An instrument developed by NASA to measure ozone indirectly by monitoring ultraviolet light. It observes backscattered ultraviolet radiation, which is solar radiation that has reached the Earth's lower atmosphere and been scattered by clouds and air molecules back through the stratosphere. TOMS measures the total amount of ozone in a column of air from the Earth's surface to the top of the atmosphere.

In 1996, the first instruments were launched on Japan's Advanced Earth-Observing Satellite and on the Earth Probe TOMS satellite. Three others have since flown. TOMS is part of NASA's long-term ‘Mission to Planet Earth’ to study the planet as a global environmental system. The Advanced Earth-Observing Satellite completed its mission in 1997, and the Earth Probe mission was completed in 2006.