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Summary of the 2024 SAGE III/ISS Meeting
Introduction
The Stratospheric Aerosol and Gas Experiment (SAGE) III/International Space Station [SAGEIII/ISS] Science Team Meeting (STM) took place on October 22–23, 2024, in a hybrid format. Approximately 50 scientists attended in person at NASA’s Langley Research Center (LaRC) – see Photo. Participants included researchers from U.S. universities, NASA LaRC, NASA’s Goddard Space Flight Center (GSFC), the NASA/Jet Propulsion Laboratory (JPL), and National Oceanic and Atmospheric Administration (NOAA) laboratories. Speakers from Canada and Germany also attended.
The history of the SAGE missions, the development and accomplishments of the SAGE III/ISS mission, and a summary of the 2022 STM appear in a previous article – see “Summary of the SAGE III/ISS Science Team Meeting,” in The Earth Observer, May–June 2023, 35:3, 11–18.
This article will summarize the content and key outcomes from the 2024 STM. The full agenda and presentations can be viewed at the SAGE III/ISS website. To access the presentations, use the link provided, then click on the Science Team tab and scroll about halfway down the page to find the 2024 meeting where they are listed.
Photo. Group photo of the in-person attendees of the SAGE III/ISS science team meeting, which took place at NASA’s Langley Research Center October 22–23, 2024. Photo Credit: NASA DAY ONE
Jun Wang [University of Iowa—SAGE III/ISS Science Team Leader] and David Flittner [LaRC—SAGE III/ISS Project Scientist] kicked off the STM. The pair welcomed all participants and invited Richard Eckman [NASA Headquarters (HQ)—SAGE III/ISS Program Scientist, now emeritus (as of January 1, 2025)] to deliver opening remarks. Allison McMahon [LaRC/Science Systems and Applications, Inc. (SSAI)—SAGE III/ISS Communications Lead] then spoke and provided logistical details for the meeting.
The morning sessions focused on project updates and the synergy between SAGE III/ISS and future missions currently in the planning phase, with potential launches in the early 2030s. The afternoon sessions were dedicated to aerosol research and the calibration/validation of SAGE III/ISS data products.
Project Operation and Data Product Briefing
David Flittner presented an update of the mission status, with over seven years and counting of data collection/analysis/release. SAGE III/ISS went through the 2023 Earth Science Senior Review (see page 15 of linked document for specific summary of the SAGE III/ISS results), and NASA HQ approved the proposal for continued operations for 2024–2026, with partial, overguide (i.e., above baseline request) funding approved to support community validation efforts, e.g., developing online quick look tools – see Figure 1 – and timely algorithm and product improvements. However, some reduction in mission staff and reorganization of work assignments have had to occur to stay within the allotted budget.
Overall, Flittner described 2024 as “a year of growth” for many on the SAGE III/ISS Team. He referenced important mission activities planned during the current three-year tenure of the new Science Team cohort. This work includes supporting the 2026 World Meteorological Organization (WMO) International Ozone assessment with a release of improved solar/lunar product in early 2025, examination of product sensitivities to variable aerosol loadings, introduction of a research product with retrieved temperature and pressure profiles, and continuing a much sought-after summer internship program.
Figure 1. An example of an enhanced tool for the community to visualize SAGE III/ISS data validation. Figure Credit: Mary Cate McKee [LaRC] Robbie Manion [LaRC] presented version 6.0 (V6) of the SAGE III/ISS data products, which were released in April 2025. Owing to a change in source ozone (O3) cross sections, this version will resolve the longstanding low bias in retrieved aerosol extinction around 600 nm. As a result, some changes in the downstream data products for inferred particle size distribution and aerosol/cloud categorization are expected. In addition, V6 will allow for recovery of hundreds of profiles previously impeded by the recent proliferation of sunspots.
Jamie Nehrir [LaRC] stated that SAGE III celebrated its seventh year onboard the ISS on February 19, 2024. [UPDATE: As of this publication, SAGE III/ISS has now passed eight years in orbit.] The payload continues to operate nominally surpassing 70,000 occultation events successfully acquired. Nehrir reported that SAGE III was not affected by the October 9, 2023, external leak from the Russian Nauka (or Multipurpose Laboratory) Module. However, the Disturbance Monitoring Package (DMP) lasers for the y- and z-axes on the instrument have been degrading. The operations team has been in a healthy dialog with the science and processing teams and external partners to determine the potential impact of these degradations on payload performance and on any ISS activities that could affect the science.
