USNS Observation Island was quietly struck from the rolls of U.S. Navy vessels and inactivated on March 31, 2014, ending the 30-year joint Army/Air Force Cobra Judy program.

Originally launched on Aug. 15, 1953 as the Empire State Mariner, a Mariner class high speed cargo ship, the ship entered the National Defense Reserve Fleet in 1954 after a few voyages. The Empire State transferred to the Navy on Sept. 10, 1956 and became the first ship equipped with a fully integrated Fleet Ballistic Missile System.

It was officially commissioned two years later on Dec. 5, 1958 as the USS Observation Island.

On Aug. 27, 1959, the USS Observation Island made history as it launched the first sea-launched A-1 Polaris missile. After conducting six launches, the Observation Island provided support to the submarine-launched Polaris test program, providing optical and electronic data collection.

Later, President John F. Kennedy watched a Polaris launch demonstration from the decks of the Observation Island on Nov. 14, 1963.

Decommissioned in January 1972, the ship was brought back into service in August 1977 and transferred to the Military Sealift Command and redesignated the U.S. Naval Ship Observation Island. At this time it was reclassified as a T-AGM23, a missile range instrumentation ship.

Between 1979 and 1981, the ship underwent a conversion with an additional platform, a rotating steel turret, added to support the Cobra Judy S-Band Radar.

The last and most advanced of the Air Force's advanced range instrumentation ships, the Cobra Judy was "considered one of the most capable radar systems ever built in the world." Installed in 1981, the AN/SPQ-11 ship-borne phased array radar stood 40-feet-high and weighed approximately 250 tons.

At seven meters in diameter, the octagonal S-band array composed of 12,288 antenna elements was capable of tracking more than 100 targets at one time. In 1985, the system and its capabilities were augmented with the addition of an X-band radar.

Measuring five-stories in height, the X-band provided additional support in terminal phase data collection.

The fully equipped USNS Observation Island/Cobra Judy had a twofold mission: monitoring compliance with strategic arms treaties worldwide and supporting military weapons test programs. At this time, the two primary customers were the Air Force Foreign Technology Division and the U.S. Army Strategic Defense Command, a predecessor to the U.S. Army Space and Missile Defense Command/Army Forces Strategic Command.

The Cobra Judy was particularly important to the command's missile defense programs.

Since fiscal year 1972, the ballistic missile defense program had focused its research and development efforts upon terminal or endoatmospheric intercepts. With the Strategic Defense Initiative, the guidance shifted to the exoatmosphere.

Additional information was needed to identify effectively targets in this new environment. Cobra Judy provided the necessary high resolution metric and signature data on midcourse and reentry phases of ballistic missiles flights with particular attention given to the size, shape, mass and precise motion of the target. This information would help recreate target trajectories and define vehicle signatures enhancing future discrimination algorithms.

As the missile defense program progressed, Cobra Judy provided support to many of the missile programs, collecting flight data on both strategic and theater missiles and interceptors throughout the test program. In addition, Cobra Judy participated in Operation Burnt Frost, the destruction of the defective American satellite in 2008.

Over the years, however with few replacement parts available, it became increasingly difficult to support and maintain the Cobra Judy radars. Nevertheless, the USNS Observation Island continued to operate and completed its final mission in December 2013. It is to be replaced by the new COBRA KING radar system housed aboard the USNS Howard O. Lorenzen.

For more than 31 years, the Observation Island/Cobra Judy averaged more than 260 days a year at sea and completed 558 nationally sponsored missions. As Ed Hotz, a Cobra Judy program manager, observed this spring. "The information collected was critical in the development of shoot-down algorithms for both tactical and strategic missile defense systems; supporting international treaty verification; [and] providing national decision makers, from the president on down, with precise actionable data on world events."