Ground-Based Midcourse Defense (GMD) is the United States' anti-ballistic missile system for intercepting incoming warheads in space, during the midcourse phase of ballistic trajectory flight. It is a major component of the American missile defense strategy to counter ballistic missiles, including intercontinental ballistic missiles (ICBMs) carrying nuclear, chemical, biological or conventional warheads. The system is deployed in military bases in the states of Alaska and California; in 2018 comprising 44 interceptors and spanning 15 time zones with sensors on land, at sea, and in orbit. In 2019, a missile defense review requested that 20 additional ground-based interceptors be based in Alaska. GMD is administered by the U.S. Missile Defense Agency (MDA), while the operational control and execution is provided by the U.S. Army, and support functions are provided by the U.S. Air Force. Previously known as National Missile Defense (NMD), the name was changed in 2002 to differentiate it from other U.S. missile defense programs, such as space-based and sea-based intercept programs, or defense targeting the boost phase and reentry flight phases. The program was projected to have cost $40 billion by 2017. That year, the MDA scheduled its first intercept test in three years in the wake of North Korea's accelerated long-range missile testing program. Description The system consists of radar and ground-based interceptor missiles for intercepting incoming warheads in space. Boeing Defense, Space & Security is the prime contractor of the program, tasked to oversee and integrate systems from other major defense sub-contractors, such as Computer Sciences Corporation and Raytheon. The key sub-systems of the GMD system are: Exoatmospheric Kill Vehicle (EKV) – Raytheon Ground-Based Interceptor (GBI) – boost vehicle built by Orbital Sciences; for every interceptor missile there are a missile silo and a silo interface vault (SIV), which is an underground electronics room adjacent to the silo. Battle management command, control and communications (BMC3) – Northrop Grumman Ground-based radars (GBR) – Raytheon AN/FPS-132 Upgraded Early Warning Radar (UEWR) – Raytheon Forward-based X band radars (FBXB), such as the sea-based X-band platform and the AN/TPY-2 — Raytheon Interceptor sites are at Fort Greely, Alaska and Vandenberg Space Force Base, California. A third site was planned for a proposed US missile defense complex in Poland, but was canceled in September 2009. In December 2008, the U.S. Missile Defense Agency awarded Boeing a $397.9 million contract to continue development of the program. In March 2013, the Obama administration announced