Go for 10 km!

With the last week spent at about 20 km from 67P/C-G, the decision has now been made to go to just 10 km.

A series of manoeuvres will reduce Rosetta’s distance from its current 18.6 km orbit (taking 7 days) to an intermediate orbit approximately 18.6 x 9.8 km (with a period of about 5 days). From there the orbit will be circularised at about 9.8 km radius, with a period of approximately 66 hours on 15 October, and the mission will enter the “Close Observation Phase” (COP). This will provide even higher resolution images of the landing site in order to best prepare for Philae’s challenging touch-down.

The new orbit will also allow a number of Rosetta’s science instruments to collect dust and measure the composition of gases closer to the nucleus.


Rosetta will stay in the 10 km COP until 28 October, when it will begin the transfer to a “pre-delivery” orbit, a slightly elliptical orbit at approximately 30 km distance from the comet centre. After another orbital change taking place about two hours before separation, the spacecraft will finally deploy Philae from a distance of 22.5 km from the comet centre, at 08:35 UT on 12 November.

A detailed timeline of spacecraft events around the landing will be provided soon.



  • Vijay says:

    This is a great achievement. Bravo ESA!!!

  • Luca says:

    I’m wondering if orbits are real “gravity driven” orbits or or Rosetta has to continuously correct her track…

    • Brian Deschene says:


      Since the Global Mapping Phase (GMP) began at ~30km, Rosetta has been following actual orbits held by gravity, as opposed to circling using thrusters as was done in “triangles” before GMP began. As this posting explains and its video shows however, some orbits were only partial (for example: only 7 days of a 14 day orbit was followed) before another change was made by thrusters to a different orbit.

  • Comeatstalker says:

    From a 9.8 km radius orbit the surface is about at an 8 km distance. That means that the Osiris image resolution is about 0,15 m side or 0.023 square meters. Please spoil us with one snapshot.

  • Jason Rowberg says:

    Emily, thanks for this update! Very exciting!

    Can you provide us with at least a high level idea why the Philae drop will occur at 22 km with a 7 hr flight time if Rosetta is able to get so much closer to the comet? Wouldn’t a closer drop provide a softer and more precise landing?


    • Matthias says:

      I repeat the question of Jason (I guess many other have the same question): What is the Background to leave the very close COP orbit of 10km and deploy the lander from the much higher altitude of 22km? A naive mind would say it should be easier to release the lander from the lowest possible altitude.

      • Jason Rowberg says:

        Thanks, Matthias. As I’ve been thinking about this, the only thing I can guess is based on the Philae notes. There are two launch mechanisms, one electronic and one mechanical (the failsafe). The electronic launch can impart a wide range of impulses to Philae, but the manual spring is something like 20cm/s I think. The notes indicated that launch plans which require impulses near the manual constant would be favored, so the failsafe would be viable.

        My guess is that landing on site J with a 10km orbit would require an electronic impulse quite a bit higher than that (due to the faster orbit). If that is correct, ESA apparently prefers the risks of a longer flight over losing the manual launch capability.

        But again, this is a guess and all of us would be grateful to know the real reason.

        • Denis says:

          There is also the issue of maintaining communication between Rosetta and Philae during the whole descent and probably the initial time spent on the surface.
          It might be easier to achieve from a higher orbit ?

  • Haerwe says:

    According to OSIRIS NAC performance data the image resolution is stated to be LESS than 2 cm .(two centimetres!)

    It is expected to “see” solids being ‘exhailed’ thru the vents and chimneys Rosetta is planned to look at..

    I describe this in detail since – based on experience – I am certain Sierks will apply the usuall image policy.

    • Comeatstalker says:

      The Osiris has a Resolution of 19 milli Radian per pixel and this mean 19 mm for every Kilometer of distance. If 10 kilometer away the pixel resolution is 10* 19 mm.
      That is 19 cm.

  • armchair explorer says:

    Could you release cyclograms of spacecraft operation and science observations? It would be helpful to better appreciate how Rosetta works.

  • Francisco Manterola Jiménez says:

    congratulatios, ESA and Rosetta team!!! i just wanna see at Philae lands on 67P/C-G in november 12!!

    Greetings from Iquique, Chile! 😀

  • cosmo says:

    Would be nice if you could update the table of trajectory correction maneuvres. Thanks!

  • Claudio says:

    This is so exciting, can’t wait for the landing moment!

  • John Palmer says:

    Some questions:
    1–How close does Rosetta need to get before its instruments can find how deep the dust is around “Cheops”?
    2–Will Rosetta be taking a closer look at the jet coming out of the duck’s neck?
    3–Is the dust likely to be electrostatically charged so that it clings to Philae’s lenses?
    4–How similar is 67P’s surface to the area on Earth where the Philae prototype was tested?
    5–Will the coma (when it develops) interfere with Rosetta’s data transfer to earth?
    6–Are there any adverts on Philae?

    Today I went to see the obelisk in Dorset that links Rosetta and Philae.

    • Comeatstalker says:

      3–Dust mooving in vacuum radiated by high energy photons and solar wind is for sure charged, thats why comet tails have a dust and plasma part. If dust is stuck on lenses it takes a lot of it to blur the images. The greater concern is if the parts in shadow that are cold get frosted by outgassing from hotter surfaces.

      5– the coma will only add to the background noise. As the Rosetta gets closer the signal grows a lot stronger and the antenna on earth or mars relay-station have no problem with an increasing coma as the antenna field of view is small. The sun ist the worst enemy to the communication.

  • Sergio says:

    Fantastic achievement.
    Bravo to all the gang!

  • Francisco Javier says:

    It’s just amazing! If I’m not wrong you mean Rosetta has just 0.26 m/s speed in its orbit around the comet. Incredibly low. How can you achieve that? Congratulations. Waiting for the landing!

  • frankuitaalst says:

    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 .
    ( 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.


    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 before one can download the simulation package .

    Fingers crossed till 12Nov !

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