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Galileo Imagery, I couldn't find a topic not specific to one moon....
Guest_Sunspot_*
post Apr 24 2009, 10:09 PM
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It's a shame its going to be at least 30 odd years before we ever get a good look at Jupiter again.
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Phil Stooke
post Apr 24 2009, 10:15 PM
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I expect the other things visible in sunlight were much higher priority than any potential earthshine images.


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DrShank
post Apr 24 2009, 10:37 PM
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QUOTE (stevesliva @ Apr 24 2009, 09:12 AM) *
Given the bandwidth limitations where they probably couldn't return every sunlit Io image they had, would Galileo have been focused on IR images of the volcanically active areas when Io was in eclipse and nearby? I'd think bandwidth coupled with Io looking interesting in non-visible wavelengths would but the nails in the coffin of visible Jupitershine images.


it would have been nice indeed. several things made it unlikely. The ccd on galileo was 8-bit, on cassini it is 16-bit (or is it 12, i can never remember). In any case, the cassini ccd has a significantly broader dynamic range and can capture low light images. even so, if the exposure isnt long enough even for cassini, compression artifacting begins to kick in. ive used quite a few of these and have seen a wide range of quality. given the lower sensitivity, and the severe restrictions on downlink and tape recorder, either you expose for the lit side or the dark side. galileo could usually do only one or the other, not both because it was not a high priority to take the same image twice. they were lucky to get 150 images of ALL targets during any given orbit. so nite side imaging took it in the teeth.


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ugordan
post Apr 25 2009, 12:40 PM
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Yes, Cassini has 12 bit A/D converters and although it typically encodes images using an 8 bit lookup table, it's still able to capture the greater dynamic range 12 bit images produce, albeit with only 256 discrete levels.

I don't think Galileo having an 8 bit dynamic range to begin with gives you much to work with if the exposures are set for sunlit surfaces. Maybe some detail could be pulled out from higher phase sunlit surfaces since those inherently use longer exposures for rocky surfaces, otherwise the brightness difference is too great.


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Bjorn Jonsson
post Apr 25 2009, 01:42 PM
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This is true and even long exposures might have been a problem due to scattered light unless the phase was relatively high. What I had in mind was something similar to Cassini's images of Iapetus (these are the best known Saturnshine images) of Io's subjovian hemisphere. The reason is that Galileo only obtained relatively low resolution images of this hemisphere. But possibly the flyby geometry was never suitable for this - it's probably time to get some SPICE kernels and start digesting them.
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Phil Stooke
post Apr 25 2009, 04:31 PM
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Cassini at Iapetus was moving very slowly, but Galileo at Io was moving very fast, so motion blur was a problem and compensation more difficult. And the long exposure would result in really bad radiation effects on the image.

Phil


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ugordan
post Apr 25 2009, 04:39 PM
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True, but Io also receives much more jupitershine being much closer to Jupiter (which in turn receives more sunlight) than Iapetus is to Saturn so that tends to cancel out greater flyby speeds somewhat.


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tedstryk
post Apr 25 2009, 08:12 PM
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In these images, compression was not the worst problem. It was a horrible amount of noise.


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john_s
post Apr 27 2009, 10:23 PM
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Actually there are a few low-resolution, global, Galileo images of Io's nightside in Jupiter shine, taken to look for condensing frosts. See Simonelli et al. 1998, Galileo Search for SO2-Frost Condensation on Io's Nightside, Icarus 135, 166-174. These are from that paper:

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John.
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tedstryk
post Apr 27 2009, 11:53 PM
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QUOTE (Sunspot @ Apr 24 2009, 10:09 PM) *
It's a shame its going to be at least 30 odd years before we ever get a good look at Jupiter again.


Sunspot, actually less than 20. The new mission is supposed to end in 2029, which is 20 years from now. smile.gif


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tedstryk
post May 1 2009, 06:24 PM
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Here is another nice view from Galileo, taken during the E15 orbit.


Attached Image




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DrShank
post May 2 2009, 04:09 AM
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QUOTE (tedstryk @ May 1 2009, 01:24 PM) *
Here is another nice view from Galileo, taken during the E15 orbit.


Attached Image


yes, this view is upside down with north at bottom. the clutch of mountains near the bright patch of Masubi (top)
is Hiiaki Montes, Shamshu Mons, plus a few others. Zal and Mongibello Mons are at bottom!


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machi
post Nov 9 2009, 06:06 PM
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Beautiful images! Io is really very photogenic object.
Here are some images from beginning of Galileo mission.
Attached thumbnail(s)
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machi
post Dec 1 2009, 11:26 AM
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Asteroid Ida in false color.
Attached thumbnail(s)
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djellison
post Dec 1 2009, 11:34 AM
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False colour? really? I've stretched the saturation to the max in Photoshop on that image, and there's no colour at all, just a slight orange tinge across the entire image.
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