The GIOVE-A, an experimental navigation spacecraft launched by the European Space Agency last December, has completed its primary objective this week when it was able to pick up signals from several Global Positioning System (GPS) satellites.

GIOVE-A will be part of the Galileo array, the EU's fleet of navigation satellites. The rest of the satellites should be launched by 2010, giving Europe an alternative to the GPS satellite positioning system, which is operated by the US military.

GIOVE-A has also allowed the European Space Agency to secure its use of the radio frequencies allocated for Galileo by the International Telecommunications Union (much to the chagrin of U.S. and multi-national telecommunication corporations, who were hoping the allocation would  lapse later this year).

The spacecraft's objective was to pick up the signals from positioning satellites currently in orbit. This would determine whether commercial geosynchronous spacecraft (which orbit in step with the Earth's spin) could use satellites, rather than ground-based instruments, to calculate their position in space. This cuts expenses significantly.

"Currently GEO satellites rely on expensive ground terminals to measure where they are," says engineer Max Meermanr at the UK's Surrey Satellite Technology, who developed GIOVE-A.

Once the entire Galileo array has been launched, the service will provide receivers on the ground with positioning information accurate to within about 4 metres.