Super-Radar, Done Dirt Cheap

This article examines Celldar (from "cellular" plus "radar"), a new radar system that uses cell-phone signals to locate and track cars, boats, or planes - even if no one inside is carrying a wireless phone. Under development since 1997 at Roke Manor Research Ltd. in Romsey, England, Celldar takes a "passive" approach in that it watches and interprets how signals from cell-phone base stations interact with objects. The hardware required is much simpler than existing radar systems, though the signal-processing software is complex.

According to this article's author, Celldar has a number of military and civilian applications. For example, passive radar systems are invisible to anti-radar weapons because they don't have their own transmitters. And because cell-phone towers are scattered far and wide in many countries, an airborn Celldar system could monitor a whole country - without being detected. In addition, Celldar could enable police and homeland security agencies to monitor shipments of illegal weapons and drugs. Further, highway officials, insurance companies, and governments could monitor vehicles to minimise road congestion or levy "pay-for-use" road taxes. There are privacy concerns, however. As the author puts it, "because passive-radar systems could be cheap enough for hobbyists to buy -- or cobble together themselves -- the technology could also become the next fad among people who own police-radio scanners or who enjoy snooping on their neighbors' comings and goings."

In addition to Celldar, a dozen other passive-radar projects are under way in the USA, Europe, and Asia. One such system harnesses an FM station's signals to study particles in the ionosphere (the top layer of the atmosphere). This system's pioneer, John D. Sahr of the University of Washington (USA), says he decided to go with passive radar "because it's incredibly cheap" - US$20,000 versus US$25 million for a comparable system (a system for small airports, he says, might cost as little as US$15,000). In addition, classified research is under way in Europe to create a hybrid surveillance system that uses both passive radar and images from TV cameras to watch suspected terrorists and criminals more closely and from a safe distance.

Click here for the full article on the Business Week site.