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Thread: Rosetta and 67P/Churyumov-Gerasimenko

  1. #46
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    [ Position ]

    Alternative idea they're tossing around apparently is to rotate the lander until the larger Panel 1 instead of Panel 2 gets sun. Lander Control Center suspects there's a shadow cast on Panel 2, which is why while it's getting sun, it's getting a pretty low amount. According to Ulamec they're also thinking about spinning up the flywheel if they have any energy remaining tomorrow. This would impart enough impulse to move Philae somewhere else.

    Rosetta has adapted its orbits to optimize communications with Philae in its new position. Next communications link around 11 pm CET tonight, possibly the last.

    [ Science ]

    - During the current communications outage Philae is drilling with SD2. Lander is at near-maximum off the ground, so SD2 has some way to go to hit the ground in the first place. Ground contact occured two hours ago before Rosetta moved behind horizon.
    - ESA basically won't run PTOLEMY due to energy saving measures. COSAC takes near-identical data more specific to the other data taken, and requires less energy than PTOLEMY. SD2 will therefore only provide the samples drilled from the ground to COSAC. PTOLEMY is the only British-led instrument onboard.
    - MUPUS sensor has been deployed into the ground. Temperature above ground is around 120 K.

    [ Location ]

    There's also some internal controversy about where Philae is. Holger Sierks, the head of the OSIRIS team, thinks Philae moved basically in the opposite direction from the one presented earlier. They're currently downloading 84 OSIRIS pictures from Rosetta taken during the descent and at the time of the bounces. Sierks thinks they'll probably have pictures in that set of both Philae going back into space after the first bounce, and of the second bounce. Cross-checking this with (more numerous) NAVCAM pictures and the CONSERT radio sounding data for the time of the landing should give them a direction to look in. OSIRIS took 1x1 km pictures centered on Agilkia, so the actual final landing site is rather likely outside that scope; having a direction tells them where to point OSIRIS next in the search of course.

  2. #47
    tankie Military Professional tankie's Avatar
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    Whatever the outcome its still a fantastic effort .


    Trust gets you killed, love gets you hurt, and being REAL gets you hated.

  3. #48
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    80% of all science originally planned for the First Science Phase has been done.

    Later-on operations don't look good so far: they're apparently getting ~2.5 Wh per day right now, but would need 50+ Wh per day just to keep the battery warm enough to remain chargable. It's possible they might get that much during perihelion (in August 2015).

  4. #49
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    Philae went into hibernation at 0036 GMT today while in live contact with Rosetta.

    Before it did so, the crew:
    - had Philae turn its body on its landing gear by 35 and lifted it by 4 cm
    - completed a run of the (energy-intensive) Ptolemy instrument
    - took another ROLIS image of the ground below Philae - Philae has now successfully imaged three different sites on the comet
    - retrieved all data from the first science phase available, including the Cosac and Ptolemy analyses of drilled material

    Only instrument that didn't run apparently was APXS, because the shutter in front of its lense did not open (possibly wedged against rock or something like that). Due to the hop, some instruments gained additional, unexpected data over what had been planned.

    The first landing and bounce of Philae has also been found in NAVCAM pictures taken by Rosetta.

  5. #50
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    The MUPUS team is unusually forthcoming with information, although their method of publishing it in some 20 Twitter posts is slightly... odd.

    MUPUS consists of four sensors:
    - a forward- (well, rearward-) looking infrared scanner (MUPUS TM)
    - a self-hammering penetrator probe (MUPUS PEN) containing 16 temperature sensors spread over 40cm length
    - temperature sensors on the anchors of the two harpoons

    The system, using TM, the anchor sensors and corroborating with production from the solar panels detected a cold steep wall in front of the lander, as well as a daily heat wave at local noon heating up that wall and the space around the lander. On the surface of the comet - derived from the infrared readings - is a fluffy, low-density cover probably consisting of dust slowly solidifying, which is roughly as soft as cigarette ash. MUPUS team speculates about a mix of mineral grains and possible organic molecules in this dust.

