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Soyuz launches Galileo satellite duo

Anatoly Zak, Spaceflight Correspondent
Sep 11, 2015, 9:03 UTC

Sen—A Russian-built rocket delivered the latest pair of Galileo satellites for Europe's own space-based global navigation network on Thursday.

The Soyuz-ST-B rocket made a night-time launch from its tropical launch pad in French Guiana on the East Coast of South America at 11:08:10 p.m. local time on Sep. 10, 2015 (02:08 UTC on Sep. 11).

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A pair of Galileo satellites is being integrated with the Fregat upper stage (background). Image credit: Arianespace

Under its payload fairing, the vehicle carried a pair of Galileo navigation satellites for the European alternative to the American Global Positioning System, GPS.  

The latest duo represents the 5th and 6th Full Operational Capacity (FOC) satellites of the Galileo constellation. However counting four In-Orbit Validation Satellites (IOV), launched in 2011 and 2012, the Galileo network has now grown to ten satellites. Continuing a tradition started last year, the latest pair were nick-named Alba and Oriana after children who won a 2011 painting contest organised by the European Commission. The same organization also sponsors the Galileo constellation, which should include 24 primary and six backup satellites as early as 2020, the project officials said shortly before this latest mission went under way. 

This was the third Soyuz launch with FOC satellites and yet another such mission is currently planned for December of this year. Soyuz also delivered two experimental Galileo satellites in 2005 and 2008.

Beginning next year, Europe's heavy Ariane-5 rocket will take over the delivery of 12 remaining satellites, carrying four spacecraft at a time. According to European officials, with only half of the satellites in place, the Galileo network will already be able to deliver services to users on the ground.

Each Galileo FOC satellite has a mass of around 750 kg and is designed to operate in space for at least 12 years. The spacecraft are assembled by OHB Systems in Bremen, Germany, and their navigational payloads are built by the British firm Surrey Satellite Technology, a subsidiary of Airbus Defence and Space.

During the latest launch, the Soyuz headed northeast across the Atlantic to align its trajectory with an orbit inclined 57.39° toward the Equator. Four boosters of the first stage separated nearly two minutes after the liftoff at an altitude of 45 km and the core booster of the second stage was dropped four minutes 48 seconds into the flight, as the rocket flew 150 km above the Earth's surface.

Following the separation of the third stage, the Fregat space tug took over the powered flight with its first engine firing delivering the pair of satellites into an initial parking orbit 23 minutes after the liftoff. The stack then climbed passively until it reached an apogee (the highest point) of the orbit three hours 38 minutes into the flight. The Fregat then fired again, making the orbit circular at an altitude of 23,522 km above the Earth. Five minutes after the completion of the burn, both satellites were released in opposite directions from their payload dispenser.

It was the 12th launch of the Soyuz rocket from its launch site in French Guiana and the 11th mission for this family of Russian rockets this year. A total of 48 orbital launch attempts have been made so far in 2015 from spaceports around the world including three failures.

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