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Outreach – SAGE (Stratospheric Aerosol and Gas Experiment)

SAGE III Carries on Critical Measurements of Stratospheric Aerosols and Ozone

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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.

Credits:
Allison McMahon (SSAI): Producer
Haley Reed (ADNET): Producer
David Flittner (NASA/LaRC): Scientist
Marilee Roell (NASA/LaRC): Scientist
Jamie Nehrir (NASA/LaRC): Engineer
Kevin Leavor (SSAI): Scientist
NASA’s Goddard Space Flight Center Conceptual Image Lab
NASA’s Scientific Visualization Studio

SAGE III Sees California Wildfire Effects in Stratosphere

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Wildfires have been burning across the state of California since August 2020. As the fires continue to rage, NASA Earth science missions have observed increased numbers of airborne particles known as aerosols across the country.

Different types of aerosols scatter or absorb sunlight to varying degrees, depending on their size, type and location. While most aerosols reflect sunlight, dark colored soot particles from fires absorb sunlight, warming Earth’s atmosphere, and shading the surface below it. When smoke from large wildfire events enters the stratosphere, these competing warming and cooling effects on the atmosphere can contribute to variability in the climate record.

In September and October, the Stratospheric Aerosol and Gas Experiment III (SAGE III) instrument aboard the International Space Station observed smoke from the ongoing wildfires using solar occultation, a measurement technique that involves looking at light from the Sun as it passes through Earth’s atmosphere at the edge, or limb, of the planet. The initial observation was made over the Eastern United States, but additional instances of increased stratospheric aerosols were observed south of California in the succeeding days. SAGE III observations show a significant increase in stratospheric aerosols when compared to data from July.

In September and October, SAGE III was clearly seeing smoke in the stratosphere from the California wildfires, and continuing to see smoke from the Australian bushfires. The red, orange, and yellow colors above the tropopause line, which separates the troposphere from the stratosphere, indicates increased levels of aerosols. Credits: NASA

Aerosols that reach the troposphere, the lowest layer of Earth’s atmosphere where most of the life on the surface exists, only remain for about a week because rain cleanses them from the air. Stratospheric aerosols can stick around for months or even years.

SAGE III measures stratospheric aerosols at nine wavelengths. The multi-wavelength data of SAGE III is unique, providing important clues to aerosol type. SAGE III data from September and October suggests the aerosols were larger than in previous months. Variation in size of the aerosol particles can also suggest a change in composition.

“Based on the context, the larger particles seen in the SAGE III/ISS data are most likely carbonaceous, or soot,” said David Flittner, SAGE III project scientist at NASA’s Langley Research Center in Hampton, Virginia.

SAGE III observations of the wildfires are supported by additional satellite and human observations. Aircraft observations of the California Creek Fire from the National Weather Service suggested convection pushed smoke to just over 9 miles (15 km) into the air, which was also observed by SAGE.

“SAGE III provides highly accurate and precise observations of aerosol properties that bridge and contextualize measurements from other instruments,” said Flittner.

This event marks yet another instance of intense fires lofting tremendous amounts of heat and moisture high into Earth’s atmosphere, creating dangerous smoke-infused clouds that resemble thunderstorms. The SAGE III instrument is still observing the stratospheric effects of the Australian fires that occurred in late 2019 and early 2020. NASA Earth scientists are tracking the frequency of these stratosphere-penetrating phenomena, also known as pyrocumulus events, and comparing them to the SAGE II instrument historical record.

 

 

20 Years of Observing Earth from the International Space Station

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After 20 years of continuous human presence, the International Space Station (ISS) has provided 241 visitors with an extraordinary view of Earth from outer space — one they have shared with the rest of the world.

Astronaut photography, formally called Crew Earth Observations (CEO), has resulted in more than 3.5 million photographs of the ever-changing blue planet. But camera-wielding astronauts are not the only ones looking down at Earth from their perch in the sky. An impressive suite of Earth Science instruments have also visited the station to capture vast amounts of data about our planet.

