Homing in on Philae’s final landing site

Based on inputs provided by the CONSERT principal investigator Wlodek Kofman, CNRS researcher at the Institut de Planétologie et d'Astrophysique de Grenoble, Grenoble, France.

Philae's final landing site, estimated by CONSERT. Credits: ESA/Rosetta/Philae/CONSERT

Philae's final landing site, estimated by CONSERT. Credits: ESA/Rosetta/Philae/CONSERT

In addition to the on-going visual searches using OSIRIS and NAVCAM images, the CONSERT experiment is helping scientists to locate Philae’s final landing site.

CONSERT, or the Comet Nucleus Sounding Experiment by Radio wave Transmission, is an experiment that works between the Rosetta orbiter and the Philae lander. It works by transmitting radio signals from the orbiter to the lander, and when the geometry is right, the signals pass through the nucleus of the comet, allowing its interior to be analysed.

The signals are received on the lander, where some data is extracted, and then immediately a new signal is transmitted back to the orbiter, where the main experimental data collection occurs. As the radio waves pass through different parts of the cometary nucleus, variations in propagation time and amplitude occur, and these can be used to determine various properties of the internal material and carry out a form of ‘tomography’.

But CONSERT is also being used to help identify the location of the lander, in combination with work performed by ESOC Flight Dynamics, the Philae lander team, the ESA Rosetta Science Ground Segment, and the OSIRIS camera team.

Focus on CONSERT. Credits: ESA/ATG medialab

Focus on CONSERT. Credits: ESA/ATG medialab

By making measurements of the distance between Rosetta and Philae during the periods of direct visibility between orbiter and lander, as well as measurements made through the core, the team have been able to narrow down the search to the strip presented in the image shown above. The determination of the landing zone is dependent on the underlying comet shape model used, which is why there are two candidate regions marked.

Planned high-resolution imaging by OSIRIS will be used to study the CONSERT predicted area.

The CONSERT team also need to know where Philae is before they can fully analyse their scientific data.





  • This is good... let's find Philae!!!

  • Sean says:

    How precisely can you determine when Rosetta will be able to photograph candidate "Where's Philae?" areas? I imagine these times must fit in with the ongoing science mission but I wonder how well you can predict the photo opportunities in advance. Is there a timetable for when Can You See Our Lander images might be available?

  • When I was young the moon landings were all the craze. We were lucky to have black-and-white newspaper clips to hang on the walls. Now we can have comet rencontre multimedia and even watch whenever we like. The comet looks rather heart-shaped. What a PR stunt 😉

  • WJB says:

    Looks like Philae will be located soon!

    Is it known approximately how far this region is from the Agilkia site? Earlier guesses were about 1 km.

    I propose that this final landing site be named "Kingston Lacy". This name is quite fitting because the Philae Obelisk itself "bounced" far away from Egypt to land in the much-less-sunny country of England, at the Kingston Lacy estate of William John Bankes (discoverer of the important linguistic clue on the obelisk).

    I first proposed this location name (and the alternative of "Iteru") a few days ago in a more detailed comment at http://blogs.esa.int/rosetta/2014/11/04/hello-agilkia/ .

    • Marco says:

      You've got my vote. That's brilliant.

    • Jacob nielsen says:

      I think the irony in this will prevent the name from becoming official. But I like it. Philaes restingplace: Kingston Lacy 🙂

    • masanori says:

      I'm not a person who recommended Agilkia but I still prefer Agilkia. I think Agilkia is still valid as nobody seems to have not decided where is the edge of Agilkia. It happened to be so large!

    • LP says:

      Sorry, somebody had that idea first... 😉
      LP says:
      14/11/2014 at 00:15
      Maybe Kingston Lacy is adequate after all...

      but sure more people thought of that too, that is not important in this age.
      It is a somewhat ironic fate, but would also shows humour.

    • BG says:

      hmmm, not sure. Perhaps if 'aliens' find the Philae lander and decide to move it to their home, then that location could be called 'Kingston Lacy' 😉

    • John Palmer says:

      I agree. I submitted "Kingston Lacy" on 18oct2014. But then Agilkia won, Philae landed and bounced several times. Since then I have heard no mention of Agilkia on TV or radio. We need a simple, prounceable name to give to where Philae is hiding, when it is finally found. I suggest "KINGSTON" as short for Kingston Lacy. I wonder if Philae will be moved again by geysers as Philae approaches the sun?

    • André says:

      It has no relevance. It is just English self boasting.

  • Dave says:

    And so, are there any clues you can give to the interior of the comet?.
    The density has been a hot bed for discussion with very strong opposed views expressed.

    Also the debate about whats in the core?, some say water, some say water ice, some say porous ice, some rock all through and some have said dirty snowball all the way through.

    Any data from Consort, would give us a lot of fun as we argue the implications.

    Also surface analysis seem to be important to all of us.

    Any chance of something?

    • emily says:

      Hi Dave, when the instrument teams are ready to present the conclusions of their analyses, then we will be able to share it here on the blog, as we have been doing so far. (I'm also looking forward to the results of CONSERT and what the experiment can tell us about the comet interior!) -Emily

  • Elisabeth says:

    I'm still impressed from this beautiful mission. I hope you can get all the informations you want to. Good luck for your work and thank you.

  • logan says:

    Hi Jacob. An independent mind is a lot more valuable in science. Hanging from the cliff... 🙂

  • Jacob nielsen says:

    Who said the farthes rim of site B? 🙂 ...but on the outside!? I prefer the 'additional candidate' only because of a hunch and the crazy steep angle of impact on the blue strip ( as I see it, though a bit less steep than thought by those aspiring for the neck 😉 ) Now Osiris team, did you get a good shot during the Philea illumination window? Then case is closed, right?

    • Jacob nielsen says:

      A steep angle at impact makes it more difficult to explain the short duration to final impact, equivalent to some 20 m vertical drop at initial speed 0m/s, as the chance of additional bouncing around would be higher, although texture in Phile size-range has the final saying, seen apart from the actual fact...

    • Jacob nielsen says:

      Isn't the outside of the rim of site B way to dusty, smoot and 'crack-free' to hide Philae? I guess the radio data point to the blue strip, but I think in fact Kingston Lacy is in the often shaded, high and rugged part of site B crater rim. Can we get to play find Wally now?

  • logan says:

    It could be nice if CONSERT teams tell us a little about the 'super-structures' of 67P. Please 🙂

    • logan says:

      "...CONSERT team also need to know where Philae is before..." Ups! Sorry about that.

    • THOMAS says:

      I agree with you, Logan. It's the 64000 dollar question. (Except that I'm not talking about "super-structures" but about the totally basic internal structure of 67P).

      Why indeed is this essential CONSERT information which, once published, will immediately designate the "winner" between the vying "dirty snowball" and "solid rock" models, still not being disclosed?

    • Robin Sherman says:

      I agree Logan, but it appears no tomography will be forthcoming until Philae is found and the chances of us getting to see it very slim. Dates for your diary.



      Apparently it is possible to live stream free these events if you register. Unfortunately work prevents me from doing so, so can I ask, Emily, Claudia or Daniel if ESA can record the Rosetta/Philae based presentations for us? If that is not possible, given the materials would then be in the public domain, make the presentation media available via this blog or the ESA website.

      • logan says:

        Thanks a lot Robin. Doesn't seem too far. This issue is 'textbook rewriting'. So they will have to make it public. At least before the media timing is over and other missions take front stage 🙂

  • logan says:

    If 'rim' material then it's a totally new scenario. Hope Philae is not within a 'chimney'.

