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Rev 164: Apr 5-23, 2012 - Enceladus E18, Tethys
jasedm
post Apr 16 2012, 06:31 AM
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A little belatedly (to post here- the article's been up for a week or two), looking ahead for this revolution (now half complete) here

WAC enceladus from 185km - great detail!

Some shots of tethys too - some are very smeared - spacecraft slewing during shuttering perhaps??

Also some enceladan plumes

Great stuff!
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jasedm
post Apr 16 2012, 07:24 AM
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Worth posting that Enceladus image here. Image rotated and enhanced a little (wow!):




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Phil Stooke
post Apr 16 2012, 11:39 AM
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Great picture! Here I have brought out more detail in the shadows.

Phil

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Bjorn Jonsson
post Apr 16 2012, 11:53 AM
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QUOTE (jasedm @ Apr 16 2012, 06:31 AM) *
Some shots of tethys too - some are very smeared - spacecraft slewing during shuttering perhaps??

Apparently all of the smeared images are UV2 images. UV2 requires a far longer exposure time than most filters. Still seems like a lot of smear though.
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Phil Stooke
post Apr 16 2012, 01:34 PM
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The WAC image taken from the same distance is a narrow crescent - so these images must be of the Saturn-lit side, hence the long exposure.

Phil



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jasedm
post Apr 16 2012, 01:46 PM
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Thanks Bjorn - that would make sense re: the smearing.

Just in case anybody is not already blown away by the accuracy of the spacecraft sequences on this mission, below is that WAC shot compared to Jason Perry's 'looking ahead' simulated view (the red square). Accurate to within a few tens of metres! All from a spacecraft 1.3 billion kilometres away, travelling past the target at 7.5km/second. Sweet.

Incidentally the yellow square is the boresight for the narrow angle camera, and although a shot was taken (N00185750), unfortunately it fell completely in the shadows in the middle of the larger shot, and is almost completely black. I'm not sure it would have been too useful anyway though...








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Phil Stooke
post Apr 16 2012, 04:13 PM
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... except that the shadows are not black, as my image above shows, so if it's not too smeared there should be plenty of detail in it.

Phil



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volcanopele
post Apr 16 2012, 04:59 PM
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The nac isn't completely black. You can make out stuff in the shadowed regions, and there are a few streaks from points that reach into the sunlight. Unfortunately, it is quite smeared and the low exposure time (5 ms) isn't the best for making out details in the shadows.


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Stu
post Apr 16 2012, 05:41 PM
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After a bit of a play about...

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jasedm
post Apr 16 2012, 06:22 PM
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QUOTE (Phil Stooke @ Apr 16 2012, 05:13 PM) *
... except that the shadows are not black, as my image above shows, so if it's not too smeared there should be plenty of detail in it.

Phil


Fair enough Phil, hope some detail can be teased out.

Incidentally, I expect to be widely lambasted here smile.gif , but could this be a hint of vented gases (see box below). Illumination is from the 'top' so one would expect that side of the canyon to be uniformly dark.
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machi
post Apr 16 2012, 06:51 PM
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This is simple gif, which gives basic clue, what can be seen in raw file N00185750 and its "raw" jpg image reduced to 1/5 size.
I think that calibrated raw version will be useful, because it'll bring some more informations about terrain in this place, than WAC image (despite smearing).
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Phil Stooke
post Apr 16 2012, 07:20 PM
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Nice! Yes, more detail from the raw data, of course, when we get it.

Phil



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Hungry4info
post Apr 16 2012, 08:37 PM
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Wow, what's the resolution of that NAC image?

Anyone notice the multiple linear, parallel grooves on Tethys? Has this been thought about in the context of this body?

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machi
post Apr 16 2012, 08:53 PM
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If distance to the terrain in those images is really 185 km, then ~11 m/pix for WAC image and ~1.1 m/pix for NAC image. So theoretically smallest visible details could be only 2.2 meters wide, but realistically, after some processing and for raw file, my guess is, that details (with high contrast) with size about 6 to 12 meters could be recognizable (some boulders, I presume).
Which is not bad result, maybe it's even record for Enceladus. If my memory is right, then best image to date had resolution ~4 m/pix (and this image was smeared too, but not so badly), so details around 8 to 10 meters were recognizable.


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Phil Stooke
post Apr 16 2012, 09:04 PM
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Hey, Hungry - wow, first time I've noticed those grooves. I wonder how far they extend.

Phil



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