Ariane 5, in 75th straight success, conducts its first launch of Europe’s Galileo satellites

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PARIS — A European Ariane 5 rocket, operating in a rarely used configuration and debuting a new satellite-dispenser system, on Nov. 17 successfully placed four European Galileo positioning, navigation and timing satellites into medium-Earth orbit.

It was the 75th consecutive success for Ariane 5, breaking the tie with its predecessor, the Ariane 4.

Operating from Europe’s Guiana Space Center, on the northeast coast of South America, the Ariane 5 ES version, with a storable-propellant upper stage instead of the usual cryogenic stage, separated the four 716-kilogram Galileo spacecraft two at a time about four hours after liftoff after two burns of the second stage engine.

Launch-service provider Arianespace, after waiting for confirmation, said the satellites were in their intended 22,900-kilometer orbit and were healthy and sending signals.

Once they have been put through several months of in-orbit checkout, the four satellites will join the 14 other Galileo spacecraft in service. Not all are fully operational but Galileo’s owner, the European Commission, said the Nov. 17 launch should permit initial Galileo services to begin by the end of this year.

The launch was the first time Ariane 5 had been used for the Galileo program. All previous launches were by Europeanized Russian Soyuz rockets, which carry two Galileo satellites into orbit at a time.

The European Commission, which is the executive arm of the 28-nation European Union, wanted to diversify its launcher supply while remaining in Europe.

Adapting the Ariane 5 to carry Galileo spacecraft into medium-Earth orbit some 22,900 kilometers in altitude, inclined 54.57 degrees relative to the equator, necessitated several changes to the vehicle.

Airbus Defence and Space provided the 435-kilogram structure that releases two satellites at a time in an interval of about 20 minutes. Because this was the inaugural use of the system, the separation in orbit of the satellites provided the most tense moments of the four-hour launch sequence.

OHB SE of Bremen, Germany, and payload provider SSTL of Guildford, England,   are under contract to build 22 Galileo satellites. The latest launch brings the total in orbit to 14. The eight remaining satellites will be launched aboard Ariane 5 rockets in 2017 and 2018.

With four in-orbit-validation satellites added into the calculation, the Galileo system now has 18 satellites in orbit and can begin to offer partial service.

The commission and the 22-nation European Space Agency (ESA), which acts as program technical manager for the commission, ultimately want 30 Galileo satellites in orbit — 24 operational plus in-orbit spares.

To get to that total, ESA is managing a competition to build at least eight, and up to 14, additional Galileo satellites. An announcement of one or more winning bidders is expected in the coming weeks.