Radar-based open-path chemical sensor created.

Researchers at the U.S. Department of Energy's Argonne National Laboratory developed an interference-free, open-path, radar-based, millimeter-wave sensor to remotely detect trace levels of airborne chemicals. The new sensor works in remote positions, for environmental monitoring (continuous emission and fenceline), leak detection, and arms-control treaty verification. However, the transmitter/detector and a reflector have to sandwich the targeted chemical plume to get accurate measurements. Millimeter-wave absorption spectra of plume chemicals are determined by measuring the swept-frequency radar return signals, with and without the plume being in the beam's path. To determine actual chemical concentrations, users match measured spectra to a spectral library.