Rosetta and Philae: one year since landing on a comet

One year since Philae made its historic landing on a comet, mission teams remain hopeful for renewed contact with the lander, while also looking ahead to next year’s grand finale: making a controlled impact of the Rosetta orbiter on the comet. This article is mirrored from the main ESA web portal. Rosetta arrived at Comet 67P/Churyumov–Gerasimenko on 6 August 2014, and after an initial survey and selection of a landing site, Philae was delivered to the surface on 12 November. After touching down in the Agilkia region as planned, Philae did not secure itself to the comet, and it bounced to a new location in Abydos. Its flight across the surface is depicted in a new animation, using data collected by Rosetta and Philae to reconstruct the lander’s rotation and attitude (Ed's note: more details on the animation to follow in a dedicated blog post) In the year since landing, a thorough analysis has also now been performed on why Philae bounced. There were three methods to secure it after landing: ice screws, harpoons and a small thruster. The ice screws were designed with relatively soft material in mind, but Agilkia turned out to be very hard and they did not penetrate the surface. The harpoons were capable of working in both softer and harder material. They were supposed to fire on contact and lock Philae to the surface, while a thruster on top of the lander was meant to push it down to counteract the recoil from the harpoon. Attempts to arm the thruster the night before failed: it is thought that a seal did not open, although a sensor failure cannot be excluded. Then, on landing, the harpoons themselves did not fire. “It seems that the problem was either with the four ‘bridge wires’ taking current to ignite the explosive […]

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