However, space aboard the station itself is limited, and the spots are highly coveted. Instruments go through a rigorous approval process and cycle through every couple of years, turning the station into a virtual swiss-army knife of interchangeable remote sensing tools. An especially comprehensive suite of Earth observing instruments are currently aboard the station, with two more approved and several more proposing to become future ISS instruments.

These instruments complement one another to provide a more complete picture of Earth systems, according to William Stefanov, branch chief for the Exploration Science Office at NASA’s Johnson Space Center, and principal investigator for the Crew Earth Observations Facility on the International Space Station. “That’s why it’s serendipitously great that all of these instruments are on the International Space Station and functioning simultaneously,” Stefanov said.

ECOSTRESS

The human crew came in especially handy for the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument, which records the temperature of plants on Earth’s surface by measuring the heat they give off. The instrument required the addition of Wi-Fi modules to transmit its data to the station, which in turn required astronauts to conduct a spacewalk to install them.

Since then, ECOSTRESS has provided new insights into the relationship between plant temperatures and water usage. It can identify plant stress down to an individual farmer’s field, when intervention and water management may still be possible to save crops.

Principal investigator Simon Hook says scientists have only just begun to scratch the surface of how the instrument can be used based on its frequent and high-resolution temperature measurements. There is work underway to use the temperature data to observe wildfires, droughts, volcanoes and heat waves, or even to identify heat patterns within urban cities.

GEDI

From fields to forests, another plant-focused instrument is the Global Ecosystem Dynamics Investigation (GEDI). Using lidar—a method of bouncing a laser off the planet and measuring how long it takes the signal to return—GEDI is creating a record of the three-dimensional structure world’s tropical and temperate forests so that Earth’s tree canopies can be mapped and tracked over time.

The vertical structure of forests, which is essentially the height of the trees and how their leaves and branches are arranged vertically, can help determine how much carbon storage is lost from deforestation or gained from growing forests. GEDI principal investigator Ralph Dubayah, professor of Geographical Sciences at the University of Maryland, College Park, says this is the biggest uncertainty we have about the global carbon cycle, and why there is so much attention put on understanding how deforestation and tree growth contribute to atmospheric carbon dioxide concentrations. GEDI is a collaborative effort between NASA and UMD.

To supply its high-power laser, GEDI takes advantage of the massive solar panels on the station. “Right now on the International Space Station we have an amazing confluence of instruments that together are able to observe ecosystem function, structure and plant composition,” Dubayah said. “And it was entirely made possible because we have this incredible science platform in the ISS.”

LIS

Being high above the clouds also makes the station a good platform for observing the weather. NASA’s Lightning Imaging Sensor (LIS) records the time, energy output and locations of lightning events around the world in the lower atmosphere. It can provide information on when storms are growing or decaying, thereby helping to improve weather forecasting models and aircraft/spacecraft safety precautions.

It complements the Geostationary Lightning Mapper (GLM) aboard the Geostationary Operational Environmental Satellite (GOES-16), which is a collaboration between NASA, the National Atmospheric and Oceanic Administration (NOAA) and industry partners, and the European Space Agency’s (ESA) monitoring of thunderstorms and upper atmosphere lightning events through the Atmosphere Space Interaction Monitor (ASIM) instrument which is on the ISS.

The data from ASIM and LIS are both able to capture the impacts of dust storms, pollution, fires, and volcanic eruptions on cloud formation and electrification. This is just one example of how ESA, and other international agencies including the German Aerospace Center (DLR) and the Japan Aerospace Exploration Agency (JAXA), are also helping advance a global understanding of our planet through ISS-instruments with Earth observations of their own.

OCO-3

Several instruments currently aboard the station are not the first of their kind. As the name might suggest, the Orbiting Carbon Observatory-3 (OCO-3) is a third iteration instrument for long-term monitoring of atmospheric carbon dioxide distributions around the globe, complementing long-term ground-based observations. It provides insights into regional carbon sources and sinks and monitors changes in the carbon cycle linked to human activity.

