Shoulder-fired missiles, or man-portable air defense systems (MANPADS), have been used by terrorists, criminals and other nonstate actors to take down civilian aircraft.In 2003, the US Department of State estimated that, since the 1970s, more than 40 civilian aircraft had been hit by shoulder-to-air missiles, causing about 25 crashes and more than 600 deaths worldwide. In 2002, for example, terrorists fired two missiles at an Arkia Airlines Boeing 757-300 carrying 271 passengers and crew as it took off from Mombasa, Kenya. Fortunately, both missiles missed their target. In 1998, a Boeing 727 airliner was targeted by rebel forces over the Democratic Republic of the Congo, resulting in the deaths of 40 passengers.Many state governments and international organizations are working to reduce the probability that these missiles will get into the hands of those who wish to target civilians. In 2005, it was estimated that, to produce the weapons, more 1 million MANPADs had been manufactured by as many as 20 countries. It is believed that, although most of the devices are secure in national inventories, excess and obsolete stockpiles exist that are easily accessible to unauthorized users.The US government and other countries and organizations continue to study the problems associated with MANPADS, weighing the benefits of potentially saving lives and reducing the economic disruption of an airline attack against the effectiveness and costs of possible solutions, among them, photonics technologies.What are MANPADS?Intended for lawful military use, MANPADS are designed to help troops defend themselves against aerial attack. About the size and weight of a full golf bag, the portable short-range surface-to-air missiles can be fired from the ground by an individual to target aircraft at takeoff or landing. Most MANPADS consist of a missile packaged in a tube, a launching mechanism and a battery. The missiles usually contain homing devices that direct the weapons toward their target. The devices are typically classified by their guidance systems or seekers: IR, which home in on an aircraft’s heat source; command line-of-site, where the operator visually targets the aircraft and uses radio controls to guide the missile; and laser guidance. Countermeasures in progressThe US Department of Defense is working to minimize the threat of shoulder-fired missiles to military and commercial aircraft through the development of onboard IR countermeasure systems. It is developing laser-based directional IR countermeasure systems, which are expected to significantly improve an aircraft’s chances against heat-seeking missiles in comparison with the alternative nondirectional IR countermeasure system technology. In 2004, the US Department of Homeland Security (DHS) launched its C-MANPADS initiative, under which defense industry contractors are developing and testing existing military defense countermeasure systems for use on commercial airlines. BAE Systems’ JetEye IR missile defense system, for example, completed its first flight on a scheduled American Airlines aircraft in 2008, beginning the final phase of the DHS program to test the suitability of the equipment for commercial aircraft. An element of the JetEye airliner IR missile protection system, the laser point-and-track “jam head” is fitted to the underbelly of a plane. Northrop Grumman Corp.’s Guardian system, which is attached to the belly of a plane, also has undergone initial testing phases and is being tested in commercial cargo flights. Both systems use an IR sensor to detect missile launches and a laser burst to redirect the attacking guidance system. At the component levelA typical shoulder-fired missile tracks the target airplane by locking onto the signature of the heat given off by the airplane. Alternate IR countermeasure technologies provide for the deployment of chaff and flares by the target to confuse the guidance system of the missile. Although these systems have been moderately successful, the MANPADS can reacquire the target and hit the airplane. An artist’s concept of a shoulder-fired missile being defeated by a laser-based IR countermeasure system on an airplane. Photos courtesy of BAE Systems. A major innovation in providing improved protection, directed IR countermeasure technology moves away from the chaff-and-flares approach. The new technology involves an IR laser mounted on a target airplane. The laser activates when a MANPADS firing is detected and confuses the eye and brains of the incoming missile. Various types of lasers in the 4- to 5-μm range, such as optical parametric oscillators and optically pumped semiconductors, have been used, with varying degrees of success. Pranalytica Inc. of Santa Monica, Calif., recently introduced a turnkey 2-W fully packaged, CW room-temperature quantum cascade laser emitting at 4.6 μm for incorporation into IR countermeasure systems. Four tier-one aerospace/defense contractors have purchased the company’s 1-W versions since 2008, according to C. Kumar N. Patel, president and CEO. Jennica Dearborn, a BAE Systems software engineer, examines a laser gimbal, an element of the JetEye airliner IR missile protection system, which includes a laser point-and-track “jam head,” a multiband IR laser, four missile-warning sensors, control and processing electronics, an aircraft interface unit and a flight deck control panel. Because multiple lasers can be incorporated into the directional IR countermeasure systems, the 2-W components provide simpler, smaller and more cost-effective technology for the task, while providing a greater range of protected area. The components offer high reliability and are energy-efficient.