The MK-46 torpedo is designed to attack high performance submarines, and is presently identified as the NATO standard. The MK-46 torpedo is designed to be launched from surface combatant torpedo tubes, ASROC missiles and fixed and rotary wing aircraft. In 1989, a major upgrade program began to enhance the performance of the MK-46 Mod 5 in shallow water. Weapons incorporating these improvements are identified as Mod 5A and Mod 5A(S). The MK-46 Mod 5 torpedo is the backbone of the Navy's lightweight ASW torpedo inventory and is expected to remain in service until the year 2015. The MK 46 originated with the RETORC I (Research Torpedo Configuration I) program conducted by the US Naval Undersea Center (NUC) at Pasadena, CA.