After a summer of around-the-clock testing in Italy, two Galileo navigation satellites have arrived in French Guiana for liftoff on a Soyuz rocket in October, the first step in a $7.3 billion effort to construct a network of navigation spacecraft 14,000 miles above Earth.

Artist's concept of two Galileo in-orbit validation satellites. Credit: ESA/P. Carril

The satellites jetted from Italy to French Guiana on separate flights Sept. 7 and Sept. 14 inside a Russian Antonov An-124 cargo plane. After unloading from the Antonov transport plane, the Galileo satellites moved into a clean room facility for final checks, fueling and encapsulation inside the Soyuz rocket's nose fairing.

Managed by the European Commission, the Galileo program is Europe's counterpart to the U.S. Air Force's Global Positioning System. Galileo will provide precise positioning, navigation and timing information to civilian and military users from a constellation eventually comprising 30 satellites.

The European Space Agency acts as the Galileo program's design and procurement agent for the European Commission.

Two of four in-orbit validation, or IOV, satellites will blast off this year on a Soyuz rocket. Another pair of Galileo IOV spacecraft will follow with a launch next year. The IOV satellites will demonstrate the capabilities of the Galileo system before deploying the full fleet of spacecraft.

The first batch of four Galileo satellites were designed by EADS Astrium and assembled by Thales Alenia Space. Each craft will weigh about 1,400 pounds at launch and will operate in an orbit more than 14,000 miles from Earth.

Teams at Thales Alenia Space in Rome worked 24 hours a day to ready the satellites for shipment to the French Guiana launch site.

The next 14 Galileo satellites, built by OHB System of Germany, will start launching in late 2012 or early 2013. OHB's factory should produce about eight satellites per year, equating to about one Soyuz launch with Galileo payloads every three months.

An Antonov An-124 cargo plane delivered the first of two Galileo spacecraft to French Guiana on Sept. 7. Credit: ESA/P. Muller

Liftoff is scheduled for Oct. 20 at 1034 GMT (6:34 a.m. EDT) from the new Soyuz launch pad at the Guiana Space Center, France's spaceport positioned on the northeastern coast of South America.

Commercial flights of Russia's venerable Soyuz rocket are moving from the Russian-controlled Baikonur Cosmodrome in Kazakhstan to French Guiana. The South American spaceport is located near the equator, giving rockets a natural boost into orbit from the Earth's faster rotation at low latitudes.

Arianespace, the commercial operator of the Ariane 5 rocket, manages the introduction of the Soyuz launcher in French Guiana.

Officials have authorized fueling of the mission's Fregat upper stage. Once the satellites are configured for launch, engineers will bolt the payloads to the Fregat and enclose the vehicle inside the Soyuz rocket's nose cone.

Four days before liftoff, Russian workers will roll the Soyuz rocket on its side from the integration building to the launch pad. After rotating the 15-story rocket vertical, crews will hoist and attach the payload fairing containing the Fregat stage and Galileo satellites.

The launch site is a replica of the existing Soyuz pads at the Baikonur Cosmodrome in Kazakhstan, except the French Guiana facility features a 170-foot-tall mobile gantry to shield the rocket from strong thunderstorms and lightning in the South America jungle. It also allows workers to mate payloads to the rocket while the Soyuz is vertical on the launch pad.

The Oct. 20 launch will use the Soyuz 2-1b configuration of the historic booster. The upgraded version features a more efficient RD-0124 third stage engine that can help the vehicle lift more mass into orbit.

The Soyuz won't fly with the same third stage that failed during the launch of a Progress space station resupply craft last month. Russian investigators blamed the Aug. 24 mishap on an obstruction in a fuel line inside the older third stage's RD-0110 engine. Launches of Soyuz rockets with the RD-0110 engine are scheduled to resume in October.