The Accessible time and elevation angle of satellite-to-ground link were simulated by using STK program. The effects of atmospheric transmittance, cirrocumulus, intensity scintillation and angle-of-arrival fluctuation were analyzed for different paths from two GEO satellites to three ground stations. Under the visibility of 5 km in city aerosol, weak turbulence and clouds, an adaptive optimal threshold method was proposed to establish the model of communicable probability of the link. The simulation results show that the average available probability of GEO in longitude 75° to Hainan ground station is best, the communicable probability attained near 93% in clear day and 66. 7% in cirrocumulus cover day. The analysis on this paper will be helpful for experiments of satellite-to-ground laser communication.%用STK仿真分析了星地激光通信链路的可见时间和俯仰角.在能见度5 km的城币大气模式下,分别计算了定位于不同经度的2颗GEO卫星对3个城市通信的大气衰减及光强闪烁、到达角起伏等效应,由此分析了晴天、卷积云条件下的大气信道功率损耗,并通过设置链路最小功率阈值来建立星地间大气信道激光通信链路可通率模型.仿真结果表明,当发射功率为10 W时,对比得出东经75°的GEO卫星地面站可通率较好,晴天能见度大于5 km的平均可通率可达到93％；卷积云时平均可通率可达到66.7％,且3个城市中对海南的可通性最好,为星地激光通信外场实验提供了一定的依据.
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