Aerosol Backscatter Measurements Using a Compact CO₂ Lidar Sensor

Abstract

There is an increasing need for air monitoring regarding hazardous organic gases which — if released into the atmosphere — have impact on the environment, on human health or might cause hazardous industrial accidents. Conventional air monitoring techniques detect only nearby pollutants and thus yield limited information on the pollutants’ local distribution. As a consequence concentrations with strong spatial variations may not be detected at all or merely as apparently diluted and small. Therefore, a pronounced progress in air monitoring is expected from the DIAL technique (DIfferential Absorption LIDAR, LIDAR: LIght Detection And Ranging), since DIAL allows to identify, quantify and localize remote atmospheric pollutants from a single sensor location (without reflecting or backscattering topographic target); concentration profiles and three-dimensional maps obtained by DIAL display spatial concentration variations as well as temporal fluctuations and concentration build ups. DIAL is based on absorption spectroscopy. Since relevant hazardous gases show characteristic absorption lines which coincide with CO₂ laser lines within the 9 to 11 µm regions¹, CO₂ laser based DIAL sensors seem to be well suited instruments for monitoring the atmosphere.