The RIM-161 Standard Missile 3 (SM-3) is a ship-based missile system used by the United States Navy and allied countries to intercept short-range and intermediate-range ballistic missiles as a part of Aegis Ballistic Missile Defense System. Although primarily designed as an anti-ballistic missile, the SM-3 has also been employed in an anti-satellite capacity against a satellite at the lower end of low Earth orbit. The SM-3 is primarily used and tested by the United States Navy and also operated by the Japan Maritime Self-Defense Force.
SM-3 block II has a wider missile body than earlier versions and decreased the size of the maneuvering fins. It still fits in Mk41 vertical launch systems. The missile is also faster and has a longer range than the Block I variants. A larger diameter kinetic vehicle that is more maneuverable and carries a sensor / discrimination upgrade.