When Rosetta meets Chury
© ESA/Rosetta/NAVCAM
The European probe arrived at its final destination: Comet 67P/Churyumov-Gerasimenko, whose shape shows some unexpected features. The spacecraft will now perform the most detailed study ever made of such an object and collect data in preparation of the deployment of the Philae robot on the comet’s surface in November.
After a 10-year long journey through space, covering 6.4 billion kilometers including five loops around the Sun, Rosetta reached its final destination: Comet 67P/Churyumov-Gerasimenko – Chury for short. Awakened from a 31-month hibernation phase in March 2014 (read article), the European probe successfully arrived close to the comet on Wednesday August 6, as planned.
Doing so, Rosetta has become the first spacecraft ever to ride alongside a comet, at a distance of 100 km and matching its pace at about 55’000 km/h. From now on and for the next 17 months, the probe will perform the most detailed study ever made of such an object and thus provide new crucial elements to better understand the origins of the solar system. But getting so close to the comet won’t be the only “first” in this mission. In November, Rosetta will also drop a lander onto the surface of this icy wanderer. Philae, a sophisticated robot, will detach from Rosetta and cling to the comet’s surface. “The landing mechanism of Philae required years of development in order to be ready for any kind of soil - hard, soft, steep, flat - and different types of gravity, as it was not possible to clearly define this information from the Earth,” says Grégoire Bourban, space engineer at the Swiss Space Center.
As it approached Chury, Rosetta took a few pictures, which reveal a number of surprising features. It appears that its shape is more complex than expected. It is composed of two nuclei, connected by a relatively narrow and brighter contact zone. Thanks to the probe’s highly precise camera, researchers were able to draw a complete 3D picture of the four-kilometer large comet. “This unexpected shape has made it difficult for us to define the right place for the lander. Indeed, five different landing sites will have to be defined before the end of August, and out of this short-list, the final site will be selected in mid-September, explains Grégoire Bourban. The following months will be critical for the mission’s success.”
Launched in 2004 by the European space Agency (ESA), the probe carries several Swiss made instruments. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of them. It was developed at Bern University with the contribution of Swiss industries, such as RUAG. Placed on the orbiter, this device will analyze the composition of the comet’s atmosphere and ionosphere and determine the temperature, average velocity, and reactions of the gas and ions released in its tail.