The in the Japan Maritime Self-Defense Force is a modified version of the equipped with the Aegis Combat System. Background The Maritime Self-Defense Force (MSDF) began construction of the Aegis-equipped in FY1988 as the core ship for air defense of its fleet. With the commission of the Kongo class, each of the four had one Tartar-equipped destroyer and one Aegis-equipped destroyer. In the 2000s, the steam-powered s were nearing the end of their life, and their Tartar Weapon Systems were becoming obsolete. As their replacements, two Aegis-equipped destroyers, Atago class, were built in the FY2002 and 2003 budget. Design The design is fundamentally an improved and scaled-up version of the Kongō-class destroyers with a 4-meter extension of the hull. Just as the Kongō class, the superstructure is larger than aboard the American counterparts, Flight IIA. One of the most obvious changes is an additional hangar to carry one SH-60K helicopter. In comparison to the Kongō class which only had a helicopter deck, these ships have better helicopter handling facilities. Another external feature is the reduction of the radar cross-sectional area. For example, the Atago class use a new stealthier plain-structure mast, which was originally designed in Japan, rather than familiar sturdy truss mast. A new modified smokestack and other improvements were also introduced to make the Atagos stealthier. The propulsion systems are almost the same as those of the Kongō class and Arleigh Burke class, powered by four Ishikawajima-Harima LM2500 gas turbines giving them a top speed of . The installation of three generators is also retained, but the output per unit is increased to 2,800 kilowatts. Equipment The class is equipped with the Aegis Weapon System (AWS). The system version was Baseline 7.1 immediately after they were put into service; then both ships have been updated to Baseline 9C with modernization. As surface-to-air missiles, The SM-2MR Block IIIA/B has been used. Since FY 2016, they have also been equipped with a missile defense capability with an Aegis BMD 5.0CU system to launch SM-3 Block IA and IB anti-ballistic missiles. The missile launcher is the same Mark 41 Vertical Launching System as the Kongo class, but the missile reloading crane has been omitted, so the number of missile cells is increased by 3 cells each on the bow and stern sides. The Kongo class had 29 cells on the foredeck and 61 cells on the afterdeck, but the Atago class