The original Sea Sparrow was an expedient design intended to provide short-range defensive fire in a system that could be deployed as rapidly as possible. The AIM-7 Sparrow was the simplest solution as its radar guidance allowed it to be fired head-on at targets and this guidance was easily provided by mounting an aircraft radar on a trainable platform. In the years after its introduction, it was upgraded to follow improvements being made in the air-to-air Sparrow models used by the US Navy and US Air Force. The ultimate version in this line of weapons was the R model, which introduced a new dual-seeker homing system and many other upgrades. After that point, the AIM-120 AMRAAM offered higher performance from a missile that was smaller and lighter, and development of the Sparrow ended in the 1990s.