Rosetta is a cornerstone mission to chase, go into orbit around, and land on a comet. It is studying the Jupiter-family comet 67P/Churyumov-Gerasimenko with a combination of remote sensing and in situ measurements. The spacecraft arrived at the comet on 6 August 2014 following a 10-year journey through the Solar System. Between August and November, the spacecraft orbited the comet and gathered data to characterise the environment and the comet nucleus. On 12 November 2014, Rosetta's lander Philae was deployed to the surface. Philae carries a suite of instruments for imaging and sampling the comet nucleus. The Rosetta orbiter will track the comet through perihelion (August 2015), examining its behaviour before, during and after.
The mission was first considered in the late 1970s and developed from a sample-return plan to the plan for a lander. It was approved in November 1993 by ESA’s Science Programme Committee. The original mission target had been comet 46P/Wirtanen, but this was changed to 67P/Churyumov-Gerasimenko when it was clear that the launch would take place in 2004.
The spacecraft was launched from Kourou aboard an Ariane 5G+ on 2 March 2004. It required four gravity assists for its journey, one by Mars and three by Earth. Rosetta had already flown by the asteroids 2867 Steins (in 2008) and 21 Lutetia (in 2010), before entering deep space hibernation in June 2011.
Rosetta achieved a number of major milestones in 2014: Following a planned exit from hibernation on 20 January, all of the spacecraft's instruments were checked as it continued on its journey to 67P/Churyumov-Gerasimenko. The first science results were obtained even before the spacecraft arrived at the comet on 6 August 2014. On 12 November 2014, Rosetta's lander Philae was deployed to the surface. Operations continue throughout 2015, with many new scientific results being reported, as well as operational highlights such as the close flyby on 14 February.
Here are the key dates of the Rosetta mission: