Researchers at North­eastern Uni­ver­sity are devel­oping tech­nolo­gies to pro­tect the United States from a variety of external threats. Pro­fessor of Elec­trical and Com­puter Engi­neering Carey Rap­pa­port is the asso­ciate director of both the ALERT (Aware­ness and Local­iza­tion of Explosive-​​Related Threats) Center and Gordon-​​CenSSIS (Bernard M. Gordon Center for Sub­sur­face Sensing and Imaging Sys­tems). Rap­pa­port is also working on the VOTERS (Ver­sa­tile Onboard Traffic Embedded Roaming Sen­sors) project as a lead researcher on the use of radar to mon­itor the con­di­tion of roads, bridges and mon­u­ments. All three cen­ters were founded with sig­nif­i­cant fed­eral funding support.

Here, Rap­pa­port dis­cusses the work he and his col­leagues have been doing to for­tify the nation’s security.

Can you explain what sub­sur­face sensing and imaging means?

It means using var­ious types of non-​​invasive methods to see below sur­faces or inside hidden regions. At the Gordon-​​CenSSIS and ALERT cen­ters, we use radar, ultra­sound, x-​​rays, vis­ible light and other wave-​​based probes to iden­tify or detect things under a sur­face, such as tumors in the body, explo­sives under clothing, buried pol­lu­tants or dam­aged coral reefs under­water. Although sensing waves have always been able to pen­e­trate below the sur­face, the chal­lenge we’ve focused on is how best to make sense of the data that scat­ters back to us.

What areas of research is the ALERT Center cur­rently investigating?

ALERT, a seven-​​university part­ner­ship, is cur­rently inves­ti­gating the use of chem­ical, elec­trical, and elec­tro­mag­netic modal­i­ties to spot sui­cide bombers, warn people about sus­pi­cious bags that have been aban­doned and deter­mine whether vehi­cles are car­rying bombs. There are so many ways to hide things, and we want to iden­tify the threats with the least amount of public dis­rup­tion. Everyone dis­likes having to unpack and undress at air­port secu­rity checks. Wouldn’t it be great if we could develop tech­nology that would effec­tively sense hidden threats without a pas­senger even having to slow down? That is one of the center’s goals.

How would the ideal sui­cide bomber detec­tion system work?

We’re working on a multi-​​modality, layered-​​sensor approach, with optical, radar, ter­a­hertz and x-​​ray sen­sors observing pedes­trians as they walk toward and then past a non­de­script sensing plat­form. The var­ious sen­sors look for dif­ferent aspects of the pedes­trian: his move­ment, the reflec­tion from radar-​​scattering objects on his skin under his clothing, the pres­ence of trace explo­sive chem­i­cals on his clothing and the x-​​ray den­sity of for­eign objects he has on his person. The goal would be to iden­tify any sus­pi­cious activity and send a warning to the operator.

You are also researching ways to make roads, tun­nels and bridges safer. How are you doing that?

The same con­cepts for sensing through clothing or within the body can be applied to looking through the road sur­face to find sub­sur­face damage. The VOTERS pro­gram builds on work that we have pur­sued for years under the Gordon-​​CenSSIS SoilBED project. We are using radar and acoustic sensing tech­niques to quickly and inex­pen­sively deter­mine bridge deck and roadway health. If we can iden­tify dif­fer­ences in con­crete strength at one loca­tion rel­a­tive to another, we can inform con­struc­tion crews exactly when and where to do spot repairs before they become multi-​​week lane-​​closing traffic night­mares. We intend to outfit fleets of com­mer­cial trucks, buses, or cars with a suite of sen­sors that will con­tin­u­ously report on road health, and save cities and towns sig­nif­i­cant inspec­tion and repair money.

What made you decide to focus your efforts on this area of research?

I like working on impor­tant research prob­lems that everyone can under­stand, employing tech­nology that many people are familiar with. But I try using these tech­nolo­gies in inno­v­a­tive and inex­pen­sive ways. I started down this path a dozen years ago when I led a project on human­i­tarian land mine detec­tion. Our guiding prin­ciple was to con­figure existing tech­nology into sys­tems that a Cam­bo­dian farmer might be able to afford. Although radar has been around for more than half a cen­tury, it has only recently been used for imaging tumors or sensing con­cealed pipe bombs or iden­ti­fying hidden pave­ment problems.

My ulti­mate goal is to find cost-​​effective and rel­a­tively pain­less ways of seeing and inter­preting obscured regions more effectively.