A constellation of six low-Earth orbit satellites, which has been proposed by the joint Taiwan - United States Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3, hereafter COSMIC) mission was launched into a 512-km orbit on 15 April 2006. After launch the satellites were gradually moved to their final orbits at 800 km. It took about 17 months for this process to be completed. During the early weeks of the movement, the satellites were spaced closely, and provided a unique opportunity to verify the high precision of radio occultation (RO) measurements. COSMIC is still observing about 1500 RO soundings per day to support the research and operational communities.