Galileo images and mosaics of Europa Options

[tedstryk]

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 ]

[Bjorn Jonsson]

It is well known that Galileo's color coverage of Europa is severly limited. I've been processing all of the Galileo color coverage that is useful for colorizing a huge (16384x8192 pixels) simple cylindrical map of Europa I'm working on. What I'm posting here are some of the more useful images. I'm still working on the well known E14 data so a color mosaic from that is not included. There is also a single 1.2 km/pixel color observation from E12 but it is extremely noisy and I'm not sure I'll get anything useful enough from it.

Very early in its mission, during the G1 non-targeted Europa flyby, Galileo obtained the best Europa color coverage of the entire mission in terms of the number of filters used. This is a planning image that appeared on the Galileo website. All of the data was downlinked and without gaps:



As shown above, only about 50% of the red image was downlinked. Fortunately, synthetic red images created from green and 756 nm images are remarkably accurate, the error compared to a real red image is typically ~1% or less. To get true color it's also necessary to create synthetic blue from green and violet. Here is a true color image from red (lower half), synthetic red (upper half), green and synthetic blue:



There is a well known false color image from these Galileo observations that can be seen here.

A few more Galileo true (or approximately true) color images, in all cases RGB from an infrared image, green and violet.

The G2 image from 968 nm, green and violet images with small gaps in some of the source images filled using data from another filter:


A C9 image from 756 nm, green and violet with small gaps filled as in G2:



A C10 image from 756 nm, green and violet with small gaps filled as in G2:


And finally a G28 image from 756 nm, green and violet. The color in this image is a bit strange and I haven't corrected it. I think the camera's calibration may have changed late in the mission and at least one thing definitely changed. From approximately orbit 26 the images appear less sharp than earlier.


In some cases I posted versions of these image several years ago but these new versions should be significantly better. In particular there is now no pinkish color around Pwyll in the C10 image.

And BTW: One unexpected 'discovery' I made while working on these is that a complete set of Galileo SPICE kernels apparently isn't available, for example the frames (FK) kernels are missing. I spent a lot of time searching but without finding a complete set of kernels. This was a big surprise to me.

[mcaplinger]

a complete set of Galileo SPICE kernels apparently isn't available, for example the frames (FK) kernels are missing...This was a big surprise to me.

Galileo predates the frames kernel concept, and it seems likely that no one has been motivated to go back and build them from scratch (we didn't have FKs for most of MGS either, but they were generated in 2007.) Some of that information is in the I kernels for the various Galileo instruments, though I didn't look at the C kernels to understand which frame(s) were in there. Historically image processing was done with the Euler angles in each image file.