Galileo images and mosaics of Europa |
Galileo images and mosaics of Europa |
Aug 22 2005, 04:03 AM
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#1
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have worked on sprucing up some global views of Europa from Galileo. There are a few more global views I hope to get to eventually. But the best two at nearly full phase benefited a lot.
[Moderator note: There are several more threads containing Galileo Europa images but they all contain several inactive image links. The main threads are: http://www.unmannedspaceflight.com/index.php?showtopic=2016 http://www.unmannedspaceflight.com/index.php?showtopic=2174 http://www.unmannedspaceflight.com/index.php?showtopic=2222 http://www.unmannedspaceflight.com/index.php?showtopic=2082 http://www.unmannedspaceflight.com/index.php?showtopic=2142 ] -------------------- |
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Feb 2 2006, 11:35 PM
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#2
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
I have been trying to make (true ?) color images of Europa using mainly Galileo data. I am using red (IR756 in some cases), green and violet images. The violet images have considerably more contrast than the green images. Using Voyager images as a crude guide it seems the blue images have a contrast somewhere between the contrast in the green and violet images. Because of this I also made synthetic blue images as B=(G+V)/2.
I am attaching two preliminary versions of my images, one image using G1 data (IR756, G and V) and a C10 image (R, G, V). Images using V and synthetic blue are included. I should be able to get more realistic results in the future, the color balance is just a crude guess and it would be more accurate to use synthetic red instead of IR756. The red images have a bit higher contrast than the IR756 images so using synthetic red would be more realistic. Also it is probably not very accurate to use the exact average of green and violet as blue. A weighted average should be more accurate. I eventually plan to use this to colorize a huge (roughly 10000x5000 pixels) global grayscale map of Europa I am working on. When complete it should be of slightly higher quality in terms of coverage than the USGS map. To colorize I need to remove limb darkening etc. because it varies with wavelength, making the color 'change' towards the limb. My biggest problem is that I do not know the wavelength-dependent photometric parameters for Europa. Does anyone know if Hapke parameters as a function of wavelength (or Galileo filter) are available somewhere ? BTW I also did something similar (synthetic blue) for images of Io, see http://www.mmedia.is/bjj/3dtest/io/index.html for details. |
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Feb 3 2006, 08:01 AM
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#3
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Somehow the IR-G-V images look more "natural" to me than the ones with a synthetic blue channel. I find the orangish colors more natural than the pinkish ones using a synthetic blue channel.
That preference may have its roots in the Voyager imagery so one comes to expect an orange colored Europa -- not neccessarily its true color at all. -------------------- |
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