    • Marco says:

      I kind of suspect that Philae is in a vent of sorts- not yet active but indubitably so by the summer. It appears that the crevice that Philae is in extends lower beyond what could be imaged by Rolis. My calculation is that a vent would dislodge Philae from its position, but not with enough force to escape gravity - Philae may end up on its head, however as the flywheel would not have spinned it this time round to stabilise.

      • logan says:

        Agree, Marco. The site is too much dust free.

        • Jacob nielsen says:

          I believe it is dust free because it is on the inner rim that is shaded relative to rotation = no dust precipotation.

  • Wouldn't it be something if we found a probe from a neighboring solar system?

  • Charles Fecht says:

    If the comet is so close to the sun, then would it be possible to land another probe on it before it leaves the solar system? Perhaps one that could provide maintenance for philae, or small, roaming probes, or just something with a little more modern tech in it.

    And this may sound a bit like science fiction cliche, but since comets can travel so fast and travel to so many more places than humans can, maybe another technological planet with life on it has also attempted the same thing. So there could be a communicator for that kind of thing.

    Even if it's not possible, maybe we can catch the next comet. 😉

    But i'm sure you already discussed this kind of thing...

    • logan says:

      Hi Fecht. With actual tech we could be there on next visit. But would have to be a multi-national effort. Those techs are distributed.

    • JP says:

      A mission like you propose would be a totally new type of mission, never made before. So you should count 7-15 years for the mission definition, design, manufacture and testing at the very least.
      And add to it the launch and necessary orbital maneuvers to reach the right place at the right time, that is another 5-10 years.

      Lucky us, the comet is actually a periodic one, with a decent period, so it remains in the solar system 😉 We could plan for this for one of its next visits, every 6.5 years.

      To conclude, I guess that even if it's possible, we'd go somewhere else with a brand new suite of instruments instead.

      • logan says:

        Hi JP. Or it could be a 'swarm' mission, where the only highly planed part would be 'the bus'. If some 'bees' fail, doesn't mean mission has failed.

  • Ken says:

    Can someone on the CONSERT team answer why a large lobe solution is not possible? I very roughly superimposed the CONSERT swaths to the large lobe in this picture as an example http://s9.postimg.org/awhn18uqn/ESA_Rosetta_Philae_CONSERT_landingsiteestimate_l.jpg

    I think a location on the large lobe would match with the power profile from the reedit AMA yesterday ESA said "Panel two seems to be looking pretty directly at a nice comet afternoon and sunset" and the rotation period is "12.4043 hours and one illumination period is about 4.5 hours " which means 36% or 130.6 degrees has sun. This is consistent with early morning sun on a large lobe solution being shadowed by the small lobe and the sun rising 2.5-3 hours "later" vs the original landing site. Since the hypothetical large lobe landing area has a similar slope as the original landing it would be consistent with afternoon and evening sun on Panel 2 per the info given. I roughly annotated a picture showing the lander locations on the large lobe (between the green lines). This picture would be show late morning sun on a large lobe landing location http://s28.postimg.org/c0q0f3rod/Comet_on_12_September_a_rotated_130_degrees_illu.jpg
    With knowing the exact time of first sun on the panels a shadow line could be drawn on the large lobe and knowing the sunset time a maximum line could be drawn - this combined with CONSERT should narrow the region down very quickly for the large lobe solution possibility.

    • logan says:

      Hi Ken. Quite intriguing your work. It assumes Flight Dynamics is not so sure about the speed vector toward the Rosetta camera after impacting. If so then they should work in a radial coordinate system with z axis being Rosetta. Thanks a lot for taking the time to present alternative scenarios [with media work].

      • logan says:

        Let's think of this fantastic scenario:
        Close an eye. Boot a small rubber ball right between your shoe's toes and look as it nears your face. What could we see from Rosetta if after impact Philae had been shoot right at us? That's the vector to be gambled at various settings.

        • logan says:

          (With an algorithm at your computers, of course) 🙂

        • Robin Sherman says:

          Note to ESA. All future solar system solid body exploration missions must carry 3D imaging equipment, preferably from 3 imagers. Recent events only serve to emphasise this point, one you and others, made some time back Logan.

          • Bruce says:

            I'm personally amazed there is not a low powered radio transmitter with a long battery life (independent of the onboard rechargeable battery) that started transmitting once Philae was launched and continued for - say - 30 days. The bounce was quite forseeable.

            For instance, aircraft black-box batteries have a shelf-life of 6 years and last 30 days. EPIRB batteries have a shelf-life of 10 years or more - although only last 24 hours once activated. Surely a low-weight low-cost solution was available.

      • logan says:

        Do we have any Doppler data?

    • logan says:

      And CONSERT team surely is to small to try to 'attach' their preliminary tomography to every possible 'slice' of the 3D model with the corresponding surface photo. Want help? 🙂

    • Prof Harvey Rutt says:

      CONSERT will give line of sight data when Philae is in direct view of Rosetta. That does not depend on dielectric constant assumptions, and give a precision distance between the two. They now have an excellent shape model, and a demonstrated ability to know Rosetta's position relative to the comet wishing tens of metres.
      The. CONSERT a position and error area are likely to be correct. It could not conceivably be that far out.

    • Robin Sherman says:

      I think Ken, Emily's post implies that the flight dynamics team and the ground science team have applied similar logic to narrow the search field from the yellow diamond to the blue and green areas. The interruptions to telemetry and low cometary activity indicate to me, only the left half of the blue strip is a viable location. An OSIRIS image taken mid afternoon of this area should contain Philae, spotting her might be different, but she will be shiny white against the black surface if she is illuminated.

      • Jacob nielsen says:

        It is not sufficient to know "time of day". Line of sight has to be considered, as Philae is stuck in hole, and isn't that an unknown factor?

      • Ken says:

        Robin, I agree with your statement - however all the logic used to narrow the search grid from the initial CONSERT "diamond" shown the day after the landing seems to be predicated on landing on the same small lobe. If you applied all those criteria to a large lobe solution I think you would get a similar sized narrow search area on the large lobe. Engineers working in a small confined problem (I am one of them) can often fall prey to not thinking out-of-the-box, and this landing was definitely out-of-the-box! I just want to know if the CONSERT data could fit a large lobe solution.

        Some other reasons I think a large lobe solution should be entertained:
        1) The velocity change between the second and third touchdown was a much high percentage then the first bounce change. This suggests landing in a high percentage of dust which is consistent with large lobe candidate landing regions which have more dusty areas

        2) Given imprecise trajectory knowledge (all we in public have) it is extremely unlikely to end up just before falling off the small lobe. It would have had to bounce the second time just so and land right before the edge. Given a Monte Carlo family of trajectories - the majority would continue off the cliff so that is the most likely rather then ending on the hairy edge.

        3) Using the velocity change from the landing point to the OSIRUS snapshot gives solutions over the cliff - calculated by others in this blog and on the unmannedspaceflight blog. Without the OSIRUS shadow of that bounce data point we don't know for sure, but it sure looks like it was headed off the cliff and the gravity gradient of the edge of the cliff would have been pulling to the large lobe.

