9-11: Upon Further Review

A look back and IEEE Spectrum's coverage of the technological advances and policy changes that occurred in the wake of the terror attacks

7 min read
9-11: Upon Further Review

IEEE Spectrum's reporting on the events and aftermath of 9/11 can be found here.

In the immediate aftermath of the day 10 years ago when a group of terrorists used commercial jets as missiles to strike the World Trade Center’s twin towers in New York City and the Pentagon, just outside Washington, D.C., the U.S. government and its citizens asked two inevitable questions: How could this have happened? How can we keep it from happening again? A big part of the answer to the second question has been technology. Improvements in areas such as communications, sensing, and surveillance have been developed along with policy changes that have allowed them to be implemented—for better or worse, depending on whom you ask.

IEEE Spectrum reported on several research efforts that got underway in response to the terrorist attacks or whose products were repurposed. At a joint IEEE Spectrum–New York Academy of Sciences press briefing held the following month, we got the first glimpse of what was happening technologically and what was up the road policywise.

To prevent a repeat of 19 hijackers entering a restricted area undeterred, research on visual surveillance got a big boost. Research areas including motion detection, tracking, face recognition, behavior recognition, and image archiving. One of the participants in the briefing reported that he was involved in a project on CCTV surveillance called funded by the European Union. Ten years later, CCTV surveillance is playing a big role in identifying the people responsible for violence and destruction during the riots that took place in London earlier this summer.

Another issue discussed during the briefing was whether it was possible to use the information on a terrorist watch list to spot the individuals as they enter a country or attempt to board a plane. The problem, as it was framed back then: you have to be able to sift through about six hundred million faces in the United States alone as they pass security checkpoints each year, and spot the terrorists and criminals among them without interfering with passenger flow. Anyone who has arrived at an airport early and waited in line for the privilege of removing their belt and shoes, then submitting to a pat-down knows that this is still a work in progress.

We also reported the call for a single, unforgeable U.S. national identity card that would allow authorities and security personnel to tell, at a glance, whether a person is in the country legally. The card—which would have included a photo, physical description, and encoded biometric information—would have been linked to a national ID system with a huge database. The idea has been a nonstarter for several reasons, among them the fact that the database would be a natural target for hackers and that the burden and cost of implementation have been laid at the feet of state departments that issue driver licenses.

When the World Trade Center towers fell, televisions across the New York metropolitan area went black. A 110-meter mast atop Tower 1 was a broadcast hub for all of the New York City area, supporting FM radio as well as nine TV stations, including local affiliates of CBS, NBC, and ABC. The Empire State Building, which once again became the city’s tallest building, has become the area’s main communications hub. But broadcast engineers have a better understanding of the value of backup transmission sites, so TV and radio broadcasts now originate from several sites, including a 120-meter-tall tower in New Jersey that transmitted signals for the first ever FM radio station. Finding other locations is still made near impossible by the fact that moving transmitters leads to interference with transmissions from adjacent broadcast markets.

These days, the U.S. federal government, states, and even local police agencies make no bones about the fact that they are keeping tabs on U.S. citizens. Every phone call, e-mail, text message or smoke signal is being monitored by some arm of the government. It all started eight days after the attacks, when then-Attorney General John Ashcroft sent draft legislation to Congress proposing significant changes to laws covering domestic and foreign surveillance. Those changes became the the PATRIOT Act, standing for Provide Appropriate Tools Required to Intercept and Obstruct Terrorism. Before then, people who assumed that they were being watched were labeled paranoid. Now, the New York City Police Department is trolling Facebook pages to sniff out gang activity. 

Experts say that if you’re outside the blast radius of a nuclear detonation, you greatly increase your chance of survival if you shelter in place (even inside a car) to limit your exposure to radiation. Another, more well known preventative measure is taking potassium iodide to prevent radiation poisoning. A decade ago, a U.S. House bill that would require stockpiling of potassium iodide for everyone within an 80-km radius of a nuclear power plant was introduced. But that bill, nor anything since has worked out the logistics for distributing the pills to the public. Even alerting people that they need to replace their personal stashes because the shelf life has ended has foundered because public officials are wary of stirring up panic or of being seen as unsure of the safety of nuclear facilities.

Great as cellular technology is, one drawback was that if you dialed the police or fire department from your handset, they would have to rely on you (despite the fact that you might be lost, panicked, or otherwise under duress) to tell them your location. Then came the E-911 initiative. It mandated that cellular carriers upgrade their networks so that when a handset dials the nation’s universal emergency number (which, theretofore, was not universal) that phone could be located to within a reasonable distance. Several carriers missed the 31 December 2005 deadline by which 95 percent of handsets were supposed to be E-911 compliant. By 11 September 2012, wireless network operators must provide locate callers within 300 meters, within six minutes of a request by an emergency services operator. Several carriers have already rolled out technology that allows customers on the same network the option of letting others track their whereabouts. So the upcoming deadline should not be a difficult standard to meet.

