A scientific and technological challenge
Charting unexplored territory
The european probe GIOTTO, launched in 1985, studyed the Halley's comet in 1986.
The study of comets began relatively late compared to that of the planetary system. When Halley's comet passed near Earth in 1986, it stimulated exceptional interest, leading to the first exploratory missions capable of conducting observations and in-situ measurements.
The European Rosetta probe aims to rendezvous with comet Churyumov-Gerasimenko by 2014. Its lander, Philae, will touch down on the surface of its nucleus. During its long trip, the orbiter spacecraft will fly by 2 asteroids, Steins and Lutetia.
The flyby of Steins on 5 September 2008 revealed that it is a small diamond-shaped object 5 km across, with a very uniform surface. Analysis of data gathered during the flyby shows that Steins has no exosphere—that is, no residual atmosphere—and no satellites. This is the first time a space probe has observed an asteroid of this type. Rosetta and Philae are now on course to encounter Lutetia in July 2010. Lutetia is probably an ‘M-type’ (metallic) asteroid, a very rare class of asteroid never observed up close before.
A cornerstone of the European scientific programme
The initial mission scenario to return comet samples, deemed too ambitious for reasons of technical feasibility and cost, was abandoned and redefined in 1993 to rendezvous with a comet nucleus by ESA's Science Programme Committee. Rosetta is the third cornerstone of Europe's Horizon 2000 scientific programme.
France is participating in this mission at several levels. National industry is working directly for ESA on the construction of the main spacecraft and the ground segment. The scientific community is involved in the instrument and engineering aspects of the programme. Lastly, CNES has helped to design, build and check the Philae lander.
A world first
Tests on the probe's solar arrays. Crédits : ESA
Rosetta travels to the outer reaches of the solar system, where one of the main challenges is generating power. Rosetta is the first probe to use solar panels so far from the Sun (600 million kilometres), meaning that the energy at the rendezvous point is about 16 times weaker than that received on Earth. Onboard power consumption must therefore be reduced to a minimum.
This mission is a world first in terms of the objectives set by the project's scientists and engineers: to make a soft landing on the nucleus of a comet and study it, both on the surface and in orbit.
Rosetta lander
This strategy will allow them to precisely observe the evolution of a comet from aphelion to perihelion when it passes closest to the Sun.