        4) reposting my other bog comment from the OSIRUS shots: A shot of the likely landing zone from another perspective that has the bounce trajectory in the plane of the picture and is well illuminated. I roughly drew 2 possible bounce / orbit ellipses (out of a large family above and below) and a possible 2nd bounce concept (red lines) to land at the middle/base of the large craters on the large lobe (just an example - I think eyeballing the CONSERT data indicates closer to the center - but the point is to show the concept absent real data) http://s28.postimg.org/57dnve0hp/Comet_on_19_September_2014_Nav_Cam_annotated2.jpg
        I think because the velocity was so high the lander was basically in orbit relative to the small lobe about the central CG point which is in edge of the large lobe. Philea just ran into the large lobe which got in the way of an otherwise nice orbit.

        5) The rock type in the large lobe landing zone craters has the vertical fractures and weird spires consistent with the large lobe landing zone pictures. I have found a few areas on the large lobe that look pretty good - a bounce in the dust and a final landing against rocks. Some can be seen in the distance towards the neck in the OSIRIS shots of the backup landing site.

        We'll just have to wait it out since we are fed so few factual crumbs - but is fun speculating none-the-less

        • Robin Sherman says:

          I have to say Ken after I saw the OSIRIs sequence of images and the direction of the bounce I posted that I thought Philae had bounced off the head lobe and fell down to the body lobe somewhere on the short end of the big lobe close to the neck. Basically using the same logic as you, however it would have taken a long time for Phiae to travel the extra distance to the lower lobe. At 0.38m/s an extra 1 to 1.5Km, maybe another hour.

          The big unknown here is the angle Philae left the first touchdown and thus the height of the bounce. ESA's estimate is 1Km so that would take around 100 minutes to go up and come down again on a level surface leaving about 10 minutes to fall further, the distance the blue area is below the level of the first landing point would seem to be plausible.

          Also we know at least two line of sight CONSERT measurements were taken which would give a pretty accurate measurement of the distance/height between Rosseta and Philae and was the basis for the original blue diamond. I understand a third line of sight measurement was taken just before Philae ran out of power so in theory that should have fixed the distance in all three dimensions, however, Rosetta's position in her orbit with respect to the comet is only known to an accuracy of 10s of metres so we get the error margin of the blue strip.

          Every guess or speculation is changed by the titbits of information we get, so when ESA tells us they have narrowed the search area, all previous speculation is invalid and we have to start again based on more up to date information.

          • Ken says:

            I googled the CONSERT details: "The CONSERT experiment involves a transmitter on the Rosetta orbiter and two perpendicular dipoles 90 degrees out of phase which are fed a coded (pseudo-noise, 255 x 100 nanosecond) radio signal and emit a 90 Mhz circularly polarized 25.5 microsecond duration pulse. The RF power of the transmission from the orbiter is 2 W. Repeated transmissions occur over about 200 milliseconds. The pulses propagate through the comet nucleus and are received by a transponder on the Rosetta lander, where they are digitized and compressed. After a known measured delay corresponding to the propogation of the signal through the strongest path, the lander transponder re-emits a new pulse at 0.2 W RF power, which travels back through the nucleus and is detected by a linear phase 86 to 94 MHz receiver on the orbiter. The time for one session is less than one second. Compilation of thousands of these sessions (~6000/orbit) will allow radio tomography of the interior of the nucleus and give information on electrical properties of the comet. The antenna and ground plane elements are made of aluminum rods with a carbon fiber mast. The antenna on the lander will consist of four metallic wire monopoles mounted so they will be within 40 cm of the surface of the comet to ensure good coupling with the ground."


            The orbiter will send a signal which will be picked up by the lander. As the orbiter moves along its orbit, the path between it and the lander will vary and so pass through differing parts of the comet. In addition, the rotation of the comet nucleus will also change the relative position of the lander and the orbiter. Hence, over several orbits, many different paths will have been obtained.


            The mean permittivity of the comet nucleus is derived from the group delay of the main path introduced when the comet is inserted into the propagation path. The permittivity enables to identify the electrical properties of the material found in the comet nucleus.

            The mean absorption of the comet nucleus is derived from the radiowave path loss as the signal propagates through the comet nucleus. The absorption identifies the class of materials found in the comet nucleus.

            The structure of the received signal, the number of different paths and their variation with the propagation path are related to the size of the cometesimals and to the reflection coefficient at internal interfaces.

            The correlation length of the measured signal as a function of the orbit position is related to the size of the irregularities or small structures inside the comet.

            The volume scattering coefficient is derived from the nature of the observed signal. The volume scattering coefficient measures the homogeneity of the interior of the comet nucleus.


            So as Rosetta has 3 orbits of CONSERT data - 2 from the first day and 1 on the last day. Each orbit is a cross-sectional slice of the comet. The signal is perturbed by the comet interior and large blocking rocks. Presumably they can identify baseline clear paths vs obstructed paths - however path reconstruction is predicated on knowing where the lander is. Its a chicken and an egg problem and thats why 2 or even more (given the adjacent rock signatures perhaps appearing as interior perturbations) solutions should be possible. The fact that the initial diamond and this release has such as different location means they are feeding in a flight dynamics solution to refine the swath positions - and thus it all is based on assumptions. Rerun the whole analysis with a large lobe initial assumption and see if the data can fit - I bet it can. Finally I don't see any evidence that a precise distance based on doppler is being calculated - it would need exact ultra stable oscillators synced on the orbit and lander and the precise timing delay of Philea's transponder calibrated with temperature - unlikely. I think it is just looking at frequency and polarization perturbation and path loss, on an unknown uncalibrated body signature - lots of unknowns here - hard to make a certain reconstruction absent other correlating data of which there is little.

            One last point I forgot to mention on the previous post on why the large lobe solution makes more sense - the likely angle of the second impact on the small lobe is shallow and the second bounce would be longer then if it hit almost at a 70-90 degree impact angle on the large lobe (see my illustration) - which would kill almost all it's velocity if it were in a dusty area which is consistent with the short second bounce really being short hop.

          • logan says:

            Hi Robin:
            "...Also we know at least two line of sight CONSERT measurements were taken which would give a pretty accurate measurement of the distance/height between Rosseta and Philae and was the basis for the original blue diamond"

            You are better informed than many of us. Thanks for that tip. 🙂

          • Robin Sherman says:

            Thanks Ken for the info on the CONSERT instrument. The point is that the signal does not have to be sent through the comet, a direct line of sight transmission can and has been used. The vacuum in between has known properties so no uncertainties and no assumptions are required. What your post does highlight is the reasons why the position of Philae is so important and how much detail it is hoped to reveal. I was under the impression it would give a fairly large scale "impression" of the interior structure, not so it appears. I am even more interested in the results from CONSERT now.

          • logan says:

            Hi Robin. Seems to be that 'line of sight' is deducted from 'cleanness' of transmission.

          • logan says:

            Void or 'line of sight' being those readings where all frequencies travels at same velocity. Non-void being those 'diffracted' readings.

          • logan says:

            Hi Robin. Sky at Night only available on UK. Will try to find somewhere else.

          • Bruce says:

            "I thought Philae had bounced off the head lobe and fell down to the body lobe somewhere on the short end of the big lobe close to the neck. "

            Hi Robin, I similarly thought Philae had bounced off the head onto the neck somewhere near the terminator between dark and light. I now realise the calculations of Philae's travel distance in the 9 minutes between the bounce and the final image (estimated at 200 metres) depend strongly on the perspective of the images from Rosetta. Knowing the location of Rosetta when it took the photos would be far more informative than knowing the height of the bounce, simply because we know how long the bounce lasted and we can estimate the gravity and trajectory from ballistic modelling.

