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The Rosetta spacecraft wakes up

“On 20th January the Rosetta spacecraft was scheduled to self-reactivate, two and a half years after it cut off all contact to ground control. It was one of the most emotional days of my life.

We launched Rosetta in March 2004 on a pioneering ten-year mission to rendezvous with a comet and land a probe on its surface, a historical first which would revolutionise cometary science. There are theories about Earth’s formation that attempt to explain why all this water has survived on its surface in liquid form and didn’t evaporate and disappear like it probably did on Mars. Many scientists believe comets are the origin of water on Earth. With the instruments we have on Rosetta we hope to be able to answer this question.

We had estimated that it would reactivate itself on 20th January because it was set to a timer. When you set a timer to wake up the next morning you know it will ring at that time, but when you set it to wake up after two and a half years you have to assume that it may drift a little, that it may not be precise. The window in which we expected to receive a signal from Rosetta was between 6.30pm and 7.30pm. There were about 15 of us in mission control room. At 6.30pm we were making jokes, taking bets on which minute the spike would appear on the computer screen, meaning a signal from Rosetta had been successfully received.

I kept jumping from being optimistic to thinking: ‘Are you crazy? You are 600 million kilometres from the spacecraft. You configured it two and a half years ago and anything could have happened in that time. Are you seriously expecting a signal?’

The two and a half years out of contact with Rosetta was entirely planned. When we first put together the mission in 1996 I thought it was crazy that it would be disconnected from ground control before reaching its target and I hoped we’d find an alternative. By 2011, I’d accepted that it was the only option: Rosetta’s trajectory through the solar system was taking it too far from the sun to produce the solar power needed to provide the craft with power. So we switched it off to save energy so it could complete the job.

By 7pm, the middle of our window, we’d quietened down a lot, and right before the moment we eventually received the signal, there was no sound in the room at all. We finally received the signal at 7.19pm. We went crazy.

Our toughest challenges still lie ahead of us. We chose the comet 67P/Churyumov-Gerasimenko because with our current technology we can only reach the comets that circle in the area between Jupiter and the sun. These comets, known as Jupiter comets, survive until they die by colliding with Jupiter or being attracted by the sun. We will drop a lander onto the surface on comet 67P/Churyumov-Gerasimenko, drill a few centimetres under the surface, and do local analyses. We will then follow the comet for almost two years from
close proximity.

This is revolutionary because comets are dynamic objects which change a lot in a very short period of time. This has never been done before and nothing like this will happen in the coming decades either. In a hundred years’ time I hope that the Rosetta mission will be remembered as the mission that decoded a secret of the solar system. ”

Follow Rosetta’s progress @ESA_Rosetta

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