On 29 March, 1960, OBSERVATION ISLAND launched the first fully-guided Polaris Fleet Ballistic Missile (FBM). During July, she gathered optical and electronic data and served as a communications relay ship in support of the first successful launch of a Polaris FBM from a submerged vessel by the fleet ballistic missile submarine GEORGE WASHINGTON (SSBN-598) on the 20th. After the historic launch the Commanding Officer of GEORGE WASHINGTON sent the message to President Eisenhower: “Polaris—from out of the deep to target. Perfect.”
Prior to being commissioned a Navy ship on 5 December 1958, OBSERVATION ISLAND was launched as a cargo ship named EMPIRE STATE MARINER in 1953. The ship served briefly with the Military Sea Transportation Service (MSTS), the precursor to Military Sealift Command (MSC), until she entered the National Defense Reserve Fleet on 9 November 1954.
In 1956, the Navy began development of Polaris as a replacement for the Regulus Cruise Missile. As a result, the EMPIRE STATE MARINER transferred to Navy custody on 10 September 1956 and received a fully integrated FBM system at Norfolk Naval Shipyard that would allow her to serve as an at-sea test platform for the Navy.
Operating out of her homeport of Port Canaveral, Florida, OBSERVATION ISLAND conducted the first at-sea launching of a Polaris missile on 27 August 1959 at the Atlantic Missile Range. For the vessels critical contributions to the Polaris program during 1959 through the submerged firing from GEORGE WASHIGNTON on July 20, 1960, the Navy awarded her the Navy Unit Commendation.
As the number of Navy fleet ballistic missile submarine grew, OBSERVATION ISLAND continued to serve as a test platform, including the launch of the A-2 version Polaris in March 1961 and the A-3 version in June 1963. On 16 November 1963, less than a week before his assassination, President John F. Kennedy visited OBSERVATION ISLAND to witness a Polaris launching from ANDREW JACKSON (SSBN-619).
On 1 April 1968, the ship was redesignated AG-154 and in June of that year, she entered Norfolk Naval Shipyard to begin a conversion to ready her for testing of the Poseidon missile. The Navy decommissioned OBSERVATION ISLAND on 1 January 1972 and she currently serves as a missile range instrumentation ship, T-AGM-23, with MSC.