Together with GEDI and ECOSTRESS, OCO-3 contributes to a more complete picture of terrestrial ecosystems. While its predecessor, the OCO-2 satellite, followed a polar orbit, OCO-3’s path aboard the station offers a denser data set for areas with large carbon fluxes, including Earth’s most biologically diverse regions like the Amazon rainforest.

The orbit also allows measurements at different times of day, which especially benefits ECOSTRESS and OCO-3 as plants and their contribution to the carbon cycle fluctuate with time of day due to variations in sun, temperature and water availability.

SAGE III

Like OCO-3, the Stratospheric Aerosol and Gas Experiment (SAGE) III, is a third-generation instrument. The successive SAGE instruments have provided an ongoing record of Earth’s upper atmospheric water vapor, aerosol and ozone – which make up the protective “sunscreen” layer for the planet.

The Stratospheric Aerosol and Gas Experiment (SAGE) III’s line of sight from the International Space Station provides a view of the aerosols and gases present in Earth’s atmosphere by taking advantage of the sunlight traveling through a slice of the atmosphere. Credits: NASA

When sunlight passes through the upper atmosphere, its unique mixture of particulates and gases create the picturesque colors of spectacular sunsets and sunrises. To replicate a sunset or sunrise view from the space station, SAGE III looks at Earth from a side angle, capturing a similar view of the atmosphere on its edge as someone watching the sunset from the ground. But from its vantage point of space, SAGE III can view the entirety of these atmospheric layers according to project scientist Dave Flittner, and sees 15 sunrises and sunsets every day.

Science manager Marilee Roell says the longevity of these observations has been crucial to monitoring and maintaining the protective ozone layer in the upper atmosphere. SAGE II closely monitored the past ozone decline from common aerosols in hair sprays and fire retardants that degraded the layer, and its data informed the Montreal Protocol Treaty, which phased out the use of these damaging chemicals.

“It’s one of the biggest success stories of science informing policy,” said Roell. “And not only is this a premier science instrument, but it’s also on the International Space Station—a crewed platform. We are kind of getting the best of both science and getting to be a part of the human spaceflight program in a peripheral way.”

TSIS-1

Additional atmospheric measurements of the sun come from the Total and Spectral Solar Irradiance Sensor (TSIS-1) – which is actually made of two instruments: the Total Irradiance Monitor (TIM) and Spectral Irradiance Monitor (SIM).

TSIS-1 continues the work of NASA’s Solar Radiation and Climate Experiment satellite by measuring the amount of sunlight that reaches Earth, and how it is distributed in wavelength.

These measurements of solar energy, along with model-based calculations of its absorption and reflection by Earth’s atmosphere and surface, provide insights into the sun’s influence on climate, the ozone layer, atmospheric circulation, and ecosystems. The data are critical inputs for modeling of Earth’s climate and atmospheric systems.

COMING SOON: EMIT & CLARREO-PF

There is still more to learn about Earth, and new instruments which can further contribute to our understanding like the Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder and the Earth Surface Mineral Dust Source Investigation (EMIT) are already scheduled to reach the station within the next couple of years.

The CLARREO Pathfinder will measure sunlight reflected off Earth, and take direct measurements of the Sun, with unparalleled accuracy. The data can then help calibrate other sensors starting in 2021. EMIT is scheduled to launch the following year in 2022 to map dust-source regions on Earth’s surface and assess the impact of dust on the warming and cooling of the atmosphere.

“It’s been really satisfying to see the range of things we have had on the space station,” said Stefanov. From imaging systems to lasers and radars, and more recently hyperspectral instruments Stefanov believes that the limit to what they can do in the future is really only limited by what scientists and engineers are able to design and the number of instrument ports available.

“There will be opportunities for new sensors to go up to the station,” he said. “And I think it will continue to develop as a very useful remote sensing platform for Earth observations going forward.”

