GIOVE Satellites Pave the Way for Galileo Network

The European Union, through the European Space Agency (ESA), is planning to construct its own satellite navigation system, that would provide users with an alternative to the American Global Positioning System (GPS). That objective is made easier by two GIOVE satellites.

About five years ago, on January 12, 2006, the GIOVE-A (Galileo In-Orbit Validation Element) satellite relayed back its first navigation signal to Earth. This was the first demonstrator of the new technology to be launched to space from Europe.

Its most important contribution was showing that Europe has what it takes to start and successfully complete such an ambitious project. If the Validation Elements work, then there is no reason why the actual satellite constellation won't work either.

GIOVE-A is still sending navigation signals today, even after its primary mission has ran out. However, experts are using the data to conduct additional calibration of receiving systems, and also to improve ground support stations.

“Having been launched on 28 December 2005, it was two weeks later on 12 January 2006 that the first Galileo In-Orbit Validation Element satellite […] began broadcasting a navigation signal synchronized with its rubidium atomic clock,” ESA says in a statement.

GIOVE-B followed shortly, on April 27, 2008. This time, in addition to a rubidium atom clock, the instrument also carried a ultra-precise passive hydrogen maser atomic clock. The goal of that instrument was to determine the differences in accuracy between the two types of clocks.

“These signals were required to formally secure Europe’s access to the allocated Galileo frequencies, while also allowing us to assess the on-orbit functioning of the two atomic clock designs at Galileo’s heart,” explains official Valter Alpe.

“Meanwhile, we could also begin to test the kind of elaborate ground processing needed for the operational Galileo system,” adds the expert, who is the manager of GIOVE operations for ESA.

“The trick of the whole satellite navigation story is that the user is receiving not just the clock timing itself but also very slight corrections transmitted in the signal stating if the clock is running a few nanoseconds early or late,” he adds.

“It takes a sophisticated ground segment to generate these corrections, but this process is essential for maintaining service accuracy,” he concludes.