PORTLAND, Ore. -- Yes, we're safer--but.
It's the answer, with a caveat, to the question that will be on everyone's mind today. But from a technologist's perspective, there are other questions to ask about where we stand five years after the 9/11 attacks. The country has spent billions on technology up- grades to detect and defuse new threats. Have we invested wisely? Are the technologies being deployed effectively? What more can be done?
"I would challenge anyone who claims we are not safer than we were on 9/11," said Tim Collins, managing director of the Purdue Homeland Security Institute at Purdue University. "Our airports were wide open then--that's why the terrorists targeted them--but now we have dual-energy computed tomography and many other detection technologies in airports that did not even exist in . But al-Qaeda is smart, so we need to need to develop technologies at a fast pace to stay one step ahead of them."
After 9/11, there was an explosion of research and development in sensor technologies, several of which have been deployed. But other technologies are languishing in red tape, according to analysts.
"We are there technologically," said Matthew Farr, senior homeland security analyst for Frost & Sullivan (San Antonio, Texas). "But we are not as safe as we could be, because only checked baggage is always scanned for explosives today. We need to deploy technologies that can detect explosives in our carry-on baggage and cargo too."
Most carry-on baggage is still scanned at airports by Cold War era X-ray machines. GE Security (Bradenton, Fla.) and L3 Communications Corp. (New York City), which split the market roughly evenly for the computed tomo-graphy (CT) scanners currently used to screen checked baggage at U.S. airports, are scrambling to close the gap. By this time next year, both companies promise, the same screening techniques now used for checked baggage will be available for carry-on bags. Analogic Corp. (Peabody, Mass.), which manufactures L3's CT scanners, has its Cobra CT scanner in testing at Boston's Logan International Airport, and the GE Security Lab at San Francisco International Airport has a similar system under test.
But many promising technologies are still years away from practical implementation. "We need to work faster developing technologies," said Joseph (Jody) O'Sullivan, director of the Electronic Systems and Signals Research Laboratory and associate director of the Center for Security Technologies at Washington University.
Beyond guns and knives
X-ray machines have been standard equipment at airports since the 1970s.
In those days, the main objective was detection of guns and knives. "The X-ray machines of today have been improved over those original devices," said John W. Wood Jr., president and CEO of Analogic. "Some automated recognition capabilities have been added. Nonetheless, Wood said, "the basic capabilities of traditional X-ray machines have not kept up with the new threats."
Both GE Security and L3 have adapted medical CT scanners for use as 3-D replacements for conventional X-ray machines. CT scanners are now used at all U.S. airports and many foreign international hubs, with more than 1,000 units installed worldwide at a cost exceeding $1 million each.
"Our goal is to bring the price down well below $500,000, so that [CT scanners] will be economical enough to use for carry-on baggage," said Analogic's Wood.
Steve Hill, chief technology officer for the Homeland Protection division at GE Security, said his company has set a price goal of $350,000.
That's still expensive compared with the less-than-$50,000 tag for conventional X-ray scanners, but the premium buys a huge increase in visibility. X-ray images are only two-dimensional, so that a gun or knife scanned by an X-ray machine looks like a thick line if it's viewed from any orientation other than the side. By contrast, CT scanners re-create a three-dimensional image that screeners can rotate to any angle to identify objects quickly.
CT scanners also let inspectors view objects hidden within other objects. "Orientation is no longer a problem, and more than that, you can actually 'unwrap' obscured objects and look inside of them," said Hill.
What's more, two power levels are used so that the density of the material can be determined. "Not only do you get shapes, but you can get information about the composition of the objects," said Hill. "The CT divides the volume into tiny little voxels [a voxel is a 3-D version of a pixel] and tells you what is inside each one, its density and effective atomic number."
That makes the machines able to detect far more than guns and knives. C4 plastic explosive, for example, has a characteristic density that CT scanners' automated software can be been programmed to recognize. The scanners use color monitors to display the differences in density (conventional X-ray images are monochromatic).
"Our automated software highlights everything in a bag with different colors and brings questionable objects to the attention of an operator, setting off an alarm," said Hill.
"Suspicious bags are diverted to a hand-inspection area, where the screener can use trace detectors or other means to determine whether the item is a threat or not," said Wood.
Trace detectors use various sensors to collect a sample from a bag that has set off an alarm. Ion trap mobility spectroscopy, which Hill said works similarly to mass spectroscopy, measures the size of the molecule by measuring a sample's transit time in a drift tube with an applied electric field. "But unlike mass spectroscopy, which must be done in a vacuum, ion trap mobility spectroscopy can be done at normal atmospheric pressure," said Hill.
