Green light for landing site J!

ESA has given the green light for its Rosetta mission to deliver its lander, Philae, to the primary site on 67P/Churyumov–Gerasimenko on 12 November.  [Read the full ESA Press Release here.]

The decision that the mission is ‘Go’ for Site J also confirms the timeline of events leading up to the landing. The animation below highlights some of the key manoeuvres before, during and after the landing (we'll provide a separate blog entry with more details about these manoeuvres at a later date).

A series of Go/No-Go decisions must be taken before separation, starting on 11 November with a confirmation from the flight dynamics team that Rosetta is on the right trajectory ahead of lander delivery. Further Go/No-Go decisions will be made during the night of 11–12 November concerning readiness and uplink of commands, culminating in confirmation of the lander readiness for separation.

Close-up of the region containing Philae’s primary landing site J. The mosaic comprises two images taken by Rosetta’s OSIRIS narrow-angle camera on 14 September 2014 from a distance of about 30 km. The image scale is 0.5 m/pixel and the image covers about 1 km square. The circle is centred on the landing site and is approximately 500 m in diameter. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Close-up of the region containing Philae’s primary landing site J. The mosaic comprises two images taken by Rosetta’s OSIRIS narrow-angle camera on 14 September 2014 from a distance of about 30 km. The image scale is 0.5 m/pixel and the image covers about 1 km square. The circle is centred on the landing site and is approximately 500 m in radius.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

A short manoeuvre must then take place around two hours before separation. This will set Rosetta on course to release Philae on the right trajectory to land on the comet. The final critical Go/No-Go for separation occurs shortly after this manoeuvre. After the release of Philae, Rosetta will manoeuvre away from the comet, before reorienting itself in order to establish communications with Philae.

As reported previously, separation will occur at 08:35 GMT/09:35 CET at a distance of approximately 22.5 km from the centre of the comet. Landing will be about seven hours later at around 15:30 GMT/16:30 CET. With a one-way signal travel time between Rosetta and Earth on 12 November of 28 minutes 20 seconds, that means that confirmation of separation will arrive on Earth ground stations at 09:03 GMT/10:03 CET and of touchdown at around 16:00 GMT/17:00 CET.

During the seven-hour descent, Philae will take images and conduct science experiments, sampling the environment close to the comet. It will take a ‘farewell’ image of the Rosetta orbiter shortly after separation, along with a number of images as it approaches the comet surface. It is expected that the first images from this sequence will be received on Earth several hours after separation. Once safely on the surface, Philae will take a panorama of its surroundings. Again, this is expected back on Earth several hours later.

Read more in the ESA Press Release: ESA confirms the primary landing site for Rosetta

 

Comments

45 Comments

  • Comeatstalker says:

    Very challenging and i guess this Stuka-Bomber missions target area is about the circle with a 3 sigma accuracy distribution. It has a lot of choices to land, lets hope it will be fruitful.

  • Martin Schäfer says:

    This starts to get very exiting!!

    I'm wondering, how Philae will be stable whilst declining to the comet. How do the technique guarantee, that Philae will land on it's feet? As I see, there are no thrusters to hold the inclination angle.

    • Comeatstalker says:

      Gyriscopic

    • Robin Sherman says:

      Hi Martin. Philae is stabilised by gyros during descent so that her feet are always pointing straight down. I believe this system will also be used if she lands on a slight slope to level the main body.

  • Bill says:

    What a pleasant surprise this morning-- a mosaic of OSIRIS images of the landing site. And, for us techno-geeks, an unannotated version. What an amazing little world-- there are new details seen right down to the limits of resolution in every new set of images.

    --Bill

    • Robin Sherman says:

      Huge thanks to the ESA team for this OSIRIS image of the landing site. AS Bill says an utterly amazing place. I've just spent 3 hours zooming and scanning all over the image. My computer screen is a 40 inch HDTV and it is staggering the amount of detail it is possible to see.

      We are going to have a field day picking out all the oddities, possible vents, craters, etc. The number of skulls and faces that leap out at you, is enough to keep you occupied for a long time.

      Apart from the area around the centre of the landing zone, I found the right side of the image most interesting. There are just too many things of note to point out here, everyone can have their own fun looking through them. Advice from anyone who knows about lava flows, lava tubes and vent holes would be appreciated, mud volcanoes as well. Someone earlier thought they could see them in an earlier image and a few things I found were very analogous to them.

      I thought there were supposed to be very few "boulders" at site J. Good luck Philae!

