Understanding the Ionosphere – Thermosphere – Mesosphere

This region, collectively called the ionosphere-thermosphere-mesosphere (ITM), is where the Sun’s energy first enters our atmosphere, and where the brilliant colors of the aurora shine. Through spacecraft observations and state-of-the-art computer models, APL scientists are striving to understand this important part of the atmosphere. APL built NASA’s TIMED spacecraft, which for more than 15 years has provided new insights into solar- and human-induced disturbances in the ITM. TIMED in part detailed how energy from the Sun is transformed in the upper atmosphere, altering the region’s composition, pressure, temperature and winds. New insights into space weather and its impact on society have come from these investigations, including effects on satellite orbits, ground-induced currents that affect the power grid, and radio wave propagation. And the lessons we learn on Earth can apply to the atmospheres and auroras of other planets.


APL has designed, built and operated more than 70 innovative spacecraft over its six decades of spaceflight experience. Click below to learn about some of the missions that made revolutionary discoveries, and spacecraft that will push the boundaries of exploration and investigate outstanding scientific mysteries.


Scientists and engineers at APL have designed, built and operated more than 300 novel space instruments and methods to conduct cutting-edge research and make groundbreaking discoveries. Click below to learn about some of these instruments and their role in shaping our understanding of space and the solar system.