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The GBU-39 Small Diameter Bomb (SDB) is a precision-guided glide bomb that is intended to provide aircraft with the ability to carry a higher number of more accurate bombs. Most US Air Force aircraft will be able to carry (using the BRU-61/A rack) a pack of four SDBs in place of a single .〔(Boeing / Lockheed Martin SDB (Small Diameter Bomb) - Designation Systems )〕 The Small Diameter Bomb II (SDB-II) / GBU-53/B, scheduled to enter production in January 2014, will add a tri-mode seeker (radar, infrared homing, and semiactive laser guidance) to the INS and GPS guidance of the original SDB. ==Description== The original SDB is equipped with a GPS-aided inertial navigation system to attack fixed/stationary targets such as fuel depots, bunkers etc. The second variant (Boeing's GBU-40 or Raytheon's GBU-53 (SDB II)) will include a thermal seeker and radar with automatic target recognition features for striking mobile targets such as tanks, vehicles, and mobile command posts.〔(Boeing Small Diameter Bomb II Successfully Engages Target in Flight Test )〕 The small size of the bomb allows a single strike aircraft to carry more of the munitions than is possible utilizing currently available bomb units. The SDB carries approximately of AFX-757 high explosive. It also has integrated "DiamondBack" type wings which deploy after release, increasing the glide time and therefore the maximum range. Its size and accuracy allow for an effective munition with less collateral damage.〔 Warhead penetration is of steel reinforced concrete and the fuze has Electronic safe and fire (ESAF) cockpit selectable functions, including air burst and delayed options.〔(Boeing: Small Diameter Bomb ). boeing.com〕 The GBU-39 has a circular error probable (CEP) of 5–8 meters,〔(SDB - Global Security )〕 which means it has a 50% probability of hitting within that distance of its intended target. CEP is reduced by updating differential GPS offsets prior to weapon release. These offsets are calculated using an SDB Accuracy Support Infrastructure, consisting of three or more GPS receivers at fixed locations transmitting calculated location to a correlation station at the theatre Air Operations Center. The corrections are then transmitted by Link 16 to SDB-equipped aircraft. In November 2014, the U.S. Air Force began development of a version of the SDB I intended to track and attack sources of electronic warfare jamming directed to disrupt the munitions' guidance. The home-on-GPS jam (HOG-J) seeker works similar to the AGM-88 HARM to follow the source of a radio-frequency jammer to destroy it.〔(Air Force to enable smart weapons to track and kill sources of electronic warfare (EW) jamming ) - Militaryaerospace.com, 13 November 2014〕〔(Guided-Bomb Makers Anticipate GPS Jammers ) - Defensenews.com, 1 June 2015〕 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「Small Diameter Bomb」の詳細全文を読む スポンサード リンク
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