GE has crafted an ion trap mobility spectroscope as a portal. As people walk through, the system puffs air, then vacuums off the results in seconds. It is installed at nine facilities thus far, and interest from other airports is claimed to be high.
"The detection fundamentals of the portal are the same as swabbing. The difference is how we gather the sample," said Hill.
New architectures for trace detectors could automate the process for bags too, so that luggage could be checked without tying up a human screener. TraceGuard Technologies Inc. (New York) has an automated collection system called CarrySafe that uses the puff-and-vacuum method on bags by wrapping a piece of baggage in an adaptive membrane that houses both air-jet and vacuum nozzles (search www. eetimes.com for article ID: 187003240).
"We believe our trace detection is even more reliable than using a swab or a hand-held vacuum, because our air jets are more powerful, and we dislodge and collect particles from all over a bag's surface," said Ehud Ganani, TraceGuard's chief executive officer, who was formerly CEO of Israeli Military Industries and, before that, vice president at Israeli military technology company Rafael Armament Development Authority Ltd.
If trace detection cannot resolve the alarm, then an operator can turn to a spectroscopic technique, such as Raman op- tical scattering, which can identify un- known substances.
"The big difference between trace de- tection and Raman spectroscopy is that traces detect the presence of the specific substances you are looking for," said Hill. "If you don't know if a specific substance is there, but you want to know, then use trace technology. If you know [a substance] is there but you don't know what it is, then you use Raman spectroscopy to identify it."
Raman spectroscopy is an optical technique, so unless a residue is visible on the outside of a bag, the bag must be opened so that a monochromatic laser can illuminate the objects inside.
Raman libraries of recognizable substances are more extensive than trace libraries, but Raman spectroscopy requires a larger sample. Trace technology concentrates on identifying the few substances of particular concern to the Transportation Security Administration, but it works with nanograms or even picograms of the substance.
"Raman spectroscopy works on substances you can see," said Hill. "If a bag is open, screeners can use Raman spectroscopy to interrogate transparent containers to find out what is inside them."
Raman spectroscopy works similarly to gas chromatography. First the screener shines a laser on the unidentified substance or container, energizing the substance and thereby driving its electrons into higher-than-normal orbits. As the electrons drop back to their ground state, they release photons. A photodetector collects the photons, and software analyzes their colors for shifts that match substances in the Raman library.
"Depending on what frequency bands the scattered signal gets shifted to, you can develop a fingerprint for what is in there," said Hill. "Then software matches those shifts with a library of known fingerprints."
If a container is not transparent, and the CT has determined that it is not empty, then the screener can turn to magnetic resonance technologies.
"CT can almost always determine whether there is something inside a container, plus we can derive some information about its characteristics, but if you really want to find out what is in there without opening it, we recommend magnetic resonance," said Hill.
Magnetic resonance is a simplified version of the technology used in medical MRI. A strong magnetic field is applied to the container, and then a radio-frequency pulse stimulates the atoms inside, thereby disturbing their dipole moments. A detector analyzes the signal that comes back as the atoms inside the container relax back to their ground state.
"Of course, our system is much smaller than the room-sized MRIs used in the medical profession, because we are not trying to make images with it, but just determine for the signature of the substance inside--this greatly simplifies both the detector electronics and the analysis software," said Hill.
Magnetic resonance can even see through most metal containers, though not through a heavy lead enclosure. (On the other hand, if the container is too dense to see inside with X-rays or MR, the screener will see a big black spot, making it obvious that something is being hidden.)
More-exotic sensors are being rapidly developed to improve automated detection systems. One is nuclear quadrapole resonance--the no-magnet equivalent to MR--which uses RF pulses to interrogate a sample and then listens for specific return signals, but without the high-strength magnetic field.
"We are field testing a system that uses nuclear quadrapole resonance to look for shoe bombs without having to take your shoes off; you just stand on it," said Hill.
Like the automatic shoe-bomb detector, all the rest of these technologies will be moving out of the back room where they are already being used for checked baggage. Raman spectroscopy, for instance, is available from GE Security in a handheld version that can be used at checkpoints for carry-on baggage.
In addition, the systems are being streamlined so that they operate rapidly and unobtrusively. For instance, the first use of the automatic shoe-bomb detector will probably be a registered-traveler express lane; travelers would stand on the unit and have their shoes checked at the same time as their IDs. GE may also put a hand pad at the same location in the express lane, so that passengers' fingers could be screened using trace technology as they wait for their IDs to be returned.
"For the future, we not only want to continue improving detection capabilities; we also want to lower false alarms and improve throughput, as well as lower the costs of owning these systems by requiring less and less intervention by people," said Hill.