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 United States Department of Defense Missile Defense Agency's (MDA) Ballistic Missile Defense System. The radar is mounted on a fifth generation CS-50 twin-hulled semi-submersible oil platform. 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, but has spent significant time at Pearl Harbor in test status. Specifications Vessel length: Vessel beam: Vessel height: from keel to top of radome Vessel draft: approximately when in motion or not on station; approximately when on station Vessel stability: remains within 10 degrees of horizontal on station (fully passive stabilization) Vessel speed: Cost: Crew: Approximately 75-85 members, mostly civilian contractors Radar height: Radar diameter: Radar weight: Radar range: Displacement: Details SBX-1 is part of the Ground-Based Midcourse Defense (GMD) system under development by the Missile Defense Agency (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. Even though the same limitation applies to the SBX, because it can be moved it mitigates this limitation. 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. The radar antenna itself is described as being . It has 45,000 solid-state transmit-receive modules mounted on an octagonal flat base which can move ±270 degrees in azimuth and 0 to 85 degrees elevation (although software currently limits the maximum