First demonstration of track sensor generating multiple tracks for separating objects. October 2010 5 October 2010 Aegis Launch on Remote Campaign First Track sensor stereo track of a dim boosted target First stereo post boost tracking of midcourse target. March 2011 9 March 2011 Second Aegis Readiness Assessment Vehicle Targeting STSS satellites acquired and tracked its target until re-entry 15 March 2011 Second full-course tracking during U.S. Missile Defense Agency's (MDA) Aegis launch Successful production of "stereo" 3-D tracking software to follow the target missile's flight path to predict its impact point. April 2011 15 April 2011 Sea-based missile defense test STSS satellites target and help to intercept an intermediate-range ballistic missile (IRBM); destruction of the IRBM on impact. July 2011 8 July 2011 STSS test on short-range air-launched target (SRALT) This test proved the STSS's ability to track dim objects that have extremely short flight timelines. End of mission The two Space Tracking and Surveillance System satellites stopped collecting data in September 2021. After being moved to higher orbits to prevent future collisions with other space objects, the two satellites were decommissioned on 8 March 2022. See also Aegis Ballistic Missile Defense System Defense Support Program Ground-Based Midcourse Defense USA 205 References External links STSS Missile Tracking Demonstrations STSS DEMO 1 (USA 208) - Orbit STSS DEMO 2 (USA 209) - Orbit Missile defense Early warning systems Spacecraft launched in 2009 Spacecraft decommissioned in 2022