6 August 2014
De 775 m/s à 1 m/s
When it woke up from deep space hibernation on 20 January, Rosetta found itself some 9 million km from the nucleus of comet 67P/Churyumov–Gerasimenko and closing in at a speed of nearly 775 m/s. Since 7 May, 10 rendezvous braking manoeuvres have reduced its velocity relative to the nucleus to 1 m/s, i.e. 3.6 km/h.
The last rendezvous manoeuvre was successfully completed today and Rosetta is now accompanying the nucleus on its elliptical orbitas the two bodies—one natural, one man-made—hurtle around the Sun at a speed of close to 55,000 km/h, 405 million km from Earth.
A first in space
"After 10 years, 5 months and 4 days travelling towards our destination, looping around the Sun 5 times and clocking up 6.4 billion kilometres, we are delighted to announce finally ‘we are here’,” said ESA’s Director General Jean-Jacques Dordain today. “Europe’s Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring our origins. Discoveries can start.”
For CNES President Jean-Yves Le Gall, "This historic rendezvous is a world first for science eagerly awaited by the global space community for 10 years. Today, Rosetta went into orbit around comet Churyumov-Gerasimenko. The science phase of the mission can now begin, with the high point in November when the Philae lander touches down on the comet’s nucleus. CNES is especially proud to have been involved from the outset more than 20 years ago in this exceptional adventure made possible by the European Space Agency.”
Flying in front of the nucleus
Rosetta is currently flying 100 km ahead of the comet, escorting it on its elliptical path around the Sun at a great vantage point to permanently observe the sunlit side with the nucleus spinning at the rate of one rotation nearly every 12.4 hrs. Over the coming weeks, the spacecraft will edge closer to study the gravitational field of the nucleus and determine the tiny body’s mass as precisely as possible to allow engineers to refine the probe’s final orbital sequence. Ultimately, Rosetta is set to go into a circular orbit 10 km from the surface of the nucleus and then descend to just 5 km to release the Philae lander.
At the same time, Rosetta’s instruments will subject the comet to close scientific scrutiny in order to identify a landing site for Philae this autumn. The date currently scheduled is 11 November, but the landing may occur earlier or later. The goal now is to identify 5 possible landing sites by the end of August and select a primary site by mid-September. The team at the Science Operations and Navigation Centre (SONC) at CNES in Toulouse is responsible for this crucial task of determining the site that best matches all of the mission’s technical and scientific constraints.
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, the German Aerospace Centre, the Max Planck Institute for Solar System Research (MPS), CNES and ASI, the Italian space agency. Rosetta is the first mission in history to orbit a comet, escort it on its course around the Sun and deploy a lander on its surface.
*The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d'Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.