The Stratospheric Aerosol and Gas Experiment (SAGE) III instrument was launched in February 2017 to the International Space Station (ISS) and continues to provide the public and science community with world-class ozone, aerosol, and water vapor data products. The annual SAGE III/ISS Science Team meeting was held as a hybrid event hosted at NASA Langley Research Center on August 13th and 14th with over 50 participants, including SAGE III summer interns and project-supported graduate students. This was the second Science Team Meeting for the cohort of Principal Investigator (PI)-led teams selected under the 3rd ROSES call targeting science with SAGE III/ISS data. Presentations from the competed science team, the mission team, and invited speakers covered SAGE III/ISS mission and data product status, research findings, synergy with other NASA and partner missions, and preliminary results of new SAGE products. Presentations highlighted the new aerosol and gas products from SAGE lunar measurements that increase the available data coverage by about 10-15%, shedding light on atmospheric composition changes in the upper troposphere/lower stratosphere resulting from natural disasters like wildfires and volcanic eruptions.

Additionally, two separate science team PIs reported on the use of SAGE data in important long-term, multi-instrument data sets for ozone and water vapor (WV) to inform the mandated ozone assessment, and comprehend and predict seasonal to decadal-scale stratospheric influences on weather variability. Dr. Sean Davis (NOAA) highlighted that SAGE III/ISS data is now fully incorporated into the Stratospheric Water and OzOne Satellite Homogenized data set (SWOOSH) and will be the primary source for WV (along with Atmospheric Chemistry Experiment-Fourier Transform Spectrometer, ACE-FTS) once Aura Microwave Limb Sounder (MLS) ceases, which already has reduced WV observations to ~ 1 week/month because of electronics lifetime concerns. It should be noted that SWOOSH is also being used by PI Prof. Brian Soden (U. Miami) to investigate the impact of stratospheric composition on CO2 radiative forcing.

Dr. H.J. (Ray) Wang (Georgia Tech) reported SAGE III/ISS data is now contributing to the Global OZone Chemistry And Related trace gas Data records (GOZCARD), which stretches back to 1979 for ozone and 1991 for WV. The newly added SAGE III/ISS data agrees well with Aura MLS having mean differences of ~5% in the stratosphere, with very little altitude variation (Fig. 1). ACE-FTS WV has a dry bias of ~10% above 10 mb and 5% wet bias below 10 mb. For ozone in Fig. 2, SAGE III and Aura MLS agree within 5% from the upper stratosphere down to the tropopause. OMPS LP ozone data in the lower stratosphere after 2022 show high biases caused by the Hunga volcanic aerosols, which was also mentioned in several other presentations (N. Richards (GSFC); M.C. McKee (LaRC)). Dr. Wang concluded that screening beyond the producer’s recommendations is needed. SAGE III retrieved ozone is not significantly affected by Hunga. These differences highlight the need for multi-instrument observations to construct an accurate record of the evolving atmosphere and enable reliable predictions of the future state of the life-essential, protective stratospheric ozone layer.

Figure 1: For water vapor, the median differences between SAGE III/ISS (ACE-FTS) and Aura MLS, (other – amls)/amls, (1/2017-6/2025). Credit: H.J. (Ray) Wang.

Figure 2: For ozone, the mean differences (other – MLS) between Aura MLS and correlated SAGE III/ISS, ACE-FTS, and OMPS-NPP LP (2017—2025). Credit: H.J. (Ray) Wang.

The 2025 wildfire season in Canada has been long and widespread with over 6.8 million hectares burned as of August 6, 2025, placing this year in the top 5 seasons, but less than half the size of the devastating 2023 season, according to the Canadian Wildfire Information System. Smoke from the fires traveled to the USA, Europe and beyond. The June 2025 release of SAGE III/ISS multi-wavelength aerosol extinction coefficient profiles allows scientists to see what smoke was transported into the stratosphere.

Figure 1a is the June 2025 zonal mean vertically resolved aerosol extinction coefficient at a wavelength of 1021 nm. Latitudes north of 40N have values 2 – 4 times larger in the lower stratosphere, < 17 km, when compared to May 2025 (Fig. 1b). Even when compared with the record setting 2023 season, the 2025 aerosol enhancements are 2-4 times over a substantial portion of the lower stratosphere. In contrast, much of the smoke from the 2023 season remained in the upper troposphere.