    PEN was then deployed to (selectable) distance chosen at about one meter from Philae. On the way out PEN probably hit a pile of stuff next to the lander, which changed Philae's attitude/tilt somewhat (beneficially). Temperature as measured by PEN dropped to surrounding space temperature. Assuming the surface was fluffy and porous, hammering started at the lowest of three settings. Automatic control loop, upon seeing no progress, switched to second setting, then third setting, progressively hammering PEN against the surface harder. MUPUS team overrode the control loop, and set the hammer to their "secret" fourth setting, which is outside design specifications. PEN gave up after trying the fourth setting against the surface for 7 minutes.

    Since the harpoons did not fire, MUPUS therefore could not take any subsurface temperatures. The harpoons were intended to take temperatures at whatever depth inside the comet the anchor would end up at, at a maximum of 2.5 meters below the lander.

    The surface itself - below the dust - is estimated to have a tensile strength of at least 2 MPa, the operating limit for the hammer. The explosives-fired harpoons are rated for 8-10 MPa maximum, and would have given a nice estimate at the full tensile strength.


    Soundtrack chosen by the MUPUS team for a MUPUS II:


  6. #51
    tankie Military Professional tankie's Avatar
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    Seems like NASA got there 1st if this vid is to be believed ???



    ROSETTA/UFO OVER COMET 67P - YouTube


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  7. #52
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    DLR has given an initial summary regarding science collected by Philae for a couple instruments (those run by German teams):

    MUPUS:
    - nothing to add to the above.

    SESAME:
    - analyzed initial landing/bounce site
    - discovered high-density ice surface under 5-6 inches of dust cover
    - found large amounts of water ice
    - registered low outgassing activity
    - team is working on deriving mechanical properties of comet

    COSAC:
    - registered organic molecules in "atmosphere" (kicked up dust, outgassing) of the comet
    - no ground sample was delivered by SD2 despite successful drilling
    - team is working on spectrum analysis for atmospheric sample

    ROLIS:
    - took ground pictures of first and third landing site
    - also took pictures of descent for first site

    CONSERT:
    - worked with Rosetta to successfully build a 3D image of the comet core

    Ulamec - the guy in charge of Philae who thought he had to be funny on the broadcasts - estimates that Philae could possibly be contacted again in spring next year, and by summer might be in a position where active recharging of its batteries would be possible. Bit optimistic in my opinion.

  8. #53
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    Last edited by kato; 18 Nov 14, at 20:15.

  9. #54
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    There have so far been two Reddit AmA sessions done by Rosetta and Philae staff - one by ESOC, the other by DLR:




    We are working on flight control and science operations for Rosetta, now orbiting comet 67P, and Philae, which landed on the comet surface last week. Ask us Anything! AMA! : IAmA

    with:
    ESOC - Rosetta Deputy Spacecraft Operations Manager : Ignacio Tanco
    ESOC - Rosetta Science Operations Coordinator / ESA Lander System Engineer : Laurence O'Rourke
    ESOC - Rosetta Spacecraft Operations Engineers : Armelle Hubault, Tiago Francisco, Matthias Eiblmeier
    ESOC - Flight Dynamics Specialists : Francesco Castellini, Ramon Pardo, Pablo Munoz
    DLR - Philae Lander Operations Manager : Cinzia Fantinati
    DLR - Philae Lander Operations Engineers : Valentina Lommatsch, Oliver Kuechemann
    ESOC Media - Senior Editor for Spacecraft Operations : Daniel Scuka

    Small note: From the names one can tell how paneuropean ESA is




    We are comet scientists and engineers working on Philae and Rosetta. We just triple-landed a robot lab on a comet. Ask us Anything! : IAmA

    with:
    DLR - Philae Lander Project Manager : Stephan Ulamec*
    DLR - Philae Deputy Operations Manager : Michael Maibaum
    DLR - Rosetta Science Manager : Ekkehart Khrt
    DLR - instrument team members : Claudia Faber (SESAME), Martin Knapmeyer (SESAME), Stubbe Hviid (OSIRIS), Ivanka Pelivan (MUPUS and ROLIS)
    Scientists : Horst Keller (DLR), Michael A'Hearn (NASA)

    * that's the guy who thought he had to crack a joke on every second line during the Philae landing TV transmissions.




