Space: Rosetta spacecraft gaining on target comet

For almost three years, the European Space Agency (ESA) craft has been deeply asleep because it was travelling so far from the sun that it couldn’t generate enough power through its solar arrays to be kept awake. Now it is falling back towards the sun, gaining on its target comet by 800 metres every second.

ESA Rosetta - Philae_on_the_comet_back_view

After a nail-biting day at ESA's mission control, we now know that an alarm clock on Rosetta woke the spacecraft at around 1000 GMT this morning, as planned. This triggered a sequence of events that culminated in the spacecraft phoning home tonight.

The signal confirming Rosetta's wake-up was expected to arrive any time after 1730 GMT, although the ESA flight team reckoned that it would be more like 1745. When the time reached 1800, however, things had started to get tense: the mission cost $1 billion, the first ever sent to orbit or land on a comet.

"I don't know how many clichés there are for tension," says McCaughrean. "Cutting it with a knife is the best I can use."

The faces got longer as the minutes dragged by. Eventually, at around 1815, the signal arrived. It was shown by a green spike on graph that stuck high above the noise.

"We've waited for 31 months: I think 30 minutes more was OK," said Gerhard Schwehm, who until recently was Rosetta mission manager. He described the acquisition of the wake-up signal as "overwhelming".

By August, Rosetta will have reached its target, an 4.6-billion-year-old icy remnant from the beginning of the solar system known as comet Churyumov-Gerasimenko. For almost two years, Rosetta will orbit this comet watching the way the sunlight melts it, creating a tail.

In November this year, it will release a small craft called Philae to land on the surface of the comet. Philae's job is to sample the pristine icy material, looking for clues to the origins of Earth's oceans and of life itself.

The flight team have now instructed Rosetta to switch to a higher-rate transmitter and send back to Earth the first of its telemetry, which will be housekeeping data on the health of the spacecraft.

One thing they will be keen to understand first is what happened to cause the half-hour delay. Rosetta's overnight reports may provide the answer.

Syndicated content: Stuart Clark, New Scientist


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