Phalanx CIWS
In 2016, four destroyers patrolling with the U.S. 6th Fleet based in Naval Station Rota, Spain, including "Donald Cook" received self-protection upgrades, replacing the aft Phalanx CIWS 20mm Vulcan cannon with the SeaRAM 11-cell RIM-116 Rolling Airframe Missile launcher. The SeaRam uses the same sensor dome as the Phalanx. This was the first time the close-range ship defense system was paired with an Aegis ship. All four ships to receive the upgrade were either Fligjt I or II, meaning they originally had two Phalanx CIWS systems when launched.