Up to 10 gigabytes-ten thousand floppy disks-of data from all 201 detectors will pass through the nerve center of the monitoring system each day. This International Data Centre will have to constantly and efficiently digest the raw feeds, says Steve Bratt, director of the prototype center, and send its readout to each country's scientists for interpretation. "We'll be producing a geophysical 'day-in-and-day-out' of the planet," he says. "To get that data and interpret it in a timely and accurate fashion is a huge challenge," says Jay Zucca, leader of the Critical Test Ban Treaty research program at Lawrence Livermore National Laboratory. But a bigger challenge will be detecting covert explosions-in the atmosphere, at sea, or underground.