Monday, December 28, 2009

A "New" Galileo View of Io

This view of Io is a combination of three images taken over a span of about 40 minutes at around 16 hours on March 31, 1997 (orbit G7).  While taken only for the purpose of optical navigation, when combined, these images show a significant amount of Io's limb (both in Jupiter shine and in sunlight).  At the very bottom, the sampling is so poor that nothing reliable could be brought out.  I also removed any "plume" that was based on only one image or that was based on one pixel (due to interpolation, such a feature might appear as big as three pixels across and therefore be deceptive).  After doing so, only one plume-like feature remained, corresponding to Io's Pele volcano.  It is exaggerated for visibility in the following image.  Please note that the processing to bring out the plume also brought out a few spurious 1-pixel features.   Missing areas of the image were never transmitted.

Since a view like this is hard to interpret, I combined this dataset with reprojected images, mainly from this orbit but a few from neighboring orbits, some adjusted to the nightside brightness where appropriate, in order to fill in the gaps.  Please note that not all the data in the above image is as overexposed on the dayside as it appears here (I stretched the contrast to aid visibility of the plume).  I also created a color overlay from this and other orbits.  Both images in this post are shown at 2.5x original size to aid visibility.

 While the above image is mostly the fill in data from G7 and other orbits described above, data from this OPNAV set was used where available.  The purpose of this image is to show Pele's plume in context.

Processed Image Copyright Ted Stryk, Raw Data Courtesy NASA/JPL

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