Invited Presentations on Synergy with New Limb Missions in Formulation
Lyatt Jaeglé [University of Washington] presented the mission concept for the Stratosphere Troposphere Response using Infrared Vertically-resolved light Explorer (STRIVE), which was recently selected for a competitive Phase A Concept Study within NASA’s 2023 Earth System Explorers Program (an element of the 2017–2027 Earth Science Decadal Survey). STRIVE fills a critical need for high vertical [1 km (0.6 mi)] resolution profiles of temperature, O3, trace gases, aerosols, and clouds in the upper troposphere–stratosphere (UTS). The system will provide near-global coverage and unparalleled horizontal sampling, producing 400,000 profiles each day. STRIVE will carry two synergistic instruments: a limb-scanning, infrared-imaging Dyson spectrometer to retrieve profiles of temperature, water vapor, trace gas concentrations, aerosol extinction, and cloud properties during day and night; and a dual-spectral, multi-directional, limb-profiling radiometer that retrieves detailed aerosol properties during day.
Björn-Martin Sinnhuber [Karlsruhe Institute of Technology, Germany] gave an overview of the Changing-Atmosphere Infrared Tomography Explorer (CAIRT), a candidate mission for the upcoming European Space Agency (ESA) Earth Explorer 11 satellite. If selected, CAIRT would provide passive infrared limb imaging of atmospheric temperature and trace constituents from the upper troposphere at about 5 km (3 mi) altitude up to the lower thermosphere at 115 km (71 mi) altitude. The presentation highlighted how these observations can provide information on how atmospheric gravity waves drive middle atmosphere circulation, age-of-air in the middle atmosphere, the descent of nitrogen oxides (Nox) from the thermosphere into the stratosphere, as well as the detection of sulfur species and sulfate (SO42-) aerosols in the stratosphere.
Aerosols
Mahesh Mundakkara [LaRC] presented the research used to generate the Global Space-based Stratospheric Aerosol Climatology (GloSSAC) product, a critical resource for analyzing and modeling the climatic effects of stratospheric aerosols. His presentation focused on assessing the Ozone Mapping and Profiler Suite (OMPS) limb profiler (LP) by comparing its data with other datasets, particularly SAGE III/ISS. (NOTE: While OMPS currently flies on the NASA–NOAA Suomi National Polar-orbiting Partnership (Suomi NPP), NOAA-20, and NOAA-21 platforms; LP is only part of OMPS on NOAA–21.) The evaluation aims to identify discrepancies and assess the suitability of OMPS-LP data for integration into the GloSSAC framework.
Jianglong Zhang [University of North Dakota] discussed the research plans of a newly funded SAGE project to investigate effective methods for improving stratospheric aerosol analyses and forecasts from aerosol models that can be used for future air quality and visibility forecasts and climate applications. Zhang also presented preliminary comparisons of collocated SAGE aerosol extinction and Cloud Aerosol Transport System (CATS) lidar aerosol extinction values in the stratosphere. [NOTE: CATS operated on ISS from 2015–2017.]
Sara Lu [The State University of New York, Albany] discussed efforts to examine smoke aerosol radiative effects in the upper troposphere and lower stratosphere using SAGE III/ISS observations. Lu explained that this project aims to produce multiyear analysis of aerosol radiative effects from all known pyrocumulonimbus cloud (pyroCb) events worldwide over a range of pyroCb intensities and various injection altitudes, geographic locations, and backgrounds. He presented findings from a pyroCb inventory compiled by the Naval Research Lab (NRL).
Xi Chen and Jun Wang [both University of Iowa] presented their new project on retrieving aerosol properties using SAGE III/ISS lunar measurements. They noted the challenges in normalizing lunar measurements caused by the Moon’s non-uniform surface. To address this, the team is developing a local normalization method to derive atmospheric transmissions from signals detected within each lunar event, enabling accurate aerosol retrieval. They reported that preliminary results are promising as evidenced by comparison with transmission product from collocated solar events – see Figure 2. This new processing will enrich the spatial and temporal coverage of SAGE III/ISS aerosol product by involving lunar events.
Figure 2. Preliminary results of the transmission derived from SAGE III/ISS lunar measurements (y-axis) and its comparison with collocated SAGE III/ISS solar measurements (x-axis). The comparisons are presented in two ways, one for the same wavelength color-coded by altitude [left] and another at the same altitude color-coded for the different wavelengths [right]. The results are for June 2017 through Novembe 2022, and the collocation criteria requires latitude separation smaller than 1˚ and observation times within 10 days. Note that if the transmission at any wavelength or altitude is smaller than 0.005, it is removed from the comparison for quality assurance purpose. Figure Credit: Xi Chen, University of Iowa Adam Pastorek and Peter Bernath [both Old Dominion University] discussed the properties of stratospheric SO42- aerosols from the infrared transmission spectra of Atmospheric Chemistry Experiment (ACE) – flying on the Canadian SCISAT satellite since 2003 – and optical extinction from SAGE III/ISS. Based on ACE infrared measurements, the researchers derived an empirical formula to determine the composition (weight % H2SO4) of volcanic plumes. They combined coincident ACE and SAGE III/ISS measurements, using bimodal, log-normal size distributions to reproduce the observations – see Figure 3. They used ACE observations of sulfur dioxide (SO2) to study the creation and destruction of stratospheric SO42- aerosols.
