Slashdot Mirror
Pictures of a Comet From 9 Meters Away
An anonymous reader writes: Back in November, the European Space Agency triumphantly put a lander on the surface of a comet and then tragically lost contact with it when it failed to anchor and couldn't harvest enough energy to stay operational. In June, the lander awoke and for a short time was able to send more data back. Now the ESA has published a bunch of pictures and scientific papers about the data gleaned from Philae's short windows of activity, including images of its descent to the surface. Phil Plait summarizes and analyzes the release. The most impressive image is from a mere 9 meters over the surface of comet 67P/Churyumov-Gerasimenko. An animated gif shows the lander's descent near the surface through a handful of pictures. Two shots of the same area from the Rosetta probe show where Philae bounced off the surface, ejecting an estimated 180kg of material in the process. It's a fascinating, close-up look at a very distant and unusual world.
The relative velocities are quite low, because there is very little gravity. So their plan was not to make a jet system that reduces the landing velocity (you may be thinking of the moon landing), but instead to use a cold-gas jet to press the lander onto the surface. That system, unfortunately did not fire. Secondly (and perhaps related?), the trigger that should launch harpoons to anchor the lander did not execute. That is why it did not land, but bounce off again.
NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
"You would have thought the cold gas thrusters would have been checked out before a landing attempt was made."
What made you think they didn't check those?
http://spaceflightnow.com/2014/11/12/comet-landing-is-a-go-despite-thruster-problem/