(PARIS) - A second test satellite for Galileo, Europe's rival to the US Global Positioning System (GPS), closed itself down for more than two weeks last month because of space radiation, concurring sources said Thursday.

The Giove-B satellite, launched in April, stopped operating from September 9 to September 24, said Franco Bonacina, spokesman at the Paris-based European Space Agency (ESA), which is overseeing the Galileo project.

It entered automatic shutdown mode in order to protect delicate circuitry from damaging cosmic rays, he told AFP.

"This sort of incident happens to almost every satellite from time to time," Bonacina said. "There are radiation peaks which cause satellites to go into shutdown mode."

Patrice de Lanversin, head of communications for Astrium, part of the EADS aerospace group, which jointly built Giove-B, said an impact by a "heavy ion" was believed to have unleashed the prolonged shutdown.

"It's quite a rare phenomenon and our engineers are now trying to determine where the incident occurred," he said.

Giove B is a 500-kilogram (1,100-pound) cube constructed by Astrium and Thales Alenia Space.

It was sent aloft after a first test satellite, Giove-A, was launched in December 2005 to lay claim to frequencies that will be used by the Galileo system.

The two experimental satellites are to be followed by some 30 satellites placed in permanent orbit at an altitude of 20,000 kilometres (12,400 miles).

The scheme, scheduled to be operational by 2013, is budgeted at 3.4 billion euros (4.76 billion dollars). Giove-A was built by a British firm, SSTL.

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