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Emily Lakdawalla • Nov 09, 2010
An awesome animation of Jupiter's clouds
Ready to see something beautiful? Here's a team effort by Björn Jónsson (who did the image processing) and Ian Regan (who tweened the animation) to create a really mesmerizing view of the motions of Jupiter's clouds. Through the magic of image reprojection, Björn has held Jupiter and its Great Red Spot still for 16 Jupiter days while the planet's belts, zones, and smaller storms swirl past.
Jupiter's cloud motions as Voyager 1 approaches This movie is based on 58 orange-green-blue color composites obtained on every Jovian rotation from January 6 to January 29, 1979. Over this period Voyager 1's distance from Jupiter dropped from 58 to 36 million km, so the resolution and sharpness of the frames increases from start to finish. The 58 frames were tweened, increasing the number of frames by a factor of 8 (that is, 7 synthetic frames are inserted between each real frame).Video: NASA / JPL-Caltech / Processed by Björn Jónsson
Every second in this movie corresponds to 1 Jupiter day or about 10 Earth hours. This movie began as a 16-frame animation of Voyager 1 images of Jupiter. Each of the 16 images was composed by Björn Jónsson from three Voyager frames taken through orange, green, and blue filters, which he reprojected into a cylindrical map, aligned, and then projected back into the slightly squashed spherical shape of Jupiter. (This reprojection step is necessary because around two minutes elapsed between each of the component images, which, because of Jupiter's fast rotation, would result in color ghosting if they were simply overlaid.) Jónsson selected sets of images featuring the Great Red Spot near the center of Jupiter's disk, one per Jupiter day, and reprojected them to maintain a constant position for the Spot. By holding the GRS still he highlights the motions of the clouds that happen from Jupiter day to Jupiter day.
Ian Regan took Jónsson's 16-frame animation (representing 16 Jupiter days or about 7 Earth days) and "tweened" it, using software to compute frames to fill in the time between each of the original 16 images. The result is a smooth animation of the motion of Jupiter's clouds.
Jupiter may appear slightly "washed out." Jónsson has attempted to reconstruct Jupiter's color as it would actually appear to the human eye, without exaggerating the colors. However, it should be noted that the Voyager camera systems were not sensitive to light in red wavelengths (the longest wavelength they could detect is in a region we'd call "orange"). Since Jupiter is colorful in red wavelengths, attempting to produce "true color" images from Voyager data results in slightly less colorful views than we can see with modern CCDs or our own eyes.