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Janus, Epimetheus and the "Orbital Switch"
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Caption NASA originale:"In their orbital ballet, Janus and Epimetheus swap positions every four years - one moon moving closer to Saturn, the other moving farther away. The two recently changed positions (the swap occurring on January 21, 2006), and Janus will remain the innermost of the pair until 2010, when they will switch positions again.
Although the moons appear to be close in the image, they are not. Janus is about 40.000 Km (appx. 25.000 miles) farther away from Cassini than Epimetheus (at left) in this view. In fact, even when they are at their closest, tugging at each other and swapping orbital positions, they are never closer than about 15.000 Km (about 9.000 miles).
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 20, 2006 at a distance of approx. 452.000 Km(about 281.000 miles) from Epimetheus and 492.000 Km (about 306,000 miles) from Janus. The image scale is about 3 Km (appx. 2 miles) per pixel on both moons".
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