Ten navigation satellites of the European Galileo constellation are now in orbit after two more spacecraft were delivered to space on Thursday.
The launch from the European Spaceport in Kourou, French Guyana, went without a hitch, marking an important milestone as one third of the planned 30-strong fleet is now in place.
The Soyuz rocket delivered the two satellites into their target orbit at 23,500km above the Earth after an almost four-hour flight.
"The deployment of Europe's Galileo system is rapidly gathering pace", said Jan Woerner, director general of the European Space Agency (Esa).
"By steadily boosting the number of satellites in space, together with new stations on the ground across the world, Galileo will soon have a global reach."
A further two satellites of the nascent global navigation satellite system are scheduled for launch by the end of this year with the full fleet expected to be up and running by 2020.
The European Space Agency, overseeing the project on behalf of the European Commission, plans to speed up the delivery by launching four satellites at once aboard a customised Ariane 5 rocket starting in 2016.
The Galileo project, Europe’s own satellite navigation constellation, designed to provide an alternative to the US GPS, has been struggling with delays and cost overruns ever since its inception in the early 2000s.
In 2006, the project faced cancellation when the public/private partnership originally responsible for its delivery fell apart and was only rescued when the European Commission decided to nationalise the programme.
The first in-orbit validation satellites were launched in 2011, with the delivery of the full operational capability spacecraft beginning in 2014.
However, the Soyuz rocket launching the first two full operational capability spacecraft last August suffered a technical malfunction, which left the two satellites stranded in an incorrect orbit.
It took months for Esa’s space controllers to find a way to adjust the orbits of the two spacecraft sufficiently to make them usable.
Further satellites are being manufactured by OHB in Bremen, Germany, with navigation payloads being provided by the UK’s Surrey Satellite Technology.