New Views on Airport Screening
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Published on Security Management (http://www.securitymanagement.com) New Views on Airport Screening By Joseph Straw As we’re all too well aware, the threats facing the aviation sector have evolved enormously over the past three decades. Once, an airport security screener’s concerns were limited to traditional guns and knives and rudimentary homemade bombs carried by would-be hijackers. Now, everything from radios and notebook computers to shoes and beverage containers may conceal bombs. Guns and knives have evolved too. They are now mass-produced in large part from organic polymers—plastic—not just metal. And seven years ago, a handful of hardware store box cutters, probably containing less metal than a typical belt buckle, helped alter the course of history. Yet in the years immediately following 9-11, airport security checkpoints advanced little from those first fielded in the 1970s—consisting of baggage x-ray machines and magnetometers. That, however, has begun to change. Carry-On Baggage One new approach, initially called “advanced technology” (AT) baggage screening, has come to be known as “dual view” (DV). The Transportation Security Administration (TSA) began testing the AT/DV machines in 2007. As of this summer, they were deployed to 250 of the 2,000 lanes at 700 TSA-run checkpoints around the country. The agency plans to field an additional 600 by the end of 2008 and another 230 early in 2009. TSA uses equipment from two companies—Smiths Detection’s HI-SCAN 6040aTiX and Rapiscan’s 620 DV. As the name implies, the dual-view technology gives TSA transportation security officers (TSOs) two views of each bag passing by the x-ray scanner, one horizontally and one diagonally from below. “What it does is it provides you with more information about the content of the bag, you see overlapping items in the bag from different cross sections,” explains Mark Laustra, a vice president for homeland security with manufacturer Smiths Detection. Threat detection is the main goal, but maximizing passenger throughput also matters for any screening technology so as not to unduly interrupt the flow of travelers. Peter Kant, Rapiscan’s vice president of global governmental affairs, explains that the dual perspective not only helps identify threats but also helps identify false alerts, which are far more likely to bring about needless secondary visual inspections that slow the checkpoint. The AT/DV systems rely on traditional “transmission” x-rays that pass through the baggage. Based on the strength and diffraction of waves received by the machines’ sensors—like light through a prism—software helps assess the density and relative atomic weight of a bag’s contents. The system can then determine which substances are inorganic—like metal—or organic, which could include plastic weapons or explosives. Software is the system’s critical element. It uses algorithms (complicated decision-making equations) to determine how to categorize an item; it then tags items in the bag with a color code for display on the TSO’s monitor. In the case of the Rapiscan system, organic items—which could include explosives or polymer-based handheld weapons—appear in shades of orange and red, and inorganic in shades of green and blue, with increased darkness indicating higher densities or object overlap. While TSOs can independently alert on any bag for secondary visual inspection, both the Smiths and Rapiscan systems’ software provide automatic algorithm-based threat detection. If, for example, the Smiths aTiX software spots a suspect substance or object, the machine superimposes a red box and arrow over that area on the monitor to ensure that operators won’t overlook it. 1 of 6 6/22/13 10:27 TSA also asked developers of this technology to make it adaptable or malleable so that it will work against unforeseen future threats as they arise. That malleability and scalability resides in the ability to write new algorithms for the software. Currently, both firms are working with the TSA on new algorithms to detect anomalies in laptop computers, and they are also trying to write code that can discern between harmless liquids, like shampoo, and explosives, like acetone peroxide. If successful, the new software may save travelers from removing liquids and laptops from bags at checkpoints. “[W]e know those are two major pain points for travelers,” says TSA spokeswoman Ellen Howe. As with prior x-ray machines, the AT/DV machines offer the TSA threat image projection (TIP) capability for training and evaluation. With TIP, simulated threat images that look real to the TSOs are regularly superimposed on real passenger bags as they pass through checkpoint x-ray machines. When TSOs alert on a simulated TIP threat, the system informs the screener that the image was only a simulation and notes the alert. If the threat