Lander update – 6 July

Discussion: 9 comments

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  Harvey Posted on 07/07/2015 at 10:25

  Obviously the lack of communication is an increasing concern.
  CONSERT is a transponder. As such it does not use the normal Philae/Rosetta S band (~~3GHz) link, but a 90MHz signal. Everything else of Philae has to go via the S band, but, provided it is switched on, CONSERT I think uniquely can reply on its own. It does not need much power.

  The nature of the CONSERT signal also means it can be integrated up to improve signal to noise (effectively reducing the noise bandwidth); after all it was designed to work *through* the comet, with prospectively high loss, so when in line of sight the higher range to the now more distant Rosetta would be less of an issue than for the S band link.

  (A question there is whether the S band can reduce data rates and narrow the bandwidth to improve range; I’ve been unable to find that out. But range improvement only goes as the fourth root of bandwidth reduction; go fro 16 to 1kb/sec to gain a factor of two range increase with equal signal to noise.)

  Antenna patterns will also be very different at 90MHz and at S band, the former crudely tending to be less directional.

  So to me the attempt to use CONSERT looks like an attempt to use a quasi-autonomous channel to get a response from Philae, using this link with very different properties and *some* measure of ‘independence’. Of course a signal would also improve location data.

  Let’s hope we hear something, via S band of from CONSERT, soon, good luck to the team.
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  Roberto Pérez Urbiola Posted on 07/07/2015 at 15:42

  Maybe the lander is not where they think it is, or maybe the orientation is not as expected (can the signal bounce?), or the obstacles around it are not where they are thought to be, or the shadows are different, or it has moved by gas pressure, or someone changed the frequency, or turned off the receiver (like one of two in Huygens probe), or there is a software error (maybe the communication IS happening), or someone is sabotaging, or the panels are getting frost, or there is interference, or someone mix-up metric and non-metric units, or someone is using a in mirror-like model of something, etc.
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  chimisse Posted on 08/07/2015 at 13:07

  When we take a closer look at the picture sent by Philae on the comet, we can imagine it’s lying on its side.

  Has this possibility been considered by the team?

  I think this could be a reason why the communication is so poor.
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    Ove Kjeldgaard Posted on 09/07/2015 at 10:40

    According to the video update, from last week: https://blogs.esa.int/rosetta/2015/07/01/video-update-from-lander-control-centre/

    So they have it included in the calculations that Philae is on its side. And it’s shown with a paper cone lying on the comet’s surface.
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  Bogdan Posted on 10/07/2015 at 10:14

  It’s very strange, has the lander moved in the months while it was asleep? How did Rosetta managed to get communication with the lander back in November? Is it not possible to use the same flight path as back then?
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    Harvey Posted on 13/07/2015 at 19:17

    They cannot go so close, the comet is now far more active and it is too dangerous for Rosetta. Aside from the relatively low risk of collision damage (because relative velocities are low) the big problem is dust confusing the star trackers. These are vital to Rosetta’s navigation. So it has to stay well away from 67P.
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    Peter Posted on 14/07/2015 at 12:59

    Just before the 60-hour-primary battery went dead, Philae was lifted 4 cm and rotated 35 degrees, and the drill was actuated, but did not penetrate. The motion was done do increase the solar panel exposition (which was 1.5 hours at that time). This motion could have shifted the communication direction, i.e. antenna. I did not read anything further about the effect of this manoeuvre.
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  Peter Posted on 10/07/2015 at 15:54

  From this picture https://www.esa.int/spaceinimages/Images/2014/11/First_comet_panoramic it is obvious that Philae lies on the side. upper right pane of image goes into sky, lower right pane goes to illuminated soil. The lander team would know, where the cameras are, and find the exact orientation. The pads make for exactly three orientations, and team should have more clues. Two rods are visible upper right, bottom. Also the sun direction is clearly visible. from the shadows, sun is to the right. Two pads, one rod, one pane are illuminated by the sun. One pad is illuminated but the soil behind it isn’t. The rods are concert antennas, from an update of 03 july 2015: https://twitter.com/DLR_en/status/616963983002730496
  I just didn’t read any analysis published by the lander team.
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  Dr. Prasanta K. Mukhopadhyay (Muki) Posted on 13/07/2015 at 21:57

  I would like to know the following:
  (1) whether can you detect any alkane biomarkers and PAHs in the comet?
  (2) What are composition of the gases it is emanating?
  (3) Is there any oil like substances?

  tHANKS
  Muki