ABSTRACT
The open-path, optical remote sensing techniques make new areas of monitoring possible. These techniques measure the interaction of light with pollutants in real time. In an open-path configuration, path lengths—the distance between a light source and a reflecting device-can range to kilometers. Thus, these techniques are ideal for characterizing emission clouds wafting over process areas, storage tanks, and waste disposal sites. Open-path optical sensing systems can monitor gas concentrations at the fence lines of petrochemical plants and hazardous waste sites. The instrumentation used in remote sensing techniques includes bistatic systems and unistatic systems. Bistatic design placed the light source and the receiver at opposite ends of the area to be monitored. A new unistatic design, developed by MDA Scientific, uses a single telescope that acts as both source and receiver. With open-path systems, sophisticated, meteorological modeling software is necessary to integrate information about regional topography and moment-to-moment changes in atmospheric conditions.
