I am always gobsmacked by the knowledge of the posters here and all the different "angles" many of you have looked at to find Philae's final resting place.

One thing I seem to recall from the 2-3 days when signals were being received from Philae before the battery ran out. This was an observation by someone at ESA that on the second or third "comet day", Philae came on exactly "on time"as was expected.

Since some of you guys have already modeled 67P's rotation and are also aware of Rosetta's position at any given time as well, I would have thought a line could be drawn on the comet which would be just "visible" to Rosetta at those moments. We would then know that Philae must lie at or near that line. I understand such occurrences happened , at least, twice if not more times. Philae was "alive" about 2 days, so roughly, 4 rotations of 67P.

Intersecting that line and the various trajectories that have been considered after Philae's various bounces should be likely candidates where Philae finally rests.

Apologies if this has been considered already !

That definitely gives you some information. But the "line" is probably pretty broad, since local features like cliffs or boulders could change the time that you regain contact significantly, presumably. Still, the Rosetta team would have all the regain/loose contact times, and I'm sure they're doing what they can with them.

Agreed. But, at least, we would know if the "likely point" was to the east or west of the first landing spot. There now is doubt seemingly which way it went when it was high up.

I just took a glance at the view from Rosetta towards 67P during the ~2 days after Philae's landing, using STK & the SPICE data.

A few observations:

- ESA positioned Rosetta so that it would be directly overhead of the Philae planned landing spot. It remained close to that viewpoint during the entire two days, though it moved quite a bit further away from 67P on Nov 13th. Philae's planned landing spot is quite close to the equator, so that means that planned landing spot passes directly under Rosetta once per rotation.

- If Philae is where ESA seems to think it is (the "blue triangle" from some of the graphics ESA folks have released, which is far side of the 'head' crater, probably in a cleft on that hillside) then interestingly enough, in that spot Philae will become visible to Rosetta at almost the exact same time as the planned landing site. In other words, the start of the radio communication window with Rosetta would be almost exactly the same from this spot as with the planned landing spot. This is true even though the two sites are around a kilometer distant from each other and in quite different topographies. This is something of a coincidence and possible what initial led some of the ESA folks to conclude that they must have ended up quite close to their planned landing site.

- Both the planned landing site and the presumed final resting site are roughly on the top of the head of 67P and not too far from each other. So it is quite true that either way radio contact would start/end at *about* the same time and local features in other location could pretty precisely mimic the other location (or nearly any other location on/around the top of the head).

- If Philae were *not* in a cleft, but more on top of one of the peaks, or even one a high spot on the far hillside (vs in the bottom of a cleft in the far hillside) it would like have come into radar contact before the landing site would. The time difference in that case would be about 30 minutes.

- Where there probably was a difference in radio contact time in the presumed final vs planned landing spot, is in the *end* of the radio transmission window. Since the presumed final resting spot of Philae is (generally) on the east side of the crater rim mountains, and the comet rotates towards the eastward, in the presumed final resting spot, Philae would lose radio contact maybe 90 minutes before it would if on the flat area of the planned landing site.

- However, there are areas very near the planned landing site that would duplicate that radio profile! For instance, if it had landed just on the east side of one of several crater walls within 200-300 meters of the planned landing site, it would also cut off the radio window about 60-120 minutes earlier than if on the perfectly flat location.

We don't know the radio start and end times precisely (ESA hasn't publicly released them, that I know of) but even presuming ESA did, it probably only told them that Philae was indeed somewhere on the head, and also that local topography was somewhat affecting the radio communications window. They might have been able to deduce from that, that Philae was likely on more of an east-facing slope (or, more precisely, that some obstacle was just to the west of Philae blocking radio communications).

Also, interestingly, it looks like to me that if ESA had known Philae's exact location it probably could have positioned Rosetta nearer the south pole and had potentially a much larger communications windows with Philae. If Rosetta was positioned high over the south pole, continuous radio communications might even have been possible. But if Rosetta were positioned, say, halfway between the equator and south pole, you'd quite certainly have a noticeably longer communications window than what they did have.

(From that position, Rosetta would also have had a continuous view of the dark side of the comet--not very interesting from the visual point of view!)

Whether and how this different positioning of Rosetta for a longer communications window would have worked would depend on the details of Philae's final position, which of course we don't know even now. Whether it would have been a good idea is another question yet. But I do think it would have been possible.

