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Rosetta - In Search of Pristine Matter

* Probe travels to the edge of our solar system
* Mini-lab anchors on a “snowball”
* Ariane 5 launch is set for February 26, 2004

Friedrichshafen, 12 February 2004

It is a journey far into our solar system, a journey into the unknown and also a journey into the past. With the Rosetta launch, one of the most exciting European space projects will be able to start at the second attempt after the launch had to be postponed for more than one year. Rosetta is to set off in February 2004 in search of pristine matter and help find answers on how life came into being. The launch window for the interplanetary mission opens on February 26.

Rosetta will be launched on its long flight to the comet "Churyumov-Gerasimenko" by the European launch vehicle Ariane 5 G+ from Kourou, French-Guyana. For approximately 13 months, it will orbit this tailed star at a distance of up to one kilometre and explore it in detail. At the same time, a kind of “mini-lab” will land on the comet's surface for surface-science investigations and analysis.

EADS Astrium is the industrial prime contractor for this challenging project of the European Space Agency ESA. Under the management of EADS Astrium engineers from Friedrichshafen , an international team has begun to "adapt" the satellite to its new destination and prepare its lift-off

again. Originally, Rosetta was planned to travel to the comet "Wirtanen" already in January 2003. Following problems with the launchers which resulted in a launch delay, "Wirtanen" could no longer be reached. The overall volume of this contract totals about € 330 million.

Rosetta tacking through the planetary system

Rosetta is the third of four major Planetary Cornerstone missions of the European Space Agency ESA. In terms of engineering, it ranks among the most difficult projects that are feasible today. It will further expand Europe 's commanding position in cometary research which it had attained with the fly-by of Halley’s Comet by the space probe Giotto in 1986.

The flight path itself already calls for new technical solutions. Even the thrust of the powerful Ariane 5 is not sufficient to directly inject the spacecraft on its way to the comet. The probe must rather gather momentum four times in the gravity fields of Mars and the Earth in order to get onto the right track. According to current planning this will take place in 2005 at the Earth, in 2007 at the Mars and the Earth and once again at the Earth in 2009. Only after the fourth swing-by manoeuvre will Rosetta be catapulted into the outer regions of the planetary system, where it will encounter the comet “67P”, as the new destination comet is also called. Thus, Rosetta reaches a maximum distance of approximately 800 million kilometres to the Sun and a distance of about 950 million kilometres to the Earth. It is the first time ever a solar-powered probe will have ventured such distances.

In between these events, Rosetta will be largely on its own. This is the reason why the technically most complex workshare is the so-called avionics pack, which is also delivered by EADS Astrium. It contains the software for the on-board computers and the attitude control system. Mind and body must operate faultlessly and to a large degree autonomously. The biggest single item under this contract, however, is the instrument platform, which is also under the responsibility of EADS Astrium.

Observation of asteroids during fly-by

Before its encounter with the comet "Churyumov-Gerasimenko", however, Rosetta will fly through the asteroid belt and closely examine at least one asteroid during its fly-by. Asteroids are bits of rock which orbit the Sun primarily in the area between the orbits of Mars and Jupiter. They are probably the building blocks for a planet which could not be formed on account of Jupiter's enormous gravitational forces. Therefore, these bodies are also called planetoids or minor planets. Astronomers know very little about them and expect to obtain valuable information on their composition and creation from the data delivered by Rosetta.

Destination – Comet "67P/Churyumov-Gerasimenko"

The rendezvous manoeuvre with "67P" will be initiated in May 2014. In August 2014, more than ten years after launch, Rosetta will have reached its destination and insert itself into an orbit around the comet. Only then will the most thrilling part of the venture start. At that time, "Chury" will be at a distance of approximately 675 million kilometres to the Sun. Here, in the icy cold of deep space, the comet is still inactive, which means it does not emanate any gases which could form a coma or tail.

During that time the surface will be imaged from a distance of a few kilometres. For the first time, scientists, and the public, will be able to clearly see a cometary surface. Details down to one metre are expected to be discernible. The camera was built by the Max-Planck Institute for Aeronomy in Katlenburg/Lindau, the experts who also developed the successful camera for Giotto.

Simultaneously, spectrometers will scan the surface in various spectral ranges down to the infrared range. These data will be used to determine the mineral and chemical composition of the surface material. The surface is expected to have the appearance of a dirty, crusted icy desert.

Halley’s Comet revealed long canyons, wide craters and up to 900-metre high hills. Nobody knows whether "Churyumov-Gerasimenko" might look similar.

