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By NASA
NASA’s Nancy Grace Roman Space Telescope will help scientists better understand our Milky Way galaxy’s less sparkly components — gas and dust strewn between stars, known as the interstellar medium.
One of Roman’s major observing programs, called the Galactic Plane Survey, will peer through our galaxy to its most distant edge, mapping roughly 20 billion stars—about four times more than have currently been mapped. Scientists will use data from these stars to study and map the dust their light travels through, contributing to the most complete picture yet of the Milky Way’s structure, star formation, and the origins of our solar system.
Our Milky Way galaxy is home to more than 100 billion stars that are often separated by trillions of miles. The spaces in between, called the interstellar medium, aren’t empty — they’re sprinkled with gas and dust that are both the seeds of new stars and the leftover crumbs from stars long dead. Studying the interstellar medium with observatories like NASA’s upcoming Nancy Grace Roman Space Telescope will reveal new insight into the galactic dust recycling system.
Credit: NASA/Laine Havens; Music credit: Building Heroes by Enrico Cacace [BMI], Universal Production Music “With Roman, we’ll be able to turn existing artist’s conceptions of the Milky Way into more data-driven models using new constraints on the 3D distribution of interstellar dust,” said Catherine Zucker, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts.
Solving Milky Way mystery
Scientists know how our galaxy likely looks by combining observations of the Milky Way and other spiral galaxies. But dust clouds make it hard to work out the details on the opposite side of our galaxy. Imagine trying to map a neighborhood while looking through the windows of a house surrounded by a dense fog.
Roman will see through the “fog” of dust using a specialized camera and filters that observe infrared light — light with longer wavelengths than our eyes can detect. Infrared light is more likely to pass through dust clouds without scattering.
This artist’s concept visualizes different types of light moving through a cloud of particles. Since infrared light has a longer wavelength, it can pass more easily through the dust. That means astronomers observing in infrared light can peer deeper into dusty regions.Credit: NASA’s Goddard Space Flight Center Light with shorter wavelengths, including blue light produced by stars, more easily scatters. That means stars shining through dust appear dimmer and redder than they actually are.
By comparing the observations with information on the source star’s characteristics, astronomers can disentangle the star’s distance from how much its colors have been reddened. Studying those effects reveals clues about the dust’s properties.
“I can ask, ‘how much redder and dimmer is the starlight that Roman detects at different wavelengths?’ Then, I can take that information and relate it back to the properties of the dust grains themselves, and in particular their size,” said Brandon Hensley, a scientist who studies interstellar dust at NASA’s Jet Propulsion Laboratory in Southern California.
Scientists will also learn about the dust’s composition and probe clouds to investigate the physical processes behind changing dust properties.
Clues in dust-influenced starlight hint at the amount of dust between us and a star. Piecing together results from many stars allows astronomers to construct detailed 3D dust maps. That would enable scientists like Zucker to create a model of the Milky Way, which will show us how it looks from the outside. Then scientists can better compare the Milky Way with other galaxies that we only observe from the outside, slotting it into a cosmological perspective of galaxy evolution.
“Roman will add a whole new dimension to our understanding of the galaxy because we’ll see billions and billions more stars,” Zucker said. “Once we observe the stars, we’ll have the dust data as well because its effects are encoded in every star Roman detects.”
Galactic life cycles
The interstellar medium does more than mill about the Milky Way — it fuels star and planet formation. Dense blobs of interstellar medium form molecular clouds, which can gravitationally collapse and kick off the first stages of star development. Young stars eject hot winds that can cause surrounding dust to clump into planetary building blocks.
“Dust carries a lot of information about our origins and how everything came to be,” said Josh Peek, an associate astronomer and head of the data science mission office at the Space Telescope Science Institute in Baltimore, Maryland. “Right now, we’re basically standing on a really large dust grain — Earth was built out of lots and lots of really tiny grains that grew together into a giant ball.”
Roman will identify young clusters of stars in new, distant star-forming regions as well as contribute data on “star factories” previously identified by missions like NASA’s retired Spitzer Space Telescope.
“If you want to understand star formation in different environments, you have to understand the interstellar landscape that seeds it,” Zucker said. “Roman will allow us to link the 3D structure of the interstellar medium with the 3D distribution of young stars across the galaxy’s disk.”
Roman’s new 3D dust maps will refine our understanding of the Milky Way’s spiral structure, the pinwheel-like pattern where stars, gas, and dust bunch up like galactic traffic jams. By combining velocity data with dust maps, scientists will compare observations with predictions from models to help identify the cause of spiral structure—currently unclear.
