Philae arrival part crash, part landing
Scientists are sure that the Philae probe bounced twice on the surface of Comet 67P before coming to rest in a crater. But they don’t know exactly where the lander is, or whether it is going to stay there. They may try to cause it to jump again, to a sunnier location.
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1. Release: Before Philae detached from the Rosetta orbiter, scientists knew that a thruster that was sup- posed to help anchor the lander to the surface wouldn’t work.
Scientists at the European Space Agency have yet to pin- point exactly where Philae ended up. They believe it is somewhere in the yellow area.
2. Descent: Philae took seven hours and was traveling at a meter per second as it neared the surface. No one was sure what type of surface it would hit.
3. Touchdown: The probe touched the comet less than 100 meters from its predicted landing area.
4. First bounce: It rebounded off the surface at 38 centimeters per second, bounced about a kilometer up into space, rotated and touched down again two hours later roughly a kilometer away.
5. Second bounce: This much smaller jump was at a speed of just three centimeters per second. Philae landed seven minutes later. 6. Landing: This time it stayed put — in a precarious position in a crater near a cliff, with one of its three feet in the air.
The lack of force from the dormant thruster left Philae vulnerable to momentum, gravity and terrain. The surface is not uniform. Some parts look like a powdery snowfield; others appear rocky, although not dense like the rock we know. A harder, shiny substance appears below the dust, which would explain why Philae bounced.
A. Thruster: The cold-gas thrus- ter failed to function and press the lander against the comet. A wax seal may not have broken as it should have. B. Harpoons: At touchdown, a harpoon system was supposed to fire into the surface to tether the lander, but it didn’t work. Mission experts may attempt to fire it again, but they fear it may backfire and push the lander away from the surface.
C. Ice screws: Screws on the feet deployed, but it is unclear whether they latched onto anything. D. Solar panels: The sun’s energy powers Philae’s two batteries. The panels are working, but they got just 1.5 hours of sunlight rather than the expected six to seven hours. Drill: The drill that is supposed to take surface samples has not yet been deployed, because it could accidentally tip the lander over.
SOURCE: European Space Agency. GRAPHIC: Bonnie Berkowitz and Richard Johnson - The Washington Post.