Astra (satellite)

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, 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.
At the time of the launch of the first Astra satellite, Astra 1A in 1988, the satellite's operator was known as Société Européenne des Satellites. 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, which by this time also operated other satellite families such as AMC, and NSS.
Astra satellites broadcast 2,600 digital television channels via five main satellite orbital positions to households across Asia, Australia, Africa, Americas, Europe, New Zealand, Middle East and North Africa. The satellites have been instrumental in the establishment of satellite TV and the introduction of digital TV, HDTV, 3D TV, and Hybrid Broadcast Broadband TV 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 10 fully-operational Astra satellites and another 3 as backup/reserve, the majority in four orbital locations - Astra 19.2°E, Astra 28.2°E, Astra 23.5°E, Astra 5°E. Astra's principle of "co-location" increases flexibility and redundancy. Orbital data for the active satellites can be accessed

Manufacture and launch

Astra satellites have been designed by Boeing Satellite Systems, Airbus Defence and Space, Alcatel Space, Lockheed Martin and Thales Alenia Space. The Astra satellites within a family are not necessarily identical. For example, of the Astra 2 satellites; Astra 2A and Astra 2C were BSS 601HPs, Astra 2B an Astrium Eurostar E2000+, Astra 2D a BSS 376 and Astra 2E, Astra 2F and Astra 2G are all Eurostar E3000s.
The satellites have been launched by Arianespace by Ariane launch vehicles from Kourou, French Guiana, International Launch Services Proton launch vehicles from Baikonur, Kazakhstan, ILS Atlas launch vehicles from Cape Canaveral, Florida, United States and SpaceX Falcon 9 Block 5 rockets also from Cape Canaveral. 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 altitude. Proton launch vehicles fitted with a fourth stage propulsion unit are capable of launching the satellites several thousand kilometres higher than Ariane launch vehicles, and so most satellites launched in this way use less fuel to reach their geostationary orbit. More recent Astra satellites are built with an all-electric propulsion system for orbit raising and in-orbit manoeuvres to save weight.

Sirius and Astra 4A

The Sirius series of satellites was started in 1993 with the purchase of the BSB Marcopolo 1 satellite by Nordic Satellite AB for direct to home broadcasts to the Nordic and Baltic regions from the 5°East orbital position. Subsequent satellites launched to this location include Sirius 2, Sirius 3 and Sirius 4 and the position's coverage has been expanded to include Eastern Europe and Africa.
In 2000, SES bought the 50% shareholding in NSAB owned by Teracom and Tele Danmark and in 2003 increased that holding to 75%, renaming the company SES Sirius AB. In 2008, Astra acquired further shares to take its shareholding in SES Sirius to 90% and in March 2010 took full control of the company. In June 2010, the affiliate company was renamed SES Astra and the Sirius 4 satellite renamed Astra 4A.
The Astra 4A designation was originally given in 2005 to part of the NSS-10 craft owned by another subsidiary of SES, SES New Skies, and positioned at 37.5°W for broadcast, data, and telecommunications into Africa, and in 2007 to part of the Sirius 4 satellite owned and operated by SES Sirius. From June 2010, the Astra 4A designation has applied to the entire satellite previously known as Sirius 4.

Failures

, the largest commercial communications satellite ever built at the time, was ordered by SES in 1997. It was launched by Proton rocket on 26 November 2002. The launch vehicle lifted off as planned and reached its parking orbit at which point the final stage of the launch vehicle 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 10 December 2002, SES instructed Alcatel Space and the French Space Agency CNES to deorbit the satellite, it broke up on re-entry over the Pacific Ocean.
On 16 January 2009, Astra 5A at Astra 31.5°E "experienced a technical anomaly leading to the end of the spacecraft's mission", some four years ahead of the spacecraft's expected end of life. Traffic carried by the satellite was transferred to Astra 23.5°E. In March 2009, SES announced that in April, the Astra 2C satellite was to be moved from the Astra 28.2°E position to 31.5°E to temporarily take over Astra 5A's mission until Astra 3B is launched to Astra 23.5°E, when another craft currently there can be released to 31.5°E. The move of Astra 2C was started in May 2009 and completed on 11 May 2009, with the first transponders coming into use at the new position in the subsequent two weeks.

Broadcasting statistics

At the end of 2021, Astra satellite broadcasts were received in 170 million households in Europe. In Germany, the largest market for Astra broadcasts, 17 million households receive TV via satellite out of 37.22 million TV households in the country with take-up of other TV delivery methods as follows:

Delivery method	TV Households	HD TV households
Satellite	17.00 million	15.93 million
Cable	15.58 million	13.24 million
IPTV	3.31 million	3.26 million
Terrestrial		1.33 million