The role that this spiral pattern plays in star formation remains similarly uncertain. Some theories suggest that galactic congestion triggers star formation, while others contend that these traffic jams gather material but do not stimulate star birth.
Roman will help to solve mysteries like these by providing more data on dusty regions across the entire Milky Way. That will enable scientists to compare many galactic environments and study star birth in specific structures, like the galaxy’s winding spiral arms or its central stellar bar.
NASA’s Nancy Grace Roman Space Telescope will conduct a Galactic Plane Survey to explore our home galaxy, the Milky Way. The survey will map around 20 billion stars, each encoding information about intervening dust and gas called the interstellar medium. Studying the interstellar medium could offer clues about our galaxy’s spiral arms, galactic recycling, and much more.
Credit: NASA, STScI, Caltech/IPAC The astronomy community is currently in the final stages of planning for Roman’s Galactic Plane Survey.
“With Roman’s massive survey of the galactic plane, we’ll be able to have this deep technical understanding of our galaxy,” Peek said.
After processing, Roman’s data will be available to the public online via the Roman Research Nexus and the Barbara A. Mikulski Archive for Space Telescopes, which will each provide open access to the data for years to come.
“People who aren’t born yet are going to be able to do really cool analyses of this data,” Peek said. “We have a really beautiful piece of our heritage to hand down to future generations and to celebrate.”
Roman is slated to launch no later than May 2027, with the team working toward a potential early launch as soon as fall 2026.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems Inc. in Boulder, Colorado; L3Harris Technologies in Rochester, New York; and Teledyne Scientific & Imaging in Thousand Oaks, California.
Download additional images and video from NASA’s Scientific Visualization Studio.
For more information about the Roman Space Telescope, visit:
https://www.nasa.gov/roman
By Laine Havens
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Sep 16, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationGoddard Space Flight Center Related Terms
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By NASA
Amit KshatriyaCredit: NASA Acting NASA Administrator Sean P. Duffy Wednesday named Amit Kshatriya as the new associate administrator of NASA, the agency’s top civil service role.
A 20-year NASA veteran, Kshatriya was most recently the deputy in charge of the Moon to Mars Program in the Exploration Systems Development Mission Directorate (ESDMD) at NASA Headquarters in Washington. In this role, Kshatriya was responsible for program planning and implementation for crewed missions to the Moon through the Artemis campaign in preparation for humanity’s first mission to Mars.
Promoting Kshatriya to NASA’s top ranks puts America’s return to the Moon through Artemis at the very core of our agency. The move exemplifies President Donald J. Trump and Duffy’s seriousness about returning Americans to the Moon and before China.
“Amit has spent more than two decades as a dedicated public servant at NASA, working to advance American leadership in space. Under his leadership, the agency will chart a bold vision to return to the Moon during President Trump’s term,” said Duffy. “Amit’s knowledge, integrity, and unwavering commitment to pioneering a new era of exploration make him uniquely qualified to lead our agency as associate administrator. With Amit we’ll continue to push the boundaries of what’s possible.”
Kshatriya’s promotion also signals how the Trump Administration sees the commercial space sector as an American economic engine. By putting a proven leader at the top, NASA is set to partner even more closely with America’s booming space industry, grow the space economy, and ensure the future of exploration is built in the United States.
Born in Wisconsin, educated at California Institute of Technology and the University of Texas at Austin, Kshatriya is one of only about 100 people in history to serve as a mission control flight director. He brings unparalleled operational and strategic experience to NASA’s executive leadership team.
-end-
Bethany Stevens
Headquarters, Washington
771-216-2606
bethany.c.stevens@nasa.gov
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By NASA
Lydia Rodriguez is an office administrator in the Flight Operations Directorate’s Operations Division and Operations Tools and Procedures Branch at NASA’s Johnson Space Center in Houston.
Over nearly two decades, she has supported nine organizations, helping enable NASA’s missions and forming lasting relationships along the way.
Official portrait of Lydia Rodriguez. NASA/Devin Boldt “I’ve had the opportunity to meet many different people at NASA who have become like family,” Rodriguez said. “I enjoy the culture and building relationships with people from all walks of life. I have learned so much from each person I’ve met and worked alongside.”
Her path to NASA began in high school, when her parents encouraged her to apply for a part-time Office Education student position at Johnson. That early opportunity gave her a glimpse into the agency’s culture — one that would inspire her to stay.
