Satellite links are going to play a key role in future quantum internet, because large distances can be handled by free-space connections. Large-distance, free-space quantum communication raises several issues, for example, how the measurement bases can be synchronized, how correlations can be demonstrated, and how the channel’s normal noise can be determined and separated from the effect of eavesdropping. Therefore, we aim to study the problems of free-space quantum key distribution in real environment.