lethality of such a system would be exponentially increased if the miniature rocket payload section would house a proximity explosive charge, instead of a grazing or impact warhead.

Countermeasures
In order to counter the occurrence of these two terrorist scenarios, combined use of logical and physical security for protecting the outer perimeter of airport runways is critical, ensuring that any shoulder launched missile will not have the necessary range potential to effect damage upon its target.

A safe zone of at least 30,000 feet radius should be secured around the airport’s outer perimeter. All maintenance personnel, airport staff and contractors trying to access the inner perimeter of the airport — including runways — will be asked for proper identification and screened for weapons or explosives using walk-through magnetometers equipped with explosive detection networked monitoring stations.

The extensive area included in the safe zone will make it difficult for organizing effective deployment of security personnel throughout the outer perimeter of the airport. However, the addition of surveillance cameras and intrusion detection systems could present a feasible solution.

For deterring the second scenario in particular, it is important to pay attention to countering alternative missile guidance technologies, not just the infrared technology presented by DIRCM.

An enhanced Doppler radar system (EDRS), electronically linked to an air-to-air missile launch system housed inside an internal weapons bay, could be used to augment the DIRCM system.

This system would map the trajectory and velocity of the incoming objects and determine if a missile threat is registered. Subsequently, the EDRS would detect the incoming threat and fire missile countermeasures before the shoulder-launched missile could cause any harm. The EDRS may have similar specifications with the multi-mode pulse Doppler radar used to provide target acquisition solutions for the JAS-39 SAAB Gripen, multi-role fighter interceptor.

Other options
Critics of this idea could argue that aerial collision of the MANPAD with the protective AAM could cause debris fallout within the airport’s perimeter, endangering ground personnel. However, the EDRS-RF guided missile can feature a high explosive dual-mode proximity/impact warhead that would minimize resulting debris upon detonation. Also, rapid firing response of the EDRS system would cause the detonation shockwave to be distant enough from the aircraft so as not to affect its flight.

Another option is to link the EDRS to a diode-pumped solid-state Ytterbium-Yttrium-Aluminum-Garnet laser unit, whose 25 to 100 kilowatt power output radiation beam can cause structural damage to the missile threat, by concentrated heating of its external surface. This directed energy weapon’s power source could be furnished by the aircraft’s turbofan engines or by an auxiliary solid-state power generator housed within the aircraft.
Experts may comment that adverse weather conditions will lower the effectiveness of this protective laser system.

However, since Ytterbium is a source of high-energy photons, the modulated light beam intensity can be increased with improved resonator design, thus presenting a concentrated laser beam even in dense fog scenarios.

The problem of protecting commercial aircraft from a missile terrorist threat is quite complex when properly addressed, and DIRCM does not present the complete solution.

About the author: Salvatore Cezar Pais is a member of the President’s Citizen Corps. He has a doctorate in Mechanical and Aerospace Engineering.

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