Joel Johnson, an Ohio State University associate professor of electric engineering, is using a new radiometric sensor that detects plastic mines that are invisible to metal detectors. The sensor detects low-frequency microwave radiation. "With lower frequencies, the advantage is that you can detect more types of objects, but the image isn't as clear as with millimeter wave technology," he says. The sensor is considered passive because it only detects radiation and doesn't emit it like other detection technologies. All objects emit some low level of microwave radiation, which is what his sensor detects. Johnson's sensor picks up the unique microwave signature that is dependent upon the material from which the object is made. Johnson and graduate student Min Zhang developed computer models that take into account the different signatures. The same technology is suitable for detecting the roughness of the ocean surface, which could help meteorologists study weather patterns. Johnson says that the National Oceanographic and Atmospheric Administration, the Department of Defense, and NASA are involved with the project and there are plans to launch the microwave sensor on a satellite in the next few years. The Office of Naval Research sponsors the project. Radiometric (Boulder, CO) is building the sensor. For more information contact Johnson at (614) 292-1606 or send e-mail to email@example.com.