Officials at the European Space Agency (ESA) are proud to announce that the GIOVE-A satellite has just reached a five-year milestone in Earth's orbit. The spacecraft is the first prototype of the Galileo satellite navigation system, which ESA is getting ready to start launching.Originally meant as a demonstrator, GIOVE-1 was launched on December 28, 2005, from the Baikonur Cosmodrome in Kazakhstan, aboard a Russian-built Soyuz delivery system.
It was the first Galileo In-Orbit Validation Element (GIOVE), and also the first European spacecraft to carry to orbit a prototype rubidium atomic clock. The instrument was designed specifically to ensure the reliability of Galileo system data.
This particular satellite went from the drawing board to reality in just two and a half years, thanks to the fruitful collaboration between ESA and prime contractor Surrey Satellite Technology Ltd from the United Kingdom.
GIOVE-B, the second demonstrator, was launched on April 27, 2008, carrying a second rubidium atomic clock, as well as an ultra-precise passive hydrogen maser. In order to ensure maximum data consistency, all Galileo satellites will feature both devices.
“Both satellites had a design lifetime of 27 months each. It is a pleasant surprise, therefore, to have GIOVE-A still fully operational after 60 months in orbit,” says ESA GIOVE activities manager Valter Alpe.
“GIOVE-B, meanwhile, is showing no sign of problems after 33 months in space. Part of their long lifespans can be put down to design margins, though luck comes into it as well,” he adds.
“The satellites have been orbiting through an exceptionally quiet time in the 11-year solar cycle, meaning they have accumulated lower radiation doses than originally anticipated,” Alpe explains.
Throughout their mission, both GIOVE satellites have demonstrated their worth, producing a wealth of data that ESA experts scanned for hints at how to make the actual Galileo satellite better.
Both atomic clocks behaved exemplary, especially the passive hydrogen maser, which demonstrated that it only loses one second every three million years.
“We needed to perform in-orbit testing of the purely European atomic clocks at the core of the Galileo system and an experimental version of the global Galileo ground mission segment could begin trials once we had the GIOVE signals-from-space,” Alpe says.
“Those same signals have also proved a very useful resource for manufacturers of Galileo receivers worldwide, allowing them to easily test their designs against a realistic version of the final Galileo navigation signal,” he concludes.