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A very small aperture terminal (VSAT) is a two-way satellite ground station or a stabilized maritime VSAT antenna with a dish antenna that is smaller than 3 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Data rates range from 4 kbit/s up to 4 Mbit/s; some upgraded modules can even reach a max downlink of up to 16 Mbit/s. VSATs access satellites in geosynchronous orbit to relay data from small remote earth stations (terminals) to other terminals (in mesh topology) or master earth station "hubs" (in star topology). VSATs are used to transmit narrowband data (e.g., point-of-sale transactions using credit cards, polling or RFID data, or SCADA), or broadband data (for the provision of satellite Internet access to remote locations, VoIP or video). VSATs are also used for transportable, on-the-move (utilising phased array antennas) or mobile maritime communications. ==History== The concept of the geostationary orbit was originated by Russian theorist Konstantin Tsiolkovsky, who wrote articles on space travel around the beginning of the 20th century. In the 1920s, Hermann Oberth and Herman Potocnik, also known as Herman Noordung, described an orbit at an altitude of whose period exactly matched the Earth's rotational period, making it appear to hover over a fixed point on the Earth's equator.〔(CelesTrak: "Basics of the Geostationary Orbit" )〕 Arthur C. Clarke's October 1945 ''Wireless World'' article (called "Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?") discussed the necessary orbital characteristics for a geostationary orbit and the frequencies and power needed for communication. Live satellite communication was developed in the 1960s by NASA, which called it Syncom 1-3.〔(NASA - The First Geosynchronous Satellite )〕 It transmitted live coverage of the 1964 Olympics in Japan to viewers in the United States and Europe. On April 6, 1965, the first commercial satellite was launched into space, Intelsat I, nicknamed Early Bird.〔(Academy of Program/Project and Engineering Leadership (APPEL) | NASA )〕 The first commercial VSATs were C band (6 GHz) receive-only systems by Equatorial Communications using spread spectrum technology. More than 30,000 60 cm antenna systems were sold in the early 1980s. Equatorial later developed a C band (4/6 GHz) two-way system using 1 m x 0.5 m antennas and sold about 10,000 units in 1984–85. In 1985, Schlumberger Oilfield Research co-developed the world's first (12–14 GHz) VSATs with Hughes Communications to provide network connectivity for oil field drilling and exploration units. Hughes Communications went on to develop VSATs for enterprise customers such as WalMart, Holiday Inn, Chrysler, and General Motors. These enterprise terminals made up the vast majority of sites for the next 20 years for two-way data or telephony applications. A large VSAT network, with more than 12,000 sites, was deployed by Spacenet and MCI for the U.S. Postal Service in the 1980s. Today, the largest VSAT Ku band network containing over 100,000 VSATs was deployed by and is operated by Hughes Communications for lottery applications. In 2007, Hughes Communications started deploying VSAT sites for consumers under its HughesNet brand on the Spaceway 3 satellite and later in 2012 on its EchoStar XXVII/Jupiter 1 satellite. By September 2014, Hughes became the first Satellite Internet Provider to surpass one million active terminals.〔http://www.hughes.com/resources/hughes-becomes-first-satellite-internet-provider-to-surpass-one-million-active-users-1〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Very-small-aperture terminal」の詳細全文を読む スポンサード リンク
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