In 1995, the European Space Agency (ESA) decided to develop a mission to comet Wirtanen as one of its Cornerstone Missions

It was named "International Rosetta Mission" after the Rosetta Stone (that was found by one of Napoleons soldiers in Egypt) which helped to decipher the ancient Hieroglyphes, a pioneering work done by J.F. Champollion in the 1820ies. In a similar way Rosetta is hoped to help the understanding of the origins of our planetary system.
The Lander has meanwhile been named "PHILAE", after a Nile island in Egypt (see NEWS).

Rosetta was launched at 08:17 UTC on 2 March, 2004 from Kourou (French Guyana) by an Ariane-5 G+ rocket. After a cruise of 10 years it will arrive at the comet Churyumov-Gerasimenko, where it will go into a orbit around the comet nucleus. From this close position, it will use sophisticated remote sensing instruments to map and characterise the object. In addition, it will detach a small package, the Rosetta Lander, to land softly on the comet core surface and make detailed in-situ investigations

Even with the presently heaviest rocket available in Europe, the Ariane 5, it is not possible to directly inject into an orbit to comet Churyumov-Gerasimenko. Therefore a complex path has been chosen which includes 4 "swing-by manoeuvres" (Earth - Mars - Earth - Earth). Here momentum is transferred between a planet and the spacecraft in a close fly by. On its way out, the Rosetta Orbiter will also visit two asteroids (21 Lutetia and 2867 Steins) to perform scientific measurements.