After being delayed for about a year because of a failure of the Ariane-5 rocket, the Rosetta spacecraft is scheduled to be launched on February 26. Rosetta is a special spacecraft, including an orbiter and a lander. And it will take up to 2014 before landing on Comet 67P/Churyumov-Gerasimenko -- with the help of a harpoon. Then, as says the European Space Agency (ESA), Rosetta will help to solve planetary mysteries.
Here is artist's rendering showing the Rosetta spacecraft with its lander around a comet (Credit: ESA)
Now, let's look at the goals of Rosetta's mission.
Rosetta’s name comes from the famous ‘Rosetta Stone’, from which Egyptian hieroglyphics were deciphered almost 200 years ago. In a similar way, scientists hope that the Rosetta spacecraft will unlock the mysteries of the Solar System.
Comets are very interesting objects for scientists, since their composition reflects how the Solar System was when it was very young and still 'unfinished', more than 4600 million years ago. Comets have not changed much since then. In orbiting Comet Churyumov-Gerasimenko and landing on it, Rosetta will collect information essential to an understanding of the origin and evolution of our Solar System. It will also help discover whether comets contributed to the beginnings of life on Earth.
"Rosetta is one of the most challenging missions undertaken so far," says Professor David Southwood, ESA Director of Science. "No one has ever attempted such a mission, unique for its scientific implications as well as for its complex and spectacular interplanetary space manoeuvres." Before reaching its target in 2014, Rosetta will circle the Sun four times on wide loops in the inner Solar System.
You might wonder why it will take ten years to reach the targeted comet. Here is why.
To reach Comet Churyumov-Gerasimenko, the spacecraft needs to go out into deep space as far out from the Sun as Jupiter. No launcher could possibly get Rosetta there directly. ESA's spacecraft will gather speed from gravitational ‘kicks’ provided by four planetary fly-bys: one of Mars in 2007 and three of Earth in 2005, 2007 and 2009. During the trip, Rosetta will also twice pass through the asteroid belt, where a fly-by with one or more of these primitive objects is possible. A number of candidate targets have already been identified, but the final selection will be made after launch.
Now, it's time to move to 2014.
Then, Rosetta will orbit the comet -- an object only about 4 kilometres in diameter -- while it cruises through the inner Solar System at 135 000 kilometres per hour. At the time of the rendezvous -- around 675 million kilometres from the Sun -- Comet Churyumov-Gerasimenko will hardly show any surface activity.
And here the 'funny' part of the story: the landing.
Over a period of six months, Rosetta will extensively map the comet's surface, prior to selecting a landing site. In November 2014, the lander will be ejected from the spacecraft from a height which could be as low as one kilometre. Touchdown will be at walking speed, about one metre per second. Immediately after touchdown, the lander will fire a harpoon into the ground to avoid bouncing off the surface back into space, since the comet’s extremely weak gravity alone would not hold onto the lander.
Here is an artist's view of the Rosetta lander hooked to the comet’s surface (Credit: ESA/AOES Medialab)
If everything goes well, Rosetta will start to run 21 different scientific experiments and send data back to Earth until December 2015.
For more information, you can check two different pages on the ESA website, Rosetta Homepage or Rosetta at a glance.
Source: European Space Agency, January 26, 2004