From the Cassini web site:
Titan’s smoggy atmosphere glows brilliantly in scattered sunlight, creating a thin, gleaming crescent beyond Saturn’s rings. At this slight angle above the ringplane, the thin F ring shines brightly. Light from Titan’s eastern and western limbs (edges) penetrates the Cassini Division, which looks like a thin gap from this angle.
This year, Cassini’s orbit has been adjusted to permit the probe to study the rings backlit by the sun (or apparently, Titan, too). Also in the plan is to study the interruption of the radio signal on its way from Cassini to the earth.
Go here for a bit of science history on the rings of Saturn. People are often surprised to learn that Galileo didn’t discover them. He saw them, certainly, but didn’t identify them as rings. First he thought they were two moons on opposite ends of the planet. Then they “disappeared” shortly after his first telescopic observations. (Every fourteen years, Saturn’s ring plane is edge on as observed from earth.) It was the Dutch scientist Christiaan Huygens who first surfaced the notion these were rings a few decades later. By 1665, the Huygens model was taken seriously by most astronomers. However, the debate of solid disk versus particles was not definitively settled until two centuries ago.