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Europe’s twin Galileo navigation satellites have successfully completed final functional testing at spaceport in French Guiana, paving way for the launch on 21 August.

Earlier this month, the two satellites were fuelled with hydrazine propellant to maintain altitude over their 12-year lifetimes.

The satellites were then installed on the flight dispenser, before the stack was put onto the Fregat stage and enclosed within its protective launch fairing.

Also called as the ‘space head’, the combined upper composite will be attached to the other three stages of the powerful Soyuz ST-B launcher.

The European Space Agency (ESA) has said that the final operations for the launch will be completed early this week prior to the planned lift-off.

"The ‘Full Operational Capability’ satellites being launched this week are significant as the first of the rest of the Galileo constellation."

On reaching 23,222km altitude, the satellites will be deployed from their Fregat by the dispenser’s pyrotechnic separation system.

Built by OHB in Germany, the twin Galileo navigation satellites will complement the existing four Galileo In-Orbit Validation (IOV) satellites, which were launched in October 2011 and October 2012.

UK-based Surrey Satellite Technology manufactured the payloads generating navigation signals to Earth.

ESA said: "Now that work has been done, the ‘Full Operational Capability’ satellites being launched this week are significant as the first of the rest of the Galileo constellation.

"A steady stream of launches is planned for the next few years, with two Galileo satellites flown per Soyuz launch and four Galileo satellites flown per launch of an Ariane 5 variant currently in preparation."

The ESA and the EU have worked together on the definition, development and IOV phases of the Galileo programme.

The European Commission is managing and funding the Full Operational Capability phase, while the ESA assumes the role of design and procurement agent on behalf of the Commission.

Image: Artistic view of the Soyuz rocket carrying the first two satellites (SAT 5-6) into orbit. Photo: courtesy of ESA-J. Huart.

Defence Technology