Analytical Comparison of Optimized Heterodyne and Direct-Detection CO2 Lidar for Atmospheric Remote Sensing*

Our recent experimental study1 of the relative technical merits of heterodyne and direct-detection CO2 DIAL for path-averaged remote sensing was carried out using LIDAR backscattered returns from topographic targets. In these studies, the average SNR's and statistical and temporal characteristics of the LIDAR returns were measured simultaneously for each detection technique. The experimental results were found to be in good agreement with a simple analysis which predicted the relative sensitivity of each detection technique for path-averaged measurements. The detection systems used in the above experiments were not optimized for either of the two detection techniques.