        • Dictomail says:

          Ken, your statement "(1) The velocity change between the second and third touchdown was a much high percentage then the first bounce change" should read "(1) The velocity change between the second and third touchdown was a much higher percentage than the first bounce change". Grammar and language are very important in expressing scientific views. Mistakes can lead readers astray to unintended paths of reasoning.

        • logan says:

          Are those line of sight data bits angular or time-lapsed?

    • logan says:

      [Just saying that alternative frames are sometimes preferable, in order to generate input sets to feed your current frame].

      • logan says:

        According to Prof Harvey:
        "... and give a precision distance between the two". If correct we have at least 2 distances. They can be as near as 360º/6000, which doesn't seem too good for triangulation. Nowadays, if we have just a single distance vector from CONCERT, plus the probability map of of Flight Dynamics, the search area could not be that big.

    • logan says:

      Hi Ken. Is 'line of sight' an status bit or a vector?

      • Ken says:

        I guess you are asking relative to Rutt's post - it's the line from the orbiter to the lander if there are no obstructions in the way (e.g. comet, cliffs). Presumably the CONSERT data has a clean signature when the lander is in the direct line of sight and perturbed (path loss etc) when something is in the way. Thus knowing the geometry there are clear visibility chunks in each comet rotational swath. Rutt appears to think there is accurate ranging data - to have a confident absolute distance (enough to narrow to the smaller lobe)- but the orbiter is far enough out with enough uncertainties that I remain unconvinced, and am not sure it has ranging (didn't see it in the search I performed). This entire mission is trying to reverse engineer what happened with tiny shreds of data - quite frustrating actually!

    • Ken says:

      To help visualize my point I took a few screen snaps from the landing movie with rough line of sight from the first CONSERT pass and annotated large and small lobe solutions in the free space field of view - red is definitely in the field of view and orange circles - could have been in the field of view (would need exact data to confirm). http://s16.postimg.org/wfiydh7o5/CONSERT_line_of_site_example.jpg

      The point is a good chunk of the large lobe could fit the same free space CONSERT swathes and thus it is worth calculating a large lobe CONSERT solution

  • Mike Whittaker says:

    I hope the possibility of detecting a glint/flare from the Philae solar panels is considered even now when Rosetta is in a favourable location and the solar angle is correct.

  • Rob says:

    @Dave - those who imagine 67P as being composed of "rock all through" are wrong. The mean density of 67P is 0.4 g/cm^3, whereas most rocks are in the 2 to 3 g/cm^3 range, at least 5 times higher.

  • THOMAS says:

    The heart shape says it all. We all indeed love this mission but we would prefer some solid scientific information, please.

  • Jason Rowberg says:

    I have little doubt that if ESA would release NAC images of the area when Philae was in daylight, this crowd would find Philae within two hours.

  • Johan Prins says:

    The blog contains a lot of questions - I also have many - but we just seem to list them here and it looks like we're alone in a vacuum - no sound returns, no answers -

  • logan says:

    It is a very precise assertion. Best wishes for it. Kudos to you to you all 🙂

    • logan says:

      If you divide it in small quadrants and give search criteria then you have your 'reserve dogs' with us 🙂

  • Mark says:

    I knew it was a mistake not getting Philae to wear a red and white striped jumper!

  • Bruce says:

    This is great news BUT it does not seem consistent with this detailed analysis by Emily Lakdawalla of the Planetary Society:


    As shown on a previous blog (http://blogs.esa.int/rosetta/2014/11/17/osiris-spots-philae-drifting-across-the-comet/#comment-201741) Philae's ground track covered roughly 200 metres in 9 minutes in a direction down the left hand side of the crater in the picture, NOT across the crater. In the 1 hour 51 minutes of the first bounce Philae surely must have covered more than the 800-1000 metres to cross the crater and in a different direction.

    I accept there are issues of perspective as the images are taken from Rosetta, which may be moving relative to the surface of 67P, but not significantly according to this data:
    Plotted here:

    Can someone knowledgeable (i.e. from ESA) please explain where the errors are?


    • Bill says:

      Emily-L and the USF-mavens are simply wrong.


      • Bruce says:

        Hi Bill,

        I think Emily's images are correct as far as the ground track of Philae goes. I am confident the interpretation of the SPICE data on unmannedspaceflight.com is wrong. I can - at least mentally - reconcile Eily's ground track and the "estimated landing area" (above) by taking into account the comet's rotation and the perspective of a "relatively" stationary Rosetta. 67P would have rotated about 4.5 degrees in the 9 minutes between touchdown and the post-bounce image of Philae.

        For example using your image:
        If Rosetta's "ground position" were to the north and west of the landing site, after a substatial bounce and 4.5 degrees of rotation, Philae's ground position would appear further south and east than its true latitude and longitude realtive to 67P.

        ps. I enjoyed your SmugMug images.

  • Robin Sherman says:

    I have been trying to match up any previous images with the blue and green areas to see if there are any likely candidates. That is nooks or cliff ledges that might allow 1.5 hours of sunlight. Unfortunately apart from one long distance shot there are no images with a clear view below the landing site B crater rim. The best view I could find is this OSIRIS image from 50Km of the landing site.


    The fact that it is an OSIRIS image helps, because it can be zoomed a lot and still show good detail. At pixel 845 x 700, bottom right corner, there is a ledge surrounded by cliffs on three sides. The open side gives a view out into space. The side to the right of this is a thin plate of cryorock which looks not unlike the plate like sheet of material seen in the CHIVAS image partially lit by the light reflected from Philae. Below and in front of this are some cryorock boulders mostly hidden by shadow in this image. At the back of the ledge is a tall solid cliff, while to the left is a less steep cliff that would cast a shadow across the ledge when the sun is behind landing site B.

    This ledge and cliff are part of a strip of surface that is significantly darker in colour than the surrounding areas and appears to be covered in a thicker layer of dust. This, as seen in other areas indicates an area of minimal comet activity. Other indicated search areas have a lighter or very light appearance which suggests they are more active. The dust detector on Philae measured very little activity and the material around Philae does appear very dark, especially the cliff and what looks like the surface layer of dust.

    The September 2nd OSIRIS image was taken with the sun high above the head, just before midday, and this spot is still in shadow close to the cliff and would only be lit when the sun moved round to the west in the afternoon at which point the shadow from the overhanging crater rim to the west would become a factor, blocking the late evening sun and giving a sunset in the northwest. This position is south of the equator, but not by that much so the amount of sunlight can only increase as 67P's southern hemisphere moves into summer as it approaches the sun. Those with a better sense of direction and global positioning will surely correct me if I am wrong.

    If this is where Philae is hiding, it looks a good spot to be, sheltered from the sun in the heat of the day. The reflected heat from the dark surroundings may keep the temperature more even and at a higher average value.

    • JP says:

      I have read during the reddit AMA that the area is illuminated during several hours per period. Only the shadow of a rock (or cliff) limits the direct Sun exposure to the mere 1.5 hours (and given the very low soil reflectance, diffuse illumination of solar panels is as good as zero when not directly illuminated).
      The lander is not in a really dark place, just in a locally shaded one. The rock size needs only to be few meters across, so there are plenty of candidates...
      Assuming the blue shade is a good candidate, Philae landscape looks more like right in the middle of the wider blue area (using the same 50 km OSIRIS image you refer to).