Lara Streiff
NASA’s Earth Science News Team

SAGE III Interns Successfully Complete Virtual Internship Program

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NASA offers a variety of internship opportunities to thousands of students across the country throughout the year. The 2020 internship program looked very different due to COVID-19. While interns were not able to be physically on-site at NASA centers, they were able to work virtually from home and gain the same professional experience.

Despite the many challenges that came with the COVID-19 pandemic, the Stratospheric Aerosol and Gas Experiment (SAGE) III on the International Space Station (ISS) team at NASA Langley Research Center in Hampton, VA was able to host a team of five student interns. The group of interns worked on various atmospheric science, mathematics and engineering projects during their 10-week virtual internship with the SAGE III mission team.

Laila Howar, a senior at George Mason University majoring in Atmospheric Science and Computer Science, worked on a project to solve the long-standing uncertainty in differentiating between clouds and aerosols. Her approach involved a supervised machine learning approach where she compared different classifiers and performed hyper-parameter optimization, as well as cross-validation, to assess the performance of the models.

“My work on SAGE III ties together everything for my future career aspirations,” said Howar. “The other interns and I can all say that our mentors have made this such an unforgettable experience for us. They provided us with countless learning opportunities and gave us the opportunity to get to know their fellow associates through shadowing.”

The SAGE III team sent the group of interns to the virtual SciPy conference which allows participants to showcase Python projects, learn from other user and developers, and collaborate together on code development.

For Ney-Ling Navarro, who virtually worked her NASA internship from Puerto Rico, the SciPy conference aligned well with her internship project and gave her an opportunity to learn more in the field of computer science. Ney-Ling worked on the Multiplicative Extended Kalman Filter (MEKF) code cleanup. Her updates fell into two categories: addressing open GitHub tickets for Python updates and updating and streamlining existing Jupyter notebooks to improve their usability.

To stay socially connected throughout the internship, SAGE III mentors hosted daily virtual coffee breaks and multiple “fireside” chats where mentors would discuss any topic of the intern group’s choosing. The group even got together for a virtual Bob Ross painting night!

The agency also connected interns across all centers through a series of online lectures on work going on across the agency, as well as virtual tours and intern meetups.

“I would say that this is not the experience I expected from a virtual internship. The amount of effort that the SAGE III team and NASA has put in to make this a great experience has done just that,” said Howar.

While COVID-19 may have changed the location of their internships, the SAGE III interns were resilient and successfully adapted to the virtual environment and using platforms such as Microsoft Teams.

“I learned over the course of my internship to arrive to virtual meetings early in case new software needed to be installed and to be ready to connect online in multiple ways in case the network was rough,” said SAGE III intern Preston Robinette.

The work that the SAGE interns completed during their internships continues to support the efforts of the mission team. A big thank you to Laila, Ney-Ling, Alexas, Preston, and Kate for all of the outstanding work and time dedicated to the SAGE III/ISS mission!

ROSES-20 Amendment 34: New Opportunity: SAGE III/ISS Science Team Added to ROSES-2020

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A.50 SAGE III/ISS Science Team seeks proposals for members of the SAGE III Science Team. Proposals are sought in six topical areas that appear below. The first five areas are presented in no particular priority order, while the sixth topic, Independent validation, is deemed of somewhat lower priority:

· Assessing Long-term Changes in Atmospheric Composition
· Aerosol and Cloud Studies
· Data Analysis and Modeling Efforts Using SAGE Data Sets
· Multi-sensor Data Product Development
· Limb Scatter Retrieval Algorithm Development or Adaptation
· Independent Validation

In addition to proposals for SAGE III/ISS Science Team membership, there is also the opportunity to propose for the position as Team Leader for the SAGE III/ISS Science Team.

Amendment 34 announces a new opportunity: SAGE III/ISS Science Team has been added to ROSES-2020 as A.50. Notices of intent are requested by September 18, 2020, and proposals are due November 6, 2020.

