SAGE LEGACY

In today’s A Lab Aloft, guest blogger Kristyn Damadeo shares the history of the SAGE investigation, scheduled for future use on the International Space Station. This technology can help researchers to better understand Earth’s atmosphere makeup, especially the health of our ozone layer.

The International Space Station houses some unique experiments and soon it will be home to an exciting new Earth science mission: SAGE III, the Stratospheric Aerosol and Gas Experiment III.

SAGE III mounts externally to the space station and is a mission to study Earth's atmosphere sponsored by the NASA Science Mission Directorate and led by NASA Langley Research Center. It will be the first Earth-observing instrument of its kind aboard station, taking accurate measurements of the amount of ozone, aerosols—tiny particles—water vapor and other key components of Earth's atmosphere.

The SAGE Legacy

SAGE III is the first of its kind to operate on station, but the SAGE family of instruments has been taking atmospheric measurements for more than 30 years. SAGE III is the fourth generation in its family operated by NASA.

The artwork above belongs to the SAGE III instrument, which is part of a family of SAGE technology developed to help research Earth’s atmosphere. (NASA Image)

The first SAGE instrument was flown on a satellite in 1979. SAGE I was a sun photometer that used solar occultation—a measurement technique using the sun as a backlight—to gather information on aerosols and important stratospheric gases in the atmosphere. SAGE I collected valuable data for nearly three years, until the power system on the satellite failed.

With SAGE I came the start of a global database for stratospheric aerosols, ozone, and nitrogen dioxide that is still used in the study of global climate. While SAGE I was active, it provided crucial input into the understanding of global, seasonal and inter-annual variability in climate and, in particular, trends in stratospheric ozone.

SAGE I was followed by SAGE II in 1984. SAGE II data helped to confirm human-driven changes to ozone and contributed to the 1987 Montreal Protocol, which banned the use of chemicals that harm the ozone layer. SAGE II lasted 21 years on orbit, allowing us not only to determine the initial extent of ozone changes, but also to measure the effectiveness of the Montreal Protocol. SAGE II saw ozone stop decreasing and begin to recover during its time on orbit.

Engineers at NASA Langley work in a clean room with the SAGE III instrument. (NASA Image)

Then in the late 1990s, SAGE III was developed by Ball Aerospace and Technology Corp. The first of the instruments was launched in 2001 on a Russian satellite, METEOR-3M. The second instrument was stored for a future flight of opportunity. The third was removed from storage and prepared for flight on the space station. The mission will enable researchers to fill an anticipated gap in ozone and aerosol data in the second half of this decade.

Ozone

SAGE III will study Earth's protective ozone layer from aboard station. Ozone acts as Earth's sunscreen. When ozone starts to break down, it impacts all of Earth's inhabitants. Humans, plants and other animals are exposed to more harmful rays from the sun. This can cause long-term problems, such as cataracts and cancer in humans or reduced crop yield in plants.

When SAGE III begins making measurements from the space station in late 2014, some models predict that stratospheric ozone should have recovered by 50 percent. The precise pattern of ozone recovery measured by SAGE III will help improve the models and refine our understanding of the atmosphere.

Particles in the upper Earth’s atmosphere cause the blue layer shown in this image of a sunrise taken from aboard the space station. SAGE III will measure these atmospheric gases from a similar perspective. (NASA Image)

Measurement Technique

SAGE III takes its measurements using solar and lunar occultation. Occultation is a technique for pointing and locking onto the sun or the moon and scanning the limb—thin profile—of the atmosphere as the sun or moon rises or sets. SAGE III will operate mostly autonomously and the data will be transmitted to the ground through the space station’s communications systems.

The space station provides the perfect orbit from which to take measurements of the composition of the middle and lower atmosphere. Our location aboard station also gives us a great view for our solar/lunar occultation technique.

Back in Action

SAGE III is scheduled to launch to the space station aboard a SpaceX Falcon 9/Dragon in mid-2014.

The SAGE III suite consists of a sensor assembly that has pointing and imaging subsystems and an ultraviolet/visible spectrometer; an European Space Agency- provided hexapod pointing system and a nadir viewing platform. The Canadian Space Agency-provided robotic arm will robotically move SAGE III from the Dragon trunk and install it on the Earth-facing side of the EXPRESS Logistics Carrier-4, or ELC 4, storage platform. 

The graphic above depicts the SAGE III instrument, which will collect data to help researchers better understand Earth’s atmosphere. (NASA Image)

The research results of the space station-mounted SAGE III will provide insights that will help humans better understand and protect Earth's atmosphere. Only by understanding these changes will we be able to mediate future impacts on our environment. Much more data and research is needed to better understand and quantify our impact on our world's climate system.

The SAGE program has a long heritage and is one of NASA's longest running Earth-observing programs. Continuous long-term data collection is necessary to understand climate. Once it is on the space station, SAGE III will help to extend a long record of atmospheric measurements for the continued health of our Earth. The observations of SAGE III from station are crucial for providing a better understanding of how natural processes and human activities may influence our climate.

SAGE has been pivotal in monitoring ozone and making accurate measurements of the amount of ozone loss in Earth’s atmosphere. Today, the SAGE technique is still the best for the job. Although new technologies have come along to measure ozone, none are as thorough as solar occultation. Through this dataset, SAGE on the station will enhance our understanding of ozone recovery and climate change processes in the upper atmosphere. We also extend the scientific foundation for further sound decisions on environmental policy, both nationally and internationally.

Kristyn Damadeo is the Education and Public Outreach Lead for SAGE III on the International Space Station at NASA’s Langley Research Center in Hampton, Va. She has previously worked as a science writer and a newspaper reporter, specializing in environmental reporting. Damadeo has a degree in Communication Arts from Ramapo College of New Jersey.