Another comparison with past perturbations to the Northern Hemisphere lower stratosphere is a time series of the aerosol extinction coefficient in Figure 2 for the latitude band 55N to 60N. Discontinuities that appear are from the occultation sampling at the higher latitudes, which is not continuous throughout the year, but does emphasize the summer months when the wildfires occur. The June 2025 enhancement can be seen for altitudes below 15 km at the right end of the series. At the other end, the 2017 Pacific Northwest fires can be seen with enhancements up to 17 km. The mid-year 2019 Raikoke volcanic eruption produced increases up to 20 km. Further measurements from SAGE will tell whether the June 2025 increases will remain in the stratosphere. Each wildfire event is unique and continued measurements of stratospheric aerosol is the only reliable means to know to what extent an extreme fire has perturbed the stratosphere and altered the energy budget and ozone chemistry.

A detailed review of the greater SAGE II/III record by Thomason and Knepp (2023) indicates that smoke injections into the stratosphere may be more prevalent in recent years. The stable, multi-wavelength measurements from solar occultation enable quantitative evaluation of the global impact by these extreme regional wildfires.

Figure 1a: Monthly zonal mean aerosol extinction coefficient profiles at wavelength of 1021 nm for a) June 2025, b) May 2025, c) June 2023.

Figure 1b: Monthly zonal mean aerosol extinction coefficient profiles at wavelength of 1021 nm for a) June 2025, b) May 2025, c) June 2023.

Figure 1c: Monthly zonal mean aerosol extinction coefficient profiles at wavelength of 1021 nm for a) June 2025, b) May 2025, c) June 2023.

Figure 2: SAGE III/ISS aerosol extinction coefficient time series for latitude range 55N to 60N. Coverage is not continuous because of occultation sampling, which produces some discontinuities. Recent enhancement can be seen below 15 km in June 2025. Other notable enhancements were produced by the Pacific Northwest fires in 2017 (up to 19 km) and Raikoke volcanic eruption in mid 2019 (up to 20 km).

References:
Thomason, L. W. and Knepp, T.: Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2022) observations of smoke in the stratosphere, Atmos. Chem. Phys., 23, 10361–10381, https://doi.org/10.5194/acp-23-10361-2023, 2023.

The Stratospheric Aerosol and Gas Experiment III installed on the International Space Station (SAGE III/ISS) mission team announces public release of newly versioned science products. This SAGE III/ISS Version 6.0 (v6) includes Solar Level 1B, Solar Level 2, and Lunar Level 2 data products.

Details of v6.0 can be found in the Release Notes and the Data Products User’s Guide. Pay special attention to these documents as the contents have changed from past versions for all three types of scientific data formats containing SAGE III/ISS data.

Major product enhancements include: filling transmission gaps, Level 1 uncertainty improvement, changes of ozone absorption cross-sections, and covariance in solar aerosol uncertainty. Derived Level 2 products developed by the SAGE Science Team that were previously available separately (aerosol/cloud flag and particle size distribution) are now included with the solar L2 package. Observations cover June 2017 through the present. Until further notice, all forward processing of SAGE III/ISS will be under v6.0, which is the suggested version, but prior legacy versions are available upon request from ASDC.

One illustration of improved data collection efficiency involves sunspots. The SAGE solar occultation data analysis has always filtered-out sunspots as part of the regular processing to release high-precision science products. Figure 1 is an example of a sunspot in the raw data, which is typically excluded when computing the Level 1 atmospheric transmission that is then used in the Level 2 processing. Early in the SAGE III/ISS mission, the exclusion of sunspot-contaminated data had little impact on the number of complete science products. However, with solar cycle 25 the increase in frequency and size of sunspots led to discarding enough scans to cause some solar occultation events to yield no science products. Figure 2 is a striking comparison of the number of sunspots measured by the NOAA Space Weather Prediction Center and the percentage of SAGE III/ISS data flagged with sunspots. To address this loss of science products, in v6 the algorithm team implemented a gap-filling technique for small gaps (< 4 points) in the fundamental data. This capability gained 103 events with accuracy similar to the non-sunspot cases. Figure 3 is the resultant v6 time-series of vertically resolved aerosol extinction coefficient at a wavelength of 1021 nm for the tropics with various terrestrial events impacting the stratosphere annotated.

Information about v6, including data availability, user documentation and quality statements, relevant links, and tools for working with the data can be found at the ASDC.

