Aegis BMD ships and Aegis Ashore sites are equipped with the AN/SPY-1 S-band radar, which is capable of providing tracking and discrimination data for ballistic and cruise missiles, aircraft, and other air or space breathing threats. It is also the main fire control radar for the Aegis Combat System. Each radar has four faces to provide a 360-degree azimuth field of view. These radars support not only the onboard Standard Missile interceptors that contribute to regional and fleet defense missions, but also provide additional tracking and early-flight discrimination data for the U.S. homeland missile defense mission. Aegis BMD ships have contributed to every Ground-based Midcourse Defense system intercept test since 2002.1
As of June 2016, there are 33 Aegis BMD ships in the U.S. Navy, five Ticonderoga-class Cruisers and 28 Arleigh-Burke class Guided Missile Destroyers, equipped with SPY-1 radars.2 Aegis ships are equipped to perform a wide-range of missions, which makes them a high demand, low density asset. Furthermore, limitations on the ships’ hardware systems have, until recently, limited the vessels’ SPY-1 radar to performing a single mission at time (i.e. air defense or ballistic missile defense).
Upgrades to Aegis Baseline 9C hardware have now become available, which allow the ships to simultaneously perform both air defense and ballistic missile defense.3 Furthermore, the majority of the Navy’s contingent of Flight IIA Arleigh Burke class Destroyers, which are not currently BMD capable, are also being upgraded to Baseline 9C, which would add their SPY-1 radars to the homeland defense network. 4