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Astra is the brand name for a number of geostationary communication satellites, both individually and as a group, which are owned and operated by SES S.A., a global satellite operator based in Betzdorf, in eastern Luxembourg. The name is also used to describe the pan-European broadcasting system provided by these satellites, the channels carried on them, and even the reception equipment. From the launch of Astra 1A in 1988 the Astra satellites were owned and operated by ''Société Européenne des Satellites'' (SES). In 2001 SES Astra, a newly formed subsidiary of SES, operated the Astra satellites and in September 2011, SES Astra was consolidated back into the parent company. Astra satellites broadcast nearly 2,400 digital television and radio channels via five main satellite orbital positions to households across Europe and North Africa. The satellites have been instrumental in the establishment of satellite TV and the introduction of digital TV, HDTV, 3D TV, and HbbTV in Europe. A book, ''High Above'', telling the story of the creation and development of the Astra satellites and their contribution to developments in the European TV and media industry, was published in April 2010 to mark the 25th Anniversary of SES. ==Satellites== There are 16 operational Astra satellites, the majority in five orbital locations - Astra 19.2°E, Astra 28.2°E, Astra 23.5°E, Astra 5°E, Astra 31.5°E. Astra's principle of "co-location" (several satellites are maintained close to each other, all within a cube with a size of 150 km〔Bains, Geoff "The Failsafe Family" ''What Satellite & Digital TV'' April, 2012 pp29〕) increases flexibility and redundancy. 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「Astra (satellite)」の詳細全文を読む スポンサード リンク
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