The NASA Stratospheric Aerosol and Gas Experiment III (SAGE III) Program is a mission designed to provide long-term data on Earth’s ozone levels, aerosols, and other gases in the atmosphere. This information is critical for understanding the effects of human activity on the Earth’s climate and environment. The SAGE III instrument is mounted on the International Space Station (ISS) and provides measurements of gases and particles in the Earth’s stratosphere and is a key contributor to understanding the Earth’s ozone layer.

The instrument measures sunsets and sunrises during which time atmospheric measurements are taken, specifically measuring the spectrum of light as it passes through selected atmospheric gasses.

SAGE III has been successfully operating on the ISS since February 2017, extending a data source that has been collecting since the 1970s. SAGE III, and its predecessors, have provided significant data used for assessing the effectiveness of international agreements around the world that protect Earth’s ozone layer. The data has been used to produce measurements to enforce the Montreal Protocol that regulates hazardous chemicals to the atmosphere used in man-made products.

SAGE III’s goal is to provide a long-term baseline of data so scientists can better detect global atmospheric changes and making recommendations and suggestions to world governments to shape policy. As time passes, the information collected by SAGE III will become increasingly valuable due to decreases in ozone-depleting substances and increasing greenhouse gases from human activity.