      • Robin Sherman says:

        Hi JP. I agree we can rule out the green area as it would seem very difficult to explain the interruption in telemetry at the beginning and end of the communication window. Because the blue area is "below" the rim of the landing site B crater this would explain those interruptions. The shape model and image show the mountainous terrain of the crater rim varies in height allowing intermittent contact with Philae, if she was somewhere in the blue shaded area. As best I can judge the left, wider side of the blue area corresponds to the darker strip of surface referred to above. There are four or five possible spots that are shaded by a cliff in this area, but most don't show a possibility of interrupting telemetry.

        The reason I suggested the ledge I did was because it is within the left side of the blue area. It is exposed to sunlight for large parts of the day but only for a couple of hours in the afternoon would the sun reach the back of the ledge near the cliff matching Stephan's description of what light was available and that sunset could be seen from Philae's position.

        I also took into account the trajectory that Philae took after her first bounce. The right arm of the cross in the OSIRIS image is almost a direct line of the path Philae took as shown in the NAVCAM image where she was first seen. Follow this line and the dark strip of surface, and the left, fatter part of the blue area is where you end up. Much conjecture was aired here about whether Philae would follow a straight line, or would the comet move under her creating a curved trajectory. Simply put, because Philae did not reach escape velocity she was still gravitationally bound to the surface of the comet and her initial vector would largely determine her flight direction. Height and distance travelled would be affected by the changing gravity field she experienced. I note the new shaded areas also match up very well with this flight path unlike the position of the original blue diamond shown. In this image that diamond, in yellow, has moved.

        The other crucial factor to be considered is one of the CIVAS images was a direct view of space. This requires a position raised above the surrounding terrain or Philae to be on a steep incline. The answer from the AMA session was that she was pretty upright, the top solar panel being exposed to an even intensity of light. Therefore I reasoned a ledge on a cliff face would be a good possibility. A ledge to the right side of the blue area would have more chance of the lower lobe appearing in the picture.

        There are a few other possibilities visible, but they each, in my opinion, fail on one of the criteria, activity, aspect, lighting or telemetry. Its my best guess, is most likely wrong, but its something we have the chance to speculate upon and I await the final resting place discovery with great interest like everyone else.

    • Without further information from the Rosetta team, we cannot with certainty say how far Philae travelled during its two bounces. However, given the horizontal speed reported for Philae as 0.5 m/s, and assuming that the comet is rotating at about 0.35 m/s on the surface of the smaller lobe, and that both speeds are in the easterly direction, it is safe to assume that the net speed of Philae over the comet's surface would be 0.15 m/s. At this speed, it would indeed have arrived about 1 km from its first touchdown site, after the final landing #3.

      The sharp change in Philae's direction after the first touchdown could have been due to momentum imparted by the surface, which is constantly under rotation. Furthermore, Philae had a horizontal speed of its own relative to the comet surface during the initial descent, as seen by its advance during the last minutes captured by OSIRIS.

      @Robin Sherman, I agree with your placement of Philae in the lower right of the Sept. 2 photo. It's highly probable.

  • Andre says:

    Wow! Seems like Philae almost escaped from the comet... The strip is located at the duck's head edge?

    • Bruce says:

      Andre - There was very little chance of Philae escaping the comet. It touched down at close to the escape velocity - about 1 m/s - to escape would reuire it to gain energy after the impact. Imapcts are usually inelastic. One estimate is the bouce velocity was aboiut 0.34 m/s - onbe third of the imact velocity and much less than the escape velocity.

  • Prof Harvey Rutt says:

    It makes little sense to release data until they have Philae's location and reprocess using that. That's the way it was meant to be used.
    It would be interesting to know what dielectric constant model was used in locating Philae, and what the estimated error bars are on the dielectric constant. Though at 90MHz ice and rock are not so different as they are at lower frequencies. I would assume location data is mainly based on direct 'in vacuum' signals though, so it may not be too sensitive to that.
    Although it works in a different way, Philae uses a scheme a little bit like DME, distance measuring equipment, ( often paired with a VOR) used in aircraft (I'm an amateur pilot), there are good descriptions of that on the web.

  • John Broughton says:

    Why can't the imaging of the candidate landing sites in December be done from closer range?

    Presumably the circular 20km orbit was chosen for having the right period to allow repeated passes over the landing site under favourable lighting conditions. Instead of a 20km circular orbit, why not an elliptical one with periapsis aligned with the small lobe and the same period of revolution, e.g. 35km x 5km from centre.

    From that orbit, Rosetta would pass as close as 3km and its 5cm-resolution images will clearly show the state of the lander and its local circumstances, especially if stereographic images are obtained.

    Such an orbit can be achieved safely if the burns are done at apapsis in a two-step process on succeeding orbits. Any localised gravitational variations affecting Rosetta at periapsis only affects the distance of the following apapsis, so there's no immediate danger of a collision with the comet. The payoff far outweighs the small amount of risk involved.

    • Robin Sherman says:

      HI John. I think they are more concerned about the increasing activity of the comet, the affect that has on Rosetta's orbit and the risk of being hit by debris, than crashing into the comet.

  • philae is a glorious experiment

  • Shawn says:

    I've been following the mission closely, and I have a question. All the news says maybe the probe will get stronger sunlight in a year. Is it possible that the small amount of daily sunlight the lander is getting could slowly recharge its battery before then, like plugging in a drained iPod for 10 minutes at a time?


    • JP says:

      if I understood well, this is possible, only if the battery temperature is high enough (I've read >0°C). Below, it will simply not recharge, ~whatever the illumination.

      • Tom C says:

        Yes, that is what I understand as well. It requires a certain number of hours of direct sunlight to warm the batteries to 0C before they can begin to charge. It would be nice if ESA would disclose that required warming time, as many people are confused by this.

      • Robin Sherman says:

        That is right JP, but the power from the solar panels must first be used to heat the battery and presumably some of the other control electronics. Thus a minimum amount of power is first required to heat the battery, about 60W I think was quoted, and anything over that can then be used to charge the batteries. Philae is getting some power from the solar panels and it is hoped that this will be enough to maintain minimum heating for the electronics and stop the battery from freezing.

    • Engywuck says:

      the battery needs to be at 0°C to be charged, so only when the local temperature gets that high - which would mean other problems.

  • the lander is reported by instrumentation to have had a specific inertially derived velocity after touchdown. How Ever photographic measurement suggest Philae had only 10 cm sec-1 . it traveled less. landed closer. . I can demonstrate..

  • Donald says:

    Given that a possibility of a bounce was anticipated I am surprised that CONSERT does not have a program to specifically locate Philae; or are we just waiting for Rosetta to come back round to the right side of the comet?

  • Dave says:

    Hi Rob
    I appreciate that solid rock would make the density wrong but so would solid ice or even a water filled solid rock crust as one person has suggested and backed up with scientific papers.
    Right at the beginning we also found out that the density did not match the fluffy snow ball made in near zero gravity model either. It was one of the first surprises, the forecast density was wrong!
    Clearly there are problems with all those models or with the way the estimates of gravity have been calculated.
    I was really making the point that there is some critical data we need to make a decision of what the comet is. Hence we need to see the inner structure, and some descent data about what the surface is.
    Hopefully this data could help produce a convergence of thinking.
    Not sure it will though there is so much faith in many people's ideas.

  • Dave says:

    Sorry gravity should of been density

  • masanori says:

    Let's calm down a little bit.

    Science needs (long) time, doesn't it. ESA need time, too, don't they. Sooner or latrer, or very later, we will see what we want to see I suspect. Let's not want to get immediately what we want!

