Results of three-year work under INTAS-ESA grant 99-822 are summarized in this paper. The autodyne lidar with new version of a dual wavelength cw CO2 laser is described. The results presented have been obtained by modeling based on solutions of semiclassical laser equations adapted for 300-km sounding range. The sensitivity of the lidar has been estimated using a phenomenological model of detection for more than 20 contaminating gases. We describe the lidar constructed around a specially developed cw autodyne laser with the enhanced performance characteristics, as well as the technique of experiments on determination of these characteristics. The tentative results of experiments quite well agree with the estimates obtained.