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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. 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.〔(''Reorganization of the Missile Defense Program: Hearing Before the S. Armed Services Comm. Strategic Forces Subcomm.'' (statement of Ronald T. Kadish) ). MDA. 13 March 2002.〕 The program is projected to cost $40 billion by 2017. ==Description== The system consists of ground-based interceptor missiles and radar which would intercept 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. 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 * Upgraded early-warning radars (UEWR) (or PAVE PAWS) – 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〔(Begich, Gates visit Alaska missile defense base ) By Tim Bradner, Alaska Journal of Commerce, June 5, 2009.〕〔(Northrop Grumman Contribution to Support Missile Defense Workforce in Alaska ). reuters.com, Oct 30, 2009.〕〔(Commanding Alaska's Guard w/ 24/7 missile defense )〕 and Vandenberg Air Force Base, California. A third site was planned for a proposed US missile defense complex in Poland,〔(【引用サイトリンク】title=Missile Defense Agency (MDA) Exhibit R-2 RDT&E Budget Item Justification )〕 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.〔"Boeing Wins Missile Deal". ''Washington Post'', December 31, 2008, p. D2.〕 In March 2013, the Obama administration announced plans to add 14 interceptors to the current 26 at Fort Greely in response to North Korean threats.〔("US to beef up missile defense against NKorea." )〕 The deployment of a second TPY-2 radar to Japan was announced at the same time.〔("Alaska's Ground Based Interceptors to Pivot US Defenses Against North Korea." )〕 While Obama said that the additional deployment was a hedge against unexpected capabilities, Chinese Ministry of Foreign Affairs spokesman Hong Lei complained that the additional defenses would impact on global strategic balance and strategic trust.〔("China: U.S. risks antagonizing North Korea." )〕 In late 2013, there are plans for a proposed Eastern United States missile defense site to house a battery of these missiles. On 30 April 2014, the Government Accountability Office issued a report stating that the system may not be operational any time soon because "its development was flawed". It says the GBI missile is "capable of intercepting a simple threat in a limited way".〔( "Mann addresses missile defense future during symposium" )〕 On 12 August 2015, David L. Mann characterized GMD as the nation's only ground-based defense against limited ICBM attacks.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ground-Based Midcourse Defense」の詳細全文を読む スポンサード リンク
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