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Astra Tech - Dental implants from Astra Tech likenaturalteeth.co.uk |
SES Astra SA, is a corporate subsidiary of SES, based in Betzdorf, in eastern Luxembourg, that owns and operates the Astra series of geostationary communication satellites, which transmit approximately 2490 analogue and digital television and radio channels via 317 (264 utilised) transponders[1] to 122.2 million households across Europe[2]. Formed in 1985 as Société Européenne des Satellites (SES), it was Europe's first private satellite operator. Its slogan is currently "Your Satellite Connection to the World". The first customer of SES Astra was Sky Television which leased four transponders on Astra 1A ahead of its launch in 1989. UK and Ireland-aimed channels ceased at 19.2°East in September 2001 with the closure of Sky's analogue service, although their digital service has been the main occupier of Astra's secondary position at 28.2°East since its launch in 1998. Astra is a member of the Hybrid Broadcast Broadband TV (HbbTV) consortium of broadcasting and Internet industry companies (also including Humax, Philips, OpenTV and ANT Software) that is promoting and establishing an open European standard (called HbbTV) for hybrid set-top boxes for the reception of broadcast TV and broadband multimedia applications with a single user interface.
[edit] Satellite detailsSES Astra operates 15 satellites from 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 close to each other, all within a cube with a size of 150 km;[3]) this increases flexibility and redundancy.
Notes
[edit] Satellite manufacturer and launchSES Astra operates satellites designed by Boeing Satellite Systems or BSS (formerly Hughes Space and Communications), EADS Astrium, Alcatel Space, and Lockheed Martin. Astra satellites within a family are not identical, for example of the Astra 2 satellites; 2A and 2C are BSS 601HPs, 2B is an Astrium Eurostar-2000 and 2D is a BSS 376. The satellites are launched by Arianespace rockets from Kourou, French Guiana or International Launch Services Proton rockets from Baikonur, Kazakhstan. The satellites are launched into an elliptical "temporary transfer orbit" from where they use onboard propulsion to reach their final circular geostationary orbits, at nearly 36,000 km altitude. Proton rockets fitted with a fourth stage propulsion unit are capable of launching the satellites several thousand kilometres higher (at the closest point of the elliptical orbit) than Ariane rockets. As a result most satellites launched in this way have to use less fuel to reach their geostationary orbit, increasing their lifetime. [edit] FailuresAstra 1K, the largest commercial communications satellite ever built at the time, was ordered by SES-Astra in 1997. It was launched by Proton rocket on November 26 2002. The rocket lifted off as planned and reached its parking orbit at which point the final stage of the rocket was to initiate a second burn to transfer the satellite to its geostationary orbit. This did not occur and the satellite was released into the parking orbit, making it unusable. The only way to recover the satellite would have been the use of a Space Shuttle, however this was rejected. On December 10 2002 SES Astra instructed Alcatel Space (the manufacturer) and the French Space Agency CNES to deorbit the satellite, it broke up on re-entry over the Pacific Ocean. On January 16, 2009 Astra 5A at 31.5° east "experienced a technical anomaly leading to the end of the spacecraft’s mission"[5] some four years ahead of the spacecraft's expected end of life. Traffic carried by the satellite (especially channels for German cable service, Kabel Deutschland) was transferred to Astra 23.5°E. In March 2009, SES Astra announced that in April, the Astra 2C satellite was to be moved from the 28.2° east position to 31.5° east to temporarily take over Astra 5A's mission until Astra 3B is launched to 23.5° east , when another craft currently there can be released to 31.5° east.[6]. The move of Astra 2C was started in May and completed on May 11[7] with the first transponders coming into use at the new position in the subsequent two weeks. [edit] See also
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