    In addition, there's been a third Reddit AmA held by some British guys who worked on the Ptolemy instrument onboard Philae. It's maybe a bit British. And possibly a bit more commercial.

    We're STFC RAL Space engineers who designed and built PTOLEMY an instrument on the Philae lander for the Rosetta mission. Ask us anything! : space
    Last edited by kato; 26 Nov 14, at 19:00.

  10. #55
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    Rosetta and Philae science is currently - today - being presented at the 2014 Fall Meeting of the American Geophysical Union (where, obviously, it's not a union, it's not just geophysics, it's not just americans, it's not a meeting but a conference, it's not Fall by any real measure, and they just barely got the 2014 right).

    Presentations have so far included sessions in which Rosetta and Philae team members have laid out planned operations as well:
    • the Philae science team is currently planning its "post-hibernation science phase", being rather confident they'll manage to wake Philae, possibly as early as February or March.
    • the first CIVA-P image of Philae's surroundings was presented - automatically taken immediately after the bounce, and a motion-blurry mess showing the surface whizzing by underneath.
    • apparently the lander team currently thinks that during the bounce in the first touchdown, Philae bounced off of ice.
    • Rosetta performed indepth searches for Philae's final landing site during Dec 10th-12th. They're waiting for the pictures to download (gotta queue, since not really high priority), and are confident that Philae should be spottable in those. They do have pictures of cliff faces with "glints" in them which they suspect could be reflections from Philae.
    • they have a terrain model of the hole Philae is in
    • in February, Rosetta will go down to 6-km altitude flybys, i.e. scratching the minimum safety altitude given so far.
    • Rosetta will perform a flight through one of the outgassing plumes of the comet later in 2015
    • guy from the lander team says that 67P/C-G is 4.57 billion years old, which makes it at least as old as the Earth (4.54+-0.05 billion years), and the oldest non-Earth object visited by a lander. The oldest rocks discovered on Earth are meteorite cores that assembled directly from the collapse of the solar nebula, and are 4.5682 billion years old.


    Main science session apparently commencing in a couple minutes.
    Last edited by kato; 17 Dec 14, at 18:20.

  11. #56
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    • The region around the pyramid-shaped boulder Cheops has been named "Imhotep Regio"
    • Cheops, as an easily distinguishable solitary surface feature, has been chosen as the origin of a coordinate system for the entire comet
    • entire surface has granular structure with "dinosaur eggs" - small spherical objects of 2-3 m diameter - at surface and deeper inside when looked at in high resolution
    • less close-up, cliffs show linear, terraced structure that's rather puzzling
    • cliffs in the comet show deep, huge cracks; they have OSIRIS pictures looking straight into them, also showing dust flowing into the cracks
    • there are suggestions the cracks stem from rotation of the comet relaxing
    • there are outgassing vents all over the comet, not concentrated to any particular region; also have pictures looking straight into one
    • the comet's coma looks "like a snowstorm" by now, with the lofted-off dust grains tumbling like snowflakes
    • density of 67P/C-G is 0.47 g/cm, porosity is 70-80% - i.e. 70-80% of the comet's 21 cubic kilometers volume are vacuous. That sounds a lot, but isn't. Clay in glacial deposits on Earth can have up to 90% porosity.

  12. #57
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    Dust:
    • MIDAS, the dust collector on Rosetta (think similar to the Stardust mission, just smaller), has more than 2000 grains on its collector in that "snowstorm" where they had originally only expected a few (3, actually).
    • MIDAS has taken the first ever 3D images of such particles in space, with nanometer resolution. Some images released at Rosetta blog the minute their rep took the podium at AGU.
    • COSIMA has detected grains up to 250 m in diameter; overall they haven't found the expected sub-micron-sized particles at all yet in the coma, only really "big" stuff
    • according to GIADA (laser field scanner), the dust grains are moving through space aggregated in "clouds"
    • most dust clouds move at 4-6 m/s away from the comet, anywhere from 0.5 to 12 m/s observed (probably depends on individual jet and grain size?).
    • between Aug 17 and Aug 24, detectors on Rosetta (MIDAS, COSIMA, GIADA) found a huge spike in dust in the area Rosetta flew through; they suspect Rosetta crossed a dust jet of the comet at that time


    The northern ("winter") hemisphere of 67P/C-G is more active than the southern hemisphere. Dust detection by GIADA points out that these are mostly over the Northern Hemisphere (they have plots/maps!). Also, COSIMA has detected some minerals - Sodium, Magnesium, Calcium - but only over the "winter" hemisphere; these are probably struck from the surface by solar wind.


