Magnifico! Galileo satellite nudged back into correct orbit

Second system still AWOL for the moment

The European Space Agency has managed to salvage one of two misplaced Galileo satellites that it is using to build an alternative to the US's GPS system.

ESA launched the fifth and sixth satellite that will make up the Galileo constellation on August 22 – but the were sent into the wrong orbit. It was initially thought the problem was down to a software fault, but in October French launch company Arianspace admitted that its boosters were at fault.

In order to make the positioning system work, ESA needs 24 satellites, plus six spares, in precise orbits around the globe so receivers on the ground can triangulate their location. The two wayward satellites went way off course in long looping orbits, but the ESA team has spent 17 days firing the thrusters on Galileo 5 to nudge the bird 3,500 kilometres and get it back into a useful position.

"The maneuvers were all normal, with excellent performance both in terms of thrust and direction," explained Daniel Navarro-Reyes, ESA Galileo mission analyst. "The final orbit is as we targeted and is a tribute to the great professionalism of all the teams involved."

The satellite is communicating with the Galileo Control Centre at Oberpfaffenhofen in Germany. Scientists are reporting that all systems are normal and the satellite may be in a good enough position to join the network as a fully functioning part of the grid.

"First, the various payload elements, especially the Passive Hydrogen Maser atomic clock, were warmed up, then the payload's first 'signal in space' was transmitted," said David Sanchez-Cabezudo, who managed the test campaign.

"The satellite-broadcast L-band navigation signal is monitored using the large antenna at Redu, with experts from OHB and Surrey Satellite Technology Ltd - the payload manufacturer, based in Guildford, UK - also on hand to analyse how it performs over time."

The ESA team is now going to focus on Galileo 6 and plan to use similar orbital maneuvering to get it into a useful position, albeit on the other side of the globe to its restarted brethren. Doing so would be a major help in ESA's plans to have the positioning system's network up and running by 2017. ®

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