SBIRS Low
SBIRS Low : SBIRS low altitude component consisting of SBIRS LEO satellites. The SBIRS Low component will be designed to provide precision midcourse tracking and discrimination data to support early interceptor commit, in-flight target updates, and target object maps for a National Missile Defense architecture. The SBIRS Low component will also support the other mission areas of the SBIR system. (Evolution of the Space and Missile Tracking System)