    Already in the news:
    • 67P/C-G has 3x the terrestrial deuterium-hydrogen ratio. This pretty much says that the comet is likely originally from the Kuiper belt, and that comets like it can not be the (sole) source of Earth's water; might point at asteroids providing Earth's water instead of comets.


    Further to above:
    • "Snowstorm": They have pictures where the area Rosetta is flying through looks like snow flurries through a car's windshield.
    • "Dinosaur Eggs" visible on surface inside cracks and vents: May point at how matter initially accreted in planetesimals.
    Last edited by kato; 17 Dec 14, at 19:46.

  13. #58
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    MIRO results:

    • Hemispheric outgassing on dayside throwing water and dust away at 700 m/s (!); no outgassing on nightside
    • Outgassing rate for water is about 0.3 Liter per second (Ceres water vapour plumes total, for a body 250 times the diameter: 6 Liter per second). Outgassing increased by factor 4 from June to August
    • Subsurface temperature measured at various depths (depending on surface material above); 70-120 Kelvin
    • The dust layer covering the surface provides extreme insulation; difference of 50 Kelvin between surface top and 1cm depth
    • Surface dust layer is only a few cm thick; water ice immediately underneath.
    • Solar flux rate implies that only at most 0.1-1.0% of surface are covered with ice (i.e. not covered by surface dust layer or rocks)

  14. #59
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    The name Imhotep Regio was also made official with ESA posting a Navcam picture of the region taken three days ago under that name while the AGU session was still ongoing (damn, they're the just-in-time people today, aren't they?):

    CometWatch 14 December | Rosetta - ESA's comet chaser

    The neck region cliff has been named "Hathor", the base of the neck "Hapi". Hapi and Hathor on December 10th:

    Attachment 38740
    Credits: ESA/Rosetta/NAVCAM CC BY-SA IGO 3.0


    VIRTIS results:

    • temperature map of comet shows up to 220 K (-50 C) surface temperature in some places, along with shadow effects at neck; possibly points of particular activity
    • high-res VIRTIS images have detected some ice in a single isolated spot on the surface, possibly revealed by landslides (local morphology suggests thus)
    • dust surface cover contains an upper layer of about 100 m completely devoid of H2O
    • Albedo of 67P/C-G is 6% (charcoal), the surface has a slight blue tint with differences - Hapi is relatively light/bright for example.


    Comet geomorphology:

    • There are examples all over the comet where pits/basins have formed due to the surface collapsing into a void beneath
    • Imhotep Regio with Cheops also has such basins, which are apparently slowly expanding - i.e. the surface sinks lower and they widen.
    • Morphology of Imhotep Regio suggests that this collapse is mostly a very slow, gentle process
    • Some of the pits/basins are up to 300 meters wide
    • Boulders in Hapi area have fallen from Hathor cliff (free-fall, not rolled).
    • All debris fields below cliffs have likely similar origin, falling rocks.
    • Dunes in Hapi have probably not formed due to "jet winds" but from compression and sliding of surface material (i.e. the voids under the surface play a role there)

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    • Comet jets are extremely bright in far ultraviolet (FUV) spectrum
    • Similarly, the outgassing northern hemisphere is 2.5x brighter in the FUV than the southern hemisphere
    • FUV emissions are themselves produced by:
      • light shining on metals, producing electrons in photoelectric effect
      • these photoelectrons impacting H2O particles (water ice) and breaking it into individual atoms.
      • the atoms then radiate in FUV.
    • The same process occurs on the comet also with carbon dioxide.
    • The southern hemisphere in this regard is "carbon rich" (CO2 dominant), the northern hemisphere is "water rich" (H2O dominant).
    • ROSINA also sees major differences in the composition of the coma above the northern and the southern hemisphere.

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