The mission will continue to provide plots of the scientific products on the browse portal for superior quality data: Quicklook and Expedited

Figure 1: Example of sunspots in SAGE III/ISS raw data for a sunset occultation event. Panels a & b are pixel (sensor) counts for multiple scans across the Sun without and with correction using the disturbance monitoring package (DMP). Panels c-e show the SAGE footprint on Sun with SDO HMI image. The abrupt dip of intensity shown in panels a & b are typically flagged and excluded when computing the Level 1 atmospheric transmission. Credit: C. Hill, https://sage.nasa.gov//wp/wp-content/uploads/2024/11/CharlesHill_SAGEIII_DMP-STM2024.pdf

Figure 2: NOAA Space Weather Prediction Center Sunspot Number and SAGE III/ISS fraction of data with sunspots. Credit: R. Manion

Figure 3: Vertically resolved SAGE III/ISS aerosol extinction coefficient at 1021 nm for the tropics. Major terrestrial events impacting the stratosphere are approximately annotated. Credit: NASA

In our continuing endeavor to make SAGE III data more accessible and to increase its utilization, the SAGE III/ISS team at NASA Langley Research Center launched enhancements and new features to the Quicklook and Expedited website for data visualization products. Some highlights of the changes made include easier navigation and display on mobile devices, as well as a new ‘Highlights’ tab to showcase major stratospheric events observed by SAGE III/ISS. This new addition to the website will provide a snapshot of images detailing the event and illustrate the efforts and analyses performed by our scientific colleagues around the world in response to these atmospheric phenomena.

Be sure to check out the new ‘Comparisons’ tab that highlights measurements by ground stations that provide valuable validation data. Observations are drawn from stations around the globe contributing to the Network for the Detection of Atmospheric Composition Change (NDACC), Southern Hemisphere ADditional OZonesondes (SHADOZ), or World Ozone and Ultraviolet radiation Data Centre (WOUDC). There you can search for a specific station and view comparison plots of ozone and water vapor over the entire data record.

The pages and the associated updates can be found at
Quicklook: https://sage.nasa.gov/sageiii-iss/browse_images/quicklook/
Expedited: https://sage.nasa.gov/sageiii-iss/browse_images/expedited/

The annual Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS) Science Team Meeting was held as a hybrid event hosted at NASA Langley Research Center on October 22 and 23, with over 50 participants. Nearly 30 technical presentations were given on topics ranging from the SAGE III/ISS mission and data product status, to research findings, plans and preliminary results utilizing SAGE products, to current and future members of the international constellation for stratospheric and upper tropospheric composition observations, to data assimilation systems (past, present and future), and to ground-based correlative measurements overlapping SAGE. This was the first Science Team Meeting for the cohort of Principal Investigator-led teams selected under the 3rd ROSES call targeting SAGE-like science, with at least 4 PIs new to the Science Team. One example of data usage was given by Dr. E. Knowland (MSU/GSFC-GMAO) regarding continuing a climate record of stratospheric water vapor (SWV) after the Aura MLS mission. She highlighted results from work as a PI during the 2nd Science Team cohort that made use of the GMAO Constituent data assimilation system (CoDAS) when it was fed SAGE III/ISS SWV observations. Key findings were:

• SAGE III/ISS stratospheric water vapor (SWV) assimilation improves SWV (R ≥ 0.48) relative to Atmospheric Chemistry Experiment-Fourier Transform Spectrometer compared to chemistry only (R ≥ 0.28)
• Assimilated SAGE III/ISS SWV captures broad, subpolar features like the tropical tape recorder, but is less able to capture isolated events
• SAGE III/ISS SWV profiles can thus continue the climate data record of Aura MLS, albeit with less coverage and fine-scale fidelity

These results lend confidence that SAGE III/ISS could serve as a bridge to future SWV observations after Aura MLS.

The mission looks forward to learning of new scientific advancements at the next annual meeting in 2025.

Credits: NASA

Updated status on stratospheric aerosols using recently released public data from SAGE III/ISS

Figure 1 below shows the bulk of the stratospheric aerosol layer around 10S latitude with slightly larger amounts in the Southern Hemisphere. This spatial distribution has been similar since early 2022 following the eruption of the Hunga Tonga–Hunga Haʻapai volcano in January 2022. However, Figure 2 shows that the core of the layer was actually refreshed somewhat by the eruption of Ruang in April 2024. This variable, but somewhat consistent, enhancement of the stratospheric aerosol layer compared to the first part of the SAGE III/ISS mission (2017) has produced a less than 1% shading of the Earth’s surface. Though small, it is non-negligible when balancing the energy budget of the Earth system, especially when examining changes in greenhouse gas contributions on these time scales.

