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Thread: Rosetta and 67P/Churyumov-Gerasimenko

  1. #76
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    ESA will begin transmitting commands to Philae "blindly" on thursday, listening whether it will reply. For now for one week.

    According to the lander crew, Philae is currently estimated to receive twice as much sunlight as immediately after landing. The lander is hardwired to first pipe any energy it gets from its solar panels into heating itself until it reaches an interior temperature of about -45C (= -50 F). If it reaches this temperature and receives above 5.5 Watt electric power, it will turn itself on and charge its batteries; it will then also turn on its communications unit every 30 minutes to listen for commands from Rosetta. If it gets over 19 Watt electric power, it will be able to perform two-way communications (i.e. turn on its transmitter). In theory, Philae can execute commands sent to it even before this though.

  2. #77
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    ESA's NAVCAM team has published "a few" pictures taken by NAVCAM, including:
    • 220 photos taken during the Mars flyby
    • 295 photos taken during the three Earth flybys
    • 620 photos taken during the two asteroid flybys (Steins and Lutetia)
    • 964 photos taken during deep-space cruise and maneuvers
    • 613 photos taken between rendezvous and landing phases at the comet

    Yes, that adds up to about 2,700. And yes, they're all free domain for use as long as you add the license disclaimer (like below the picture below)

    Available here:
    ROSETTA / NAVCAM / Cruise phase (before comet encounter)
    ROSETTA / NAVCAM / Comet phase / Prelanding phase (between comet encounter and landing)

    Pictures like this one. All black and white. Not bad for a mere engineering camera though.

    Attachment 39534
    ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

  3. #78
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    Rosetta ran into some trouble during its March 28th flyby of the comet - at 14 km distance, its star trackers lost visual contact with the background stars due to the by now even more intensified "snow storm" of the inner coma, locking onto the glint of comet dust particles instead; several hundred dust particles were wrongly assumed by the star trackers to be stars, hence giving the flight computer impulses to shift back to the right attitude with a number of control burns.
    The flight team recognized this problem, especially when the attitude drift started pointing Rosetta's main communications antenna away from Earth, leading to a reduced signal, and began reconfiguring the flight software to rely on Rosetta's internal gyros until the attitude shift was corrected. Near the end of reconfiguration (24 hours later), the "snow storm" got more dense and Rosetta shifted into an automatic safety recovery mode in which it shut off its scientific instruments and basically devoted itself to saving the spacecraft - by moving 200 km away from the comet.
    At that distance the flight crew recovered Rosetta from its safety mode to regular function and began re-planning trajectories to bring Rosetta back in closer to the comet. Rosetta performed a loop that brought it out to 400 km distance by Thursday, from where it then flew back in to a point at 140 km distance (reached yesterday).

    There's an interesting "Snow Storm" picture from 385 km distance taken on April 2nd by NAVCAM, with the surrounding dust a bit more highlighted. Rosetta would have flown through the outer area of that jet visible in the picture when it encountered the above problems.

    As for the dust Rosetta does encounter, the GIADA team has recently published another paper. During the orbital phase, Rosetta encountered "dust showers" pretty regularly twice per week, each lasting up to 30 seconds; the dust consisted of two different kinds - compact material up to 1mm in diameter and 0.8-3.0 g/cm density (pretty standard minerals) that is currently theorized to have been processed in the newborn solar system and fluffy material up to 2.5mm in diameter and under 0.001 g/cm (lighter than air!) that is theorized to be interstellar dust predating the birth of the sun.
    Interestingly, the "fluffy" material due to its shape carries higher electric charges which leads to it being repelled by Rosetta's own charge (generated by the plasma environment and solar wind) - hence this dust being distinctly different in that it is significantly slowed down and disrupted before impact. This disruption, i.e. the fluffy material falling apart in Rosetta's electric field creates the longer showers of extremely slow "subparticles" that impact Giada. With regard to this material Rosetta's charge effectively acts like a "shield". In the Star Trek sense.

  4. #79
    Official Thread Jacker Senior Contributor gunnut's Avatar
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    Quote Originally Posted by kato View Post
    Well, they snapped another one just before leaving.

    This one, also from 28 km and looking like it's high time to leave:

    Attachment 39186
    ESA/Rosetta/NAVCAM CC BY-SA IGO 3.0
    It almost looks like Gobotron from this picture.

    "Only Nixon can go to China." -- Old Vulcan proverb.

  5. #80
    Official Thread Jacker Senior Contributor gunnut's Avatar
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    How much more fuel does it have to keep doing these maneuvers?
    "Only Nixon can go to China." -- Old Vulcan proverb.

