Rosetta comet-chaser completes 'big burn'

Europe's comet-chaser Rosetta has taken a big step towards making its historic rendezvous with a 4km-wide ball of ice and rock in early August, the BBC reports.

Controllers confirm the spacecraft conducted a major orbit manoeuvre on Wednesday without incident.

The near-eight-hour thruster burn was designed to slow the satellite's speed relative to Comet 67P/C-G.

More adjustments are required, but the operation was a significant event in ensuring Rosetta meets its target.

The pair are roughly 500 million km from Earth and separated by about a million km, and closing.

Wednesday's big burn was initiated at 15:23 GMT (16:23 BST; 17:23 CEST). It was intended to take out a big chunk (almost 300m/s) of the velocity Rosetta had (755m/s) with respect to 67P/Churyumov-Gerasimenko.

Engineers at the European Space Agency's (Esa) "mission control" in Darmstadt, Germany, will have to examine in detail the telemetry they received from the satellite but confirmed on Thursday that the manoeuvre was "completed nominally."

"The thrusters and propulsion system overall performed very well, and we had a nominal completion of the burn at 22:39 UTC (00:39 CEST Thursday)," said Rosetta Spacecraft Operations Manager Sylvain Lodiot.

"It will take a few days for the flight dynamics team to analyse data and determine the final actual change in speed, but it won't be too far from what we planned," he told the mission blog.