CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Race of the Moons
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Race of the Moons
PIA 06174

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  This movie, showing six of Saturn's small ring-region moons as they raced around the planet, was made from images taken by Cassini on November 15, 2004.

The moons appear in following order (their diameters are given in parentheses): Janus (179 kilometers, 111 miles), Atlas (30 km, 19 mi), Epimetheus (113 km, 70 mi), Prometheus (86 km, 53 mi), Pandora (81 km, 50 mi) and Pan (28 km, 17 mi). Each moon is marked by a colored circle that corresponds to the key at lower left.

While little detail on the moons is visible, it is possible to discern the irregular shapes of the larger ones seen in this movie. The rings are overexposed due to the long exposure times used (2 seconds per image): doing so makes the smaller, fainter moons (especially Pan) easier to detect. The direction of the moons' motion is prograde, or clockwise as seen from Cassini's vantage point beneath the ringplane.

In addition to the moons, knots in the F ring are visible here, as are several faint ringlets on both sides of that ring's bright core. Faint knots also appear sporadically within the narrow Encke gap, where tiny Pan resides.

The movie consists of 73 images and spans a period of just over 14.5 hours, about an orbital period of the particles in the F ring.

The individual frames were taken at 12 minute intervals in visible light with Cassini's narrow angle camera. The spacecraft was about 4.5 million kilometers (2.8 million miles) from Saturn when the images were taken. Image scale is approximately 26.5 kilometers (16.5 miles) per pixel.

[Caption updated on October 4, 2005.]

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission, visit and the Cassini imaging team home page,

Credit: NASA/JPL/Space Science Institute
Released: January 18, 2005 (PIA 06174)
Image/Caption Information

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