<P> The radar is derived from the radar used in the THAAD theater ballistic missile defense system, and is a part of the layered ballistic missile defense (BMDS) program of the United States Missile Defense Agency (MDA). One important difference from Aegis is the use of X band in the SBX . Aegis uses S band, and Patriot uses the higher - frequency C band . The X band frequency is higher still, so its shorter wavelength enables finer resolution of tracked objects . </P> <P> The radar was described by Lt. Gen Trey Obering (former director of MDA) as being able to track an object the size of a baseball over San Francisco in California from Chesapeake Bay in Virginia, approximately 2,900 miles (4,700 km) away . The radar will guide land - based missiles from Alaska and California, as well as in - theater assets, depending on the mission . </P> <P> The vessel is classed by ABS and has the IMO number of 8765412 . </P> <P> The first such vessel is scheduled to be based in Adak Island, Alaska, part of the Aleutian Islands . From that location it will be able to track missiles launched toward the US from both North Korea and China . Although her homeport is in Alaska, she will be tasked with moving throughout the Pacific Ocean to support her mission . The hull code number given to the SBX vessel, "SBX - 1," indicates the possibility of further units of the class . In circumstances when a vessel is required to be continually on duty over a long period of time, common naval practice is to have at least three units of the type available to allow for replenishment, repair and overhaul . Three further vessels of the CS - 50 / Moss Sirius design were under construction or contract at the Severodvinsk Shipyard in Russia as of early 2007, but were configured for oil production . On May 11, 2011, Col. Mark Arn, the SBX project manager for MDA, said that the "SBX is the only one of its kind and there are no current plans for another one". In July 2011, a Missile Defense Agency spokesman explained that other, smaller radars in the Pacific will "pick up the slack" while SBX is in port with its radar turned off . </P>

What is the big golf ball in pearl harbor