Figure 1: Latitude – altitude cross-section of SAGE III/ISS stratospheric aerosol extinction coefficient for August 2024.

Figure 2: Aerosol extinction time series for tropics during the SAGE III/ISS mission. Most notable recent events are January 2022 eruption of Hunga Tonga and April 2024 eruption of Ruang.

NASA’s internship programs offer opportunities year-round for students to undertake meaningful and challenging projects that truly make an impact on humanity. Selected students are provided with training, mentoring, and career development throughout their session with some of the best minds in the world.

With over 100 applicants to the mission’s internship program, the Stratospheric Aerosol and Gas Experiment (SAGE) III on the International Space Station (ISS) team at NASA’s Langley Research Center in Hampton, VA selected three undergraduate student interns to work on a team science and engineering project during the 10-week summer session.

Matilda Damon, Linnea Johansson, and Riley Runyon worked together on developing the SAGE III limb scattering science processing code. Experimental SAGE III measurements of atmospheric limb scattered sunlight provide an innovative way to collect atmospheric data such as stratospheric ozone and aerosol. If successfully implemented, SAGE III atmospheric observations would cover a much larger range of times and Earth locations, providing even more atmospheric data to the public.

Currently, the SAGE III instrument uses solar and lunar occultation to capture these data products for the public. Such measurements only occur when the orbiting ISS experiences a sunrise, sunset, moonrise, or moonset. SAGE observes the light from the Sun or the Moon that passes through the atmosphere during both rise and set events to measure gases and particles in that region of the atmosphere. Occultation is a measurement of transmitted light, not scattered light. Adding limb scattering products to the SAGE inventory would add considerable value.

The intern team worked on coding a software Multiplicative Extended Kalman Filter (MEKF) that provides SAGE with an absolute attitude reference during limb scattering measurements. By combining solar edge detection with attitude rate data from the Disturbance Monitoring Package (DMP) subsystem aboard the SAGE III payload, the MEKF-derived attitude will supply high-accuracy telescope pointing information, which is important for ensuring the accuracy of the limb scattering atmospheric retrievals. The DMP is a three-axis ring laser gyroscope that the students used for attitude dead reckoning. Pointing error slowly accumulates as an angle random walk while dead reckoning in the absence of an occasional absolute attitude correction. Their filter will work to reduce the effects of this random walk between absolute measurements. To show how the filter impacts the attitude estimation, they also compared DMP dead reckoning directly with the filter results. To accomplish this, they relied heavily on quaternion mathematics. Quaternions are hypercomplex 4-D numbers that can represent rotations in 3-D space and are used for more than just aerospace applications. Your phone likely uses quaternion math to determine whether you’re holding it in portrait or landscape mode!

In addition to their limb scatter remote sensing project, the interns attended weekly SAGE III science and mission operations team meetings, weekly mentor check-ins, and several presentations on other missions, projects, and facilities at Langley. They particularly enjoyed learning about the history of NASA Langley’s Gantry.

Matilda Damon is a rising sophomore at Brown University studying astrophysics, engineering, and planetary science. At Brown, she rows for the Varsity Women’s Crew team, which helped prepare her for productive teamwork during her internship at NASA. She flies planes and studies astronomy in her free time at Brown.

“Knowing that code we wrote will help produce the gold standard of atmospheric data for the world is incredibly exciting. I am grateful to my mentors and peers for the opportunity to contribute to the SAGE III mission and for all the wisdom they imparted to me. Our mentors not only taught us coding, math, and science relevant to the mission, but also life skills such as collaboration, coding resource management, overcoming setbacks, and critical thinking,” said Damon.

Linnea Johansson is a rising junior at Washington and Jefferson College studying physics and mathematics. At school, she is a member of the varsity soccer team. She is also a leader of the Special Olympics Club and the Society for Physics Students. In her free time, she enjoys being outside and reading.

“This has been an incredible experience to help contribute to SAGE III. Working alongside my mentors has been rewarding and has taught me many valuable skills such as coding, version control, and working in a professional environment. I have also enjoyed the bonds that I have formed with the other interns,” said Johansson.

Riley Runyon is a rising junior at Washington and Jefferson College majoring in physics and mathematics. He is the leader of his school’s Climbing and Outdoors Club. He spends his free time running and playing his guitar.

