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
wavelength (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.
Purple color indicates regions where there is a lack of particles of size
less than 5 centimeters (about 2 inches). Green and blue shades indicate
regions where there are particles smaller than 5 centimeters (2 inches)
and 1 centimeter (less than one third of one inch). The saturated broad
white band near the middle of ring B is the densest region of ring B,
over which two of the three radio signals were blocked at 10-kilometer
(6-mile) resolution, preventing accurate color representation over this
band. From other evidence in the radio observations, all ring regions
appear to be populated by a broad range particle size distribution that
extends to boulder sizes (several to many meters 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.
