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Philae returns ‘unprecedented images’ before falling asleep

The European Space Agency’s (ESA) ‘Philae’ probe made history last week by landing on a comet. The lander is now ‘asleep’ until sunlight reaches it.

Last Wednesday, following a seven-hour descent, the ESA’s Rosetta mission soft-landed its Philae probe on the surface of Comet 67P/Churyumov–Gerasimenko. The ESA says that the successful landing was against the odds: Philae bounced twice after its first touchdown on the comet, and finally come to rest in the shadow of a cliff in the late afternoon. Since touchdown, Philae has completed its main mission by returning all of its ‘housekeeping data’, as well as science data from the targeted instruments, including ROLIS, COSAC, Ptolemy, SD2 and CONSERT. In addition, the lander’s body was lifted by about 4 cm and rotated about 35° in an attempt to expose more panel area to sunlight. But as the last science data fed back to Earth, Philae’s power rapidly depleted and Rosetta lost contact with the lander early on Saturday morning. The spot where Philae landed is in the shadow meaning it cannot capture solar energy to recharge its battery. From now on, it will not be possible to contact Philae unless sufficient sunlight falls on the solar panels to generate enough power to wake it up. However, before drifting off to sleep, the lander returned unprecedented images of its surroundings. The ESA notes, ‘While descent images show that the surface of the comet is covered by dust and debris ranging from millimetre to metre sizes, panoramic images show layered walls of harder-looking material. The science teams are now studying their data to see if they have sampled any of this material with Philae’s drill.’ Although Philae is now in hibernation, the ESA team is hopeful that there will be much more to come from the pioneer lander. Stephan Ulamec, lander manager at the DLR German Aerospace Agency, noted, ‘We still hope that at a later stage of the mission, perhaps when we are nearer to the Sun, that we might have enough solar illumination to wake up the lander and re-establish communication.’ Rosetta was launched on 2 March 2004 and travelled 6.4 billion kilometres through the Solar System before arriving at the comet on 6 August 2014, making her the first spacecraft to rendezvous with a comet. She is now the first to deliver a probe to a comet’s surface. Alvaro Giménez, ESA’s Director of Science and Robotic Exploration, noted, ‘Decades of preparation have paved the way for today’s success, ensuring that Rosetta continues to be a game-changer in cometary science and space exploration.’ Although Philae is expected to remain asleep for the near future, the Rosetta spacecraft will be highly active. Over the coming months, Rosetta will start to fly in more distant ‘unbound’ orbits, while performing a series of daring flybys past the comet, some within just 8 km of its centre. The ESA says that the data collected by the orbiter will allow scientists to watch the short- and long-term changes that take place on the comet, helping to answer some of the biggest and most important questions regarding the history of our Solar System. For more information, please visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

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