    • Robin Sherman says:

      Hi Bill. Did you notice in your area G (Cleopatra) there is a huge X to mark a spot where Philae should land. Its visible even without zooming in. Lets hope there is buried treasure under it. Come on you people at ESA, 67P has issued you a challenge. (Well another one, above and beyond the one you've already got that is.)

  • Clive Hartland says:

    So begins one of the most important aspects of the mission, the automated landing of Philae.
    It sounds like it will be pointed at the landing site center and then fired off into its new home.
    I wonder now how soon we will see any of the pictures?

    Clive

    • Melle says:

      Most important I'm not sure.
      The orbiter is packed with instruments that will study the wake up of the comet for the next year, and beyond. A loss of the Lander would be very sad, but certainly not a failure for the overall mission.

      Most exciting and glamorous aspect, certainly.

  • Comeatstalker says:

    The orbital fun-park is quite impressive, if this goes well then standing ovations are required. If not then we still have a nice descent all the way to the surface, and the applauds are still there but a bit damped.

    A Stuka release procedure is quite impressive but accurate as well, during the WW2 it was practiced a lot.

  • Kasuha says:

    Is it expected that Philae will be able to anchor itself regardless where in the area it hits the surface, or will it be able to affect the landing site during the descent? Some places in the target area seem to be quite hazardous.

  • graham says:

    Apart from some sort of flywheel internally Philae is not controlled in its descent. It all depend on the speed of Rosetta relative to the rotating comet, and the thrust applied to Philae in some sort of opposite motion to that of Rosetta itself. There are apparently two ejecta mechanisms one which is variable and a second, in reserve, which applies a fixed thrust. Ideally the first will be set to the thrust of the reserve, so in the event of the first failing the second will do the same job. Its clearly a risky operation and Rosetta has been in transit now for over 10 years and the mechanisms were probably in place some time before launch. So there is no opportunity to fix anything should it go wrong. Then on landing the thrust down jet, the harpoons (will it be one or both of them?) and the fixing mechanisms all have to work. And the lander has by chance have to find itself on the right kind of surface.
    All in all, its simple - what on comet could go wrong!!!!!

  • Anders says:

    I was also interested in the stabilisation issue and found this in the Philae documentation:

    As Philae descends it will fall slowly without propulsion or guidance, gradually gathering speed in the comet's weak gravitational field, although its attitude will be stabilised via an internal flywheel.

    /Anders

    • Stardust says:

      In theory if it looses its foothold it could straighten itself up again if it still is intact after a toppling over.

      I think for the next generation of comet survey it would be better to have a device that acts like a spider anchoring a simple net and crawl around all over the place.

      • Robin Sherman says:

        If Philae topples down a steep slope and ends up on her head, could the cold gas jet be used in an attempt to push her the right way up?

  • Robin Sherman says:

    Loved the video too. Nicely simple but informative.

    • Kamal Lodaya says:

      What will be the landing force approximately? It appears from the video that at touchdown time Rosetta will be more than 25 km away and heading further out from 67P. The Rosetta cameras should still be looking at the landing site to see what can be seen visually at the time of impact. Is it also interesting to see if something happens to the jets at the neck shortly after the landing as a result of the touchdown?

  • Jacob Nielsen says:

    this picture reveals a rubble pile. But things are not clumped together chaotically. nor are they visibly stratified. The order seems to be created by the nucleus' own rotation: the direction of rotation being around 10 o'clock. Look at the "open quarry" in the top, middle: lighter colored objects mixed with indeterminably smaller, darker stuff. I say it all came dropping down from the "skies" of 67p, and met the nucleus in its spin, as it all "precipitated" down and in direction 4 o'clock. Had they arrived from elsewhere it would have been to fast: craters and destruction, and there is not much of that. Now the "big ones" they may be from different origin, but I assume they are one and the same: crystalline and similar: Cheops sized and smaller. Now if there is no H2O on the surface, they are not enormous H2O hailstone, but I think they are something similar: thrown into the air during perihelion "season", resting for some time in the coma, and then slowly agglomerated to several tonnes of matter. In this gravity that may have taken a month to happen and then, gently, they drop back onto the nucleus. The finer stuff, I imagine is amorphous, able to form soft plains, carbon rich. they don't seem to mix, but they seem to form simultaneously, or sequentially, over multiple repeats. One possibility is that the whole surface is remodeled after each perihelion, otherwise it is difficult to explain why something that is prone to sublimation will continue to exist. An escape from this problem would be that sublimation, jets, ejecta etc. comes from the interior and is heated mainly by tidal forces. I have seen no estimates of how much the coma shades the surface from solar radiation... so much to know, so little data... anyway: weather forecast after perihelion: cloudy with a chance of monster hail.

