In the first of what is planned to be three launches, an Arianespace, Ariane 5 heavy-lift launch vehicle has lifted-off from Kourou, French Guiana, carrying four Galileo GPS satellites for the EU. The launch took place at 1306 GMT, 17 November, from the Ariane Launch Complex No. 3 (ELA 3) at the European Spaceport. The four spacecraft will be placed into Medium-Earth Orbit (MEO) – about 23,000 km – nearly four hours after the launch.
The Galileo satellites are built and integrated by OHB Systems, Germany however, their payloads are supplied by SSTL, UK, a subsidiary of Airbus DS. This launch will bring the number of Galileo satellites in-orbit to 18, the complete constellation will consist of 24 satellites plus two in-orbit spares.
The Ariane 5’s second stage has had to be altered for the Galileo missions, replacing the modern hydrogen-fuelled HM7B engine, with an older hydrazine and nitrogen tetroxide powered Aestus engine, due to the latters ability to be restarted multiple times in-orbit. The second stage will release the satellites a small distance from their intended orbit – 300 km – allowing it to enter a safe graveyard orbit beneath the spacecraft, whilst they lift themselves into the desired orbit.