Rosetta will be launched on the 12 January 2003 by Ariane-5 from Kourou, French Guiana on a mission of more than ten years. The Rosetta mission is an interplanetary mission with the objective to rendezvous with, and make in-situ measurements of comet 46 P/Wirtanen.

Comet 46P/Wirtanen imaged with the MPG/ESO 2.2 m Telescope in September 1996. Comet 46 P/Wirtanen was discovered on 15 January 1948 at Lick Observatory by Carl A. Wirtanen. The dust coma and the already developed dust tail are visible.

The Rosetta Orbiter will be the first spacecraft ever to go into orbit around a comet nucleus. It will also be the first to observe the changes that occur in comet activity as the nucleus travels towards the inner Solar System. The spacecraft will also carry the Rosetta Lander (Surface Science Package) to the nucleus and deploy it onto the comet's surface.

The Rosetta spacecraft will undergo an eight year journey, after which it will perform its rendezvous manoeuvre with the comet on the 29 November 2011 and make in-situ measurements in August 2012. Studies will be made of the nucleus of comet Wirtanen and its environment in great detail for a period of nearly two years, the near-nucleus phase starting at a heliocentric distance of about 3.25 AU, with far-observation activities leading ultimately to close observation (from about one km distance).

To be able to fly alongside its target comet, the Rosetta spacecraft must put itself into the same orbit as the comet around the Sun.

The above figure shows the several fly-bys required for Rosetta to achieve its rendezvous with Comet Wirtanen. Rosetta's orbit grows in stages until it matches the comet's.

At the Earth's distance from the Sun, Comet Wirtanen travels faster than that of Earth. No rocket now available could give Rosetta the extra speed it needs to catch the comet. Instead, the spacecraft will swing past Mars and twice past the Earth, exploiting the planets' gravity to gain the necessary energy.

The spacecraft will also pass close to two asteroids, Otawara and Siwa on its route. Scientists want to know whether some of the asteroids orbiting near the Earth are in fact dead comets. The dark coloured Siwa may be more similar to what a defunct comet would look like.

The Rosetta design is based on a box-type central structure, 2.8 m x 2.1 m x 2.0 m, on which all subsystems and payload equipment are mounted. Two solar panel wings, each of 32 m², extend outwards from the side faces, giving a total span of about 32 m tip to tip. Rosetta is the first spacecraft to travel further than Mars and rely on the diminishing power of the Sun's rays, for warmth and electric energy. For this reason ESA is developing special low-intensity, low-temperature solar cells.

The figure above shows the Rosetta spacecraft design.

Attached to the face opposite the high-gain antenna, until its release, is the Lander. The payload instruments are accommodated on the top of the spacecraft, and the subsystems on the base of the spacecraft. The instrument panel on the top of the spacecraft almost always points towards the comet during the main scientific phase of the mission, while the antennas and solar arrays point towards the Sun and Earth (at such great distances the Earth is relatively speaking in the same direction). The spacecraft attitude concept is such that the side and back panels are shaded throughout all nominal mission phases, offering a good location for radiators and louvres. This will normally be facing away from the comet, minimising the effects of cometary dust.

The Rosetta mission will offer a major step forward in cometary science. It will provide detailed observations of the comet nucleus and its close environment and will provide unique sample analysis capabilities, thus satisfying to a large extent the objectives of the original comet-nucleus sample-return mission.

The figure above shows the Rosetta spacecraft with its side mounted solar panel wings extended and the high gain antenna on its rear side.

This mission follows from the 'reconnaissance phase' of cometary comae and nuclei by the fast fly-by's of ICE at comet Giacobini-Zinner, Vega 1 and 2, Susei, Sagigake and Giotto at comet Halley and the Giotto Extended Mission to comet Grigg-Skjellerup,

The Rosetta Homepage at the European Space Agency.

Rosetta's onboard instruments will concentrate on the in-situ investigation of cometary matter and the structure of the nucleus, with the added potential of studying the evolution of cometary processes as a function of heliocentric distance. The spacecraft will study the appearance of the comet's surface, its composition and temperature distribution and analyse the gas and dust emitting from its nucleus. It will determine dust and gas emission rates and investigate the interaction with the solar wind.

The obiter payload comprises eleven separate scientific investigations, plus the lander. For a list of these scientific investigations, and links to the specific investigations please visit the Related Links page.

The function of the Lander will be to make in-situ studies of the composition and structure of the nucleus material.

Image of the Rosetta Lander. The Lander science will focus on the in situ study of the composition and structure of the nucleus material.

After the asteroid flyby in 2008, the spacecraft enters a heliocentric drift phase to intercept the comet at a point close enough to allow communication with Earth. The spacecraft will lower its velocity relative to that of Comet P/Wirtanen from 100 meters/second at 500,000 kilometre distance to a speed low enough to allow it to go into an elliptic polar orbit about the nucleus, using the images of the comet as it gets closer to fine-tune the approach. This will occur in August 2011, about 3150 days after launch. A landing site will then be chosen and the probe will be released in August 2012 to land on the comet's surface and perform in-situ measurements.

The Rosetta Lander Web Server at the Max-Planck-Institut für Aeronomie.

This page was last updated September 2002.