Celebrating two years at the comet

We’re celebrating Rosetta’s two year anniversary at Comet 67P/C-G (tomorrow!) with a new animation visualising the spacecraft’s incredible adventure flying alongside the comet.

The animation begins on 31 July 2014, during Rosetta’s final approach to the comet after its ten-year journey through space. The spacecraft arrived at a distance of 100 km on 6 August whereupon it gradually approached the comet and entered initial mapping orbits that were needed to select a landing site for Philae. These observations also enabled the first comet science of the mission. The manoeuvres in the lead up to, during and after Philae’s deployment on 12 November are seen, before Rosetta settled into longer-term science orbits.

In February and March 2015 the spacecraft made several flybys. One of the closest flybys triggered a ‘safe mode’ event that forced it to retreat temporarily until it was safe to gradually draw closer again. The comet’s increased activity in the lead up to and after perihelion in August 2015 meant that Rosetta remained well beyond 100 km distances for several months.

In June 2015, contact was restored with Philae again – albeit temporary, with no permanent link able to be maintained, despite a series of dedicated trajectories flown by Rosetta for several weeks.

Following perihelion, Rosetta performed a dayside far excursion some 1500 km from the comet, before re-approaching to closer orbits again, enabled by the reduction in the comet’s activity. In March–April 2016 Rosetta went on another far excursion, this time on the night side, followed by a close flyby and orbits dedicated to a range of science observations.

The animation finishes at 9 August 2016, before the details of the end of mission orbits were known. A visualisation of the trajectories leading to the final descent to the surface of the comet on 30 September will be provided once available.

The trajectory shown in this animation is created from real data, but the comet rotation is not. An arrow indicates the direction to the Sun as the camera viewpoint changes during the animation.

Comments

17 Comments

  • Kamal says:

    Emily: That was fun. You could have added the proposed finale at the end.

  • logan says:

    Today is tomorrow.

    Cheers! 😀

    If my Space Exploration memory doesn't fail, Rosetta is Queen of Orbital Dance,

    http://blogs.esa.int/rosetta/2016/07/29/new-vangelis-album-inspired-by-esas-rosetta-mission/

  • logan says:

    On dreaming of future explorations, string linked twin explorers would do quite a dance! On low fuel. Do you dare, even to code the simulator?

    • logan says:

      Not a good idea on active comets: Big particulate impacts would introduce hard to timely damp oscillations.

      Strings discarded.

  • Ramcomet says:

    Hats off to the Rosetta and Philae teams! A sense of deep appreciation for what has been accomplished here. And so fascinating how the orbits and maneuvers are done.
    Long live the legacy of these spacecraft and the fine people behind them, working for well over a decade to produce such a large body of data, it will be studied for decades to come!
    Also, many thanks for allowing us to join the ride, too.

  • A. Cooper says:

    Hi Emily

    You wrote

    "A visualisation of the trajectories leading to the final descent to the surface of the comet on 30 September will be provided once available."

    May I make a serious suggestion for a specific small area to be targeted for a flyby? I had already found the area on the body that, according to stretch theory, matches to the landing site. That was done in recent stretch blog posts. (Stretch theory isn't mainstream and is not supported by Rosetta mission scientists).

    I've now done a post showing exactly what layers nested on each other at the shear line when the head was still attached according to the theory. It includes the delaminated material, now on the body, that used to sit over the exact landing site location.

    More importantly, there's a hole hosting a well-known jet on the body that matches to the sink hole next to the landing site. Presumably Rosetta will overfly that hole at just one or two hundred metres before landing, taking data as it does so. If Rosetta were to overfly the matching jet area as low as is possible in the final stages, I'm quite sure this data would be invaluable. It could be used to understand the source material for the sink hole and how the sink hole formed. Here's the post:

    https://scute1133site.wordpress.com/2016/08/08/part-52-the-body-lobe-match-to-rosettas-landing-site-includes-suggested-flyby/

    • Harvey says:

      The Osiris NAC only focusses to 1km, & the WAC to 500m.
      There is a picture somewhere of the PI taken at much shorter distances, but I suspect it is misleading; you can severely degrade superb resolution & still have a recognisable image - but no more information than you got at longer range, but in focus.
      The other major issue would be motion blurring. Light levels are now much lower, and you might not have enough light for a short enough exposure to avoid blurr at close range due to Rosetta motion & comet rotation..
      So imaging at such close range may well not be feasible, or yield new information.
      http://pdssbn.astro.umd.edu/holdings/ro-a-osiwac-3-ast1-steinsflyby-v1.4/document/osiris_ssr/osiris_ssr.pdf

      • Marco Parigi says:

        Hi Harvey,

        The real benefit of close passes are also the other instruments (incidentally is the NAVCAM better at close range?)

