Europe’s first two Galileo satellites were successfully launched on 21 October, marking an important step towards deployment of an operational European satellite navigation system by 2014.
In a historic ‘first’ for the European spaceport in French Guiana, the launcher was a Russian Soyuz vehicle.
Soyuz is a medium-sized vehicle and complements the European Space Agency’s Ariane 5 launcher for large payloads and the smaller Vega, planned to debut in 2012.
The satellites are orbiting at an altitude of 23,222km and carry passive hydrogen maser atomic clocks developed by Selex Galileo, which will drift by only one second in three million years. That means that signals sent to Earth will carry the time of transmission measured to unprecedented accuracy. This information is used to calculate the location of the receiver, using the transit times of the signals and the positions of the sending satellites in space.
The atomic clocks and navigation signal generators have already been space qualified on the GIOVE A and B test satellites.
Following the launch the satellites were controlled by a joint team from the European and French space agencies (ESA and CNES) in Toulouse, before being handed over to the Galileo Control Centre operations team based at Oberpfaffenhofen, near Munich, for checking of the satellites, payloads and orbits.
GfR, a subsidiary of the German aerospace centre DLR, operates the control centre under contract to the European Union and the European Space Agency. The other control centre for the mission is located at Fucino, in Italy.
A global network of ground stations will receive signals from the Galileo satellites and the timekeeping of the on-board clocks will be compared continuously with reference clocks on the ground.
Two more satellites will be launched in August 2012. Then, with signals from four satellites available, location calculations based on Galileo data will be performed for the first time. This is the in-orbit validation phase, where the correctness of the interactions between the satellites and the ground infrastructure will be verified.
By 2014 there should be 18 satellites in orbit, enough to offer three services: open (free and available to anyone), public-regulated (robust encrypted signals for emergency services, transport authorities and similar bodies), and search and rescue.
As the size of the constellation increases to its full complement of 30 satellites, commercial and safety-of-life services will be introduced, combining two encrypted signals for higher data throughput rate and higher accuracy authenticated data.
Construction and operation of the Galileo system is being financed by the European Union. The programme is expected to deliver €90bn of value over a period of 20 years, through public and social benefits and additional revenues for industry.