On or about June 16, 2020, this Amendment to the NASA Research Announcement “Research Opportunities in Space and Earth Sciences (ROSES) 2020” (NNH20ZDA001N) will be posted on the NASA research opportunity homepage at: http://solicitation.nasaprs.com/ROSES2020 and will appear on SARA’s ROSES blog at: https://science.nasa.gov/researchers/sara/grant-solicitations/roses-2020/.

More information on science data processing may be found here under the “Data Access” tab.

Questions concerning A.50 SAGE III/ISS Science Team may be directed to Richard Eckman, who may be reached at richard.s.eckman@nasa.gov.

NASA’s SAGE III Instrument Observes Aerosol Spike from Australian Fires

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The devastating southeastern Australian bushfires that started last September spewed smoke and aerosols higher into the atmosphere than some Earth-observing instruments have ever measured.

After months of hot and dry weather, the fires erupted in the heavily populated areas of New South Wales and Victoria burning millions of acres of land, destroying thousands of homes, and taking dozens of lives across the country. Now that the fires have been extinguished, NASA scientists are still seeing lingering effects of this natural disaster.

NASA’s fleet of space-based instruments help scientists and researchers understand how these fires can effect the Earth. Working collaboratively, these NASA systems can detect actively burning fires, track smoke and aerosol transport, help to create air quality forecasts, and observe long-term impacts to wildlife and ecosystems.

Between November 2019 and the end of January 2020, the Stratospheric Aerosol and Gas Experiment (SAGE) III instrument, mounted on the International Space Station (ISS), saw a dramatic increase in the amount of stratospheric aerosols above Australia.

Aerosols are tiny, airborne, solid and liquid particles in the atmosphere. Most aerosols are naturally occurring, including windblown dust from deserts, sea salt, smoke from wildfires, and ash from volcanic eruptions. Stratospheric aerosols can play a role in the destruction of ozone, which acts as Earth’s sunscreen to protect humans from harmful ultraviolet rays from the Sun. In addition, depending upon their size, type, and location, stratospheric aerosols can also either cool Earth’s surface, or warm the atmosphere, contributing to variability in the climate record.

In November, SAGE III saw increased amounts of aerosol in the upper part of the troposphere (approximately below 12 km for mid-latitudes), but the loading in the stratosphere, just above the troposphere, remained normal. At the end of December and into early January, the intrusions of aerosols into the stratosphere became more consistent in the SAGE III science data due to pyrocumulonimbus storms, or pyroCbs. These pyroCbs occur when fires loft enough heat and moisture into Earth’s atmosphere, creating powerful clouds that cause dangerous smoke-infused thunderstorms.

“Different from typical stratospheric sulfate aerosol, pyroCb injected aerosols are of larger size, according to SAGE III/ISS data, and most likely carbonaceous (soot), based on the context,” said David Flittner, SAGE III project scientist at NASA’s Langley Research Center in Hampton, Virginia.

Extreme fire activity was seen above Australia from the International Space Station in January 2020.
Credits: NASA Earth Observatory

Approximately once a month, the orbit of the ISS allows SAGE III to make high-resolution, vertical observations of the stratosphere within a specific latitude region. Visiting latitudes south of Australia for this regular monthly check-up, SAGE observed the increased aerosol loading at successively higher altitudes: 15 km in early January, 20 km in late January/early February, 25 km in early March, 30 km in late March, and just over 30 km in May.

“A process called the diabatic heating effect causes the aerosols resulting from the wildfires to absorb sunlight and heat the air around them, and rise higher into the stratosphere. This process causes the aerosols to remain in the atmosphere longer before slowly falling back to the Earth’s surface, than if there was no substantial diabatic heating,” said Kevin Leavor, SAGE III scientist.

Initially, SAGE III scientists saw the aerosols from the fires drift east toward South America, as well as towards the southern extent of the SAGE III observation range (70°S). In more recent observations, aerosols have been drifting towards the tropics. Based on events in the past that produced large amounts of stratospheric aerosols, such as the Pacific Northwest wildfires in 2017, scientists expect the effects of the Australian wildfires to stick around for at least a year.