        There have been a lot more interesting chemistry sniffed out closer to the comet.. 200m may yield further, never before encountered, chemistry - Of course, it would need to fly away from the surface to have enough time to analyse, transmit and confirm the information.

        Also, I can imagine that there can be "duck synchronous" orbit segments that can be tried which may be better for steady long exposure images.

        • A. Cooper says:

          Yes, I was more interested in ROSINA detecting new species or having the enhanced ability to detect differential values of low abundance species more accurately. Also the fact that if you're right over the target, you know more exactly where it's come from. What follows is sort of a statement of the obvious but I still needed to think it through to understand it for myself.

          This comment from Kathrin Altwegg to Harvey always stuck in my mind and is somewhat relevant here, though not entirely relevant because the dust issue has essentially disappeared if Rosetta is going so close.

          http://blogs.esa.int/rosetta/2016/06/14/krypton-and-xenon-added-to-rosettas-noble-gas-inventory/#comment-601705

          The 1/r^2 issue for local densities still applies but the difference between general detection at larger distances and a very close flyby is that I suspect Rosetta will be flying through a number of local sources in sequence rather than detecting them all at once from 10-300 km away as in Kathrin's comment. This is what would give you the high resolution: flying through a number of little 1/r^2 clumps directly above their source and overflown in sequence.

          In reality I suspect this idealised sequential scenario would be highly smudged but hopefully, the signal-to-noise ratio of low abundance species would be enhanced when actually overflying the source. This principle would of course apply to sampling by ROSINA at the close distances achieved just before landing as well.

          So if there were particular species ratios and absolute abundances for the landing site and its purported body match these would be known to come from those sites. The same would apply to the sink hole next to the landing site and its purported match.

          The principle here is a bit like scanning a water colour inch-by-inch to detect the colours used rather than sampling the muddy-brown water used for dunking the brush in. The former might still contain a 'species mix' of two or three colours in any one square inch section but the jar of water (read 10-300km) contains every colour used for all the square inches in the picture. Little-used colours have a low signal to noise ratio in the jar but a high signal to noise ratio in the square inch in which they were actually used.

          I wouldn't necessarily expect the abundances/ratios to be the same at the landing site and the match. They are what they are. I should add that the flyby suggestion isn't about using ROSINA to prove stretch theory.

      • logan says:

        Hi Harvey. That 'trick' was done -apparently- by closing aperture and increasing exposure time. Not a productive strategy on the final valuable minutes before touch down.

        Don't believe cameras would be in the downlink agenda of the last path, excepting 1 or 2 preciously timed shots.

        Those minutes are for instrumentation.

        • logan says:

          [The 'trick' being actually tested could talk of something bold (at last) being pondered at the Bridge, like a close flyby of some of the highest peaks of Coraline] 🙂

      • Jiri says:

        Hi Harvey,

        the WAC can be focussed to 15 m distance by removing all filters from the beam (WAC has two filter wheels, one behind tho other, each with an "empty" position that is used when a filter in the other wheel is selected. Combining the "empty" positions of both wheels effectively removes the equivalent parallel plate filter thickness from the optics, making the WAC "near-sighted"). This mode was demonstrated in the MPS clean room by taking Holgers picture at 15 m.

        • Harvey says:

          Thanks. That wasn't listed as a camera 'mode' in what I had read, but makes sense.
          If I get a moment I'll do the sums. I'd *guess* 15m may be rather the near point of the effectively in focus field range, rather than the actually focus point.
          Filters likely to be 2-3mm thick and n~-1.5 so easy to do.

  • Harvey says:

    Mass spec's are very sensitive instruments, so maybe.

    But the comet is now far colder, and the vapour pressure of the more interesting molecules drops extremely rapidly with temperature. The degassing will probably now be dominated by the small, light, volatile species like CO, O2 etc.

    Yes, we are now much closer, Rosetta might fly through a plume, but the big molecules will be pretty scarce.

    • Marco Parigi says:

      Hi Harvey,

      I think the close Rosina experiment should be done anyway, because we should expect surprises. Philae was sniffing around well before 67P got very active after the cold soak of aphelion and found plenty of interesting organics up close.

      I'm sure they will do the experiments, but not expecting anything as you say.

    • A. Cooper says:

      Yes, plume is the mot juste. As opposed to "small 1/r^2 domes" which I was contemplating!

Comments are closed.