The Mk-15 Phalanx CIWS provides ships with an inner layer point defense capability against Anti Ship Missiles (ASM), aircraft, and littoral warfare threats that have penetrated other fleet defenses. Phalanx automatically detects, evaluates, tracks, engages, and performs kill assessment against ASM and high speed aircraft threats. Phalanx is the only deployed close-in weapon system capable of autonomously performing its own search, detect, evaluation, track, engage and kill assessment functions. Phalanx also can be integrated into existing ship combat control systems to provide additional sensor and fire-control support to other installed ship weapon systems.
The Block 1 upgrade offered various improvements in radar, ammunition, rate of fire, and computing. These improvements were intended to increase the system's capability against emerging Russian supersonic anti-ship missiles. Block 1A introduced a new computer system to counter more maneuverable targets.
The Block 1B PSuM (Phalanx Surface Mode) adds a forward looking infrared (FLIR) sensor to allow the weapon to be used against surface targets. This addition was developed to provide ship defense against small vessel threats and other "floaters" in littoral waters and to improve the weapon's performance against slower low-flying aircraft. The FLIR's capability is also of use against low-observability missiles and can be linked with the RIM-116 Rolling Airframe Missile (RAM) system to increase RAM engagement range and accuracy. The Block 1B also allows for an operator to visually identify and target threats.