  • Chris says:


    I have a suggestion to make that may bring philae back online. a long shot that may actually be impossible. But nevertheless if it hasnt been considered it aught to be.

    Where can I find a "suggestion box" or some way of proposing my idea?

  • John Broughton says:

    Hi Robin. I'd be surprised if the comet is releasing anything more substantial than microscopic dust particles at present. Their relative velocity would actually be higher at 20km than at close range, due to acceleration imparted by the solar wind.

    As a compromise, once the lander has been spotted from the planned orbit, Rosetta could then image it from low altitude and make a quick retreat.

    • logan says:

      Sound adventurous. Like the idea, but not quite sure of the scientific of engineering profit of such a near close-up.

    • Robin Sherman says:

      Hi John. Firstly I agree with the second part of your post, the exact orientation of Philae in her current position is critical to the interpretation of several instruments' data. It would require some sort of closer flyby than presently planned to determine this orientation properly.

      The first assumption is not so. Particles of quite large size, of the order of centimetres, can be seen in all the comet images we have seen in the past couple of weeks. True they are likely to be fluffy, icy, snowflake type objects, but if one hits the lens of OSIRIS or the NAVCAM, the rest of the Rosetta mission is potentially completely ruined. This opinion of danger to the Rosetta orbiter is not mine, but Andrea Accomazzo's, the flight director of the mission.

      Personally I think, while cometary activity is still relatively low, and if OSIRIS images from 30Km can not define Philae's position accurately enough, such a one off elliptical transfer orbit when the planned move from the current 30Km orbit back to 20Km takes place, makes a great deal of sense. How practical that is, I don't know, but I am sure it is a solution that the flight control team could calculate and carry out.

    • Kamal Lodaya says:

      John: Interesting idea. Once we see a real big jet open up, perhaps viewing it from nearer but relatively safely might be rewarding.My guess is viewing Philae from closer may give good headlines but not yield that much data.

  • Lucas says:

    That is great! If they find Philae, will they be able to move it a sunnier region?

    • logan says:

      Hi Lucas. Quite probably Philae will wake up by himself in the sprint. The hurry to locate him is about giving precision to an extremely important experiment performed on-board: CONCERT. CONCERT will give to us kind of a 'tomography' of 67P comet.

  • Chris says:

    I can't help think that one of the great leaning outcomes of this mission is that a second micro satellite should be included in any future lander mission. The purpose of an additional micro sat would be purely to provide triangulation of signals between the main orbiter and lander to provide for an accurate location of the lander relative to the orbital satellites. The second micro satellite need only to be the size of a mobile phone to achieve this. There would also be accuracy and redundancy benefits from deploying a small network of micro sats... Given the advances in technology since Rosetta was built I'd imagine all this could be included still within a smaller payload of a similar mission if it were launched today.

    • Baznr says:

      It would be enough a flashing powerled...

      • logan says:

        Four. Legs and head. Specific to a certain filter on Rosetta 🙂

      • logan says:

        And what about those supermarket radio tags? or those used by satellite localization services? 🙂

        • Cantalloube says:

          Consert instrument aboard Philae is some sort of an active (I mean powered & amplified) high performance radio tag... 😉

          A second satellte is not necessary, as long as orbiter ranges the "tag" from different viewpoint with velocity vectors not aligned...

          A given range and Doppler rate means that the "tag" is on a circle in space (the center of which is along the orbiter velocity vector, and circle plane orthogonal to velocity vector).

          If you have 2 measures of range and Doppler rate at different times, and the orbiter velocity vector changed significantly, you have a second circle and you have triangulated your tag...

          If you make your calculations in a nucleus-fixed coordinate system, the orbiter velocity vector changes a lot due to the combination of nucleus rotation and orbiter rotation along its orbit.

          It a matter of hours to have high accuracy triangulation...

          ...high accuracy at the radar wavelength scale of course 😉

    • logan says:


  • sandel says:

    that landing site is hidden from most pictures :/

    ma e a few superimposed landing area and comet instances


  • Thor says:

    Although you and I already know the core is rock, it'll be interesting to watch how 'mainstream theorists' try to squirm out of their dirty snowball stories without actually admitting they were wrong this whole time.

    • Robin Sherman says:

      What is more interesting is the number of conspiracy theories, rubbishing of actual measurements and outright refusal to accept the views and theories of highly experienced and qualified professional scientists in order to maintain an incoherent and ubsubntaniated theory of an Electric Universe.

    • Sovereign Slave says:

      Perhaps so, Thor, but by the same token I’m quite happy they’re there doing the science they are, which has been a remarkable achievement. Got to keep in mind that much of the debate is comparing apples to oranges in many minds. I mean, literally pretty much everyone living today has been told from early elementary school through college and afterwards that the standard model theory is fact. It is supported by our educational systems, research institutions, public funding, popular culture, science fiction, movies, TV and radio shows, books, magazines, on and on. The reality is that EU theory simply does not fit in or even compute within that framework, and is so radically different that it would actually replace standard model theory and its vast culture. You can’t expect a tiger to change its stripes, and I certainly don’t expect any of the ESA scientists to suddenly come out and confirm EU theory for this and many other reasons. The foremost is that it would be presumptuous because they simply don’t have the background or education in the electrical field or EU theory to do so. They know what they know, but EU theory is certainly not a part of what they know. So, whatever puzzles they run across will be contained and explained within what they do know, which is the framework and tenants of standard model theory. Yes, some things may be difficult to explain, and surprises may abound, but that just means tweaking the theory they have, not abandoning it completely in preference to something they have no background or orientation in. Also, endorsing something like EU theory would create huge upheaval and backlash within the scientific community. It would be akin to whistleblowing, and would be treated as such. I can think of no faster way to ruin a science career than to declare standard theory wrong and EU theory right (although wearing a girl shirt is apparently a close second, as totally ridiculous as that is). Also there are HUGE financial considerations that its hard to just walk away from. My background is in marketing and advertising, and truth be told, the standard model theory industry is a huge marketing success, to the tune of multi multi billions of dollars (and Euro’s) a year. It’s exotic, it’s dynamic, it’s mysterious, its imaginative, and there’s always some new improved latest theory to get people excited about. In a word, it plays incredibly well to a crowd. Financially, EU is comparatively just a bunch of rag tag beggars with little better than a Commodore computer and a vision. Scientifically they have no place in the mainstream financial structure, which after all is what determines who and what gets funded, who and what gets recognition, what gets presented by whom, and what gets published by whom (ultimately, what gets believed or not). So, while it is frustrating that EU theory doesn’t get financial backing by the PTB, it’s great that there are dedicated and highly intelligent scientists doing projects like Rosetta and that they are sharing information that we can pick at. I also appreciate the fact that they are gracious enough to have their interpretations openly challenged in this blog. And who knows, perhaps standard model theory IS right, though it seems as much nonsense to me as EU theory seems to them.

  • Guy Haworth says:

    It will be interesting to see how accurate the remarkable http://www.youtube.com/watch?v=WF3anN_A1mw&feature=youtu.be is.

    On balance, I think the mission got lucky on the landing - but it was luck that was thoroughly deserved.

    I look forward to the paper on the accuracy of the first touchdown - a brilliant feat of navigation that should not be overlooked.


