Why is Iridium System a Real Global Mobile Satellite Communication System?

Iridium satellite system is a global personal satellite mobile communication system in low orbit proposed by Motorola in 1987. It can combine the existing communication network to realize global digital personal communication. The system was originally designed as 77 small satellites, which run around seven polar orbits, so it was named because the number of satellites was the same as that of iridium atoms. Later, it was changed to 66 satellites orbiting six polar orbits, but the original name was still used. The height of the polar orbit is about 780km, and there are 1 1 satellites in the orbit, and there are 1 spare satellites on each orbital plane, each weighing about 700kg.

The concept of iridium system was put forward in 1987 by Barry Bertig, an engineer from Motorola, USA. Iridium satellite system is a personal digital satellite mobile communication system covering the whole world with 77 small satellites in low orbit, aiming at the limitations of traditional terrestrial cellular telephone network. It can be combined with the existing communication network to achieve seamless global coverage, and the total cost of the system is about 5 billion US dollars. Because the original design of the system used 77 small satellites, which respectively revolved around seven polar orbits, the iridium system was named because the number of satellites was the same as that of iridium atoms. Later, due to the design modification, the constellation structure was changed to 66 satellites orbiting six polar orbits, but the system name was still iridium system.

Iridium satellite system adopts on-board processing, on-board switching and inter-satellite link technology. Inter-satellite link is a major feature that distinguishes iridium satellite system from other satellite mobile communication systems. Its function is equivalent to placing a cellular network in the air, so the performance of the system is extremely advanced, but it also increases the complexity and investment cost of the system.

Iridium system market is mainly located in business travelers, maritime users, aviation users, emergency assistance and remote areas. The roaming scheme designed by iridium satellite system not only solves the roaming between satellite network and terrestrial cellular network, but also solves the cross-protocol roaming between terrestrial cellular networks, which is another characteristic of iridium satellite system different from other satellite mobile communication systems. Iridium system not only provides voice services, but also provides fax, data, positioning, paging and other services.

The roaming scheme designed by iridium satellite system not only solves the roaming between satellite network and terrestrial cellular network, but also solves the cross-protocol roaming between terrestrial cellular networks, which is another characteristic of iridium satellite system different from other satellite mobile communication systems. Iridium system provides four main services: Iridium global satellite service, Iridium global roaming service, Iridium global paging service and Iridium global payment card service, and also includes many value-added services similar to GSM. The system is technically successful, but it has stopped providing services to public users due to various operational problems.

From 1987 when Motorola put forward the concept of iridium satellite system to 1998, 1 1, the system has been put into operation all over the world. After about 12 years of hard struggle, I was forced to apply to the court for bankruptcy protection on 1999, and it took a long time. In the process of deciding whether to further destroy 66 giant constellations in LEO polar orbit 780 kilometers from the ground, it was repeated several times and finally came back to life at the end of 2000. American Iridium Company's proposal to acquire this Iridium Company was approved by the Bankruptcy Court in Shinan District of new york, and Iridium Company acquired all the assets of Iridium Company, including satellite constellation, terrestrial network and all its real estate and intellectual property rights. At the same time, the US Department of Defense only exchanged $72 million for the right to use Iridium's satellite telephone network to provide confidential telephone services for the US Navy and special operations forces stationed around the world. In addition, Iridium signed a contract with Boeing to operate and maintain this satellite constellation, and reached a commercially operable clause with Motorola to continue to provide corresponding user equipment. Therefore, the iridium satellite system can rely on its advanced space segment equipment and simplified ground gateway and control facilities to further operate at lower operation and maintenance costs. It is estimated that the number of users reached the peak around 2004 (about 654.38+0.5 million), and then it gradually declined and died out around 2065.438+00.

Iridium system has launched all 66 satellites needed for on-orbit operation on May 1998, and the joint debugging of six gateway stations was completed on May 1998. The experiments of satellite and satellite, satellite and ground, satellite and mobile phone have been completed. At the end of May 1998, Thailand, Japan and the United States have completed it. The installation of iridium satellite system at Beijing gateway station began in mid-July, 1998, and the first telephone call in China in September was 1998+0.

Iridium system was put into commercial operation in the world on June 1 998+065438+1October1. Iridium business in China was put into commercial operation in the middle of 1999.