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本世纪60年代以前,世界上各大洲间通信大多是利用无线电波通过电离层反射而实现的。电离层象一面高悬太空的镜子,能将电波反射到远方。由于它的密度与高度经常随时辰、季节变化而变动,使通信不稳定。通信卫星的出现,从根本上改善了这种状况。卫星通信系统是由空间部分(通信卫星)和地球部分(卫星地面站)两大部分组成。它是利用人造卫星作为中继站来转发无线电波,在两个或多个地面站之间所进行的通信。
Before the 1960s, most of the communications between continents in the world were made using radio waves through ionospheric reflections. The ionosphere is like a mirror suspended from the sky that reflects the waves to the far side. Because of its density and height often with time, seasonal changes and changes, making the communication unstable. The emergence of communications satellites has fundamentally improved this situation. Satellite communications system is composed of space (communications satellite) and the earth part (satellite ground station) composed of two parts. It is the use of artificial satellites as a relay station to forward radio waves, conducted between two or more ground stations.