Lydia Rodriguez in the Mission Control Center Viewing Room during the Expedition 72 plaque hanging ceremony at NASA’s Johnson Space Center in Houston. Rodriguez takes pride in the practical support she has provided to her colleagues. She spent years in the Engineering Travel Office, helping team members plan their travel around the world. In 2013, the team was honored with a Group Achievement Award.
“I am proud of being confident and able to help others with their bookings and questions,” Rodriguez said.
Her NASA career has also taught her important lessons. Change has been a constant since she joined the center in 2008, and she has learned to adapt.
One of the greatest challenges came after Hurricane Harvey in 2017, when her home was flooded. Rodriguez learned to ask for support and leaned on employee resources at Johnson.
“I’ve learned that I am a resilient individual who takes on new challenges often,” she said. “What has helped me overcome obstacles is focusing on the mission and showing compassion toward people. We are all here for a reason and a purpose, and together we can accomplish greater things.”
Lydia Rodriguez skydiving for the second time in Houston. To the Artemis Generation, Rodriguez hopes to pass on the excitement of being part of the next frontier of space exploration.
“Take full advantage of the opportunities and resources available,” she said. “Meet new people, ask for help, never stop learning, growing, and contributing your experiences. Hopefully it will inspire others to do the same.”
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By NASA
5 min read
Astronomers Map Stellar ‘Polka Dots’ Using NASA’s TESS, Kepler
Scientists have devised a new method for mapping the spottiness of distant stars by using observations from NASA missions of orbiting planets crossing their stars’ faces. The model builds on a technique researchers have used for decades to study star spots.
By improving astronomers’ understanding of spotty stars, the new model — called StarryStarryProcess — can help discover more about planetary atmospheres and potential habitability using data from telescopes like NASA’s upcoming Pandora mission.
“Many of the models researchers use to analyze data from exoplanets, or worlds beyond our solar system, assume that stars are uniformly bright disks,” said Sabina Sagynbayeva, a graduate student at Stony Brook University in New York. “But we know just by looking at our own Sun that stars are more complicated than that. Modeling complexity can be difficult, but our approach gives astronomers an idea of how many spots a star might have, where they are located, and how bright or dark they are.”
A paper describing StarryStarryProcess, led by Sagynbayeva, published Monday, August 25, in The Astrophysical Journal.
Watch to learn how a new tool uses data from exoplanets, worlds beyond our solar system, to tell us about their polka-dotted stars.
NASA’s Goddard Space Flight Center
Download images and videos through NASA’s Scientific Visualization Studio.
NASA’s TESS (Transiting Exoplanet Survey Satellite) and now-retired Kepler Space Telescope were designed to identify planets using transits, dips in stellar brightness caused when a planet passes in front of its star.
These measurements reveal how the star’s light varies with time during each transit, and astronomers can arrange them in a plot astronomers call a light curve. Typically, a transit light curve traces a smooth sweep down as the planet starts passing in front of the star’s face. It reaches a minimum brightness when the world is fully in front of the star and then rises smoothly as the planet exits and the transit ends.
By measuring the time between transits, scientists can determine how far the planet lies from its star and estimate its surface temperature. The amount of missing light from the star during a transit can reveal the planet’s size, which can hint at its composition.
Every now and then, though, a planet’s light curve appears more complicated, with smaller dips and peaks added to the main arc. Scientists think these represent dark surface features akin to sunspots seen on our own Sun — star spots.
The Sun’s total number of sunspots varies as it goes through its 11-year solar cycle. Scientists use them to determine and predict the progress of that cycle as well as outbreaks of solar activity that could affect us here on Earth.
Similarly, star spots are cool, dark, temporary patches on a stellar surface whose sizes and numbers change over time. Their variability impacts what astronomers can learn about transiting planets.
Scientists have previously analyzed transit light curves from exoplanets and their host stars to look at the smaller dips and peaks. This helps determine the host star’s properties, such as its overall level of spottiness, inclination angle of the planet’s orbit, the tilt of the star’s spin compared to our line of sight, and other factors. Sagynbayeva’s model uses light curves that include not only transit information, but also the rotation of the star itself to provide even more detailed information about these stellar properties.
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This artist’s concept illustrates the varying brightness of star with a transiting planet and several star spots. NASA’s Goddard Space Flight Center “Knowing more about the star in turn helps us learn even more about the planet, like a feedback loop,” said co-author Brett Morris, a senior software engineer at the Space Telescope Science Institute in Baltimore. “For example, at cool enough temperatures, stars can have water vapor in their atmospheres. If we want to look for water in the atmospheres of planets around those stars — a key indicator of habitability — we better be very sure that we’re not confusing the two.”
