physical elevation to 80 degrees). The maximum azimuth and elevation velocities are approximately 5-8 degrees per second. In addition to the physical motion of the base, the beam can be electronically steered off bore-sight (details classified). There are currently 22,000 modules installed on the base. Each module has one transmit-receive feed horn and one auxiliary receive feed horn for a second polarization, totaling 44,000 feed horns. The base is roughly 2/3 populated, with space for installation of additional modules. The current modules are concentrated toward the center to minimize grating lobes. This configuration allows it to support the very-long-range target discrimination and tracking that GMD's midcourse segment requires. The radar is never pointed at land, for the safety of the inhabitants. In addition to the power consumed by the radar, the thrusters which propel the vessel are electric and require substantial power. The maximum speed is approximately . To support this and all other electrical equipment, the vessel currently has six 3.6-megawatt generators (12-cylinder Caterpillar diesels). The generators are in two compartments, one port and one starboard. 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. 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 away. The radar will guide land-based missiles from Alaska and California, as well as in-theater assets, depending on the mission. The vessel is classed by ABS and has the IMO number of 8765412. 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