CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Epimetheus' Shadow

The shadow of the moon Epimetheus is cast onto Saturn's rings, striking the outer-most part of the A ring and only just nipping the F ring.

Epimetheus (113 kilometers, 70 miles across) is not shown. Bright specks in the image are background stars.

The novel illumination geometry created as Saturn approaches its August 2009 equinox allows moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. To learn more about this special time and to see movies of moons' shadows moving across the rings, see PIA11651 and PIA11660.

This view looks toward the unilluminated side of the rings from about 59 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 30, 2009. The view was obtained at a distance of approximately 1.6 million kilometers (994,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 77 degrees. Image scale is 9 kilometers (6 miles) per pixel.

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. 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 Equinox Mission visit, and

Credit: NASA/JPL/Space Science Institute
Released: July 10, 2009 (PIA 11533)
Image/Caption Information
  Epimetheus' Shadow
PIA 11533

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Alliance Member Comments
mipsandbips (Jul 10, 2009 at 7:06 PM):
Compared to the image "Groundhog Day on Saturn" (image 3/23/09),
the elapsed time between the capture of these two images is about
19 weeks. The camera angle view here in contrast to that image is
a difference of 86 degrees. Revisiting the "Groundhog Day" photo
reveals a very thick and dark shadow of Epimetheus across the A ring
taken on 1/8/09 which was below the ring plane. Here,
at the above angle ring plane view, the shadow cast onto the A ring
is much lighter, thinner and narrow and stretches further towards the
Encke gap than the image in "Groundhog Day".