Europe's Rosetta probe has arrived at a comet after a ten-year chase. In a first for space history, the spacecraft was manoeuvred alongside a speeding body to begin mapping its surface in detail. The spacecraft fired its thrusters for six and a half minutes to finally catch up with comet 67P/Churyumov-Gerasimenko.
"We're at the comet!" said Sylvain Lodiot of the European Space Agency (ESA) operations center in Germany.
"After ten years, five months and four days traveling towards our destination, looping around the Sun five times and clocking nearly seven billion kilometers, we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, director general of ESA.
Launched on board an Ariane rocket in March of 2004, Rosetta has taken a long route around our Solar System to catch up with comet 67P.
In a series of fly-pasts, the probe used the gravity of the Earth and Mars to increase its speed during the six billion kilometer chase.
David Shukman says: You could almost feel the sense of relief in the corridors that, after managing a ten-year trek through space with extraordinary accuracy, and after investing more than one billion euros, all has gone so well. The signal took nearly 23 minutes to reach us and, when it came, it was a dip in a line on a graph. But this showed that the final burn to reach the comet had finished and this key moment was the trigger for a wave of pride rather than jubilation.
Getting a spacecraft to match the speed of a comet and effectively ride alongside it is a landmark in space exploration. But the hard work starts now.
To save energy, controllers at ESA's center in Darmstadt, Germany, put Rosetta into hibernation for thirty months.
In January of 2014 they successfully woke the craft from its slumber as it began the final leg of the daring encounter. For the past two months, Rosetta has been carrying out a series of maneuvers to slow the probe down. The comet is traveling at fifty-five thousand kilometer per hour. The spacecraft's speed has been adjusted so that, in relative terms, it will be flying beside the comet at a slow walking pace of nearly four kilometers per hour.
At a distance of 550 million kilometers from the Earth, messages are taking over twenty minutes to get to Rosetta. The distances involved are so great that the complex final command sequence for the crucial thruster burn had to be issued three days earlier.
"This arrival phase in fact is the most complex and exotic trajectory that we have ever seen," said Jean-Yves Le Gall, president of the French Space Agency CNES.
Rosetta will have to continue to fire its thrusters every few days to maintain a hyperbolic orbit at a hundred kilometers above the rotating rock. The craft will then travel alongside the comet for the next fifteen months, studying it with a range of instruments.
Rosetta has been taking increasingly detailed photographs of 67P as it gets closer. The mysterious comet has been dubbed the "rubber duck", as some images seem to show the familiar shape as it twirls in space.
Total cost of the mission is said to be just over a billion euros. The probe weighed in at three thousand kilograms at liftoff back in 2004, with over half of that made up of propellant It has two fourteen-meter long solar panels to provide electrical power. The orbiter carries eleven experiments. The lander, Philae, carries nine experiments, including a drill to sample beneath the surface
Project scientist Dr. Matt Taylor, said: "For me this is the sexiest, most fantastic mission there's ever been. It's ticking a number of boxes in terms of fascination, exploration, technology and science, predominantly science."
As it moves towards the Sun, 67P will warm up and its trailing halo of gas and dust, known as the coma, will increase, offering the orbiter the chance to do some detailed scientific work. "We've seen evidence of the out-gassing of the coma, the outer atmosphere of the comet, this is made of dust and gas," said Dr. Taylor. "We have instruments on board that will start sniffing for this gas and taste it, we will also be collecting some of this dust and touching the coma itself. Hopefully that will occur sometime this week."
The mission gets even more ambitious in November of 2014, when, after moving Rosetta closer to 67P, mission controllers will attempt to put the Philae lander on the surface.
The lander will use harpoons to anchor itself, and will carry out a series of experiments, including drilling into the material that makes up the comet. The mission aims to add to knowledge of comets and their role in ferrying the building blocks of life around the early Solar System.
Rico says it'll be fascinating to see what they find when they harpoon the comet...
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