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国际通信卫星Ⅲ号是第一个全球性商用卫星通信系统。在1970年中期,已有五颗卫星分别在大西洋,太平洋和印度洋的上空运转,它们同设在28个国家中的40个地面站开展了通信业务,共用了48部地面天线。每颗卫星的容量是1200路4千赫带宽的双工音频信道。在同步赤道轨道上,每颗卫星相对于地面站保持静止状态。它们进行自旋稳定,使其总是朝向地球,利用机械消旋定向天线以求获得全球复盖。从地球到卫星的点对点通信使用了6千兆赫的频段,从而卫星到地球则按照国际无线电通信咨询委员会(CCIR)的推荐用了4千兆赫的频段。该系统可在轨道中运行五年。到70年6月,这五颗卫星已累积工作达48个月,该时这些卫星的十部应答机中,还有九部能正常工作,第十部应答机的增益虽已降级,但还可用作通信转发器。
International Telecommunications Satellite III is the first global commercial satellite communications system. In the mid-1970s, five satellites had been operating over the Atlantic Ocean, the Pacific Ocean and the Indian Ocean respectively. They carried out communications with 40 ground stations in 28 countries and shared 48 terrestrial antennas. The capacity of each satellite is 1200 duplex 4 kHz bandwidth audio channel. On a synchronized equatorial orbit, each satellite remains stationary relative to the ground station. They spin stable so that they always face the earth, using a mechanically deconvolved antenna for global coverage. Point-to-point communications from Earth to satellite use a 6 GHz band, so that the satellite to Earth uses a 4 GHz band as recommended by the International Radio Communication Advisory Committee (CCIR). The system can run in orbit for five years. By June 70, the five satellites had accumulated 48 months of work, at which time nine of the ten transponders of the satellites were working properly. Although the gain of the tenth transponder had been downgraded, Can be used as a communication repeater.