The Rosetta Mission to Comet Wirtanen An important mission to a comet will be launched by the European Space Agency (ESA) in early 2003. This mission, a cornerstone of the ESA programme, is called Rosetta. Just as the Rosetta Stone allowed Jean Francois Champollion to read the hieroglyphs of ancient Egypt, the Rosetta comet chaser will allow the scientists to read the origins of the solar system and, possibly, of Life in the solar system. The mission goal is a rendezvous with a comet named Wirtanen while it is still more than three times farther away from the Sun than planet Earth. This kind of space rendezvous requires approaching the comet with a relative velocity almost equal to zero, and performing tricky flight manoeuvres. In-situ studies While it circles the comet, Rosetta will carry out prolonged and detailed studies of the nucleus and its environment. This takes place while the comet approaches the Sun and the surface of the nucleus is gradually heating up. At the same time, more cometary material is released - the astronomers say that it is getting more and more "active". In addition, a small module will land on the surface of the 1-km nucleus. It will deploy various miniaturised instruments to determine its physical and chemical properties. All the instruments are now being completed in European or American laboratories and will be integrated on-board the spacecraft or its lander. Asteroid fly-bys During its eight-year journey to the comet, Rosetta will also observe two asteroids during close fly-bys - they are named Otawara and Siwa.

This is a reproduction of a photo made by adding twelve images of the nucleus of Comet Wirtanen near aphelion, obtained with the VLT on May 17, 1999

An artist's impression of the Rosetta mission to comet Wirtanen