A test spacecraft for Europe's future satellite-navigation system has been rocked by a surge of space radiation.
The incident forced the Giove-B satellite to adopt a "safe mode" for almost a week in which only essential power systems were kept running.
European Space Agency (Esa) engineers have brought the satellite back up and are now studying what happened.
Giove-B carries the technologies that will be incorporated into the Galileo network when it becomes operational.
These include the atomic clocks which European Parliament Approves Military Use of Galileo Satellite ...
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Giove-B, and its sister demonstrator Giove-A, are the first European missions to fly in the high-radiation environment of a medium-Earth orbit (MEO), at an altitude of 24,000km.
This region of space is known to have a high intensity of fast moving particles that can disrupt spacecraft electronics. But the conditions are reasonably well understood, and engineers will want to know why Giove-B experienced the glitch. Giove-A is unaffected.
The demonstrators will be followed by 30 operational satellites and they will all need to be protected against similar incidents.
Galileo is envisaged as a rival to - but technologically complementary with - the American GPS (Global Positioning System).
It is touted as a key high-technology venture for the EU.
Galileo is designed to improve substantially the availability and accuracy of sat-nav signals.
These signals already play a fundamental role - not just in navigation, but also in electricity distribution, the functioning of e-mail and the internet, and in the security of financial transactions and many other economic activities.
Galileo's improved clocks are expected to deepen and extend this role.
The better penetration and guarantees of service promised by Galileo should also give many more entrepreneurs the confidence to build business plans around sat-nav, say supporters.
It is supposed to become fully operational by 2013.
(BBC)
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