Figure 3. Combined transmittance fitting results from Atmospheric Chemistry Experiment– Fourier Transform Spectrometer (ACE-FTS), and SAGE III/ISS measurements demonstrate an improved characterization of sulfate particle size distribution using bi-lognormal (mode) distributions compared to a single lognormal distribution. The panels on the left show the transmittance fitting [top] and residuals [bottom] for the mono-mode distribution model, while the center panels show the transmittance fitting [top] and residuals [bottom] for the bi-mode distribution. The right panel illustrates the contributions of fine and coarse mode components to the total transmittance. The measurements for this figure were taken approximately four months after the January 2022 Hunga Tonga–Hunga Haʻapai eruption at a tangent height of 23.6 km (14.5 mi) in ACE occultation (ss100628), with coincident SAGE measurements from that same period (2022041609). Figure Credit: Adam Pastorek, adapted from a Figure in a paper published in Journal of Quantitative Spectroscopy and Radiative Transfer in January 2024. Sean Davis [NOAA, Chemistry Science Lab] presented on his research aimed at constraining decadal variability and assessing trends in stratospheric composition and tropospheric circulation using SAGE III/ISS and complementary satellite data sets. The team continues to include the SAGE water vapor and O3 products in the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) dataset. Davis also highlighted preliminary work evaluating V6 data in comparison to the former V5.3. He discussed line-of-sight, transmission-based filtering for O3 profiles and O3 diurnal variability corrections.
Lars Kalnaajs [University of Colorado, Boulder] presented results from two studies of particle size distributions from SAGE aerosol extinction data. Kalnaajs summarized results from two papers in review. His team paired the Optical Particle Counter collected from balloon platforms with SAGE II data to derive the parameters for bi-mode aerosol size distribution. They also presented the work of using SAGE III extinction ratios, 448/756 versus 1544/756, to derive monomodal lognormal size distribution, which allows them to compute distribution moments and compare these to in situ measurements taken over Sweden in the winters of 2002 and 2004.
Anne Thompson [GSFC, emeritus] presented on the Southern Hemisphere Additional Ozonesondes (SHADOZ) network and how that SHADOZ data are a satellite validation standard and can also be used to assess ozone trends in the upper troposphere and lower stratosphere. Thompson emphasized that SHADOZ O3 profiles are the only standard process to obtain measurements from surface to mid-stratosphere at 100–150 m (328–492 ft) resolution. Such measurements are essential to validate O3 measurements from SAGE-derived products. She also presented an update on the free tropospheric and lowermost stratospheric (LMS) O3 trends from eight equatorial SHADOZ sites. Newer calculations confirm that an apparent LMS seasonal decline (July–September) is associated with a roughly 100 m (328 ft) upward trend in tropopause height.
DAY TWO
The second day started with Jack Kaye [NASA Earth Science Division—Associate Director for Research for the Earth Science Division, emeritus as of April 30, 2025] providing a historic perspective on SAGE and comments on its context within NASA’s overall Earth science program. A technical session was held with three invited presentations, followed by three additional sessions where science team members presented their research on trace gas studies, including data product calibration and validation. The meeting concluded with updates from the SAGE project team on the SAGE III/ISS website and ongoing operations aboard the ISS. In his presentation, Kaye shared about his past involvement with the SAGE program and his perspective on its future in the context of flight missions for Earth observations.
Invited Presentations on Advanced Modeling and New Satellite Mission For UTS
Steven Pawson [GSFC] presented on the comprehensive modeling and analysis capabilities of
Upper troposphere and lower stratosphere (UTLS) dynamics and composition in the Goddard Earth Observing System (GEOS) model Pawson discussed the Global Modeling and Assimilation Office’s (GMAO) recent support for the Asian summer monsoon Chemical and CLimate Impact Project (ACCLIP) mission and the trend analysis of stratospheric O3. He also discussed future plans for GMAO, including improving the representation of water vapor in UTS through data assimilation and increasing horizontal and vertical resolution in the GEOS model.
Kostas Tsigaridis [Columbia University] presented recent research on the composition and climate impacts of increasing launches to Low Earth Orbit (LEO). Assuming that there are 10,000 launches per year and all launches use liquefied natural gas (LNG) as a propellant, the team compiled launch-related emission inventories and highlighted key uncertainties that could significantly affect climate predictions – particularly the impact black carbon has on the radiative balance and heterogeneous chemistry of the UTS. In addition, water vapor was found to contribute to the heating of the stratosphere and to a nontrivial amount of O3 depletion – 13 Dobson units (DU) on the global mean.
