Philae, the plucky comet lander from the European Space Agency's Rosetta mission, was confirmed today as alive and well, but in a precarious position.
After Philae hit its target on comet 67P/Churyumov–Gerasimenko on November 12, its harpoons failed to deploy, leaving the lander unsecured. The data it beamed back to Rosetta — which is orbiting the comet and relays information to mission control — suggested that it had bounced twice before coming to a rest. But information was in short supply, because soon after the landing the mothership went beyond the comet’s horizon, severing communications.
Data transmitted to Earth today revealed that the lander is now stable and that its instruments are working, but it is stuck, probably at a steep angle, against the bottom of a cliff. The first picture released from Philae shows one of the lander’s three feet against a craggy backdrop (see picture at right). Later, the agency released another image, this time a panoramic view showing the position of the probe's feet. The mission team also superimposed a sketch of the lander suggesting its position (see picture at the top).
Briefing journalists today at the European Space Operations Centre in Darmstadt, Germany, Philae lead scientist Jean-Pierre Bibring said the cliff meant Philae is largely in the shade, which could be a problem for powering long term operations. Philae’s primary batteries will only last 64 hours after it separated from Rosetta. By the time of the briefing at 14:00 central European time, 28 hours had already elapsed. Once those batteries run dry, Philae will be relying on solar panels. From its shady zone, Philae will get just 1.5 hours of sunlight every 12 hours, said Koen Geurts, Philae's technical manager at the German aerospace centre (DLR).
In a separate briefing to journalists in France, Marc Pricher, director of the Toulouse site of the French space agency CNES, described Philae’s location as what could be the opening a cave, or perhaps next to a boulder. The constraints on power would mean that the Philae’s work program would have to be adjusted, he said.
The fact that Philae is unsecured means that it could be difficult for its drill to obtain samples of the comet, because the mechanical action will create a reaction force that could make the craft bounce again, or tip. "Drilling without being anchored...is dangerous," said Ulamec. Drilling will certainly not happen today but is not ruled out, added Bibring.
Securing Philae by attempting again to fire its harpoons could also be dangerous for the same reason, Ulamec explained to journalists on the evening after the landing. The comet's gravity is 100,000 times weaker than that on the Earth, and if the harpoons failed to hook onto the surface, the momentum could push the lander back up into space, he said. “That would be highly embarrassing.”
On-board instruments revealed that after accurately hitting its target site, Philae bounced as high as 1 kilometer from the surface, Ulamec added. It fell back to the ground two hours later, bouncing a second time by a shallower hop of a few minutes, before settling in its current position.
Rosetta has yet to locate the lander with its cameras. But data from Philae’s radar device suggest that the lander ended up around 1 kilometer from the site where it first touched down.
This article is reproduced with permission and was first published on November 13, 2014.