Saturday, December 18, 2010

Updated: Io Over Jupiter's Terminator (and also a bit of historical perspective)

On March 4, 1979, Voyager 1 snapped an exquisite mosaic of Io as it completed a transit above the Jovian cloud tops. This is an improved version of a mosaic of images it took that I posted in August.

The next set is a comparison to show just how far planetary imaging has come.  The top row shows the best images of the Jovian moons Io and Ganymede from the Pioneer mission in the early 1970s as they flew by Jupiter.  The Pioneer probes were spin stabilized which (at least in those days) made it impossible for them to carry a true camera, so they had to scan line by line to build up an image. 
The bottom row also shows images of  Io and Ganymede, this time from the mid 2000s, taken by the Hubble Space Telescope.  For comparison, please keep in mind that they don't show the same parts of each  moon and the illumination angle is different, especially for Io.  Still, the Hubble images, taken from low earth orbit, are far superior.  How far we have come!

Processed Images Copyright Ted Stryk
Raw Voyager Data Courtesy NASA/JPL
Raw Pioneer Data Courtesy NASA/Ames
Raw Hubble Data Courtesy NASA/STScI


F. Marchis said...

Nioce job!
For the comparison you could have used observations of Io taken with Adaptive Optics in the NIR. They are not "as colorful" but have a better spatial resolution sicne we are using 8-10 m class telescopes to record them

Ted Stryk said...

As for the comparison, I am astounded by the quality of the AO images that you have published. However, I am not clear on the copyright status of such data, so I generally avoid them (also, I don't have raw data to process).
And yes, in this case the color image probably does provide for a more direct comparison with Pioneer. This is by far the highest resolution visible light set from Hubble. The ACS High Resolution Channel observed it three times, and each time it observed exactly the same side. My image combines all three datasets.