NASA's Stratospheric Aerosol and Gas Experiment III (SAGE III) comprised two launches: the first was launched in December 2001 on the Russian Метеор-3М spacecraft, and the second in February 2017 on a SpaceX Falcon 9 and then externally mounted on the International Space Station (ISS).

SAGE III on Метеор-3М (SAGE III/M3M) was a third generation, satellite-borne instrument and a crucial element in NASA’s Earth Observing System (EOS). The instrument was launched on the Russian Метеор-3М spacecraft in December 2001. The SAGE III mission enhanced our understanding of natural and human-derived atmospheric processes by providing accurate measurements of the vertical structure of aerosols, ozone, water vapor, and other important trace gasses in the upper troposphere and stratosphere. Human-derived changes in climate and ozone threaten the health of our planet. They also threaten global economic development and the use of new technologies like high-speed aircraft. By understanding the effect of human activities on the atmosphere, national and international leaders can make informed policy that mitigates or prepares for future climate change.

SAGE III on the ISS is the second instrument from the SAGE III project. This ISS-based instrument uses a technique known as occultation, which involves looking at the light from the Sun or Moon as it passes through Earth’s atmosphere at the edge, or limb, of the planet to provide long-term monitoring of ozone vertical profiles of the stratosphere and mesosphere. The data provided by SAGE III-ISS includes key components of atmospheric composition and their long-term variability, focusing on the study of aerosols, chlorine dioxide, clouds, nitrogen dioxide, nitrogen trioxide, pressure and temperature, and water vapor. SAGE data has historically been used by the World Meteorological Organization to inform their periodic assessments of ozone depletion. These new observations from the International Space Station will continue the SAGE team's contributions to ongoing scientific understanding of the Earth's atmosphere.

The initial release of SAGE III-ISS products focuses on solar occultation. While not included initially, later releases will include lunar occultation and water vapor data. Subsequent data releases will follow a monthly release schedule.