USNS Mission San Juan ( T - AO - 126 ) SS " Mission San Juan was a Type T2 - SE - A2 tanker built for the United States Maritime Commission during World War II . After the war she was acquired by the United States Navy as USS " Mission San Juan . Later the tanker transferred to the Military Sea Transportation Service as USNS " Mission San Juan " . She was a member of the and was named for Mission San Juan Bautista in San Juan Bautista , California . Service history . As oiler , 1943 – 1958 . " Mission San Juan " was laid down on 30 July 1943 under a Maritime Commission contract by Marine Ship Corporation , Sausalito , California ; launched on 14 October 1943 , sponsored by Mrs . Derrill D . Standifird ; and delivered to the Maritime Commission on 31 January 1944 upon completion . Chartered to Deconhill Shipping Company in February , 1944 the tanker spent the remainder of the war supplying fuel oil to American and Allied Forces overseas , during which time she was awarded the National Defense Service Medal . Shortly after the cessation of hostilities , " Mission San Juan " was placed in the Maritime Commission Reserve Fleet at Mobile , Alabama on 9 April 1946 . Acquired by the Navy on 21 November 1947 she was retransferred to the Naval Transportation Service the same date . Designated as " Mission San Juan " ( AO - 126 ) , she served as such until 1 October 1949 when the newly formed Military Sea Transportation Service took over the functions and ships of the Naval and Army Transportation Services . Acquired by MSTS on 1 October , she was designated USNS " Mission San Juan " ( T - AO - 126 ) and was placed in service with a civilian crew . During the Korean War , she carried fuel to the forward operating bases and continued in this duty until after the war , until 12 February 1958 when she was placed out of service by MSTS , stricken from the Naval Vessel Register and transferred on the same date to the Maritime Administration and laid up in the Reserve Fleet at Beaumont , Texas . As tracking ship , 1964 – 1970 . Reacquired by the Navy on 28 October 1964 , " Mission San Juan " was moved to the General Dynamics Shipyard , Quincy , Massachusetts , for conversion into a missile range instrumentation ship . During this conversion , she was jumboized by fitting a new 72 - foot section amidships and virtually rebuilt in order to accommodate the required electronic equipment . Renamed " Flagstaff " and designated AGM - 21 on 8 April 1965 , she was again renamed , on 1 September 1965 , to " Mercury " . Accepted by MSTS for service on 16 September 1965 , she was designated as USNS " Mercury " ( T - AGM - 21 ) and assigned to MSTS Atlantic for duty . During the Project Gemini series of orbits , she served as an important link between the astronauts and the control stations at Cape Canaveral . She carried out this duty until the summer of 1967 when she returned to the yard at Quincy for the installation of satellite terminals . Upon completion of this installation on 18 September 1967 , she was reassigned to MSTS , Atlantic , but shortly thereafter was reassigned to MSTS , Pacific . There she was to play an important part in the Project Apollo moon shot tests as she provided important communication links between the Apollo moon craft and earth tracking stations . As bulk - carrier , 1970 – 1984 . The ship was sold on 23 June 1970 to Matson Navigation Co . for conversion to a bulk - carrier at the Willamette Iron and Steel Works , Portland , Oregon , and renamed SS " Kopaa " . Sold in February 1981 to California & Hawaii Sugar Co . , she was sold for scrapping at Taiwan in October 1984 .