Since 1981 the Royal Signals and Radar Establishement and the Royal Aircraft Establishment, United Kingdom, have made vertical and horizontal sounding measurements of aerosol backscatter coefficients at 10.6 μm using an airborne continuous wave focused CO2 Doppler lidar, the Laser True Airspeed System (LATAS). The heterodyne signal from the LATAS detector is spectrally analyzed. Then, in conjunction with aircraft flight parameters, the data are processed in a six-stage computer algorithm: set search window, search for peak signal, test peak signal, measure total signal, calculate signal-to-noise ratio (SNR), and calculate backscatter coefficient. ¿American Geophysical Union 1991