ESA prepares for first ever in situ analysis of a comet
On 6 August, the European Space Agency’s (ESA) ‘Rosetta’ became the first ever spacecraft to rendezvous with a comet. Since then, she has been whizzing through space alongside Comet 67P/Churyumov–Gerasimenko as her team prepares to make contact. Now, the ESA has announced the site on which Rosetta’s lander, known as ‘Philae’, aims to touch down. Philae, a 100 kg lander, is planned to reach the surface on 11 November, where it will perform indepth measurements to characterise the nucleus in situ, in a totally unprecedented way. The team has dubbed the targeted area as ‘Site J’. They say it is an intriguing region of the comet that offers unique scientific potential, with hints of activity nearby, and minimum risk to the lander compared to the other candidate sites. But choosing a suitable landing site has not been an easy task and a backup, Site C, has also been selected. Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center, elaborates, ‘As we have seen from recent close-up images, the comet is a beautiful but dramatic world – it is scientifically exciting, but its shape makes it operationally challenging.’ Ulamec continues, ‘None of the candidate landing sites met all of the operational criteria at the 100% level, but Site J is clearly the best solution.’ If successful, the team will make space history once again by making the first ever in situ analysis of a comet. It’s hoped that the observations will offer unparalleled insight into the composition, structure and evolution of a comet. Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument at the IAS in Orsay, France, notes, ‘Site J in particular offers us the chance to analyse pristine material, characterise the properties of the nucleus, and study the processes that drive its activity.’ Rosetta reached the comet last month following a 10-year pursuit. Then the race to find the landing site began. By 24 August, using data collected when Rosetta was still about 100 km from the comet, five candidate regions had been identified for further analysis. Since then, the spacecraft has moved to within 30 km of the comet, affording more detailed scientific measurements of the candidate sites. In parallel, the operations and flight dynamics teams have been exploring options for delivering the lander to all five candidate landing sites. Last week, a host of involved experts met to consider the available data and to choose the primary and backup sites. The landing is expected to take place in mid-November. Once deployed from Rosetta, Philae's descent will be autonomous, with commands having been prepared by the Lander Control Centre at DLR, and uploaded via Rosetta mission control before separation. When the lander touches down, at the equivalent of walking pace, it will use harpoons and ice screws to fix it onto the surface. It will then make a 360° panoramic image of the landing site to help determine where and in what orientation it has landed. 'No one has ever attempted to land on a comet before, so it is a real challenge,' says Fred Jansen, ESA Rosetta mission manager. 'The complicated 'double' structure of the comet has had a considerable impact on the overall risks related to landing, but they are risks worth taking to have the chance of making the first ever soft landing on a comet.' For more information, please visit: http://rosetta.esa.int/(opens in new window)
Countries
Germany, France