John Petersen doesn’t like surprises, but he studies them for a living. The director of the Arlington Institute, a scenario-planning outfit in Virginia, helps the government think about the unthinkable. His latest inquiry: What if the US Global Positioning System stopped working? It’s not as far-fetched as it might sound. Eighteen of the 28 satellites in the GPS constellation are operating past their intended lifespan or suffering from equipment failure. There have been three launch incidents in the past five years, and the Air Force, which maintains the 20-year-old network, is overburdened with competing space priorities. Given the circumstances, planners are concerned with the system’s health. “If GPS were to fail completely, the cost would be incalculable,” Petersen says. “Civil aviation, trucking, shipping, and telecommunications would be worst hit, but countless other industries would be affected.” Internet activity would slow to a crawl, because many backbone operators rely on precise GPS time stamps to route data. Agribusiness and commercial fishing could be blinded, causing food prices to skyrocket. The $12 billion market for GPS devices would be sent reeling, and the arrival of location-based wireless services would be set back years. Full Story