To test their model, Sagynbayeva and her team looked at transits from a planet called TOI 3884 b, located around 141 light-years away in the northern constellation Virgo.
Discovered by TESS in 2022, astronomers think the planet is a gas giant about five times bigger than Earth and 32 times its mass.
The StarryStarryProcess analysis suggests that the planet’s cool, dim star — called TOI 3384 — has concentrations of spots at its north pole, which also tips toward Earth so that the planet passes over the pole from our perspective.
Currently, the only available data sets that can be fit by Sagynbayeva’s model are in visible light, which excludes infrared observations taken by NASA’s James Webb Space Telescope. But NASA’s upcoming Pandora mission will benefit from tools like this one. Pandora, a small satellite developed through NASA’s Astrophysics Pioneers Program, will study the atmospheres of exoplanets and the activity of their host stars with long-duration multiwavelength observations. The Pandora mission’s goal is to determine how the properties of a star’s light differs when it passes through a planet’s atmosphere so scientists can better measure those atmospheres using Webb and other missions.
“The TESS satellite has discovered thousands of planets since it launched in 2018,” said Allison Youngblood, TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “While Pandora will study about 20 worlds, it will advance our ability to pick out which signals come from stars and which come from planets. The more we understand the individual parts of a planetary system, the better we understand the whole — and our own.”
Facebook logo @NASAUniverse @NASAUniverse Instagram logo @NASAUniverse By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Alise Fisher
202-358-2546
alise.m.fisher@nasa.gov
NASA Headquarters, Washington
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Last Updated Aug 25, 2025 Related Terms
Astrophysics Exoplanet Atmosphere Exoplanets Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research Goddard Space Flight Center Kepler / K2 Stars TESS (Transiting Exoplanet Survey Satellite) The Universe View the full article
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By NASA
Explore This Section Earth Earth Observer Editor’s Corner Feature Articles Meeting Summaries News Science in the News Calendars In Memoriam Announcements More Archives Conference Schedules Style Guide 9 min read
Harmonized Landsat and Sentinel-2: Collaboration Drives Innovation
Introduction
Landsat, a joint program of NASA and the U.S. Geological Survey (USGS), has been an invaluable tool for monitoring changes in Earth’s land surface for over 50 years. Researchers use instruments on Landsat satellites to monitor decades-long trends, including urbanization and agricultural expansion, as well as short-term dynamics, including water use and disaster recovery. However, scientists and land managers often encounter one critical limitation of this program: Landsat has a revisit time of eight days (with Landsat 8 and 9 operating), which is too long to capture events and disasters that occur on short timescales. Floods, for example, can quickly inundate a region, and cloud cover from storms can delay Landsat’s ability to get a clear observation on damage.
In 2015, the European Space Agency’s (ESA) Copernicus Sentinel-2A mission joined Landsat 7 and 8 in orbit. It was designed to collect comparable optical land data with the intention of leveraging Landsat’s archive. Two years later, ESA launched Sentinel-2B, a satellite identical to Sentinel-2A.
Led by a science team at NASA’s Goddard Space Flight Center (GSFC), the USGS, NASA, and ESA began to work on combining the capabilities of Sentinel-2 and Landsat satellites. This idea was the impetus behind Harmonized Landsat and Sentinel-2 (HLS) project, a NASA initiative that created a seamless product from the Operational Land Imager (OLI) and Multi-Spectral Instrument (MSI) aboard Landsat and Sentinel-2 satellites, respectively. HLS Version 2.0 (V2.0) is the most recent version of these data and had a global median repeat frequency of 1.6 days in 2022 by combining observations from Landsat 8 and 9 and Sentinel-2A and B. The recent addition of Sentinel-2C data will provide even more frequent observations. With near-global coverage and improved harmonization algorithms, HLS V2.0 paves the way for new applications and improved land monitoring systems – see Animation 1. HLS data are available for download on NASA Earthdata: HLSL30v2.0 and HLSS30v2.0. These data can also be accessed through Google Earth Engine: HLSL30v2.0 and HLSS30v2.0.
