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Daphnis, July 2010
jasedm
post Jul 5 2010, 10:46 AM
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Moved the Daphnis discussion to a new thread - Admin

I'm really looking forward to the Daphnis images (they should be safely on board Cassini by now)
Although planned images are pretty distant for a body of this size, the perturbations of the ring material either side of the Keeler gap behind and ahead of the moon in it's orbit should be spectacular....
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peter59
post Jul 6 2010, 04:23 PM
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QUOTE (jasedm @ Jul 5 2010, 11:46 AM) *
I'm really looking forward to the Daphnis images (they should be safely on board Cassini by now)
Although planned images are pretty distant for a body of this size, the perturbations of the ring material either side of the Keeler gap behind and ahead of the moon in it's orbit should be spectacular....

You are right, it is spectacular:
http://saturn.jpl.nasa.gov/multimedia/imag...1/N00156644.jpg



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ugordan
post Jul 6 2010, 05:14 PM
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Almost missed it! Natural-ish color RGB composite:
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elakdawalla
post Jul 6 2010, 06:41 PM
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I'd hazard a guess that the "almost-miss" was intentional, in order to see the structure in the wakes as well. I'd think it'd be better to capture as much of one of the two wave trains as possible, to see how they change as they get sheared out & damped with time. Nice version, as always! I'll be posting it as soon as the Society website comes back online... mad.gif


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jasedm
post Jul 6 2010, 07:39 PM
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Magnificent!
Worth bearing in mind that the image above encompasses a mere ~ 1/100th of the radial width of the main ring system - it's a real close-up, and yet, I count at least 50 discrete divisions within that 600km or so. Incredible fine-structure, due presumably to various resonances with the nearer moons and moonlets. Perhaps some of these discrete ring demarcations are caused by Mimas, Pandora, Prometheus, Atlas and even Pan.
Very noticeable too, that although Saturn is only just 'this side' of equinox, the long shadows demarcating vertical relief have all but disappeared.

Simply breathtaking.
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machi
post Jul 6 2010, 07:48 PM
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Three superresolution Daphnis images. Only part around Daphnis from whole 1024×1024 images.

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pat
post Jul 6 2010, 08:46 PM
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QUOTE (elakdawalla @ Jul 6 2010, 06:41 PM) *
I'd hazard a guess that the "almost-miss" was intentional, in order to see the structure in the wakes as well. I'd think it'd be better to capture as much of one of the two wave trains as possible, to see how they change as they get sheared out & damped with time. Nice version, as always! I'll be posting it as soon as the Society website comes back online... mad.gif


Ahh, nope --we'd intended Daphnis to be at the centre of the image. Its yet another example of how uncertainties in the ephemerides of "rocks" and deviations from the predicted spacecraft trajectory can combine to shift moons towards the edge or even completely off frame, especially during close flybys. As it turns out I think that getting greater longitudinal coverage of the edge waves on one side of the gap might actually be better than more limited coverage on both up- and downstream edges.

All nine images are 12-bit and in none of them is Daphnis over-exposed, unfortunately the auto-stretch applied to the raws isn't ideal for every image resulting in Daphnis appearing to be over exposed.
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machi
post Jul 6 2010, 08:46 PM
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Color version.
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ugordan
post Jul 6 2010, 08:51 PM
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QUOTE (pat @ Jul 6 2010, 10:46 PM) *
All nine images are 12-bit and in none of them is Daphnis over-exposed

Most excellent!


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jasedm
post Jul 6 2010, 09:10 PM
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QUOTE (pat @ Jul 6 2010, 09:46 PM) *
Ahh, nope --we'd intended Daphnis to be at the centre of the image.


Thanks Pat for the insight - it's nice to know you chaps are human. Awesome achievement nonetheless.
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Floyd
post Jul 6 2010, 10:07 PM
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Lots of ground (ring?) truth for the modelers. Really fantastic images. I love the images of Daphnis, but the ring dynamics is totally awesome.


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NickF
post Jul 6 2010, 10:52 PM
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In, for example, http://saturn.jpl.nasa.gov/multimedia/imag...1/N00156646.jpg we can see a lot of granularity in the outermost ring edge. This may be a naive question, but are we looking at individual ring particles here?


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Floyd
post Jul 6 2010, 11:24 PM
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According to Emily's blog, the gap is 42 km across, so the structure you see at the outer edge are clumps on a scale of about 1 km. Particle themselve are mostly meters to mm, 10-3 to 10-5 smaller.


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Phil Stooke
post Jul 7 2010, 02:42 AM
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"Very noticeable too, that although Saturn is only just 'this side' of equinox, the long shadows demarcating vertical relief have all but disappeared. "

Actually when you look carefully you can see lots of small shadows in these images. The real problem is just that the light direction is not ideal for seeing shadows at their best. OK, not 'long shadows', I grant you, but there's quite a lot going on all the same.

Phil


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nprev
post Jul 7 2010, 02:52 AM
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It's a real stunner, all right... well done yet again, Cassini people! smile.gif

Yeah, it looks like there are some shadows from things <1 km in there to me, too. Clumps of particles?


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