Sea-based X-band Radar

The Sea-Based X-Band Radar (SBX-1) is a floating, self-propelled, mobile active electronically scanned array early-warning radar station designed to operate in high winds and heavy seas. It was developed as part of the Missile Defense Agency's Ballistic Missile Defense System.

The radar is mounted on a fifth generation CS-50 twin-hulled semi-submersible drilling rig. Conversion of the vessel was carried out at the AmFELS yard in Brownsville, Texas; the radar mount was built and mounted on the vessel at the Kiewit yard in Ingleside, Texas. It is nominally based at Adak Island in Alaska (though, as of April 2015^[update] has never put into port at Adak). It has spent significant time at Pearl Harbor in test status.

SBX-1 is part of the Ground-Based Midcourse Defense (GMD) system under development by the MDA. The decision to place the system on a mobile sea-based platform was intended to allow the vessel to be moved to areas where it is needed for enhanced missile defense. Fixed radars provide coverage for a very limited area due to the curvature of the Earth. However, the same limitation applies to the SBX. SBX's primary task is discrimination of enemy warheads from decoys, followed by precision tracking of the identified warheads. Testing has raised doubts about the system's ability to perform these tasks, to deal with multiple targets, and to report accurately to command authorities.

The vessel has many small radomes for various communications tasks and a large central dome that encloses a phased-array, 1,800 tonne (4,000,000 pound) X band radar antenna. The small radomes are rigid, but the central dome is not - the flexible cover is supported by positive air pressure amounting to a few inches of water. The amount of air pressure is variable depending on weather conditions.

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