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The earth atmosphere is an unavoidable part of the satellite-ground laser communication link, which has a serious impact on the laser signal transmission. Poor weather conditions will cause the equipment at ground sites to be disabled, heavy cloud cover will interrupt the communication line, as well as the attenuation caused by atmospheric absorption and scattering will introduce an average reduction in signal power. Moreover, the irradiance scintillations introduced by atmospheric turbulence will cause the jitter of the received power and the deterioration of the bit error rate of laser communication. The speckle effect of laser caused by phase distortion will cause the decrease of tracking accuracy and the fiber coupling efficiency of PAT (pointing, capturing, tracking) unit. The sky background brightness, direct sunlight, etc., can cause the overall performance of the acquisition, tracking, and communication system to decline. The atmospheric polarization disturbance will decrease the mixing efficiency of coherent laser communication system, and the deflection effect of atmosphere will affect the alignment accuracy of PAT unit, and so on. All of these can seriously affect the transmission and communication of laser signals, and become the technical bottleneck restricting the development and application of high-speed satellite-ground laser communication. In this study, based on several typical optical stations in different geographical areas including the Ali site in Tibet, the Delingha site in Qinghai and so on, the research on the availability of atmospheric channel for laser communication is carried out. The characteristics of atmospheric channel of ground stations are analyzed, including the cloud cover, atmospheric transmittance, irradiance, atmospheric turbulence and so on, and the availabilities of single station and multi-station are discussed, aims to establish an evaluation system for the study of atmospheric channel availability of ground sites, as well as to put forward the availability criteria for atmospheric channel, and the results will provide scientific basic data for the performance of the ground optical receiving network for laser communication.
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