CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Atlas' Ring Shadow Premiere

Atlas joins other moons casting shadows on Saturn's rings as the planet approaches its August 2009 equinox.

Atlas (30 kilometers, 19 miles across) orbits in the Roche Division between the A ring and the thin F ring, and the moon can be see here casting its shadow on the A ring and across the narrow Keeler Gap. 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.

Stars can be seen through the rings and in the background. They appear elongated because of the camera's long exposure time.

This view looks toward the unilluminated side of the rings from about 51 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 28, 2009. The view was obtained at a distance of approximately 1.5 million kilometers (932,000 miles) from Atlas and at a Sun-Atlas-spacecraft, or phase, angle of 82 degrees. Image scale is 9 kilometers (5 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: August 5, 2009 (PIA 11551)
Image/Caption Information
  Atlas' Ring Shadow Premiere
PIA 11551

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Alliance Member Comments
stowaway (Aug 5, 2009 at 1:01 PM):
Yeah Atlas! Welcome to the club!