Possible effects on ozone

Aerosols from wildfires, as well as volcanic eruptions, can have an effect on Earth’s Antarctic stratospheric ozone hole.

During winter in the polar regions, aerosols grow to form polar stratospheric clouds (PSCs). The large surface areas of these cloud particles provide sites for chemical reactions to take place. These reactions lead to the formation of large amounts of reactive chlorine and, ultimately, to the depletion of ozone in the stratosphere.

“The increased aerosol content in the south polar stratosphere resulting from the Australian wildfires might have an effect on the 2020 ozone hole by altering the number of PSC particles and the timing of the processes involved in ozone hole chemistry,” said Flittner. Scientists observed enhanced ozone destruction occur after the April 2015 eruption of the Calbuco volcano in Southern Chile.

“Although the timing is slightly different (January for the peak of the fires vs. April for the volcanic eruption) and the composition of the enhanced aerosol is different (carbonaceous vs. sulfate), in light of the response to Calbuco, I am interested to see if the Australian wildfires will influence the 2020 Antarctic ozone hole season,” said Flittner.

Because the fires could have a potential impact on ozone levels at the pole, areas of low ozone could sweep out over regions in the southern hemisphere. New Zealand and parts of South America, such as Argentina and Chile, have been affected in the past by areas of low ozone moving overhead. With reduced amounts of ozone, which acts as Earth’s protective sunscreen, there could be an increase in sunburns, skin cancer and cataracts in humans and reduced crop yield in plants.

“SAGE III is helping to contribute science data to the models that will give a better understanding to what is happening to the ozone in those regions,” said Marilee Roell, SAGE III science manager.

Monitoring fires and eruptions

In addition to the Australian wildfires, SAGE III has seen numerous other notable stratospheric aerosol events throughout its three years in orbit on the International Space Station.

SAGE III saw significant stratospheric aerosol loading events in the Northern Hemisphere resulting from large wildfires in the Pacific Northwest in 2017 and in Alberta, Canada and Siberia, Russia in mid to late 2019.

In addition to the wildfire events, volcanic emissions from the eruptions of Ambae on the south Pacific island of Vanuatu in mid-2018, and Ulawun in Papua New Guinea in mid-2019, introduced significant amounts of aerosols into the stratosphere and greatly increased the concentration of aerosols measured at altitudes observed by the SAGE III instrument. Additionally, the Raikoke volcano on the northwest Pacific Kuril Islands erupted in June 2019 emitting the largest amount of sulfur dioxide into the atmosphere in the past decade. The resulting plume quickly moved toward the equator and was observed at high stratospheric altitudes for several months afterward.

Stratospheric aerosol particles can block sunlight from reaching the ground by absorbing or scattering light, which can then exert a cooling effect on the Earth’s surface. A data measurement called the stratospheric aerosol optical depth tells scientists how much direct sunlight is prevented from reaching the ground by the concentration of aerosol particles in the stratosphere. Since the SAGE III/ISS record began in June 2017, the stratospheric aerosol optical depth record has increased globally by a factor of 2 or 3 due to the various wildfires and volcanic eruptions observed in the past three years. To put this in perspective, the current optical depth record remains a factor of 20 less than after the Mt. Pinatubo eruption in 1991. The Mt. Pinatubo eruption had the most major stratospheric impact in the last 50 years and caused the global troposphere to cool by approximately 1 degree F.

“There has been a significant amount of variability in stratospheric aerosol loading across the globe. Typically, we associate dramatic changes in stratospheric aerosols with volcanic eruptions, but these wildfire events mimic minor volcanic eruptions,” said Flittner. “We have seen major wildfire events three times now in less than three years. This has been unique for historical SAGE observations stretching back to the mid-1980s.”

The SAGE III/ISS stratospheric data complements observations from other NASA satellites such as trace gas data from the Microwave Limb Sounder (MLS) showing record amounts of carbon monoxide (CO), a by-product of wildfires, and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) sightings of stratospheric aerosol plumes. Using these data sources, NASA scientists will continue to monitor the effects of the Australian wildfires on Earth’s atmosphere for the months to come.

