An introduction to the Pentagon's plans for the Space Based Infrared System, known as SBIRS (pronounced "sibbers"). If fielded as planned, SBIRS would consist of two sets of satellites. The so-called SBIRS High constellation, consisting of four satellites in geosynchronous Earth orbits and two sensors in elliptical high Earth orbits, would primarily provide early warning of missile launches and track rockets until their heat-generating boosters burn out.