On the fourth anniversary of its first-light measurements, we are taking a look at some of the critical data collected by NASA’s Stratospheric Aerosol and Gas Experiment III (SAGE III) aboard the International Space Station. Launched to the station in February 2017, SAGE III is the most recent in a series of SAGE instruments that have measured stratospheric gases and aerosols from space. The SAGE family of instruments started in 1979 and is one of NASA’s longest-running Earth-observing programs.
Data from SAGE II helped confirm human-driven changes to the ozone layer, which contributed to the 1987 Montreal Protocol that banned some of the most destructive industrially-produced ozone-depleting chemicals. Stratospheric ozone acts as a sunscreen for the Earth, filtering out harmful solar radiation by absorbing some of the Sun’s ultraviolet rays, providing people, animals and plants some protection from that harmful radiation.
This latest SAGE III instrument is helping scientists monitor the recovery of ozone resulting from the reduction in emissions of ozone-depleting substances called for under the Montreal Protocol. SAGE III has also measured the intrusion of aerosols into the stratosphere from intense wildfires in Australia and California, and from volcanic eruptions. Those aerosols, which can remain in the stratosphere for months or even years, can lead to variability in the climate record. Water vapor, a potent greenhouse gas that can be lofted into the stratosphere by extreme storms, is also visible to SAGE III. Though it’s normal to have some water vapor in the stratosphere, using SAGE data, scientists can better understand how year-to-year changes in tropical weather affect the amount of water vapor in regions of the stratosphere influenced by the tropical weather circulation.
SAGE III makes measurements using solar and lunar occultation, a technique that involves looking at light from the Sun or Moon as it passes through Earth’s atmosphere at the edge, or limb, of the planet. The SAGE III payload on the space station is managed by NASA’s Langley Research Center in Hampton, Virginia and was developed in partnership with the European Space Agency, Ball Aerospace Technology Corporation, and NASA’s Johnson Space Center in Houston.