Adam Bourassa [University of Saskatchewan, Canada] introduced the satellite mission for High-altitude Aerosol, Water vapor, and Clouds (HAWC), planned as the Canadian contribution to the NASA Atmosphere Observing System (AOS) for launch in 2031 – a key component in NASA’s next generation Earth System Observatory. Bourassa highlighted the three Canadian instruments, which include limb profilers for water vapor and aerosol in the UTS and a far infrared imaging radiometer for ice cloud microphysics and radiative budget closure. He discussed instrument requirements and development progress as well as results from recent sub-orbital testing of prototypes on the NASA Earth Resources (ER)-2 and stratospheric balloons.
Trace Gases
Brian Soden [University of Miami] presented a new project that will use SAGE data to constrain climate sensitivity in climate models. Climate models differ substantially in their calculation of the radiative forcing from carbon dioxide (CO2), and these intermodel differences have remained largely unchanged for several decades. Soden highlighted the role of stratospheric temperature in modulating the radiative forcing from CO2. He explained that models that simulate a cooler stratosphere simulate a larger radiative forcing for the same change in CO2 compared to models that posit a warmer stratosphere. He added that determining the cause of the model biases in stratospheric temperature – particularly the role of water vapor in driving this intermodel spread – is an area of active research.
Ray Wang [Georgia Institute of Technology] compared the uncertainty analysis of SAGE III retrieved O3 and water vapor data in V5.3 to the same parameters in V6.0. He then compared the SAGE III data to the correlative measurements from other platforms. For O3, the differences between SAGE and measurements from the Microwave Limb Sounder (MLS) on NASA’s Aura platform are less than 5% in the stratosphere. SAGE V6.0 ozone values are systematically about 1–2% higher than those from V5.3 O3 – due to changes in how the O3 cross-section is represented in each version. For water vapor, SAGE data agree with MLS and Frost Point Hygrometer (FPH) data within 5%. Wang showed some differences between SAGE water vapor data retrievals using V5.3 and the same data obtained using version 6.0. He also said that a two-dimensional (i.e., spatial and temporal) regression model can be used to minimize sampling bias in climatology derived from non-uniform satellite measurements – ensuring more accurate representation of long-term trends.
Emma Knowland [GSFC/Morgan State University, Goddard Earth Sciences Technology and Research II (GESTAR II), now NASA HQ—SAGE III/ISS Program Scientist] discussed the progress of assimilating SAGE III water vapor data product into NASA’s GEOS re-analysis. Her team’s work demonstrated that while the number of solar occultation observations a day from SAGE III/ISS is about 1% of the total number of profiles observed globally by MLS, the chemical timescales of water vapor in the lower stratosphere are long enough that the SAGE III/ISS data can provide a valuable constraint on GEOS re-analysis, especially in the absence of MLS data – see Figure 4.
Figure 4. Hovmöller diagrams of the vertical distribution of 15°S–15°N average water vapor anomalies in upper troposphere–stratosphere with water vapor relaxed to a climatology [top left] and from data assimilation of SAGE III/ISS water vapor into the Goddard Earth Observing System (GEOS) model [bottom left]. Scatter plots show water vapor mixing ratios (y-axis) with [top right] and without [bottom right] data assimilation compared independent observations from the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) data (x-axis). The ACE–FTS data were not used in data assimilation. This shows that data assimilation of SAGE data improves the agreement with ACE-FTS – especially in the lower stratosphere (400 to 500 K). Figure Credit: Emma Knowland [NASA] Melody Avery [University of Colorado, Boulder] discussed using SAGE data and data from the Cloud–Aerosol Lidar with Orthogonal Projection (CALIOP) instrument (on the former Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission) to study thin clouds and aerosol distributions in the tropical tropopause region (TTL). Avery explained that these distributions from V5.3 of SAGE-III/ISS and V5.41 of CALIOP are shown to agree well, and CALIOP observations of cloud frequency are shown to be a sensitive metric for defining the width of the Hadley Cell near the tropical tropopause. Combining SAGE and CALIOP data produced a longer timescale to constrain and evaluate climate models that currently do not agree on how the tropical width at this altitude varies. They found that results derived using SAGE V6.0 versus V5.3 differ on the order of 2% in the TTL region.
Pamela Wales [GESTAR II] introduced a new project that leverages SAGE III/ISS measurements to explore diurnal characteristics of O3 and nitrogen dioxide (NO2) in GEOS model products. Her team is exploring potentially using a GEOS reanalysis of stratospheric trace gases collected by MLS as a transfer standard to evaluate the consistency between the SAGE III/ISS solar and the less frequently measured lunar retrieval. They are also assessing uncertainties in stratospheric NO2 in the GEOS Composition Forecast (GEOS-CF) model using SAGE III/ISS and complementary satellite instruments. This work will inform how effectively GEOS-CF can be used in air quality studies to remove the stratospheric signal from column retrievals of NO2.