    • logan says:

      Agree. Kudos and Kudos to Flight Dynamics. There are other Teams directly involved on the landing. Would like to know them 🙂

  • John Broughton says:

    Hi Robin,

    The spots seen in NAVCAM images may simply be a combination of background stars, cosmic ray artifacts and hot pixels, rather than bits of the comet. If that's what some of them are, ESA is yet to point that out and release a sequence of images showing them drifting through space.

  • logan says:

    Michael Koch has been so nice to update his 3D trajectory model according to different arguments. Looks good to me. And present a 3rd CONCERT border scenario.


    • Robin Sherman says:

      Certainly the first 3 plots were my first interpretation. Unfortunately there is a fundamental error in Michael's calculations. The comet does not rotate about the length of the comet, it rotates end to end. The axis of rotation runs north south through the neck region inclined at 26 degrees from the vertical with respect to the orbital plane, incidentally only 3 degrees different from the Earth, hence the seasons on 67P.

      The rotation of the comet will act to reduce the easterly vector of Philae, the amount depending on the height and the resulting reduction in how much Philae was still bound to the surface by gravity, and hence the slightly more southerly, shorter trajectory to the blue shaded area would seem correct.

  • logan says:

    How much trustful is the inertial data once the inertial wheel is off?

  • Joe says:

    It would be interesting to see a composite image processed to highlight all the areas that get daylight for 1.5hours in the same phase as the lander did and darken any areas with the wrong amount/phase of light. With the right source images and the right processing this should be possible.

  • Patrick says:

    How about launching a huge thin mirror and reflect sunlight to Philiae to charge its batteries? Would that technological speaking be possible?

  • Luis Gonzalez says:

    Just had a thought. Once we find the actual location of the lander, is there any possibility we could position the orbiter and orient the solar panels on it to reflect some sunlight onto the solar panels on the lander?

  • logan says:

    Just made a quick look at Rosetta lander user manual. Huge the engineering task.Have said in the past that We have to look at the age at which Philae was designed. Another thing is to look directly at it.
    Used to think of Philae as a drone. No, wrong. It's a lightly programmable automata. Great part of security, energy and heat management is literally hard-wired.
    Kudos to all Engineering Teams.

  • Cantalloube says:

    I am a bit surprised by the low accuracy of the CONCERT localisation.
    To what I understood, CONCERT is a radar on the orbiter and an active transponder on the lander. Hence the task of locating Philae is equivalent to locate a transponder. On Earth at low range, when the radar fly on a linear trajectory, synthetic imaging alow to retrieve only two position parameters hence the position depends on the terrain altitude.

    But this is definitely NOT the case when the trajectory is
    not linear. If I assume that the orbiter trajectory is not exactly on the equatorial plane, the direct path signal (which is certainly the much stronger component of the signal recieved) can only be focused at a single position in 3D nucleus coordinate (in the purely equatorial orbit case there is ambiguity between two points one on each "hemisphere"). Since CONCERT was on also during the visibility phase, we can use only signal from open space propagation (which do not require assuming anything on the propagation through the nucleus).

    Normally, the localisation thus obtained would not be dependent on 3D model of the nucleous (and in fact would produce one very accurate "ground control point" on further 3D models).

    If it is what lead the CONCERT team to suggest the second and smalled ellipse labelled "additional candidate assuming shape model deviation" it should be instead labelled "Philae is here, (and we thus know the altitude of that point with an higher accuracy than previously estimated from OSIRIS mapping)"

    (If you did'nt guess, I am a radarits 😆 )

    Can't wait for radar images of the inner nucleus...

    • Jacob Nielsen says:

      "Can't wait for radar images of the inner nucleus..." - but you will have to! I absolutely do not follow your explanation, but you still sound competent to me somehow 😉 . I judge Philea to be in the "Philea is here" spot mainly because the terrain etc. fits perfectly + it's dust-free, which is what will be maintained by the comets rotation in this location. Please stay with us Cantalloube.

      • Sovereign Slave says:


        Philae is no longer on P67, its on P68. That's why we can't find it. According to my theory of white matter proposed in an earlier blog (where orbital diameters of atomic elements are expanded due to cataclysmic interstellar forces, creating white matter as opposed to black hole type matter), much of P67 is composed of this white matter, which explains its low density. After Philae's battery died, it no doubt got assimilated by the white matter that P67 is composed of ( and yes, though little Philae no doubt put up a brave struggle, resistance was futile). When normal matter is assimilated by white matter, it creates a mini singularity, essentially an inter-dimensional space time phase shifting stringy white energy worm hole that Philae slipped through to the next alternative comet, which is P68. Only hope is to grab a small black hole to suck it back into our own dimension.

        • Jacob nielsen says:

          ? Ok, so you don't like the idea of dark matter or 'space-time curvature'. Or maybe anything else that is practicaly irrelevant to everyday human life? But I don't see the link to my post? I know the basics of radar localisation by transmission and echo, but not enough to operate a flight control. Should I then doubt the concept of microwaves? Or the highly sophisticated use of them?

          • Sovereign Slave says:

            Hi Jacob, your right, my post should have been at bottom, my choice was based strictly on yours being related to where Philae might be, and my tongue in cheek reply to that. So my apology, poor form indeed.

            While I know I am guilting of enjoying poking irreverent fun at the standard model, it struck me that your reply said why better than I ever have. It's because it IS so "irrelevant to everyday human life," which to me totally disqualifies it from the realm of science, yet so much of the science is presented through the filter of standard model mythology.

            I think much of the problem is that the field seems fixated on answering huge origin questions, like what are the origins of the universe, and our solar systems, which are way way beyond the scope of the scientific method. But standard model theory has created purely hypothetical models based almost exclusively on imagination, assumed and presented them as true, and then works those assumptions backwards to explain the details of what we observe in the universe. For instance, as has been pointed out before, no one has ever directly observed the Oort belt, it is just assumed to be there based on a whole string of other assumptions that have never been subjected to any scientific method. Yet the Oort belt is presented as fact, and then we have the next layer of assumption that P67 is from the Oort belt, with the next layer of assumption being that we now basically know its composition since it is from the Oort Cloud, on and on. Anyway, I know I'm now ranting, but I do believe that if the astronomy related fields took the completely honest approach of simply listing in a document what they have actually scientifically proven or strictly observed in space without bias, that document would be very very short, probably less than a page. The rest is pure speculation that I honestly believe does not serve the best interests or advancements of the field.

          • Jacob Nielsen says:

            the "problem" here is in fact that science is in such a late state of development, that the missing bits of the puzzle can be considered either only few - or the edges of the puzzle have never been found, and so it may be infinitly bigger. The focus on those tiniest fractions of the beginning of time in big bang theory may be of more value to the mathematically inclined than to (anyone else) Still I believe it is important to keep modelling, to prove ror disprove the coherence of existing theories, and to produce working models to be able to expand the knowledge of the physical world a little bit further. What Bohr & Einstein (et.al.) did 100 years ago can be percieved as utterly irrelevant to most, yet it led to nuclear bombs and GPS and more wonderful inventions.

            When discovering something far away from the human sphere (be it tiny, tiny or far, far away or way, way back) sometimes it must me treated as a "black box" that produces a set of features. Later the black box may open and while those previously found features still hold true, the view on the contents may change, and lead to new theories and the discovery of new black boxes.

