Her conversion to the first naval ship having a fully integrated Fleet Ballistic Missile System was authorized 15 October 1957, and partial completion of the project was accomplished at Norfolk Naval Shipyard, Portsmouth, Virginia.
before she commissioned 5 December 1958 as Observation Island (EAG-154), Captain Leslie M. Slack, USN, in command.

During the conversion there were no major hull or engineering changes made other than installation of a roll stabilization system.
However, extensive alterations were accomplished in the superstructure and hold areas so as to accommodate the Fleet Ballistic Missile (FBM) Weapons System.
Observation Island departed her homeport of Norfolk 3 January 1959, underwent shakedown at Guantanamo Bay, and then operated on the Atlantic Missile Range off Cape Canaveral, conducting dummy missile launches and communications tests.

In March 1959, Observation Island returned to Norfolk Naval Shipyard for installation of additional equipment, including the Ships Inertial Navigation System (SINS).
In June she steamed for her new homeport, Port Canaveral, Florida, and made preparations for the first at-sea launch of a Polaris missile.
Designated UGM-27, the missile was successfully launched from Observation Island 27 August 1959.

Following this milestone, Observation Island returned to Norfolk Naval Shipyard for installation of a fire control system to enable her to launch more sophisticated guided versions of new generation Polaris missiles.
She also received a new launcher, the developmental prototype of those installed in the ballistic missile submarines.

This work was completed in January 1960 and Observation Island returned to Port Canaveral to continue Polaris test launch operations.
After a total of six launchings, the ship commenced support of Polaris launchings from submarines.
She provided optical and electronic data gathering services, and acted as communications relay station between submerged submarines and the supervisor of range operations at the Cape.
The first successful fully guided Polaris missile launching from a submerged submarine took place 20 July 1960 from USS George Washington (SSBN-598).
Through October Observation Island also supported launches from USS Patrick Henry (SSBN-599).

Following further modifications at Norfolk Naval Shipyard in the fall of 1960, Observation Island returned to Port Canaveral in December to continue fleet ballistic missile support work and systems test and evaluation.
She received the Navy Unit Commendation 15 December; launched the new A-2 Polaris 1 March 1961; and supported the first submerged A-2 launch from USS Ethan Allen (SSBN-608) 23 October 1961.

In late 1961 Observation Island served as a survey ship on the Atlantic Missile Range, and in January 1962 she again put in at Norfolk Naval Shipyard, this time for modifications preparatory to launching the new A-3 Polaris.
Returning to Port Canaveral in March, she supported ballistic missile submarines through the following autumn, when she steamed for two months of operations on the Pacific Missile Range.

Observation Island was back at Port Canaveral by Christmas 1962, and until June 1963 she expanded her role of oceanographic survey in the Atlantic Range.
She conducted the first successful at-sea launches of the A-3 Polaris 17 and 21 June.
President John F. Kennedy came on board 16 November 1963 to observe a Polaris launch, six days before his assassination.

Observation Island was redesignated AG-154 on 1 April 1968.
She commenced an extensive ten month conversion 24 June at Norfolk Naval Shipyard in preparation for support of the Poseidon C-3 missile program.
The summer of 1969 found her once again at Port Canaveral, ready to resume experimental missile launchings, to assist in the training of submarine crews, to assist in ballistic missile submarine shakedown operations at Cape Kennedy, and to support other important phases of the development and deployment of the fleet ballistic missile weapons system.

While the Observation Island was stationed at Port Canaveral, adjacent to NASA at Cape K
Her conversion to the first naval ship having a fully integrated Fleet Ballistic Missile System was authorized 15 October 1957, and partial completion of the project was accomplished at Norfolk Naval Shipyard, Portsmouth, Virginia. before she commissioned 5 December 1958 as Observation Island (EAG-154), Captain Leslie M. Slack, USN, in command.
During the conversion there were no major hull or engineering changes made other than installation of a roll stabilization system. However, extensive alterations were accomplished in the superstructure and hold areas so as to accommodate the Fleet Ballistic Missile (FBM) Weapons System. Observation Island departed her homeport of Norfolk 3 January 1959, underwent shakedown at Guantanamo Bay, and then operated on the Atlantic Missile Range off Cape Canaveral, conducting dummy missile launches and communications tests.
In March 1959, Observation Island returned to Norfolk Naval Shipyard for installation of additional equipment, including the Ships Inertial Navigation System (SINS). In June she steamed for her new homeport, Port Canaveral, Florida, and made preparations for the first at-sea launch of a Polaris missile. Designated UGM-27, the missile was successfully launched from Observation Island 27 August 1959.
Following this milestone, Observation Island returned to Norfolk Naval Shipyard for installation of a fire control system to enable her to launch more sophisticated guided versions of new generation Polaris missiles. She also received a new launcher, the developmental prototype of those installed in the ballistic missile submarines.
This work was completed in January 1960 and Observation Island returned to Port Canaveral to continue Polaris test launch operations. After a total of six launchings, the ship commenced support of Polaris launchings from submarines. She provided optical and electronic data gathering services, and acted as communications relay station between submerged submarines and the supervisor of range operations at the Cape. The first successful fully guided Polaris missile launching from a submerged submarine took place 20 July 1960 from USS George Washington (SSBN-598). Through October Observation Island also supported launches from USS Patrick Henry (SSBN-599).
Following further modifications at Norfolk Naval Shipyard in the fall of 1960, Observation Island returned to Port Canaveral in December to continue fleet ballistic missile support work and systems test and evaluation. She received the Navy Unit Commendation 15 December; launched the new A-2 Polaris 1 March 1961; and supported the first submerged A-2 launch from USS Ethan Allen (SSBN-608) 23 October 1961.
In late 1961 Observation Island served as a survey ship on the Atlantic Missile Range, and in January 1962 she again put in at Norfolk Naval Shipyard, this time for modifications preparatory to launching the new A-3 Polaris. Returning to Port Canaveral in March, she supported ballistic missile submarines through the following autumn, when she steamed for two months of operations on the Pacific Missile Range.
Observation Island was back at Port Canaveral by Christmas 1962, and until June 1963 she expanded her role of oceanographic survey in the Atlantic Range. She conducted the first successful at-sea launches of the A-3 Polaris 17 and 21 June. President John F. Kennedy came on board 16 November 1963 to observe a Polaris launch, six days before his assassination.
Observation Island was redesignated AG-154 on 1 April 1968. She commenced an extensive ten month conversion 24 June at Norfolk Naval Shipyard in preparation for support of the Poseidon C-3 missile program. The summer of 1969 found her once again at Port Canaveral, ready to resume experimental missile launchings, to assist in the training of submarine crews, to assist in ballistic missile submarine shakedown operations at Cape Kennedy, and to support other important phases of the development and deployment of the fleet ballistic missile weapons system.
While the Observation Island was stationed at Port Canaveral, adjacent to NASA at Cape K
USNS Observation Island (T-AGM-23)