Luis Millán [JPL] presented work on the change of stratospheric water vapor mass after the Hunga Tonga–Hunga Haʻapai (Hunga) volcano eruption in 2022. Millán found an increase (~10%) of total stratospheric water vapor – a potent greenhouse gas. Given their advanced age, MLS, ACE-FTS, and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on NASA’s Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) mission (Heliosphere Division), are nearing the end of their missions, leaving SAGE III/ISS as the primary instrument for monitoring the plume’s evolution. Millán discussed how the SAGE III/ISS measurements might be sufficient to observe the dispersion of the excess Hunga water vapor from stratosphere in coming years. He also discussed a 39-year plus record of stratospheric water vapor mass using the overlapping periods between SAGE II, MLS, and SAGE III/ISS.
Ryan Stauffer [GSFC] presented the operation and outcomes of the Ticosonde balloon-borne O3 and water vapor sonde project in San Jose, Costa Rica. Ongoing since July 2005, Ticosonde has collected over 700 O3 profiles and 270 water vapor profiles for climate and pollution studies and satellite validation. Because Ticosonde is the only long-term water vapor sonde station in the tropics, the stratospheric water vapor data is vital for validation of SAGE-III/ISS and MLS profiles. Ticosonde has been used to verify the success of updated water vapor retrieval algorithms for both instruments – which now agree within a few percent up to 25 km (15 mi) altitude.
Natalya Kramarova [GSFC] showed the comparison of O3 profile retrieved from SAGE III with those derived from the OMPS-LP sensor – which is part of OMPS on NOAA-21 – from February 2023–June 2024. Diurnal corrections using the Goddard Diurnal Ozone Climatology (which is described in a 2020 article in Atmospheric Measurement Techniques) is applied to account for differences in measurement times between SAGE III’s sunrise or sunset observations and NOAA-21 LP’s midday measurements. Once the time correction is made, results show good agreement between the two instruments in depicting vertical ozone distribution across different geographical regions (e.g., tropics and mid-latitudes) and under various conditions (e.g., near the edge of the Antarctic O3 hole in October 2023). The mean biases between NOAA-21 LP and SAGE III are typically within ±5% between ~18–45 km (11–28 mi).
Project Team and Operations Highlights
Michael Heitz [LaRC] showed that V5.3 and previous versions of the SAGE III/ISS data product had a noticeable – and unphysical – dip in the retrieved aerosol extinction between 520–676 nm. This dip has been referred to as the aerosol “seagull.” However, adoption of a new absorption cross-section database into the V6.0 algorithm reduced the aerosol seagull effect significantly. Kevin Leavor [LaRC] presented new developments for the SAGE III/ISS quick look website. Mary Cate McKee [LaRC] introduced a new feature of the quick look website that showcases comparisons of O3 and water vapor sonde data at over 40 stations. Sonde data is sourced from the Network for the Detection of Atmospheric Composition Change (NDACC), GSFC’s SHADOZ, and the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Heitz explained that the comparison plots are updated continuously as new coincidences occur, providing the community with valuable insight to the quality of SAGE III/ISS data relative to this external network of ground stations. Future additions to the website include aerosol and lidar comparisons, additional plot statistics, and comparisons with novel homogenized datasets.
Returning to a topic discussed in Jamie Nehrir’s presentation, Charles Hill [LaRC] showed that the SAGE III Disturbance Monitoring Package (DMP) correction to the data product – which was implemented beginning with V5.3 – has significantly reduced the product uncertainties caused by ISS vibrations. Approximately 7% of SAGE III occultation events are highly disturbed by mechanical vibrations, and the DMP correction has improved pointing registrations in these events significantly. The DMP’s x-axis gyroscope failed on August 8, 2023 – but this loss did not significantly affect the DMP correction to scan plane elevation. Future possible losses of either the y- or z-axes will end active correction of ISS disturbances.
Conclusion
Jun Wang, David Flittner, and Richard Eckman led the closing discussion that highlighted the growing interest in atmospheric composition change – particularly due to emissions from large wildfires and volcanic eruptions in recent years. This increasing interest contrasts with the declining availability of observational data from the upper troposphere, following the retirement of CALIPSO in late 2023 and the planned decommissioning of Aura’s aging limb instruments in 2026. This gap underscores the critical importance of SAGE III/ISS data – not only for current UTS research but also for the next 5–7 years, during which no new limb measurements are planned.
