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SeaRAM CIWS

Originally posted by Wikipedia:

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 and U.S. Navies.

It was intended originally and used primarily as a point-defense weapon against anti-ship cruise 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. As of 2005, it is the only U.S. Navy missile to operate in this manner.