The RIM-116 Rolling Airframe Missile (RAM) is a small, lightweight, infrared homing surface-to-air missile in use by the German, Japanese, Greek, Turkish, South Korean, Saudi Arabian, Egyptian, Mexican, UAE, and U.S. Navies. It was originally intended and used primarily as a point-defense weapon against anti-ship missiles. As its name indicates, RAM rolls as it flies. The missile must roll during flight because the RF tracking system uses a two-antenna interferometer that can measure phase interference of the electromagnetic wave in one plane only. The rolling interferometer permits the antennas to look at all planes of incoming energy. In addition, because the missile rolls, only one pair of steering canards is required. , it is the only U.S. Navy missile to operate in this manner. The Rolling Airframe Missiles, together with the Mk 49 Guided Missile Launching System (GMLS) and support equipment, make up the RAM Mk 31 Guided Missile Weapon System (GMWS). The Mk-144 Guided Missile Launcher (GML) unit weighs and stores 21 missiles. The original weapon cannot employ its own sensors prior to firing, so it must be integrated with a ship's combat system, which directs the launcher at targets. On U.S. ships, it is integrated with the AN/SWY-2 Ship Defense Surface Missile System (SDSMS) and Ship Self-Defense System (SSDS) Mk 1 or Mk 2-based combat systems. SeaRAM, a launcher variant equipped with independent sensors derived from the Vulcan Phalanx CIWS, is being installed on Littoral Combat Ships and certain s. Development The RIM-116 was developed by General Dynamics Pomona and Valley Systems divisions under a July 1976 agreement with Denmark and West Germany (the General Dynamics missile business was later acquired by Hughes Aircraft and is today part of Raytheon). Denmark dropped out of the program, but the U.S. Navy joined in as the major partner. The Mk 49 launcher was evaluated on board the destroyer in the late 1980s. The first 30 missiles were built in FY85, and they became operational on 14 November 1992, onboard . SeaRAM was developed in response to concerns about the performance of gun-based systems against modern supersonic sea-skimming anti-ship missiles. It was designed as a companion self-defense system to Phalanx, Service The RIM-116 is in service on several American and 30 German warships. All new German Navy warships will be equipped with the RAM, such as the new s, which will mount two RAM launchers per ship. The Greek Navy has