Abstract: The atmospheric channel characteristics of laser communication ground station determine the equipment performance. Four candidate sites, Ali in Tibet, Delingha in Qinghai, Daocheng in Sichuan, and Xinglong in Hebei China, were selected for statistical inspection of the effects on laser communication, including the factors of cloud coverage, atmospheric transmittance, sky background radiation, and atmospheric turbulence. It was shown that Ali is the best for single station availability; Ali-Delingha-Xinglong is the best for the three-station combined availability, more than 85% in full year under 60% cloudiness. For the four stations under 60% cloudiness, the combined availability can be 91%~96% in May to August, and reaches more than 98\% in other months. The atmospheric optical properties of the four candidate sites meet requirement of laser communication. The high altitude sites have obvious advantages in atmospheric transmittance and background radiance. The atmosphere coherence length in night is larger than 10 cm in Ali and Daocheng, and 8~12 cm in Delingha, and just higher than 6 cm above for Xinglong. In multi-station combined mode, good sites, with sufficient high availability and meeting optical communication requirements, could be selected in high altitude and less cloud areas.

Key words: laser communication, availability, atmospheric optical characteristics, candidate site