Specially designed Cassini orbits place Earth and Cassini on opposite
sides of Saturn's rings, a geometry known as occultation. Cassini
conducted the first radio occultation observation of Saturn's rings on
May 3, 2005.
Three simultaneous radio signals at wavelengths of 0.94, 3.6, and 13
centimeters (Ka-, X-, and S-bands) were sent from Cassini through the
rings to Earth. The observed change of each signal as Cassini moved
behind the rings provided a profile of the distribution of ring material
and an optical depth profile.
This simulated image was constructed from the measured optical depth
profiles of the Cassini Division and ring A. It depicts the observed
structure at about 10 kilometers (6 miles) in resolution. The image shows
the same ring A region depicted in a similar image (PIA07874), using
a different color scheme to enhance the view of a remarkable array of
over 40 wavy features called "density waves" uncovered in the May 3 radio
occultation throughout ring A.
Color is used to represent information about ring particle sizes based on
the measured effects of the three radio signals. Shades of red indicate
regions where there is a lack of particles less than 5 centimeters (about
2 inches) in diameter. Green and blue shades indicate regions where there
are particles of sizes smaller than 5 centimeters (2 inches) and 1
centimeter (less than one third of an inch), respectively.
Note the gradual increase in shades of green towards the outer edge of
ring A. It indicates gradual increase in the abundance of 5-centimeter
(2-inch) and smaller particles. Note also the blue shades in the vicinity
of the Keeler gap (the narrow dark band near the edge of ring A). They
indicate increased abundance of even smaller particles of diameter less
than a centimeter. Frequent collisions between large ring particles in
this dynamically active region likely fragment the larger particles into
more numerous smaller ones.
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 was designed, developed and
assembled at JPL. The radio science team is based at JPL.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov. For more information on the radio science team visit
http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-rss.cfm.
