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 of 0.94, 3.6, and 13 centimeter
wavelengths (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
as a function of distance from Saturn, or an optical depth profile.
This simulated image was constructed from the measured optical depth
profiles. It depicts the observed ring structure at about 10 kilometers
(6 miles) in resolution. Color is used to represent information about
ring particle sizes in different regions based on the measured effects of
the three radio signals.
Shades of purple, primarily over most of the inner ring (ring B) and the
inner portion of the next ring (ring A), 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, primarily in outer ring A and within
most of ring C. From other evidence in the radio observations, all ring
regions appear to be populated by a broad range of particle size
distribution that extends to boulder sizes (several to many meters or
yards across).
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.