Just as a cautionary note -- until the actual vs. predicted signal acquisition times are released, I would take statements made during those crazy hours of the landing and surface ops with a grain of salt.

We don't have the needed data to find Philae on the surface. Hopefully ESA does, or will in the future. But without the needed data, I believe all we here on the forum can do is guess.

-the other Doug

The search area for Philae is about 3-400m x 200m, covered with boulders, cliffs, and very rough, according to Holger Sierks (in the above mentioned tv interview on NDR, German television).
So you get lots of similar signatures in terms of signal coverage. Philae is hidden somewhere between these small structures. If there would be more constraints, they would have applied them.

Thanks for the link to the German TV programme. I don't speak German, but I got the idea.

I paused the video to try and get a good view of the images and one did seem to show a cleft/niche/alcove with two bright pixels that could have been Philae. This indeed matches the spot I have suggested for a few weeks now. Until now I have only posted on the ESA Rosetta blog, but as a regular reader of Emily's great blogs at the Planetary Society, I thought I'd post here too. Here is a link to my Flickr image for Phiaes landing. Other images can be accessed from there to save me posting dozens of images or links.

https://www.flickr.com/photos/124013840@N06/16058382452/

P.S. Thanks to everyone for all the great posts, images, explanations etc.

If you look at the images, which was possible at thew "Night of Science" in Göttingen, it is easy to identify 10 or 20 bright, two or three pixel structures. All of those have the same chance to be the lander. With the OSIRIS image available you can not answer the question, so we need to wait for better images.

Latest ESA NAVCAM image has been posted on the Rosetta blog.

http://www.esa.int/var/esa/storage/images/...2015_NavCam.jpg

This image contains a little gem. A plume of gas and dust can be seen rising directly from the surface of the comet at about pixel 1200 x 1230. I have created a couple of closer views in the images below.

https://www.flickr.com/photos/124013840@N06/15697071534/

https://www.flickr.com/photos/124013840@N06/16133265469/

The feature you point to looks totally consistent in brightness and texture with other surface features in that image. If that were a real jet that bright and dense, it surely would cast a shadow.

Hard to say if it's a plume or a weird rock, without a "comparison image"

It's a rock.

Yep It's a rock formation. Thanks for the other image.

[newbie - first time poster - however I've been reading this blog since the landing and post a bit on the Rosetta blog. I like the quality of speculations / analysis done here (despite the *extremely* limited data to go on).]

Flug, I like your thoughts on the dots - however I think it is worth pursuing more as it could be something more. My hunch is that the left two dots are a kicked up object/boulder by Philae and it's shadow - it is very unlikely that such a large object would be there coincidentally with that rate, vector and size, As for the right side object, I think it may be Philae's shadow itself - it rotates, is a similar size and is in a weird position which could be consistent with a very high elevation lander.

I don't know the exact Rosetta look angles (I know Flug had a summary on them - but Brian had few posts on them as well which seem to disagree. I don't know if this data is accurate or not - but as an example of a fit to my scenario I very simply annotated Brian's picture from awhile ago: 3 dots possible trajectories figure (green is rosetta look angles, yellow is the sunline for the 6 points. ignore the complete ovals - just interested in the arcs that cover the witnessed points from the landing site.)

The point is less the exact accuracy of the picture and exact trajectory - rather the conceptual scenario. The landing kicked up a large boulder almost vertically up to make the left black object (it's CG material and it's dark and moving so less exposure time per area / more likely to be rocky angles which won't reflect back into the camera and blocking the higher light flux comet) and it's associated shadow, and the Philae trajectory can be solved assuming the right side shadow is in fact from it (admittedly it may not be - but I think it's more likely the lander than another kicked up boulder - one big boulder could be believable - several is pushing it).

Can someone gin up a Philae trajectory that fits with the right side shadow? It may dramatically change where we look for the lander (like the other direction entirely as seen in my picture!)

Hello All!
First post here, discovered this site September 2014, been following this thread since.
I've been following Rosetta mission since the beginning, albeit this is not relevant...
I'll run the risk of breaking rules, since I have an hitching question:

Did this really happen?
http://www.seti.org/weeky-lecture/rosetta-...mov-gerasimenko

ADMIN: OK, a couple of things. 1) Are you asking if the talk happened? You can assume that it did since they regularly hold talks; 2) It is recommended that you never run the risk of breaking Forum rules.