The camera on board the orbiter will also look for level terrain, since Rosetta will deploy a lander on the surface in November 2014. This vehicle was developed under the leadership of the German Aerospace Centre (DLR).

Although "Churyumov-Gerasimenko" is about four times larger than the original destination "Wirtanen", the lander must be anchored on the surface. Otherwise there might be the danger that the lander would break away from the comet's surface. The higher attraction of "67", however, is not an advantage because a higher mass also translates into a higher approach and impact speed – for which the lander's legs have not been designed. This problem, however, was resolved by a special shock-absorbing system, a development in which EADS Astrium, Friedrichshafen , was also involved.

The lander will carry a series of complex instruments for the analysis of surface samples. Additionally, a camera will take panoramic pictures. It has been developed by the Berlin-based DLR Institute of Planetary Exploration in co-operation with French researchers. It is even planned to lower a micro-camera into the bore-hole to determine the structure of the cometary crust.

While Rosetta orbits the comet, the latter will approach the Sun. "Chury" will wake up from the icy cold and start to heat up. Gases will evaporate from its surface and inside. They will drag along dust particles, and "67P" will thus form a coma and a tail. The eleven measuring instruments on board Rosetta will then begin the study of gas and dust.

Approximately one year after Rosetta’s encounter with the comet, "67P" will have reached the orbital point nearest the Sun, where it is most active. A few months later, the spacecraft mission will be completed. "Churyumov-Gerasimenko" will then withdraw again into the outer and icy regions of the planetary system.

For the first time, scientists will thus have the opportunity to see "live" how a cometary surface evolves in the course of the "seasons". The pictures taken by Giotto already showed that, apparently, huge gas jets spout out of the crevasses in the surface. Rosetta will show this process in much more detail and thus help unravel further mysteries that surround the comets.

Comets - the archives of primeval times

The gathered data will be of inestimable value to the scientific community, as the instruments on board the lander, in a way, will tap an archive which has preserved unaltered material from the time of formation of the solar system. Pristine matter can be found on no other celestial body, with the possible exception of some asteroids. On the Earth and also on other planets, source material from which the planets were formed, continuously evolved in the course of the last 4.6 billion years. Chemical, geological and biological processes transformed the atmosphere and rocks thereby destroying any information from primeval times.

Comets, by comparison, are so small that no geological processes such as erosion or plate tectonics take place. There are presumably billions of cometary nuclei that slowly move around the Sun far outside Pluto's orbit. It is only when one of them ventures into the inner solar system that it will heat up so that gas will evaporate and it will appear as a tailed star in the sky.

Comets spend most of their "life" in the outer regions of the solar system where temperatures drop to nearly absolute zero. The cometary material is thus preserved in a deep-freeze state. Scientists therefore hope that Rosetta will help them determine the chemical composition of protosolar nebula in order to further explore the creation of our solar system and thus of the Earth. In other words: Rosetta will be looking for the roots of our existence, the formation of life.

Rosetta – the name

This also explains the name of the spacecraft. It refers to the "Rosetta Stone“, an Egyptian inscription stone, discovered by a soldier in the Napoleonic Army in 1799, near the Egyptian city Rosetta. By means of the inscription on that stone, the French scholar, Jean-François Champollion, detected the first clues to deciphering the Egyptian hieroglyphics, thereby opening the historians’ way to our cultural roots.

67P – Churyumov-Gerasimenko

The comet Churyumov-Gerasimenko was detected in 1969. Initially, Klim Churyumov examined a picture of the comet Comas Solá taken by Swetlana Gerasimenko and detected the comet on it. P67 has a size of about three by five kilometres and rotates about its one axis in about twelve hours. It needs approximately six and a half years for one Sun orbit. In doing so, its distance to the Sun varies between 194 and 858 million kilometres. The cosmic object is viewed as a "dusty" comet. For preparing the Rosetta mission, "Churyumov-Gerasimenko" was inspected in detail by the Hubble Space Telescope. In March 2003, one of its cameras took approximately 60 images by which astronomers could get a rough idea of the comet's shape (similar to a rugby ball).

EADS Astrium is the leading satellite company in Europe . It is wholly owned by EADS SPACE. In 2002, EADS SPACE had a turnover of approximately 2.2 billion euros and 12,300 employees in Germany , France , the United Kingdom and Spain . The satellite activities of EADS Astrium cover complete civil and military telecommunications and Earth observation, science and navigation programmes, and all spacecraft avionics and equipment.

Mathias Pikelj
Tel.: +49/(0)7545/8-9123
Fax: +49/(0)7545/8-5589
mailto: mathias.pikelj@astrium.eads.net

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