SAGE III/ISS remains essential for profiling key atmospheric constituents, including water vapor, aerosols, O₃, and NO₂. The long-term, consistent data record provided by the SAGE series of instruments since the late 1970s – including SAGE III/ISS since 2017 – has been invaluable for studying past and future changes in atmospheric composition within the UTS. To further support research and applications of SAGE data products, participants discussed the possibility of proposing a special collection of articles in AGU journals.
Overall, the 2024 SAGE III/ISS meeting was a success. Participants received valuable updates on the status of SAGE III/ISS operations, data product calibration and validation, and new developments. The meeting also showcased the collective expertise and excellence in driving advancements in UTS research, from climate change studies to data assimilation for chemistry transport models and contributions to multi-sensor data fusion.
Jun Wang
University of Iowa
jun-wang-1@uiowa.edu
David Flittner
Langley Research Center
david.e.flittner@nasa.gov
Richard Eckman
NASA Langley Research Center
richard.s.eckman@nasa.gov
Emma Knowland
NASA Headquarters
k.e.knowland@nasa.gov
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Chaitén Volcano in southern Chile erupted on May 2, 2008 for the first time inn 9,000 years. NASA satellites that monitor changes in vegetation near volcanoes could aid in earlier eruption warnings.Jeff Schmaltz, MODIS Rapid Response Team, NASA Goddard Space Flight Center Scientists know that changing tree leaves can indicate when a nearby volcano is becoming more active and might erupt. In a new collaboration between NASA and the Smithsonian Institution, scientists now believe they can detect these changes from space.
As volcanic magma ascends through the Earth’s crust, it releases carbon dioxide and other gases which rise to the surface. Trees that take up the carbon dioxide become greener and more lush. These changes are visible in images from NASA satellites such as Landsat 8, along with airborne instruments flown as part of the Airborne Validation Unified Experiment: Land to Ocean (AVUELO).
Ten percent of the world’s population lives in areas susceptible to volcanic hazards. People who live or work within a few miles of an eruption face dangers that include ejected rock, dust, and surges of hot, toxic gases. Further away, people and property are susceptible to mudslides, ashfalls, and tsunamis that can follow volcanic blasts. There’s no way to prevent volcanic eruptions, which makes the early signs of volcanic activity crucial for public safety. According to the U.S. Geological Survey, NASA’s Landsat mission partner, the United States is one of the world’s most volcanically active countries.
Carbon dioxide released by rising magma bubbles up and heats a pool of water in Costa Rica near the Rincón de LaVieja volcano. Increases in volcanic gases could be a sign that a volcano is becoming more active.Josh Fisher/Chapman University When magma rises underground before an eruption, it releases gases, including carbon dioxide and sulfur dioxide. The sulfur compounds are readily detectable from orbit. But the volcanic carbon dioxide emissions that precede sulfur dioxide emissions – and provide one of the earliest indications that a volcano is no longer dormant – are difficult to distinguish from space.
The remote detection of carbon dioxide greening of vegetation potentially gives scientists another tool — along with seismic waves and changes in ground height—to get a clear idea of what’s going on underneath the volcano. “Volcano early warning systems exist,” said volcanologist Florian Schwandner, chief of the Earth Science Division at NASA’s Ames Research Center in California’s Silicon Valley, who had teamed up with Fisher and Bogue a decade ago. “The aim here is to make them better and make them earlier.”
“Volcanoes emit a lot of carbon dioxide,” said volcanologist Robert Bogue of McGill University in Montreal, but there’s so much existing carbon dioxide in the atmosphere that it’s often hard to measure the volcanic carbon dioxide specifically. While major eruptions can expel enough carbon dioxide to be measurable from space with sensors like NASA’s Orbiting Carbon Observatory 2, detecting these much fainter advanced warning signals has remained elusive. “A volcano emitting the modest amounts of carbon dioxide that might presage an eruption isn’t going to show up in satellite imagery,” he added.
Gregory Goldsmith from Chapman University launches a slingshot into the forest canopy to install a carbon dioxide sensor in the canopy of a Costa Rican rainforest near the Rincón de LaVieja volcano.Josh Fisher/Chapman University Because of this, scientists must trek to volcanoes to measure carbon dioxide directly. However, many of the roughly 1,350 potentially active volcanoes worldwide are in remote locations or challenging mountainous terrain. That makes monitoring carbon dioxide at these sites labor-intensive, expensive, and sometimes dangerous.
Volcanologists like Bogue have joined forces with botanists and climate scientists to look at trees to monitor volcanic activity. “The whole idea is to find something that we could measure instead of carbon dioxide directly,” Bogue said, “to give us a proxy to detect changes in volcano emissions.”