    • logan says:

      You have a point here Jacob. 67P was 'spining' as it was accreted.

    • Jacob nielsen says:

      I forgot to list a couple of things in support of a high rate of precipitation: no.1: in more photographs, unexplained light, irregular "filaments" are seen on a space background, possibly a shape in a stage in aggregate forming? Or possibly larger objects passing at some speed relative to both lens and 67p during aperture time.. No.2: when viewing the landing video, which shows rotation, I find it possible, that the direction of rotation would help build up/maintain the nucleus irregular shape, when subject to "spray painting" by precipitation, in part consisting of "dust" and in part larger agglomerated matter, that would all stem from evaporated/ ejected material from the nucleus. Anyway, not all has to be blown away? Coarser object, that contribute less to the visibilty of the tail(s) would, eventually, drop back down again.

      • Robin Sherman says:

        Lets call this "Coma Fallout Theory". I'm sure there must be some material that returns to the comet, heavier dust particles for sure. The only issue I can see is how fast the solar wind removes particles and gas from the coma into the tail. One would think that as the density of the coma increases it would create more of a barrier to the solar wind and material closer to the nucleus protected from its effects.

        The other issue is the chaotic motion of dust and gas in the coma is going to limit the size of any "clumps" that might form. That would be something that can be calculated when the energy density/temperature of the coma is measured and is something the mission is aiming to do. Would there be enough static charge in the coma to create lightning as is seen in volcano dust clouds?

        • Jacob nielsen says:

          Hi Robin, one of the prerequisits for agglomerate forming, would be some (chaotic) motion, to enable particle encounters and merging. Probably there will be a maximum theoretical size. What do you think it might be? Pebble? Cheops? In any case: Rosetta will get to know, and that is great. And then: lightning. I'm sure someone in here would love some discharge action, and I don't mind, as long as I, a small object, get to keep my gravitational attachment to Earth

          • logan says:

            As for an actual electric signal (to my little mind):

            Why upper lobe seems to be more of crumbling down toward its gravity center? Why that 'dry' feeling?

            Why then lower lobe seems to be collecting a lot more dust and dirt?

          • logan says:

            Turbulence.
            Remember hailstones?

          • logan says:

            Imagine a gigantic 'tubular' turbulence. Displacing placidly. Made of dust, clumps, crystals and other small objects...

            Writing Prompt.

            😉

          • logan says:

            As from Wikipedia data there seems to be a limit for comets too. The list they have stablish it around 10^13 or 10^14 kg. My very personal guess is that is has to do with the size of 'tubular' turbulences in the solar 'bow'. (other conditions apply 😉 )

  • Birgit Hofmann says:

    Hello Emily, hello rosetta-team, hello ESA !

    Can we see after the landing of philae , panorama-picture´s from the surface of the comet, photograped by the lander ?

    Yes, that´d be very great !!!!

    • emily says:

      Hi Birgit
      As I replied on a different thread: Once safely on the surface, Philae will take a panorama of its surroundings, which is expected back on Earth several hours later.

  • Stardust says:

    It would be nice to get a highest possible Osiris resolution picture and this time with a filter wheel inserted that shows something spectacular.

  • Stardust says:

    Seeing the landing zone makes it a bit of hope for the best mission, once landed just about anywhere within several hundred meters its to stay put and be happy with whatever it finds there. For a first time that is most likely enough.

    Im sure that whatever is the outcome of this mission it will be presented in a form that opens the port to another journey of this kind.

    In our solar-system all orbiting obstacles observed so far, if they have no erosion on their surface, are full of traces of impacts. This makes me believe that this comet as well has no erosion of concern and that its face looked like this over a billion years ago. To believe that this is a place full of water is just about as believing that our dehydrated moon is made out of cheese.

    The space cowboys all over the world have an urge to find water for their horses. On our moon there is not a lot and on Mars there is more carbon oxides than water. On planetoids, asteroids and comets not much is found. Its a bit strange that major goals of missions are to find water as we do not value this substance at all back home.

    • Robin Sherman says:

      There are a few billion people in other parts of the world who would disagree with your comment about the value of Water, especially fresh, unpolluted Water.

