The Stratospheric Aerosol and Gas Experiment (SAGE) is a series of remote sensing satellite instruments used to study the chemical composition of Earth's atmosphere.
Specifically, SAGE has been used to study the Earth's ozone layer and aerosols at the troposphere through the stratosphere.
The SAGE instruments use solar occultation measurement technique to determine chemical concentrations in the atmosphere.
Physically, the SAGE instruments measure ultraviolet/visible energy and this is converted via algorithms to determine chemical concentrations.
SAGE data has been used to study the atmospheres aerosols, ozone, water vapor, and other trace gases.