“There are plenty of satellites we can use to do this kind of analysis,” said volcanologist Nicole Guinn of the University of Houston. She has compared images collected with Landsat 8, NASA’s Terra satellite, ESA’s (European Space Agency) Sentinel-2, and other Earth-observing satellites to monitor trees around the Mount Etna volcano on the coast of Sicily. Guinn’s study is the first to show a strong correlation between tree leaf color and magma-generated carbon dioxide.
Confirming accuracy on the ground that validates the satellite imagery is a challenge that climate scientist Josh Fisher of Chapman University is tackling with surveys of trees around volcanoes. During the March 2025 Airborne Validation Unified Experiment: Land to Ocean mission with NASA and the Smithsonian Institution scientists deployed a spectrometer on a research plane to analyze the colors of plant life in Panama and Costa Rica.
Alexandria Pivovaroff of Occidental College measures photosynthesis in leaves extracted from trees exposed to elevated levels of carbon dioxide near a volcano in Costa Rica.Josh Fisher/Chapman University Fisher directed a group of investigators who collected leaf samples from trees near the active Rincon de la Vieja volcano in Costa Rica while also measuring carbon dioxide levels. “Our research is a two-way interdisciplinary intersection between ecology and volcanology,” Fisher said. “We’re interested not only in tree responses to volcanic carbon dioxide as an early warning of eruption, but also in how much the trees are able to take up, as a window into the future of the Earth when all of Earth’s trees are exposed to high levels of carbon dioxide.”
Relying on trees as proxies for volcanic carbon dioxide has its limitations. Many volcanoes feature climates that don’t support enough trees for satellites to image. In some forested environments, trees that respond differently to changing carbon dioxide levels. And fires, changing weather conditions, and plant diseases can complicate the interpretation of satellite data on volcanic gases.
Chapman University visiting professor Gaku Yokoyama checks on the leaf-measuring instrumentation at a field site near the Rincón de LaVieja volcano.Josh Fisher/Chapman University Still, Schwandner has witnessed the potential benefits of volcanic carbon dioxide observations first-hand. He led a team that upgraded the monitoring network at Mayon volcano in the Philippines to include carbon dioxide and sulfur dioxide sensors. In December 2017, government researchers in the Philippines used this system to detect signs of an impending eruption and advocated for mass evacuations of the area around the volcano. Over 56,000 people were safely evacuated before a massive eruption began on January 23, 2018. As a result of the early warnings, there were no casualties.
Using satellites to monitor trees around volcanoes would give scientists earlier insights into more volcanoes and offer earlier warnings of future eruptions. “There’s not one signal from volcanoes that’s a silver bullet,” Schwandner said. “And tracking the effects of volcanic carbon dioxide on trees will not be a silver bullet. But it will be something that could change the game.”
By James Riordon
NASA’s Earth Science News Team
Media contact: Elizabeth Vlock
NASA Headquarters
About the Author
James R. Riordon
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By NASA
Teams at NASA’s Michoud Assembly Facility in New Orleans move a liquid hydrogen tank for the agency’s SLS (Space Launch System) rocket into the factory’s final assembly area on April 22, 2025. The propellant tank is one of five major elements that make up the 212-foot-tall rocket stage. NASA/Steven Seipel NASA completed another step to ready its SLS (Space Launch System) rocket for the Artemis III mission as crews at the agency’s Michoud Assembly Facility in New Orleans recently applied a thermal protection system to the core stage’s liquid hydrogen tank.
Building on the crewed Artemis II flight test, Artemis III will add new capabilities with the human landing system and advanced spacesuits to send the first astronauts to explore the lunar South Pole region and prepare humanity to go to Mars. Thermal protection systems are a cornerstone of successful spaceflight endeavors, safeguarding human life, and enabling the launch and controlled return of spacecraft.
The tank is the largest piece of SLS flight hardware insulated at Michoud. The hardware requires thermal protection due to the extreme temperatures during launch and ascent to space – and to keep the liquid hydrogen at minus 423 degrees Fahrenheit on the pad prior to launch.
“The thermal protection system protects the SLS rocket from the heat of launch while also keeping the thousands of gallons of liquid propellant within the core stage’s tanks cold enough. Without the protection, the propellant would boil off too rapidly to replenish before launch,” said Jay Bourgeois, thermal protection system, test, and integration lead at NASA Michoud. “Thermal protection systems are crucial in protecting all the structural components of SLS during launch and flight.”
In February, Michoud crews with NASA and Boeing, the SLS core stage prime contractor, completed the thermal protection system on the external structure of the rocket’s liquid hydrogen propellant fuel tank, using a robotic tool in what is now the largest single application in spaceflight history. The robotically controlled operation coated the tank with spray-on foam insulation, distributing 107 feet of the foam to the tank in 102 minutes. When the foam is applied to the core stage, it gives the rocket a canary yellow color. The Sun’s ultraviolet rays naturally “tan” the thermal protection, giving the SLS core stage its signature orange color, like the space shuttle external tank.
