SBIRS will be a consolidated system that will meet United States infrared space surveillance needs through the next 2-3 decades. SBIRS is intended to be an integrated “system of systems” including multiple space constellations and an evolving ground element. The baseline SBIRS architecture consists of four Geosynchronous Earth Orbit (GEO) satellites; two sensors on Highly Elliptical Orbit (HEO) satellites; Low Earth Orbit (LEO) satellites; a ground system consisting of a CONUS-based Mission Control Station (MCS), a backup MCS, a survivable MCS, and oversees relay ground stations and relocatable terminals; and associated communications links. The SBIRS is designed to meet the missile defense, missile warning, technical intelligence, and battlespace characterization mission requirements identified in the JROC-validated SBIRS Operational Requirements Document. The SBIRS program will begin replacing the operational Defense Support Program (DSP) ground segment in 1999 and begin replacing the DSP satellites in 2002.