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On January 20th, the Rosetta spacecraft came to life after a two-and-a-half year nap.
Prepare to be amazed by what it does next!
Rosetta will be the first spacecraft to orbit a comet,
and then hitch a ride around the sun.
Here are five things you need to know about this landmark mission.
I'm Sophie and welcome to The Countdown.
In 2004, the European Space Agency launched Rosetta.
At first, the spacecraft stayed relatively close to the sun,
flying by Earth, Mars and even two asteroids.
This helped Rosetta pick up energy and align itself with Comet 67P/Churyumov–Gerasimenko.
Reaching the comet, however, meant traveling out past Jupiter,
800 million kilometers away from the heat of the sun.
To conserve energy during this leg of the voyage,
Rosetta entered a state of hibernation in June 2011.
By January of this year, it had returned close enough to use its solar panels.
Now that it could power up, Rosetta was ready to wake up.
On the morning of January 20, Rosetta's internal alarm clock went off.
It fired its thrusters to slow its rotation and orient its solar panels towards the sun.
Then it looked at the surrounding stars to check its position
before rotating towards Earth and pointing its antenna at us.
Finally, it fired off a signal saying it was awake.
The signal reached Earth loud and clear.
You can see it in this picture where it looks like a green spike.
Now Rosetta was ready to chase down its target.
Why do we want to visit Comet 67P/Churyumov–Gerasimenko?
Well, this comet is in just the right place.
It's still out in the cold depths of the solar system
but on its way towards the heat of the sun.
As it warms up and its ice melts, the comet will spew dust and gas into space, creating tails
and Rosetta will track this transformation as it occurs.
Comets give us a glimpse of the solar system's youth
and may have helped seed Earth with water and organic molecules.
An up-close-and-personal look can help us learn much more about these objects.
Because it's still millions of kilometers from its destination,
Rosetta won't enter into orbit until August.
As the craft circles, it will map the surface of the comet in detail.
Previous missions, such as Giotto and Stardust, have flown near comets.
The closest we got was the Deep Impact space probe in 2005.
But Deep Impact just shot a hunk of metal at its comet, gathered samples and then went on its way.
Rosetta will stay in orbit for an entire year,
so it will be able to track how the comet changes as it moves closer to the sun.
Rosetta will do more than just orbit.
In November, it will release its Philae lander onto the surface.
Three spider-like legs will help Philae hit the ground safely
and maintain an upright position.
Because the gravity of the comet is relatively weak,
Philae will anchor itself by sticking a harpoon in the ground.
The lander and its suite of instruments will give us an even better look at the nucleus of Comet 67P.
I'm Sophie Bushwick, and that's your countdown.
For more episodes of our show and other spacey stuff,
visit the spacelab channel on You Tube
or follow us on Twitter @sa_spacelab
And if you've got any topics you'd like to see in the future, let us know in the comments.