Amid the questions about how to prevent another 9/11, we were all still curious about what set off the collapse of the towers. We talked to the a civil engineer who headed the investigation into the towers’ destruction. Even before his team began its work, they were hopeful that computer programs capable of modeling impact, fire, and structural performance would reveal the points of failure.


Remote sensing techniques were relied upon by search and recovery teams to assess what was inside the mountains of rubble at Ground Zero even when it was clearly to dangerous for humans to traverse the piles of twisted steel and concrete. A plane flying 1500 meters above lower Manhattan scanned the scene and generated detailed images of the composition of the debris down as far as 9 meters below street level. But sophisticated as lidar, radar, sonar, and a host of other technologies have become, they still haven’t been able to help ferret out antipersonnel landmines and improvised explosive devices before they kill.

Also on hand shortly after the attacks were more than a dozen remote-controlled robots that used lights, video cameras, two-way audio, and night vision to give rescue teams an idea of where to search, as well as an up-close glimpse of the obstacles separating them from any survivors. Robotics is always advancing. But as we saw this year in the aftermath of the nuclear accident at the Fukushima power plant in northern Japan, robots still have limitations that still vex designers.

In the weeks after the terror attacks, U.S. Senator Judd Gregg (R-N.H.) introduced a bill aimed at making encrypted data accessible to law enforcement. The measure would have required that codes for breaking encryption be stored with a government or other agency and made available to law enforcement by court order. But who at this point trusts government agencies to keep this information secure when we hear of incidents involving laptops containing sensitive information going missing, hackers invading computer systems, or employees selling information.

XM Satellite Radio Holdings Inc., Washington, D.C., became the first company to launch a satellite radio service when it debuted on 25 September 2001 in San Diego and Dallas. Programming originated from XM’s Washington, D.C., studios. The launch came a week after the U.S. Federal Communications Commission granted XM and then-rival Sirius Satellite Radio Inc. (which launched later that year) temporary approval to operate its repeater stations–a move strongly opposed by wireless telephone carriers, who argued that the service would interfere with their portion of the spectrum. In 2008, the two companies merged.


For every measure, there will eventually be a countermeasure. Referring to the terrorists who slammed planes into the World Trade Center and the Pentagon, John Parachini, the executive director of the Washington, D.C., office of the Center for Nonproliferation Studies of the Monterey Institute of International Studies, said, "They found the loopholes and ran right through them in a low-tech way.” He reminded us that we needed to rethink how we secure ourselves against terrorist attacks. Not a single bomb blew up before the planes themselves exploded. And the provocateurs needed no more reconnaissance than a vague familiarity with the locations of the World Trade Center and the Pentagon.

Another article pointing out the need to think with the mind of a terrorist in order to anticipate their moves, notes that a classic terrorist tactic is luring emergency workers in with one destructive act before delivering the second. In the case of 9/11, the second plane slammed into the South Tower approximately 18 minutes after the first crash. The kamikaze hijackers counted on the rescuers reacting precisely as trained–rushing into a building regardless of its structural integrity. The result: more than 300 firefighters perished

What was the big delay in getting Wall Street back up and running after the Twin Towers crumbled? investment banks didn’t have their computer systems at ground zero, so the major number-crunching and back-office processing were not affected. The people were what was hard to replace. Among the people lost on 9/11 were a group of high-level technologists who were at the World Trade Center for a meeting about how to streamline trading and post-trade processing, so that the settlement process, from the time the order is executed until the time the trade is confirmed, would take just one day, instead of three days.

As we learned more about what happened in the minutes before the planes slammed into the buildings, a troubling question emerged: Would U.S. military commanders really have given the order to shoot down commercial jets with civilians on board if the fighter planes had arrived in time to intercept them? Another nagging question is why it took so long to figure out that something had gone terribly wrong.

Once a year, a select group of scientists and engineers gathers at Dugway Proving Ground, a salt flat in the Utah desert 65 kilometers from the nearest traffic light. They are there by invitation of the U.S. Defense Department's Joint Program Office for Biological Defense to compete in an unusual showdown: to field-test their systems for detecting biological warfare agents. They and other groups have made tremendous breakthroughs in sensing of biological and chemical agents. Earlier this year, an airport in the UK rolled out a system that can analyze a closed container and indicate whether it contains contraband.  



The Conversation (0)