Saturn's rings oscillate on a 15-year cycle. During this cycle observers on Earth can see the rings clearly because they are tilted or "open". The rings will then rotate and become nearly invisible to observers on Earth because the view becomes "edge-on" or "closed". When Cassini first arrives at Saturn, the rings are tilted, or open. This configuration of the rings allows Cassini to see the Earth and Sun become obscured by the rings. This phenomenon is called an "occultation" and provides unique scientific opportunities allowing scientists to derive information about the structure and evolution of the ring system.
This plot gives the polar view (top) and edge-on view (bottom). In the polar view the inner dashed circle represents the orbit of Titan and the outer dashed circle represents the orbit of Iapetus. Saturn and its rings are represented by the yellow circles in the centre. The scales on the axes are in Saturn radii.