Animation 1. This visualization shows the change in vegetation in Maryland from January 1 to December 30, 2016, using Normalized Difference Vegetation Index (NDVI) data from Harmonized Landsat Sentinel-2 (HLS). The visualization shows land on both sides of the Chesapeake Bay, where red represents bare soil and green indicates healthy, growing vegetation. Animation credit: Michael Taylor [Science Systems and Applications Inc. (SSAI)], Matthew Radcliff [USRA], and Jeffrey Masek [GSFC]. Caption adapted from Laura Rocchio [SSAI] The Dawn of HLS
The story of HLS begins before the launch of Sentinel-2A in 2015. Jeffrey Masek [GSFC], who was at that time project scientist for Landsat 8, led a group of researchers who wanted to find a way to harmonize Landsat data with other satellite data. Their aim was to create a “virtual constellation” similar to how weather satellites operate.
“HLS meets a need that people have been asking for for a long time,” said Masek.
What began as a research question with an experimental product evolved into an operational project with the involvement of the Satellite Needs Working Group (SNWG). SNWG is an interagency effort to develop solutions that address Earth observation needs of civilian federal agencies. Every two years, SNWG conducts a survey of federal agencies to see how their work could benefit from satellite data. The answers span the gamut of application areas, from water quality monitoring to disaster recovery to planning how best to protect and use natural resources. SNWG brings these ideas to NASA, USGS, and the National Oceanic and Atmospheric Administration (NOAA) – the three main U.S. government providers of satellite data. These agencies work together to create and implement solutions that serve those needs. NASA plays a critical role in every step of the SNWG process, including leading the assessment of survey responses from over 30 federal agencies, managing and supporting the implementation of identified solutions, and encouraging solution co-design with federal partners to maximize impact.
The HLS surface reflectance product was an outcome of the very first SNWG solution cycle in 2016. This product was expanded, following additional SNWG requests in 2020 and 2022. The 2020 cycle saw the creation of nine HLS-derived vegetation indices, and the 2022 cycle aimed for a six-hour latency product.
The U.S. Department of Agriculture (USDA) now uses HLS to map crop emergence at the field scale in the corn belt, allowing farmers to better plan their growing seasons. Ranchers in Colorado use the dataset to decide where to graze their cattle during periods of drought. HLS also informs the use and termination of cover crops in the Chesapeake Bay area. In 2024, the Federal Emergency Management Agency (FEMA) employed HLS to identify where to focus aid in the aftermath of Hurricane Helene.
A New and Improved HLS
In the July 2025 issue of Remote Sensing of Environment, a team of researchers outlined the HLS V2.0 surface reflectance dataset and algorithms. The team included seven NASA co-authors, members of the 2018–2023 Landsat Science Team, and ESA. The lead author, Junchang Ju [GSFC—Remote Sensing Scientist], has been the technical lead on HLS since its inception. Co-author Christopher Neigh [GSFC—Landsat 8/9 Project Scientist] is the principal investigator on the HLS project. V2.0, which was completed in Summer 2023, incorporates several major improvements over HLS V1.4, the most recent publicly available HLS product. HLS V1.4 covered about 30% of the global land area, providing data on North America and other select locations. HLS V2.0 provides data at a spatial resolution of 30 m (98 ft) with near-global coverage from 2013 onward. The dataset includes all land masses except Antarctica. HLS V2.0 also has key algorithmic improvements in atmospheric correction, cloud masking, and bidirectional reflectance distribution function (BRDF) correction. Together, these algorithms “harmonize” the data, or ensure that the distinct Landsat and Sentinel-2 datasets can effectively be used interchangeably – see Animation 2.
Animation 2: The visualization provides the Normalized Difference Vegetation Index (NDVI) data from Harmonized Landsat Sentinel-2 (HLS) for farm fields south of Columbus, NE. The red represents bare soil and green represents healthy, growing vegetation. The animation runs from January 1 to December 30, 2016. Animation credit: Michael Taylor [SSAI], Matthew Radcliff [USRA], and Jeffrey Masek [GSFC]. Caption adapted from Laura Rocchio [SSAI] HLS V2.0 in Action
The increased frequency of observations improved the ability of the scientific community to track disaster recovery, changes in phenology, agricultural intensification, rapid urban growth, logging, and deforestation. Researchers are already putting these advances to use.
The land disturbance product (DIST-ALERT) is a global land change monitoring system that uses HLS V2.0 data to track vegetation anomalies in near real-time – see Figure 1. DIST-ALERT captures agricultural expansion, urban growth, fire, flooding, logging, drought, landslides, and other forces of change to vegetation. Amy Pickens [University of Maryland, Department of Geographical Sciences—Assistant Research Professor] said that HLS is the perfect dataset for tracking disturbances because of the frequency of observations.
