The European Space Agency (ESA) expects to get its Galileo satellite navigation system deployment back on track to provide a functional service from early 2015, if final tests of the first two new-generation satellites go to plan.
Technical problems in development of the spacecraft, being built by OHB in Germany with navigation payloads by Surrey Satellite Technology in the UK, have held up their launch, but barring further surprises they should fly in spring 2014, as a dual payload by Soyuz launcher from Kourou, French Guiana. The first is undergoing thermal vacuum testing this month, and the second should start testing in January.
Speaking at ESA’s mission control centre – the European Space Operations Centre – in Darmstadt, near Frankfurt, after watching the successful lift-off of the Swarm magnetic field measurement mission, director general Jean-Jacques Dordain says that, barring further technical problems, the next two launches would be the first of a two satellites every three months regime, as planned two years ago when ESA and the European Union finally broke a cycle of Galileo programme delay to approve the budget for a fast-track launch schedule.
In any case, he added the four satellites already in orbit – of an earlier design used to validate the system – are performing beyond expectations. Where specification had been 4m accuracy horizontally and 8m vertically, the four-satellite “in-orbit validation” constellation was providing 2m by 4m accuracy.
That performance, says Dordain, is “fantastic”, adding: “Technical problems are the price we pay for innovation.”
With only four satellites, a ground user can only receive a Galileo navigation signal a few times a day. Eventually, 27 spacecraft will provide constant, global coverage. That goal had been a target for 2019, but ESA won’t be looking to make up for lost time to finish the constellation that quickly.
It takes time, notes Dordain, to integrate new satellites into the system, and in any case it would not be possible to manufacture 22 satellites faster than planned without massive new investment. Launcher availability is also a limiting factor. Ultimately, he says, it is necessary to optimize between cost and benefit, and paying vast sums to speed up deployment doesn’t make sense.
Depending on availability of spacecraft, one way to speed up deployment will be to launch four at once, a capability ESA will have from end-2014, when a special variant of its Ariane 5 heavy lifter designed for the purpose becomes available.
Source: FlightGlobal.com
