Pan, the innermost known satellite, was found from photographs taken by Voyager during its encounter with Saturn. It was discovered by Mark R. Showalter in 1990, 9 years after the Voyager encounter. Pan is located 133,583 kilometers from the center of Saturn and is within the Encke Gap of Saturn's A-ring. It acts as a shepherd and is responsible for keeping the Encke gap open. It has a diameter of 20 kilometers.