Wednesday, March 3, 2010

Galileo Full-disk mosaic of Io Redux

Well, a couple of weekends ago, I got bored.  I don't know why.  I think I was watching some Olympic coverage, and NBC was doing one of their endless athlete profiles.  Anyways, I started playing around with some of the Galileo images from C21.  Okay, I was watching Olympic coverage AND playing around with these images...

These images were acquired during an encounter on July 2, 1999 and form a global color mosaic, using the camera's violet, green, and 756 nm NIR filters, of Io's anti-Jovian hemisphere.  A completed color version of this data, assembled by then-grad student Moses Milazzo, was publicly released about two months later using two different stretches: one where each color channel was stretched the same and another where each color channel was stretched individually (emphasizing color variations across the surface).

So why process these images into a mosaic when a perfectly cromulent version was released by the project more than 10 years ago?  Well, first, the released version clipped the limb and terminator in the images off during the process of reprojecting the individual frames into an orthographic projection map.  So limb topography and volcanic features very close to the limb are cut off.  Second, I wanted to adjust each image based on the new USGS basemap, taking into account some incorrect camera twists in the spice kernel information, so less color fringing should be seen.  Finally, I wanted to include the two visible plumes in the data set in the mosaic itself.

You can download the finished version now [7.36 MB PNG image].  A labeled version of the image is shown above.

There were some gores in the image data that I've filled either with a single filter (Red or Green) gray-scale image or with data from orbit E4 (December 1996).  I was going to have all the gores filled with that earlier, lower resolution data, but in most cases (except for a gore at lower right), it didn't quite look right so I went with just one of the gray-scale images.

I hope you all enjoy!

No comments:

Post a Comment