Space-Based Infrared System (SBIRS)
The Space-Based Infrared System (SBIRS) is a United States military early warning, defense, and coordinated characterization satellite constellation that operates in the infrared domain for any space surveillance needs of the United States government. SBIRS was designed to replace the Defense Support Program’s early warning system during the Persian Gulf War after the United States Department of Defense realized it needed better satellite eyes for short-range ballistic missiles in the Persian theater. The program had frequent budget issues in the early 2000s and had an estimated project cost of over $10 billion by 2007.  The Lockheed Martin Corporation is the primary contractor of the program with Northrop Grumman as the main subcontractor.
The satellite constellation was planned to operate in GEO, in high-elliptical orbit (HEO), and interface with ground control centers. Successful launches of SBIRS craft include SBIRS High GEO 1, two classified HEO satellites, GEO-3, and GEO-4. Future GEO satellites were planned but most of the money for SBIRS had been moved to other programs by the beginning of 2019. In February 2018, the United States Air Force (SBIRS is now managed by the United States Space Force) announced that they were interested in seeking “a survivable missile warning capability by the mid-2020s” to replace SBIRS in the near future. 
Another aspect of the SBIRS program is the SBIRS Low contract, now named the Space Tracking and Surveillance System (STSS). Its purpose was to provide a LEO constellation similar to SBIRS operation in GEO and HEO. As of 2011, no new flight tests have been performed with the STSS program and it is believed to be stuck in a financially-driven type of development limbo.