A series of experimental mini-satellites launched by the Korea Aerospace Research Institute as part of its long-term plan for the nation’s space development. STSAT-1 launched on 27 September 2003 and was placed in a Sun-synchronous near-circular orbit at an altitude of 686 km. STSAT-2 launched on 25 August 2009 aboard the maiden flight of the nation’s Naro rocket, but a separation failure occurred and the satellite failed to reach a stable orbit. STSAT-3 launched on 21 November 2013 as a primary payload on a Dnepr-1 vehicle from the Dombarovsky launch site and successfully placed in Earth orbit where it is still operates, providing astronomical infrared imagery of our Galaxy and of the cosmic background radiation, as well as Earth observations to provide infrared and hyperspectral imagery for Earth environmental monitoring, land classification research, and monitoring of water quality.