COSMIC makes use of radio signals from Global Positioning System (GPS) satellites. As the GPS signals pass through the atmosphere, the signals’ paths are bent and their progress is slowed. The rate of these changes depends on the atmosphere’s density along the path. COSMIC’s low-Earth-orbiting satellites take advantage of this effect by intercepting the GPS radio signals just above Earth's horizon and precisely measuring the bend and signal delay along the signal path. Illustration: Broad Reach Engineering