is real, the belt stops, and the bag is diverted for secondary screening. If the screener misses a simulated threat, the omission is recorded. Missed TIP images are reported to the screeners’ supervisors. A TSO may then be assigned additional training or to be asked to take other action. Checked Baggage Explosives detection systems (EDS) are large, belt-fed machines used to scan unopened checked luggage, in which explosives pose the only critical onboard risk. Drawing on technology adapted from medicine, EDSs are basically computed tomography (CT) x-ray machines, which, like the new AT/DV x-ray machines, use software to interpret data from multiple x-ray diodes. These machines, most manufactured by either L-3 or GE Security, have a tube-shaped gantry consisting of a massive lead sheath enclosing a spiral array of 11 x-ray diodes. The tube rotates around the bags as they ride a conveyor belt through the machine. The machine’s software interprets transmitted x-rays to generate a detailed, three-dimensional image of the bag and its contents, including identification of potential explosives. Some forms of EDS have been around for a decade or more, but the technology continues to advance. For example, the throughput of traditional EDS machines is roughly 300 bags per hour. Rapiscan, however, plans to field a technology that can work four times faster, called the Real Time Tomography (RTT) system, Kant says. Rather than a rotating gantry with 11 diodes, the RTT systems rely on 400 stationary diodes performing the same function, providing 1,000 to 1,200 data points for software analysis in a single instant. The vastly increased amount of data will aid in detection, while the instantaneous scan would speed the process. The added speed of the RTT system would require multiple screeners to review baggage images if the machines are to provide their maximum throughput. Kant, however, says that one RTT machine would replace several traditional EDS machines. Passengers Passenger screening is also evolving to keep up with changing threats. Threats now include not only guns, knives, and plastic explosives but also liquid explosives, radioactive materials, and pathogens. These threats have increased the need to move beyond the traditional metal detector, but that creates special challenges because humans cannot be subjected to the same x-rays as baggage. Full-body imaging. One way that this challenge is being met is with the full-body scan systems, which use backscatter x-ray or millimeter wave technology. These generate much lower levels of radiation (less than 10 microREM versus 100 milliREM allowed per year). While they rely on different bands of the electromagnetic spectrum, backscatter and millimeter wave machines operate on the same principle. Like radar or sonar, the machines project energy onto an object, and the software interprets what is reflected back. Generally, the waves penetrate clothing unaffected, are absorbed by hard objects like guns or explosives, and are “scattered,” or reflected back to varying degrees by organic material, including flesh. A backscatter machine is about the size and shape of a vending machine; the subject gets scanned twice—once while standing facing the machine, then again while facing away from it. The millimeter wave machines that TSA has purchased, manufactured by L-3 Communications, are hexagonal booths with dual sensors that simultaneously 2 of 6 6/22/13 10:27 sweep across a subject’s front and posterior. They produce a photo negative-like image of a bare body with inorganic threats in black. The technology works, but it has run into opposition based on privacy concerns. The American Civil Liberties Union has dubbed the machines a “virtual strip search” and “an assault on the essential dignity of passengers that citizens in a free nation should not have to tolerate.” TSA defends the technology. The agency notes that it is far less invasive than the traditional physical search. In fact, passengers subjected to secondary screening at Phoenix Sky Harbor International Airport, when given a choice between a physical pat down and a full-body scan, choose the latter 90 percent of the time, according to TSA. Civil libertarians counter that most people don’t know exactly what the images entail. “Determining how the public feels about this is going to affect the future of it,” Howe says. To address the privacy concern, TSA has asked manufacturers to tweak the algorithm to blur the face in the image. Certain backscatter systems offer what may be a more desirable privacy feature: the subject’s body is presented not as a full image, but instead as a white outline reminiscent of the chalk outline at a crime scene. Threat objects are superimposed. To boost privacy further, the TSO who views the full scans is sequestered from the checkpoint. If the TSO spots a potential threat, he or she radios the checkpoint to order a pat down.