See other posts from January 2011

Two fine color Cassini animations: Prometheus rotating, Tethys and Dione dancing

Posted By Emily Lakdawalla

2011/01/20 11:23 CST

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Cassini flew rather close to Prometheus on January 27, 2010, passing within 40,000 kilometers. At the time I made my own rather poor color version of one set of the images. But now that the high-quality, archived versions of the images have become available at the Planetary Data System, Daniel Macháček has reached into the dark side of Prometheus and pulled out an incredible amount of detail where the potato-shaped moon is illuminated by Saturnshine. He produced an animation that morphs among the three sets of four-filter color images that Cassini snapped during the flyby:

While I am posting cool Cassini animations, here's another color animation (this one made from raw images) by Ian Regan of Tethys and Dione passing in the night. The sequence was captured by Cassini on December 6 and includes a total of 75 images captured sequentially through red, green, and blue filters. Cassini's taken these "mutual event" movies since early in the mission but it's only since a year or so ago that they switched to taking them with color filters rather than the clear filter; the result is images that have the science value they need (these animations are taken in large part to help increase the precision of our measurement of the moons' orbits), plus they have extra added public interest value because they have the color information needed to represent them as "true color." The color is cool but it's a huge amount of extra added work to convert each 3-image set into single color frames; I'm happy Ian stepped in to do this!

Before you click the play button, try to guess which moon is in front! Dione is the darker of the two.