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Awesome Cassini mutual event movies

Posted by Emily Lakdawalla

23-12-2009 13:04 CST

Topics: pretty pictures, Cassini, Rhea, Saturn's small moons, global views, Saturn's moons, many worlds, Saturn, Mimas, animation, Saturn's rings

I love posting animations of Cassini images that I compose from frames grabbed from the mission's raw images website, but they are shoddy compared to the versions that eventually come out from the mission's imaging team. Today they released four really cool versions of mutual event movies, animations showing motions of two or more of Saturn's moons past each other. These movies are not captured just for their coolness value; they are essential for fine-tuning our measurements of the precise orbits of each of Saturn's moons.

For all four of these movies, the original data consisted of 10 to 20 individual frames, captured as Cassini was in motion with respect to the moons and Saturn. The imaging team has reprojected all the images to a common point of view (correcting somewhat for the motion of the spacecraft, which I think mostly accomplishes the goal of keeping the rings still) and then "tweened" the animation, interpolating additional, synthesized frames between the actual data to make the movies run more smoothly. I uploaded them all to my Facebook page so that I could embed them below; for much higher-resolution versions and detailed captions, follow the links to the individual animations.

Tethys, Pandora, and Prometheus dance among the rings

Animation and caption credit: NASA / JPL / SSIhttp://photojournal.jpl.nasa.gov/catalog/PIA1169115 images captured by Cassini over 33 minutes were concatenated into this view, and then additional frames were interpolated among them to smooth the animation. In the movie, Prometheus (86 kilometers, 53 miles across) enters the frame from the right and passes behind Tethys (1,062 kilometers, 660 miles across). Prometheus appears as a tiny bright dot beyond the main rings. Pandora (81 kilometers, 50 miles across) can also be seen at the bottom of the frame. The unlit side of the planet is on the left. Prometheus and Pandora's average speeds are each about 16 kilometers per second (36,000 mph). Tethys travels at an average speed of about 11 kilometers per second (25,000 mph). n this view, Tethys, at a distance of approximately 1.2 million kilometers (746,000 miles), is closest to Cassini. Prometheus is farthest from the spacecraft at a distance of approximately 1.6 million kilometers (994,000 miles). The part of the rings at the bottom of the image is closer to Cassini than the rings at the top of the image. This view looks toward the northern, sunlit side of the rings from about 1 degree above the ring plane.

Posted by Emily Lakdawalla on Wednesday, December 23, 2009
Janus, Rhea, and Saturn movie

Animation and caption credit: NASA / JPL / SSIhttp://photojournal.jpl.nasa.gov/catalog/PIA1169212 images captured by Cassini over 24 minutes were concatenated into this view, and then additional frames were interpolated among them to smooth the animation. At the start of the movie, Janus (179 kilometers, 111 miles across) appears as a small dot just below the rings on the left of the frame. The larger Rhea (1528 kilometers, 949 miles across) also starts on the left but can be seen moving more slowly across the frame. Janus is traveling almost twice as fast as Rhea with an average speed of about 16 kilometers per second (36,000 mph) compared to Rhea's average speed of roughly 8 kilometers per second (18,000 mph). In this view, Janus is approximately 2.3 million kilometers (1.4 million miles) away from NASA's Cassini spacecraft. Rhea is closer to the spacecraft, approximately 1.9 million kilometers (1.2 million miles) away. In the original images, the scale for Rhea was 11 kilometers (7 miles) per pixel. The images have been scaled down by a factor of two to reduce the movie's dimensions to a viewable size.

Posted by Emily Lakdawalla on Wednesday, December 23, 2009
Rhea, Janus, Mimas, Pandora, and the ansa of Saturn's rings: movi

Animation and caption credit: NASA / JPL / SSIhttp://photojournal.jpl.nasa.gov/catalog/PIA1169312 images captured by Cassini over 19 minutes were concatenated into this view, and then additional frames were interpolated among them to smooth the animation. At the start of the movie, Rhea (1,528 kilometers, 949 miles across) is at the lower left and moving to the right, as seen by Cassini. Janus (179 kilometers, 111 miles across) is near Rhea in the lower left. Mimas (396 kilometers, 246 miles across) is near the center top and is moving left. About one-third of the way through the movie, Pandora (81 kilometers, 50 miles across) enters the frame on the right, orbiting just beyond Saturn's rings. Mimas is farthest from Cassini at a distance of approximately 2.5 million kilometers (1.6 million miles). Rhea is closest to the spacecraft at a distance of approximately 1.9 million kilometers (1.2 million miles). Mimas travels at an average speed of 14 kilometers per second (31,000 mph). Janus' and Pandora's average speeds are each about 16 kilometers per second (36,000 mph). Rhea is the slowest of this quartet, traveling at an average speed of about 8 kilometers per second (18,000 mph).

Posted by Emily Lakdawalla on Wednesday, December 23, 2009
Mimas, Rhea, and the rings

Animation and caption credit: NASA / JPL / SSIhttp://photojournal.jpl.nasa.gov/catalog/PIA1169110 images captured by Cassini over 6 minutes were concatenated into this view, and then additional frames were interpolated among them to smooth the animation. n this video, Mimas (396 kilometers, 246 miles across) moves in front of the rings. Rhea (1,528 kilometers, 949 miles across) reveals the delicate separations within the rings as the thin line of the F ring appears before the backdrop of the mid-southern latitudes of the moon. Mimas travels at an average speed of 14 kilometers per second (31,000 mph). Rhea's average speed is about 8 kilometers per second (18,000 mph).In this view Rhea, at a distance of approximately 2.7 million kilometers (1.7 million miles), is farther from Cassini than Mimas. Mimas is closer to the spacecraft at a distance of approximately 2 million kilometers (1.2 million miles).

Posted by Emily Lakdawalla on Wednesday, December 23, 2009
 
See other posts from December 2009

 

Or read more blog entries about: pretty pictures, Cassini, Rhea, Saturn's small moons, global views, Saturn's moons, many worlds, Saturn, Mimas, animation, Saturn's rings

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