  • Margarita says:

    Great blog post and I'm looking forward to more. But, Emily, will you see if your spell checker is turned on?
    "seperate blog entry" . Err: you meant "separate"
    http://www.re-vision.com/spelling/separate.html

    • emily says:

      Proof that a human being wrote this blog post 😉 Thanks for noticing. It's corrected.

  • logan says:

    Doesn't look like Kansas 😉

  • logan says:

    You won this. I'll have to go and buy a pair of glasses.

  • Robin Sherman says:

    Hi Jacob. I never did get the hang of Statistical Mechanics while at University, with absolutely no information to go on either, what size the clumps would reach I have no idea. If I were to hazard a guess, taking the rings of Saturn as plausible guide, I think it would be millimetres rather than metres. It would take an awful long time to make something as big as Cheops. Many Kuiper belt objects and asteroids have small satellites though, its not beyond the bounds of possibility Cheops and its companions were once satellites dragged down to the surface by the friction with the growing coma. Remember for most of its existence 67P has not ever been close to the Sun and so its coma would have, until then, been minimal.

    I have seen those possible particles in the pictures, but their distance from Rosetta and the comet are unknown, that is if they are not moving background stars, camera or processing artefacts. I think the coma fallout would be a dusty mist rather than a hail storm. What conditions are like when a comet gets close to the Sun might be different, with a whole lot more energy in the system, just as with weather systems on Earth. Dust Devils? Tornados? Would the coma behave like a planetary atmospheric system once it reaches a certain density? We might find out I guess.

    • Cometstalker says:

      The escape velocity on the comet is a limiting factor to bad weather and just about anything that moves on the comet above 10 meters per second has an almost flat trajectory aether leaving the comet or bounce into something. The escape velocity is under 1m/s. On earth its almost 10 km/s so our local weather is not limited by gravity. Once any dust or vapor is a bit outside the comet its pushed away by the solar wind so not even a proper concentration of the atmosphere will occur and i guess it never will be over a 0.1 millibar pressure on the surface. The worst part of the environment on the comet is the hard radiation and the chance of micro meteorites as there is no protective layer. The small and shallow craters without a rim and the size of about 2 tto 5 meters indicate high speed impacts.

      • Robin Sherman says:

        You old Killjoy. You're right though. If, as seems likely, the solar wind has stripped the atmosphere of Mars, 67P has got no chance with its feeble gravity, however busily it adds material to the coma.

        It could just by accident, given all that trash its picked up, have swallowed a huge lump of superconducting material , some iron and a bit of Neodymium and have a massive magnetic field. 🙂

  • Dave says:

    Stardust,
    The comet is eroding constantly hence the comet coma. The std model thought originally that comet was all dirty ice and so expected the sublimation or erosion to come from the surface, however they have found no ice on the surface, so now say the sublimation takes place under the surface, so you might expect to see some surface change from collapse even in low gravity.
    There is another theory that the partials in the solar wind electrical erode the surface also could be responsible for water in the coma. The comet is eroding in plain site which ever mode of erosion you believe in.

    • Cometstalker says:

      I suppose comets as well as loosing some material also can pick up some stuff on its journey. It might loose dust and vapours but regain some of this including bigger objects as well, hence craters. The solar-wind contains more then just protons and lighter atoms, the whole atomic table is in this wind. If analyzing the Orion nebula we can see the ionized gases and measure their content with optical and radio telescopes but i don't know of any method to analyze the contents of its dust. Although for sure it contains just about what is in our vicinity up to uranium, so those guys over there will possible believe in snowball comets as well in about 5E12 years. We should plan a visit and give them a spoiler to enlighten them because by then we might know what comets are all about.

      • Jacob nielsen says:

        Hi Cometstalker, to me it looks like 67p is about 50 percent covered in dust, at places several meters thick. Do you percieve likewise? If so, how do you imagine it getting there and staying there?

      • Jacob nielsen says:

        Perceive...

  • frankuitaalst says:

    Fingers crossed till 12Nov !!

    It will be a hell of a job to get Philae landed safely on the selected place .

    In the forum hereunder there is a simulation tool which lets you simulate the landing of Philae , or at least get some feeling how Philae might behave and what it means to navigate Rosetta.

    ( The simulation was not done by ESA officials , it is a private initiative , based on available informatiion in this website ) . Thanks to ESA for providing some data.

    http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl?num=1407351475/0.

    The comet 67P is simulated as two point masses orbiting each other with period 12.6 h .
    Total mass is 1.03 e+13 kg .

    For simplicity the sim relaeses the lander at half the Rosetta's speed.

    Maybe it is necassary to register at the website before one can download the simulation package .

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