“I loved every second of it. My mentors and coworkers are the coolest, most eclectic bunch of people I’ve ever had the privilege of knowing. Because of them and the work they assigned to me, I feel like I’ve learned how to think and work like an engineer and a scientist—systematically, precisely, and cautiously,” said Runyon.

The innovation, hard work, and dedication of the SAGE III summer internship team will continue to support and benefit the Langley mission team for the foreseeable future.

To apply for the next session of NASA internships, please visit intern.nasa.gov.

NASA Langley’s Richard Eckman and Robert Damadeo were elected to the prestigious International Ozone Commission (IO3C) at this year’s Quadrennial Ozone Symposium, held in Boulder, Colorado, from July 15-19, 2024. Membership in the IO3C is highly selective, limited to about 30 leading scientists globally, and is determined through a peer election process. Members serve four-year terms with the possibility of renewal, contributing to the global study and analysis of atmospheric processes related to ozone.

The IO3C plays a crucial role in organizing studies of ozone worldwide, including ground-based and satellite measurement programs to better understand atmospheric composition and ozone dynamics. The study of ozone, Earth’s sunscreen, is important because of the large role it plays in protecting the Earth from harmful levels of ultraviolet solar radiation, as well as its role as a greenhouse gas in Earth’s climate system.

Eckman started his career in atmospheric science research almost 40 years ago as a grad student at the University of Colorado. In 1988, he joined the NASA Langley Atmospheric Sciences Division and was involved in atmospheric modeling and data analysis. Over the last 15 years, Eckman has been managing the Atmospheric Composition Modeling and Analysis Program (ACMAP) at NASA Headquarters, as well as serving as the Program Scientist for the Earth science instruments on the Deep Space Climate Observatory (DSCOVR) and the Stratospheric Aerosol and Gas Experiment (SAGE) III on the International Space Station.

“I am honored to be recognized by the IO3C and elected as a member of the commission. It’s been a dream career, and the IO3C recognition is like icing on the cake,” said Eckman.

Damadeo currently serves as a Co-Principal Investigator for the SAGE IV project, and the Lead Algorithm Scientist for the SAGE III on ISS mission.

Not only has Damadeo worked on past, present and future SAGE missions, but he continues to do extensive research on long-term trends in stratospheric ozone. In particular, he has been a part of the LOTUS (Long-term Ozone Trends and Uncertainties in the Stratosphere) effort since its inception in 2016 and is currently the leader. LOTUS is an APARC (Atmospheric Processes And their Role in Climate) sponsored effort whose primary goal is to foster collaboration within the scientific community to provide vital contributions to the World Meteorological Organization (WMO) Ozone Assessment in an organized and cohesive way. Work performed under LOTUS has been responsible for a significant amount of content featured in the 2018 and 2022 Assessments.

“I am honored to be elected to the IO3C by my peers and colleagues,” said Damadeo.

To learn more about the IO3C, please visit https://www.io3c.org.  

The 3rd cohort of SAGE III/ISS Science Team selections have been made from proposals submitted to the NASA ROSES 2023 A.30 solicitation. Total funding of the 10 investigations selected is approximately $4.8 million, over a period of three years, to begin by mid-year 2024. The range of topics touch all the current occultation science products with a majority emphasizing stratospheric aerosols, including 4 related to smoke in the stratosphere. Several proposals point to the unique position of the SAGE III/ISS mission to carry forward the record of stratospheric water vapor from heritage missions to future, yet unnamed, ventures. Many projects will combine SAGE III/ISS data with other datasets to examine questions spanning time scales outside the growing 7-year mission record.

The Principal Investigators are:

Sean Davis (NOAA Earth System Research Laboratory)
Lars Kalnajs (University of Colorado at Boulder)
Cheng-Hsuan Lu (State University of New York at Albany)
Luis Millan Valle (Jet Propulsion Laboratory)
Mahesh Varma Mundakkara Kovilakam (ADNET Systems, Inc./NASA Langley Research Center)
Brian Soden (University of Miami, Key Biscayne)
Pamela Wales (Goddard Space Flight Center)
Hsiang-Jui (Ray) Wang (Georgia Institute of Technology)
Jun Wang (University of Iowa, Iowa City)
Jianglong Zhang (University of North Dakota)
In addition, Professor Jun Wang has been selected as the Science Team Leader.

Further details on the selections can be found here.
The SAGE III/ISS mission looks forward to advancements and new insights to be gained by the new Science Team.