During its three years on ISS, the SAGE III instrument has collected science data measurements on several high stratospheric aerosol events across the globe.
Credits: NASA Langley/Kevin Leavor

SAGE III Sees Mercury Transit the Sun

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SAGE III is a planet finder! (… at least in our immediate neighborhood.) It was able to detect Mercury during its recent transit across the sun.

The Stratospheric Aerosol and Gas Experiment (SAGE) III instrument uses the Sun to collect data on stratospheric ozone, aerosols, water vapor, and other trace gases during sunrise and sunset from orbit on the International Space Station (ISS). These measurements are taken every 46 minutes, on average.

To take measurements, SAGE III uses a technique known as occultation, which involves looking at the light from the Sun (or Moon) as it passes through Earth’s atmosphere at the edge, or limb, of the planet. The space station provides a unique vantage point from which to take those measurements. 

A small part of sunrise and sunset events occur outside of the atmosphere (exo-atmospheric) providing a clear view of the solar disk. With the exo-atmospheric scans, SAGE III can clearly detect decreases in the Sun’s photon intensity from sunspots, or as in this case, planets transiting across the Sun. The instrument detected a slight, but noticeable, decrease in the solar intensity at the time of the Mercury transit.

In the graph below, the elevation mirror scans the instrument’s boresight (blue line) across the Sun’s disk, turning around to perform another scan across the disk in the opposite direction. The red curve shows the photon intensity received from one of SAGE III’s sensors. The small decrease in intensity is from the planet Mercury as it blocked the sunlight to SAGE III during its transit across the center of the Sun (purple circles).

Power restored to SAGE III/ISS!

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After 27 days in survival mode during the ExPRESS Logistics Carrier (ELC) 4 power loss, the SAGE III/ISS instrument doesn’t have to worry anymore. The instrument’s full power was restored thanks to the all-woman spacewalk on October 18. 

On October 21, the SAGE III/ISS operations team successfully completed the payload activation at 2:15 pm ET (18:15 UTC) following the week-long ISS activities to restore power to the ELC 4. All telemetry and currents are nominal and the mechanism tests confirmed that the mechanisms are in nominal working order.

Science collection was resumed with a commanded limb event collected at 2:28 pm ET followed by a successful sunset event acquisition at 2:50 pm ET. A successful lunar event was acquired at 4:30 pm ET. The payload is continuing to collect nominal science event data, and the team will continue to monitor and extensively analyze the telemetry over the coming days to verify that the instrument is in nominal working order.

The SAGE III mission benefited from the excellent work performed by the all-woman Extravehicular Activity (EVA) team who replaced the power regulator that restored primary power to the SAGE III payload, allowing the instrument to resume nominal science collection of stratospheric ozone, aerosol, and water vapor measurements.

NASA astronauts Christina Koch and Jessica Meir conduct the first all-woman spacewalk on October 18, 2019.
Credits: NASA TV

SAGE III Team Attends AGU Fall Meeting

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Members of the SAGE III/ISS mission team attended the American Geophysical Union (AGU) Fall Meeting from December 10th – 14th, 2018 in Washington, D.C. Conference visitors were able to experience the SAGE III instrument installed on the exterior of the International Space Station through a virtual reality demonstration. SAGE III Program Scientist, Dr. Richard Eckman, gave a hyperwall talk on ozone monitoring and recovery. SAGE III Project Scientist, David Flittner, and other mission team members gave presentations on SAGE III science data products and mission validation efforts.

 

IMG_5887

SAGE III Science Challenges Aboard the ISS

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Operating an occultation science instrument aboard a manned, frequently visited spacecraft the size of a football field poses many challenges to data collection and quality. The Stratospheric Aerosol and Gas Experiment (SAGE) III instrument, currently on board the International Space Station (ISS), is equipped with the tools necessary to mitigate and control these challenges.

