The Space Based Infrared System (SBIRS) is a military satellite system being developed to replace the Defense Support Program and perform a range of missile warning, missile defense, technical intelligence, and battle space awareness missions. SBIRS is to consist of four GEO satellites, two sensors on host satellites in highly elliptical orbit, two replenishment satellites and sensors, and fixed and mobile ground stations.
The first SBIRS satellite was launched in May 2011. The second satellite was launched in March 2013. The third satellite is expected for delivery in late 2015. The program plans to fully meet operational requirements in 2019 once it has established the full on-orbit constellation of highly elliptical orbit sensors, four geostationary orbit satellites, completion of its first two software blocks, and delivery of its mobile ground assets. The production contract for the fifth and sixth satellites is expected to be awarded in early 2014.