          • Sovereign Slave says:

            No reply button to your latest 28/11/2014 09:31 entry below, so am replying here. All good points, and I agree by and large. Modeling is of course a necessary step toward scientific progress. However, as you point out, models and theories should only be maintained until either proven or disproven. But much of standard model is impossible to prove or disprove, and so stays comfortably out of reach of real scientific scrutiny while at the same time propagating to the point of being incredibly bloated with ad hoc, contradictory, and even ridiculous speculation. And then other things like using red shift to gauge distance have been completely disproven, yet this is ignored while it remains in the model and continues even to this day to be used to support other theories and models. The electric universe is also a working model explaining much of what we see in the universe. I've been reading their daily articles at http://www.thunderbolts.info for years, and what they present is extremely compelling. It doesn't violate common sense or things that are found in everyday life, but is based on proven, known phenomena that are then being extended as possible explanations to phenomena in space.

  • André says:

    It is about the same as finding a dropped black small screw on a gray black-dotted carpet. All viewing through a long thin tube which is yanked away 90% of the time.
    One would need a shimmer of coïncidental light which would reflect from a bare part of the screw.

    Maybe post before and after photos online. Have these sliced in parts and let people volunteer to analyse segments. Let them vote and/or mark changed spots. See what comes up from that.

  • deezee says:

    What if the lander took a bizzare hop and missed
    the edge of the lobe entirely? Would it then land
    at this oddly illuminated location seen in the lower
    right image of Nov.20th NAVCAM montage
    provided on an ESA blog?

    zoomed and captioned image at;


  • amieres says:

    So I calculated Philae's first bounce using variable acceleration depending on distance to center of mass The resulting elevation for the second touchdown is -139. That means a point 139 meters closer to the center of mass than the initial landing. That indicates it fell of the cliff but not completely.
    This is based on an initial speed of 38 cm/s.


    With other speeds the landing elevation varies a lot:
    36 cm/s => -397 mts
    37 cm/s => -266 mts
    38 cm/s => -139 mts
    39 cm/s => -16 mts
    40 cm/s => 103 mts

    As you can see it is very sensitive to the initial speed.

    Assumptions used:
    P67 Mass = 1e13
    1st Landing Radius = 2000 mts
    Total bounce time = 6660 seconds

    Data points calculated ~32000

    This trajectory still is a good approximation:

    • frankuitaalst says:

      Good approach Amieres . I think you calculate acceleration in the vertiical (h) direction . Is it possible also to take into account the "horizontal ' acceleration , while the spaccraft should also gain speed as it moves towards the center , Such as :

      ah = GM* (h/r) / r²
      ax = GM* (x/r) / r²
      r² =sqrt ( x^2+h^2) , h= distance to center

    • Ken says:

      I like your methodology. A few considerations - It seems like a simple mass model of 2 spheres for the 2 lobes would be more accurate and probably have the impact point further up towards the large lobe - as the neck has a very low downward gravity component - I think once it went over the cliff - the large lobe would begin to accelerate it towards it and dominate the field.

      Also I think your picture has the trajectory off by a little bit. I found a image that may be closer to the plane of travel. http://s27.postimg.org/cjasor4s3/Comet_on_12_September_landing_site_annotated.jpg

      I annotated the landing site and the OSIRIUS image point (I have no idea how high up the lander was at that point - but in the large lobe scenario it would have had mostly a tangential component so I drew it that way)(also it is interesting to see in this picture how different the terrain looks from the overhead view - the purple circles are correct I'm sure). My trajectory lines are just ellipses and so aren't accurate - however they show families of impacts regions - which are roughly in the purple zone which would be bounded by the small lobe shadow as the feasibility region (per the lander team power information given). I also have plotted a lower red line that traces a shadow I saw on the OSIRUS image right after landing that I think is real - so that approximate trajectory is shown as well as a ground track possibility.

  • Ben Stone says:

    No one can deny the success of the Rosetta Spacecraft; it has performed every task to perfection. The imagery captured of the comet G67’s surface is unsurpassed. ESA should be excessively proud of Rosetta’s performance as well as its great contribution to the global knowledge of the Comet Astronomy.
    With this said, I think the ESA has been overly self-congratulatory in regards to the performance of the Philae Lander. I realize this was not done as an act of dishonesty; rather it was a very human reaction by persons that are emotionally connected to the Philae Lander Project. In such situations objectivity has little chance of functioning. Early on one ESA quote proclaimed “…the [Philae] lander achieved the first-ever controlled touchdown on a comet nucleus.”, but the facts were that the lander suffered two major failures to its surface landing system. The first happening before the lander was even released from Rosetta, the cold gas jet thrusters that fire upon contact with the comet’s surface to help secure the lander failed to prime and start-up. This left only the Harpoon system to secure the lander, and then once this had failed to operate as well, there was nothing left to keep Philae in-place where it had touched down, rather away it went on an uncontrolled two and half hour bounce across the comet’s surface. At the exact moment when the Control Center members were ecstatically celebrating the success of their lander’s “controlled touchdown”, Philae was in the midst of its now famous double-bounce maneuver that resembled more of a “crash” and less of the publicized “controlled” landing.
    ESA defined the Philae Probe’s mission very specifically as the following : …1.) to land successfully on the surface of the comet, 2.) attach itself, and 3.) transmit data from the surface about the comet's composition. You can argue the “success” of the landing in both directions, but #2 of the mission list was a definite failure. Now due to the lander’s “lack of attachment”, many of the scientific tests that were planned for determining the comet’s composition are now in jeopardy. To make matters worse Philae came to rest at the base of a rock shelf in the shade of a cliff. Now Philae’s exposure to the Sun has been significantly reduced along with its ability to recharge its batteries from its solar cells. At the moment the lander continues to be in a state of “Hibernation”, which is an up-beat way of saying “Shut-Down”. Regardless, in this present in-active state Philae is unable to perform the battery of tests that were intended to help determine what the comet’s composition actually is. So much for mission goal 3.).

    • André says:

      As someone local here put it: your kind are complaining about a second division soccerteam playing Reàl Madrid in Bernabéu stadium, winning by 7-0 but missing the 8-0 due to a showlace gone untied.

  • deezee says:

    Thanks Ken,, We might rule out that location entirely since visibility of jets one the neck -like seen in the panorama- may not be possible. ...
    The sight suggested at the edge of the intended lobe [ https://imgur.com/a/jbQuD ] might have that visibility, but notice that the base of the jet is visible,,, that seems to require bleacher seating..

    • logan says:

      Well as seen in nov20 mosaic, there are more than the neck's jets.

  • frankuitaalst says:

    I wonder if somewhere ESA released an x,y,z - coordinate system in which the landing site is indicated ? Would also be nice to have the rotation axis indicated in this picure ,. If ESA would also release the postion of Rosetta at the time the descend picture was taken , and indicate in which direction Philae flew away ( vx,vy,vz) then we could run a two body ( being the comet ) simulation to get an idea where Philae might have landed the second time . Perhaps somebody already did this ?

  • Francesco Scarinci says:

    Please, leave us a picture of the comet's place where Philae is lying.
    Is it possible a battery recharge when nearer to the Sun?

  • oliezekat says:

    Où suis je, et dans quel état j'erre, cette éternelle question ^^

    On plaisante, mais c'est fascinant la manière dont vous essayez de reconstituer ce qui s'est passé.

  • masanori says:

    Interesting interview with CONSERT team members on this subject, posted on 2nd Dec on CNES site


    telling how they came to the graphic in this ESA blog from the graphic which was first presented in the press conference on 13rd Nov. Good job CONSERT team!!

    Another intetesting point to me is that it seems even in CONSERT team Philae is treated as a boy!

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