Experimental Optical Satellite Downlink Irradiance Statistics and Turbulence Conditions Estimation

The employment of free space optical (FSO) communications for satellite-to-ground and ground-to-satellite applications has gained a lot of attention. Many experiments and studies are conducted to explore the feasibility of FSO for satellite applications. The main purpose of these studies/experiments, under cloud free line of sight (CFLOS) conditions, is the characterization of laser beam propagation and especially the characterization and mitigation of atmospheric turbulence. Although turbulence effects are minimized through the aperture averaging technique on the downlink, they remain the dominant fading mechanism on the uplink. Hence, the effects of turbulence must be analyzed; therefore the estimation of the atmospheric parameters should take place. In this paper a methodology for the estimation of turbulence conditions along the slant path for optical satellite communications is reported. This methodology is based on the use of downlink data for the estimation of turbulence parameters. The proposed methodology is applied to downlink experimental data of ARTEMIS GEO optical link experiment. Moreover, experimental irradiance statistics for two receiving apertures (ESA's terminal and LUCE terminal in ESA's Optical Ground Station (OGS) in Tenerife Spain) are reported, while the aperture averaging factor and the scintillation for a point receiver is computed for the experimental data.