Galileo Imagery, I couldn't find a topic not specific to one moon.... |
Galileo Imagery, I couldn't find a topic not specific to one moon.... |
Dec 9 2007, 07:50 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4405 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Here is a combination of all of Galileo's global color views of the Galileans. I have left out the large Europa mosaic because much of its color data is pulled from other orbits. I have also left out colorized views. Due to inconsistent filter selection, there some variation between images. I posted the Europa set in another thread, but I figured I would add the views of Ganymede and Callisto.
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Apr 24 2009, 12:25 AM
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IMG to PNG GOD Group: Moderator Posts: 2256 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Having seen what Cassini has done at Saturn I'm becoming surprised there aren't any really nice Jupitershine images of the Galileans (especially Io's Jupiter facing hemisphere). This shouldn't have been very difficult since Jupiter is much brighter than Saturn. Of course the downlink was severely limited but despite this I'm a bit surprised.
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Apr 24 2009, 02:12 PM
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Senior Member Group: Members Posts: 1598 Joined: 14-October 05 From: Vermont Member No.: 530 |
Having seen what Cassini has done at Saturn I'm becoming surprised there aren't any really nice Jupitershine images of the Galileans (especially Io's Jupiter facing hemisphere). This shouldn't have been very difficult since Jupiter is much brighter than Saturn. Of course the downlink was severely limited but despite this I'm a bit surprised. 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. |
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Apr 24 2009, 10:37 PM
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Member Group: Members Posts: 207 Joined: 6-March 07 From: houston, texas Member No.: 1828 |
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. -------------------- Dr. Paul Schenk, Lunar and Planetary Institute, Houston TX
http://stereomoons.blogspot.com; http://www.youtube.com/galsat400; http://www.lpi.usra.edu/science/schenk/ |
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Apr 25 2009, 12:40 PM
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Senior Member Group: Members Posts: 3652 Joined: 1-October 05 From: Croatia Member No.: 523 |
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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