Galileo Imagery, I couldn't find a topic not specific to one moon.... Options

[tedstryk]

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.

[elakdawalla]

TTT -- I probably shouldn't refer to my image database in blog entries -- I mean the internal planetary.org image database that is used to populate our website with pictures. I'm proud of it because when we redesigned our website late in 2005 it's one of the things I demanded -- an image library where we can upload one copy of an image, with caption and credit, and it auomatically produces the three browse sizes we use, and spits out the formatted html code for our pages, and we never lose the files or have to rewrite captions, something we used to do regularly before the redesign. I suppose in a future redesign we ought to make this publicly searchable but, I'm very sorry to say, the idea didn't occur to me when we were doing the redesign.

--Emily

[tedstryk]

That is a really cool feature. By the way Emily, I really like the description of the kind of work I do (the explanation of the difference between what I do and what scientists do - at least most of the time (you will understand in a month or two)). In trying to portray what an object in space looks like, there are often trade-offs. Planetary objects don't have big gores in the side of them and discolored sections where one or two filters didn't cover. So, for the sake of producing a nice picture, creating convincing gapfill is important. However, if such images were used for science, such methods could lead some unfortunate person to think that they had discovered a truly different region. I will admit that I am MUCH more pliable with what I am willing to do with Galileo images than with other probes, as its coverage is so spotty. Where I draw the line is cloning over gaps with fictional features or features from another region - I always use actual images of the missing region or a gray fill that is roughly keyed to the surrounding albedo features. I realize, however, that those folks who produce maps for renderings to be viewed at any angle really don't have a choice but to clone missing regions.

For Galileo, I have even tried to play around with some of the better Opnavs. Sometimes there is a rotation sequence as Galileo approached a moon (usually Ganymede) which allows one to build up. Here is Ganymede on orbit J0 (after insertion and approaching the G1 encounter).



Here is Europa on orbit G2 using the same technique.



For the most part, these are tiny images (there are closer opnavs, but due to the compression formula, the data is so skeletal that recovery is impossible). The reason I bothered to figure out a recovery technique is that there are a handful of shots that would have been great "Kodak Moments" had the High Gain Antenna worked, but Galileo didn't have the luxury of taking such pictures. I wanted to test the technique before I bothered with some more difficult images. Here is one from orbit E4. On the left side, the only change I have made is to de-interlace Ganymede, which only has every third row (every fourth row near the top). I reconstructed the missing parts of Io using high phase data from other orbits and the hole in Ganymede from other shots in the sequence of opnavs. I colorized the images based on other orbits.

[tedstryk]

I have re-reworked the closer I32 global view, and in the process I noticed something - you can see the planetshine - lit hemisphere. I know there are plenty of images showing this in much more detail, but I was mainly taken by the fact that I had worked with this dataset so much and never noticed this. The reason is probably that I was focused on making the image black in all areas off the limb except for the faint plume on the upper right. However, due to glow from the daylit hemisphere, the background is actually brighter than the planetshine on the right side of the image, so I probably destroyed it in earlier versions. I wiped out color in the planetshine area because it was not picked up in all filters, making for a very odd appearance. The first image is my new "regular" version, the second is with the planetshine area enhanced.