Stratospheric Aerosol & Gas Experiment Headed to ISS

SAGE III can detect ozone, aerosols, and other trace gases by using light from the sun and the moon to peer into the Earth's atmosphere. Credit: NASA — SAGE III can detect ozone, aerosols, and other trace gases by using light from the sun and the moon to peer into the Earth’s atmosphere. Credit: NASA

Among the 5,500 pounds of cargo SpaceX is sending to the International Space Station (ISS) as part of CRS-10 is SAGE III, a stratospheric aerosol and gas experiment. Similar to its predecessors, SAGE III, once mounted to the ISS, will provide vertical profiles of ozone, aerosols, nitrogen dioxide, and water vapor in the Earth’s atmosphere. It does so by taking occultation measurements when the sun or moon is rising/setting, about 15-16 times each day. In addition to light from the sun, the moon will also be used as a light source to detect ozone.

Measurements from SAGE III on the International Space Station will be used to observe long-term trends of stratospheric ozone concentrations and help determine whether or not the ozone layer is recovering. Data from SAGE III will also be used to help refine the accuracy of three-dimensional models used to understand the atmosphere and predict future atmospheric changes. There are three key science goals from SAGE III: access the state of recovery in the distribution of ozone, re-establish the aerosol measurements needed by both climate and ozone models, and gain further insight into key processes contributing to ozone and aerosol variability.

The sun sends a variety of radiation to the Earth, including UV-A, UV-B, and UV-C ultraviolet radiation. UV-C are the most harmful rays and are completely absorbed by the Earth's atmosphere. The ozone layer helps reduce UV-B and UV-A rays from reaching the surface. And while ozone is beneficial in the stratosphere, it is a pollutant at the surface, creating smog conditions in places where there's such a build-up in the troposphere. Credit: NASA — The sun sends a variety of radiation to the Earth, including UV-A, UV-B, and UV-C ultraviolet radiation. UV-C are the most harmful rays and are completely absorbed by the Earth’s atmosphere. The ozone layer helps reduce UV-B and UV-A rays from reaching the surface. And while ozone is beneficial in the stratosphere, it is a pollutant at the surface, creating smog conditions in places where there’s such a build-up in the troposphere. Credit: NASA

Ozone (O3) is a gas composed of three oxygen atoms and plays a vital role for life on Earth. Ozone is both a natural and man-made gas that can be found in Earth’s upper atmosphere, also known as the stratosphere, and the lower atmosphere, also known as the troposphere.

In the stratosphere, roughly 10-30 miles up above the Earth’s surface, ozone reduces the amount of harmful ultraviolet (UV) radiation that reaches the Earth’s surface. Commonly known as the “ozone later”, this layer of ozone blocks harmful radiation that could lead to increased incidences of sunburn and sun-related skin cancers, damaged eyes such as cataracts, and harm the productivity of crops.

While ozone is helpful in the stratosphere, it is a pollutant near the Earth’s surface in the troposphere. Surface-level ozone and tiny airborne solid and liquid particles known as aerosols, can also be harmful.

With SAGE III active once it is mounted to the ISS, scientists hope to better measure, monitor, and understand the ozone in the atmsophere.