On 22 February 1960, "Grayback" modified her missile launching system and simplified her complex electrical circuits. After this, she again took up deterrent missile strike missions. Over the next 2½ years she completed seven missions for a total of nearly 18 months at sea, much of this time submerged. In addition to Yokosuka, both Adak, Alaska, and Pearl Harbor also served as termination points for these patrols. On her nine patrols she spent more than 20 months at sea and logged over 130,000 miles (209,000 km) on deterrent missile strike missions.