Dave Huber, NASA LaRC Algorithm Developer, creates algorithms for the SAGE III instrument to manage these issues in space. “In an ideal scenario, SAGE III would have a clean line of sight to make measurements, there would be no motion disturbances or vehicles visiting the ISS, and the instrument would collect data at the right time and positioning of the Sun,” said Huber.

Because this scenario is not always the case, the payload contains two Contamination Monitoring Packages (CMPs) and a Disturbance Monitoring Package (DMP) to manage issues as they arise. The two CMPs contain crystals that vibrate at different frequencies based on what type of contamination may land on the instrument. The DMP consists of three highly precise laser ring gyros that can detect disturbances and their magnitude.

Blockage of the instrument’s field of view to the sun by ISS modules or visiting vehicles can be a challenge for SAGE III. These modules tend to reflect stray-light glint, or small flashes of light, onto the payload’s detector. These challenges cause instances where data collection is prevented or only partial data is captured. To ensure an accurate scan of the atmosphere is taken, measurements from the payload’s photo electric diodes, which are used for pointing at the sun, are utilized to screen partially blocked events. Huber’s algorithms can detect blockages within these measurements, and drop the scans affected. Using these pointing system measurements have shown striking results before and after even small blockage events.

While not just creating blockage issues for SAGE III, visiting vehicles also outgas while on the ISS, and can create a contaminated environment around SAGE III. If the two CMPs determine the environment’s contamination levels are high, the payload’s clear door will close to protect its sensors and allow science data collection to continue.

Many disturbances to science data collection can occur aboard the ISS. The station routinely will maneuver or use a mechanical arm to remove items for installation from visiting vehicles, with both causing mechanical vibrations. Being in low earth orbit, the station is frequently being re-boosted which can cause disturbances to the SAGE III payload. Even movement from the astronauts aboard the ISS can affect instrument pointing and measurements. SAGE III uses the Disturbance Monitoring Package (DMP) to measure all of the small motions from the ISS, and then uses the measurements to help identify and reduce noise found in the instrument’s signal created by these disturbances. A simple detection and mitigation algorithm using the measurements of the DMP is already in place, while a more advanced method will use the laser ring gyro rates to improve pointing accuracy in the future.

The internal clock of the ISS drifts slowly, and scientists assume positions of the sun based on time. This can create issues for scientists when processing data collected, as their assumed position of the sun can be off with the time drift. “When time is slightly off on the ISS, scans can show a three to four-kilometer shift in our ozone profiles, which is more than noticeable,” said Huber. Huber and a team of engineers at LaRC have created and implemented an algorithm to correct for the time drift when processing science data.

Despite the many challenges having a science instrument aboard the ISS, the SAGE III algorithm and science teams continue to find methods to collect the most accurate, quality data products for the science community interested in stratospheric ozone, aerosols, and water vapor.

 

During a recent astronaut spacewalk, the SAGE III instrument was caught on camera mounted on the ISS. Astronaut activity on the ISS can cause disturbances to the payload and science data collection. Photo credit: NASA Astronaut Ricky Arnold

 

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Space Station Live: Wise Eye in the Sky

 

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SAGE III Promo

 

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NASA X Episode I: SAGE III Monitoring Earth

 

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SAGE III Integration and Test Timelapse

 

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Space Station Live: Studying Earth’s Sunscreen

 

SAGE III Sun Look Test Video

SAGE III Sunlook Test

 

NASA Launchpad: SAGE III/ISS

NASA Launchpad: SAGE III/ISS

 

NASA Real World: Ozone

NASA Real World: Good Ozone, Bad Ozone

 

NASA's Our World: Sunsets

NASA’s Our World: Sunsets and Atmosphere

 

SAGE III/ISS Overview Video

SAGE III/ISS Overview Video

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Mission Brochure

 

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SAGE III/ISS Fact Sheet

 

The SAGE Legacy's Next Chapter: SAGE III on the International Space Station

SAGE Earth Observer Article

 

SAGE III International Collaboration

SAGE III/ISS International Collaboration

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