Europe’s £3.4bn satellite navigation project will advance to the next stage this weekend with the launch of the Giove B spacecraft.

Once completed, the Galileo system will act as a European rival to the US-based global positioning system (GPS), offering public access to location data gathered by 30 orbiting craft.

The European Union and the European Space Agency deployed their first satellite, Giove A, in December 2005. If Saturday’s launch is successful, Giove B will replace its predecessor and act as a testbed for the world’s most accurate clock ­- a Passive Hydrogen Maser device, correct to within one thousand millionths of a second.

Data sent by Galileo could be vital to mobile network operators, according to Bob Cockshott, technology translator for the UK’s Location and Timing Knowledge Transfer Network.

As internet-like packet switching systems are used to relay call data, accurate timing will play an important role in keeping everything aligned, he said.

“The Americans already use satellites to synchronise their base stations, but if there’s a problem with GPS they lose their telephone systems,” said Cockshott. “Galileo will provide another source to rely on.”

Cockshott says that the Galileo system will produce location data accurate to within half a metre of a specified site.