Philae’s bouncing, tumbling landing sequence


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Scientists and engineers have pieced together the bouncing and tumbling land sequence that Philae went through before it came to rest on Comet 67P/C-G, including the possibility that the second touch down was actually the spacecraft grazing a crater rim.

After the first touchdown, the spin rate started increasing. As the lander bounced off the surface, the control electronics of the flywheel were turned off and during the following 40 minutes of flight, the flywheel transferred its angular momentum to Philae. After this time, the lander was now spinning at a rate of about 1 rotation per 13 seconds;

At 16:20 GMT spacecraft time the lander is thought to have collided with a surface feature, a crater rim, for example. “It was not a touchdown like the first one, because there was no signature of a vertical deceleration due to a slight dipping of our magnetometer boom as measured during the first and also the final touchdown,” says Hans-Ulrich. “We think that Philae probably touched a surface with one leg only – perhaps grazing a crater rim – and after that the lander was tumbling. We did not see a simple rotation about the lander’s z-axis anymore, it was a much more complex motion with a strong signal in the magnetic field measurement.”

Following this event, the main rotation period had decreased slightly to 1 rotation per 24 seconds. At 17:25:26 GMT Philae touched the surface again, initially with just one foot but then all three, giving the characteristic touchdown signal. At 17:31:17 GMT, after travelling probably a few more metres, Philae found its final parking position on three feet.

The search for the spacecraft itself, sitting on the surface, continues.

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3 comments

  • Competential

    Hayabusa 2 which will be launched November 30 (depending on time zone) will drop a 10 kg lander on an asteroid, which will hop around. Intentionally this time! While I’ve read about the hopper (developed in Europe), it is not well illustrated in this animation, which however shows the other advanced maneuvers of this piece of Japanese robotics at its best:
    http://jda.jaxa.jp/result.php?lang=e&id=2e032c23f72832dba634998602294f69

    Interplanetary missions are getting more and more capable and interesting. First there were flyby’s, then there were orbiters, then there were stationary landers, then there were rovers. Next up is, well, other stuff. Asteroid redirection is one such new concept, regardless of what one think about the current specific ARM mission. Maybe in the future we will smash two asteroids together at high speed?

    New Horizons will fly by Pluto with a camera, because it is the first time. But mature planetary targets like Mars and Jupiter (which has had 6 flyby’s and 1 orbiter) have advanced beyond the era of first generation probes like MRO and Galileo. Maven has no camera but has the very specific scientific target to study its atmosphere. Juno has no science camera (just a toy cam for outreach purposes) but is specialized on examining the deep interior of the giant planet. There’s no lack of inventiveness in planetary probe designs.

  • Competential

    Maybe the scientific community should take over designing launchers too? The great innovations in probe design is at contrast to the very conservative and old fashioned launcher development, as I described in a previous comment here today.
    (And I forgot about the impactor that Galileo carried, and itself impacted Jupiter too).

  • wodun

    Launchers are covered but what we all need is a true space ship that only operates in space. The people making probes should be able to help with some new forms of propulsion.

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