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    I've only seen one rough estimate for this, and that was 250 kg remaining fuel after entering orbit (out of ~1570 kg total fuel at launch). That's good for a 330+ m/s delta-v budget. I'd estimate each of the twice-per-week burn maneuvers done since then to eat up anywhere from 1.0-2.0 kg of fuel depending on exact speeds and vectors involved, i.e. those 250 kg should be good for 80+ weeks if conservatively used (30 of those weeks have passed since then, so my estimate would be up to 150-160 kg fuel remaining).

    That estimate is probably pretty close since the fuel is officially budgeted to last "at least" until the end of this year - the nominal mission end unless extended.

  7. #82
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    Latest NAVCAM picture, from 137 km distance taken on Wednesday (8 hours after the referred to 140 km point was reached):

    Attachment 39589
    ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

    Central is the underside of the large lobe - Imhotep regio with Cheops, one of the small dots at the upper end of the central "sandy" area. Resolution is around 12 m/pixel.


    Owing to the difficulties explained four posts above Rosetta's entire trajectory plans were rehashed. Rosetta is currently moving in from the 140-km point to a point 100 km from the comet (to be reached tomorrow), where it will then begin triangular "orbits" of the comet - similar to how it started orbiting the comet last September. During these, Rosetta will do exactly preplanned moves up closer - on the legs of the triangle - while moving towards predefined points - the ends of the triangle -, thus being independent from star trackers, navigation camera and such for knowing where it is moving towards. The flight team will monitor the environment around Rosetta during the various points of these triangular flights, which are now planned to continue throughout April. If all goes well, they go deeper in with the orbits. Science operations are being limited for April, and the teams are jointly evaluating and reassessing how to perform certain experiments without endangering Rosetta.

    During the April orbit phase Rosetta will attempt to hail Philae again, starting from Sunday morning 2 AM UTC+0.

  8. #83
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    Pretty awesome presentation of "How to land on a comet" by Rosetta mission leader Fred Jansen:

    Fred Jansen: How to land on a comet | Talk Video | TED.com

    17 minutes, well worth it. Extremely professionally done.

  9. #84
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    Rosetta is preparing for perihelion on August 13th:

    http://blogs.esa.int/rosetta/2015/07...or-perihelion/

  10. #85
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    The japanese interplanetary micro-probe Procyon has monitored 67P/C-G's halo using its geocorona camera, ascertaining its current size at 300,000 km diameter.

    ESA, meanwhile, has posted an anyglyphic 3D picture of a jet taken by Rosetta: http://blogs.esa.int/rosetta/2015/10...met-jet-in-3d/ (requires red-blue glasses)

  11. #86
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    Quote Originally Posted by kato View Post
    ESA's NAVCAM team has published "a few" pictures taken by NAVCAM, including:
    The archive linked to above currently contains 20,465 pictures.

    - 2,608 NAVCAM pictures taken from landing until March 2015
    - 5,685 NAVCAM pictures taken from departure until the landing
    - 12,172 OSIRIS pictures taken from departure until the landing

    Rosetta just performed a 3-week excursion into the outer coma (1500 km from the comet) and during its return is slated to be around 400 km from the comet by now.

  12. #87
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    Surface Detail: Picture taken by OSIRIS NAC on Rosetta two days ago. Distance was 7.054 km in a close flyby.

    Name:  comet-300x300.gif
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    Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

    Picture enlarged two-fold by me. Original resolution is 0.13m/pixel - the above 600x600 px image shows a section of 39x39 meters (127.7 x 127.7 ft). The large rock in the center is about 10 meters (32 ft) across. Full picture here - showing an area of 266 x 266 meters at the same resolution.

    Current final plans involve Rosetta landing near Agilkia, i.e. Philae's landing spot, at the end of September. For reference to the above, the wingspan of Rosetta is nearly wide enough to go from end of the above picture to the other.
    Last edited by kato; 30 May 16, at 19:41.

  13. #88
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    Rosetta has found Philae and took quite a great picture of it.

    Name:  Philae_close-up_labelled_node_full_image_2.jpg
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    Credits ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

    5 cm/pixel resolution, from 2.7 km.

    More information here.

    The DLR Philae team made a little video for Philae fans before it was found:



    Rosetta's mission ends on Sep 30th, with it then being sent closer-in in order to take upclose pictures of pits in the Ma'at region to try to find out a bit more about the interior before Rosetta is sent to touch down on the comet. Video for Rosetta's mission end from ESA:

    Last edited by kato; 06 Sep 16, at 21:19.

  14. #89
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    P.S.: The image archive had another 8,494 NAVCAM and 13,172 OSIRIS pictures added since March - there are now 42,621 pictures taken by NAVCAM and OSIRIS published.

    OSIRIS consists of two cameras, one narrow-angle (NAC) and one wide-angle (WAC). The published images now include 8,481 NAC pictures and 6,671 WAC pictures at 67P/C-G. A further 2,032 pictures were taken during the asteroid flybys at Lutetia and Steins and 2,198 during swingbys at Mars and Earth, with the remainder during deep-space cruise phases.

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