Having recently completed application of the thermal protection system, teams will now continue outfitting the 130-foot-tall liquid hydrogen tank with critical systems to ready it for its designated Artemis III mission. The core stage of SLS is the largest ever built by length and volume, and was manufactured at Michoud using state-of-the-art manufacturing equipment. (NASA/Steven Seipel) While it might sound like a task similar to applying paint to a house or spraying insulation in an attic, it is a much more complex process. The flexible polyurethane foam had to withstand harsh conditions for application and testing. Additionally, there was a new challenge: spraying the stage horizontally, something never done previously during large foam applications on space shuttle external tanks at Michoud. All large components of space shuttle tanks were in a vertical position when sprayed with automated processes.
Overall, the rocket’s core stage is 212 feet with a diameter of 27.6 feet, the same diameter as the space shuttle’s external tank. The liquid hydrogen and liquid oxygen tanks feed four RS-25 engines for approximately 500 seconds before SLS reaches low Earth orbit and the core stage separates from the upper stage and NASA’s Orion spacecraft.
“Even though it only takes 102 minutes to apply the spray, a lot of careful preparation and planning is put into this process before the actual application of the foam,” said Boeing’s Brian Jeansonne, the integrated product team senior leader for the thermal protection system at NASA Michoud. “There are better process controls in place than we’ve ever had before, and there are specialized production technicians who must have certifications to operate the system. It’s quite an accomplishment and a lot of pride in knowing that we’ve completed this step of the build process.”
The core stage of SLS is the largest NASA has ever built by length and volume, and it was manufactured at Michoud using state-of-the-art manufacturing equipment. Michoud is a unique, advanced manufacturing facility where the agency has built spacecraft components for decades, including the space shuttle’s external tanks and Saturn V rockets for the Apollo program.
Through Artemis, NASA will send astronauts to explore the Moon for scientific discovery, economic benefits, and build the foundation for the first crewed missions to Mars.
For more information on the Artemis Campaign, visit:
https://www.nasa.gov/feature/artemis/
News Media Contact
Jonathan Deal
Marshall Space Flight Center, Huntsville, Ala.
256-544-0034
jonathan.e.deal@nasa.gov
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s coverage of the April 8, 2024, total solar eclipse has earned two nominations for the 46th Annual News & Documentary Emmy Awards.
The Academy of Television Arts & Sciences announced the nominations on May 1, recognizing NASA’s outstanding work in sharing this rare celestial event with audiences around the world. The winners are set to be unveiled at a ceremony in late June.
“Total solar eclipses demonstrate the special connection between our Earth, Moon, and Sun by impacting our senses during the breathtaking moments of total alignment that only occur at this time on Earth,” said Nicky Fox, associate administrator for science at NASA Headquarters in Washington. “NASA’s Eclipse coverage team perfectly encapsulated the awe-inspiring experience from start to finish for viewers around the world in this once-in-a-lifetime moment in American history. Congratulations to the entire NASA Eclipse coverage team for their two much-deserved Emmy award nominations!”
The two nominations include:
Outstanding Live News Special for the agency’s live broadcast coverage of the 2024 total solar eclipse. NASA’s live broadcast coverage of the 2024 total solar eclipse was the most ambitious live project ever attempted by the agency. The broadcast spanned three hours as the eclipse traveled 3,000 miles across seven states and two countries. From cities, parks, and stadiums, 11 hosts and correspondents provided on air commentary, interviews, and live coverage. Viewers tuned in from all over the world, including at watch parties in 9 locations, from the Austin Public Library to New York’s Times Square. An interactive “Eclipse Board” provided real time data analysis as the Moon’s shadow crossed North America. Live feeds from astronauts aboard the International Space Station and NASA’s WB-57 high-altitude research aircraft were brought in to provide rare and unique perspectives of the solar event.
In total, NASA received almost 40 million views across its own distribution. Externally, the main broadcast was picked up in 2,208 hits on 568 channels in 25 countries.
Outstanding Show Open or Title Sequence – News for the agency’s show open for the 2024 total solar eclipse. NASA’s show open for the 2024 total solar eclipse live broadcast explores the powerful connections between the Sun, humanity, and the rare moment when day turns to night. From witnessing the Sun’s atmosphere to feeling the dramatic drop in temperature, the video captures the psychological, emotional, and cultural impact of this celestial phenomenon.
For more information about NASA missions, visit:
https://www.nasa.gov
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Last Updated May 08, 2025 Related Terms
General 2024 Solar Eclipse Eclipses Heliophysics Heliophysics Division Science Mission Directorate Solar Eclipses The Solar System Explore More
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