Both passengers for Arianespace's third Soyuz flight from French Guiana are entering their final processing phase, which includes fueling of the two Galileo navigation satellites prior to their integration on the launcher for liftoff in October.

As part of the activity, Galileo Flight Model #3 (FM3) was fueled this week in the Spaceport's S5 payload preparation facility.

Galileo FM3 and its "sister" FM4 co-passenger subsequently will be integrated side-by-side on a dispenser for their shared ride aboard the Soyuz ST launcher, joining another pair of similar European navigation satellites lofted by Arianespace on the Soyuz launcher's maiden Spaceport flight in October 2011.

These initial four Galileo platforms were built by a consortium led by the Astrium division of EADS, which produced the platforms and has responsibility for the payloads, while Thales Alenia Space handled the assembly and testing tasks.

Once all four of these spacecraft are operating from medium Earth orbit, it will mark an important milestone for the Galileo program - as this is the minimum number required to provide navigational fixes, enabling full system testing for the In-Orbit Validation (IOV) phase.

When complete, the Galileo constellation will consist of 30 satellites.

Arianespace has responsibility for deploying the entire Galileo constellation, utilizing a mix of its medium-lift Soyuz and heavy-lift Ariane 5, underscoring the company's flexibility in orbiting satellite constellations.

The Arianespace launch services for Galileo began with the 2005 and 2008 orbiting of two experimental satellites - Giove-A and Giove-B - from Baikonur Cosmodrome in Kazakhstan by Arianespace's Starsem affiliate.

This was followed last October by Arianespace's maiden Soyuz launch from French Guiana that carried the constellation's first two operational satellites.

Galileo is a program initiative of the European Commission and European Space Agency (ESA), with each spacecraft carrying an optimized atomic clock for navigation and a powerful transmitter to broadcast precise navigation data worldwide.