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Spokes
 

 

 

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Summary

Description Dark spokes dance around Saturn's B ring in this series of movies comprised of images taken with Cassini's wide-angle camera.

This animation is a concatenation of spoke movies acquired by NASA's Cassini spacecraft in the second half of 2008 on Aug. 21, Sept. 19, Sept. 26, Oct. 11, and Nov. 25.

As Saturn nears equinox in August 2009 and the sun angle on the ring plane decreases, spokes become common sights in Cassini images, just as they were in Voyager images (See PIA02275). The planet's orbital period is 29.5 years, so Saturn has nearly made one complete trip around the sun since the flybys of the two Voyager spacecraft in 1980 and 1981, allowing Cassini to closely match Voyager's viewing geometry.

Each of these five movies shows the sunlit side of the rings at low solar phase, or spacecraft-rings-sun, angles. The spokes appear dark against Saturn's B ring at low phase angles because the particles within them scatter light more efficiently in the forward direction (away from Cassini) than the surrounding larger ring particles. In the opposite viewing geometry, at high phase angles, spokes appear bright relative to surrounding ring particles (See PIA07807).

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 mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

The original NASA QuickTime movie was manipulated by exporting frames to TIFF images. Selected frames were then reduced in size and converted into a GIF animation.
Date 26 September 2008(2008-09-26)
Source http://photojournal.jpl.nasa.gov/catalog/PIA11144
Author NASA/JPL/Space Science Institute
Other versions
21 August  2008(2008-08-21) sequence: 7.5 seconds at 300 pixels and low bitrate of 51kbps
21 August 2008(2008-08-21) sequence: 7.5 seconds at 300 pixels and low bitrate of 51kbps  
19 September  2008(2008-09-19) sequence: 7 seconds at 300 pixels and low bitrate of 48kbps
19 September 2008(2008-09-19) sequence: 7 seconds at 300 pixels and low bitrate of 48kbps  
26 September  2008(2008-09-26) sequence: 7.5 seconds at 300 pixels and low bitrate of 48kbps
26 September 2008(2008-09-26) sequence: 7.5 seconds at 300 pixels and low bitrate of 48kbps  
11 October  2008(2008-10-11) sequence: 10 seconds at 300 pixels and low bitrate of 39kbps
11 October 2008(2008-10-11) sequence: 10 seconds at 300 pixels and low bitrate of 39kbps  
25 November  2008(2008-11-25) sequence: 10 seconds at 300 pixels and low bitrate of 52kbps
25 November 2008(2008-11-25) sequence: 10 seconds at 300 pixels and low bitrate of 52kbps  
21 August  2008(2008-08-21) sequence: 7.5 seconds at full size and bitrate of 528kbps
21 August 2008(2008-08-21) sequence: 7.5 seconds at full size and bitrate of 528kbps  
19 September  2008(2008-09-19) sequence: 7 seconds at full size and bitrate of 545kbps
19 September 2008(2008-09-19) sequence: 7 seconds at full size and bitrate of 545kbps  
26 September  2008(2008-09-26) sequence: 7.5 seconds at full size and bitrate of 471kbps
26 September 2008(2008-09-26) sequence: 7.5 seconds at full size and bitrate of 471kbps  
11 October  2008(2008-10-11) sequence: 10 seconds at full size and bitrate of 470kbps
11 October 2008(2008-10-11) sequence: 10 seconds at full size and bitrate of 470kbps  
25 November  2008(2008-11-25) sequence: 10 seconds at full size and bitrate of 372kbps
25 November 2008(2008-11-25) sequence: 10 seconds at full size and bitrate of 372kbps  
All five sequences together at full 1016×1016 pixels size: length 44s, 1,888kbps
All five sequences together at full 1016×1016 pixels size: length 44s, 1,888kbps  

Licensing

Public domain This file is in the public domain because it was created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.)

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EXIF data:
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Mime type image/jpeg
Image input equipment manufacturer Canon
Image input equipment model Canon PowerShot A60
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Date and time original image was generated 2006:03:18 12:57:49
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