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Rosetta, rendez-vous with History

A spacecraft meets a comet for the first time: the ESA probe with an 'Italian heart' enters the orbit of 67P Churyumov-Gerasimenko and opens a new chapter in the exploration of the solar system

Confirmation came at about 11:30 pm, Italian time: after 10 years of travel in the depths of the Solar System – almost a third of which passed in 'hibernation' - and seven months after its awakening, Rosetta has finally entered the orbit of the comet 67P Churyumov-Gerasimenko. 'Centring' a tiny body of rock and ice (nucleus of just 4 km) after having covered billion of km within the solar system.

No man-made spacecraft was has ever been able to 'hook' a comet: in 1986 the Giotto probe arrived 560 km away from the comet Halley, this time Rosetta is almost six times nearer (100 km), and above all, it’s there to stay.

Now the ESA probe with an Italian heart and its comet are about 405 million km from the planet Earth, more or less halfway between the orbits of Jupiter and Mars, and have begun their journey together towards the sun, launched at a speed of 55 thousand km per hour.

The extraordinary event was followed live from the ESA-ESOC center in Darmstadt, with a live transmission of the rendezvous, in the presence of the heads of all organizations involved. Among others, the Director General of the ESA Jean-Jacques Dordain, the chairman of the board of the German Space Agency (DLR) Johann-Dietrich Worner, the president of the French Space Agency (CNES) Jean-Yves Le Gall and the president of the Italian space Agency (ASI) Roberto Battiston.

"After ten years, five months and four days - said Dordain excitedly - we can finally say: we’ve made it! We can now begin the exploration of our origins".

"It was like trying to throw a grain of sand from Darsmtad to Rome, hitting an atom" said Battiston during his speech. "And this was possible - he added - thanks to the joint efforts of Europe and the support of Italy, which has greatly contributed to the mission and its scientific aspect. I wish to thank the INAF, National Institute of Astrophysics, the Universities of Milan and Padua, but also Thales Alenia Space with their industrial contribution".

The President of the ASI then addressed a particularly deep-seated remembrance, applauded by the audience, to Professor Angioletta Coradini, who passed away nearly three years ago, "to whom the planetary science community owes a great deal" and who has made a fundamental contribution to Rosetta, designing and developing the Virtis instrument.

Today is just the latest in a series of ten manoeuvres begin in May to adjust the speed and trajectory of Rosetta gradually adapting it to those of the Comet ('adjustment' manoeuvres that will continue in order to keep it in the 'artificial' orbit of 67P Churyumov-Gerasimenko): if just one of these had not succeeded perfectly, the whole mission would have failed.

"We've have travelled a remarkably long way since the idea of this mission was discussed at the end of the seventies, and approved in 1993 - said Alvaro Giménez, ESA's Director of Robotic exploration - and now we are ready to rewrite what we know about comets for decades to come".

In the coming weeks Rosetta will approach closer and closer to the Comet (pictured here on the right in one of the last 'shots' of Osiris) up to halving the current distance and will begin to draw a detailed map that is essential to decide on which point of the comet’s surface the next big event of the mission will take place: the release and landing of the Philae lander, scheduled for November 11.

"At the end of August - said Enrico Flamini, ASI Chief Scientist, directly involved in the selection of potential 'landing sites' – an initial meeting will take place to identify a shortlist of five possible sites, amongst which, in mid-September, two will be identified, not just one, to have an alternative back-up available".

Launched on March 2, 2004 from Kourou, French Guiana, Rosetta has so far travelled more than 6,000 million kilometres. There were several "meetings" during its journey: the probe exploited the "gravitational slingshot" effect once around Mars three times around the Earth and made two fly-bys with the asteroids Steins in 2008 and Lutetia in 2010.

Rosetta was then placed in a state of 'hibernation' for 31 months: for the part farthest from the Sun, when it travelled towards Jupiter's orbit where its solar panels could not guarantee sufficient power for instruments and on-board equipment. It then woke automatically, controlled by an internal clock and without signals from Earth, on January 20.

After waking, Rosetta continued the adventure in the final and principal stage of its epic journey: the comet 67P/Churyumov-Gerasimenko, which it arrived to today - 'entering' its orbit, 100 km away - and that it will escort in its approach to the Sun until the end of 2015, with the aim to make a series of detailed investigations on its characteristics. To do so, it will risk an undertaking never attempted before: the release of a lander, Philae which, we repeat, will land on the surface of the comet in November.

Rosetta is an ESA mission with contributions from its member states and NASA. The Philae lander was developed by an international consortium led by the DLR, MPS, CNES and ASI.

The Italian participation in the mission consists of three scientific instruments aboard the orbiter: VIRTIS (Visual and InfraRed Thermal Imaging Spectrometer) under the scientific responsibility of the IAPS (INAF Rome), GIADA (Grain Impact Analyser and Dust Accumulator) under the scientific responsibility of the Parthenope University of Naples, and the WAC (Wide Angle Camera) of OSIRIS (Optical Spectroscopic and Infrared Remote Imaging System) under the scientific responsibility of the University of Padua. Aboard the lander, is the Italian samples acquisition and distribution system SD2 (Sampler Drill & Distribution), under the scientific responsibility of the Milan Polytechnic, and the subsystem of the solar panels.