DIST-ALERT was created through Observational Products for End-Users from Remote Sensing Analysis (OPERA), a project at NASA/Jet Propulsion Laboratory (JPL). OPERA products respond to agency needs identified by the SNWG. In 2018, SNWG identified tracking surface disturbance as a key need. OPERA partnered with the Global Land Analysis and Discovery (GLAD) lab at University of Maryland to develop the change detection algorithm.
To track changes in vegetation, the DIST-ALERT system establishes a rolling baseline – meaning that for any given pixel, the vegetation cover is compared against vegetation cover from the same 31-day window in the previous three years. The primary algorithm detects any vegetation loss relative to the established baseline. A secondary algorithm flags any spectral anomaly (i.e., any change in reflectance) compared to that same baseline. This approach ensures that the algorithm catches non-vegetation change (e.g., new building or road projects in unvegetated areas). Used together, these algorithms can identify long-term changes in agricultural expansion, deforestation, and urbanization alongside short-term changes in crop harvest, drought, selective logging, and the impacts of disasters. On average, DIST-ALERT is made available on LP DAAC within six hours of when new HLS data is available. Currently, the dataset does not provide attribution to disturbances.
Figure 1. In March 2025, wildfires burned through South Korea, resulting in heavy vegetation loss. [left] Output of the DIST-ALERT product on NASA Worldview from May 8, 2025, with vegetation loss in percent flagged with varying levels of confidence. Yellow and red represent areas with confirmed vegetation cover losses of right] Natural-color image captured by the Multi-Spectral Instrument (MSI) aboard Sentinel-2C on May 8, 2025. The large brown burn scar in the center of the image corresponds to vegetation loss detected by DIST-ALERT. It stands in contrast to the surrounding green vegetation. Figure credit: NASA Earthdata Disturbance alerts already exist in some ecosystems. Brazil’s National Institute for Space Research [Instituto Nacional de Pesquisas Espaciais (INPE)] runs two projects that detect deforestation in the Amazon: Programa de Cálculo do Desflorestamento da Amazônia (PRODES) and Sistema de Detecção de Desmatamento em Tempo Real (DETER). The GLAD lab created its own forest loss alerts – GLAD-L and GLAD-S2 – using Landsat and Sentinel-2 data respectively. Global Forest Watch integrates GLAD-L and GLAD-S2 data with Radar for Detecting Deforestation (RADD) observations – derived from synthetic aperture radar data from Copernicus Sentinel-1 – into an integrated deforestation alert.
The implementation of these alert systems, some of which have been around for decades, have been shown to impact deforestation rates in the tropics. For example, a 2021 study in Nature Climate Change found that deforestation alerts decreased the probability of deforestation in Central Africa by 18% relative to the average 2011–2016 levels.
DIST-ALERT is distinct from other alert systems in a few ways. First, it has global coverage. Second, the rolling baseline allows for tracking changes in seasonality and disturbances to dynamic ecosystems. When HLS V2.0 data are input to DIST-ALERT, the system is also better at identifying disturbances in cloudy ecosystems than other individual alert systems – because it is more likely to obtain clear observations. This also enables it to identify the start and end of the disturbance more precisely.
Pickens said that the DIST-ALERT team is already working with end-users who are implementing their data product. She has spoken to some who use the system to help logging companies prove that they are complying with regulations. The U.S. Census Bureau is also using DIST-ALERT to monitor fast-growing communities so that they can do targeted assessments in the interim between the larger decennial census.
Alongside DIST-ALERT, OPERA has also been developing the Dynamic Surface Water eXtent (DSWx) product suite, which employs HLS to track surface water (e.g., lakes, reservoirs, rivers, and floods) around the globe – see Figure 2. These new products represent the new applications made possible by the HLS interagency and international collaboration.
Figure 2. The map shows flood extent and estimates of flood depth in areas west of Porto Alegre, Brazil on May 6, 2024. The flood extent is from the Observational Products for End-Users from Remote Sensing Analysis (OPERA) Dynamic Surface Water eXtent product, which uses Harmonized Landsat Sentinel-2 data. The flood depth estimate is from the Floodwater Depth Estimation Tool (FwD ET). The darkest blue areas represent floodwater at least 5 m (20 ft) deep. Much of the inundated floodplain is light blue, which equates to depths of between 0.1–1 m (4–40 in). Figure credit: Lauren Dauphin [NASA’s Earth Observatory], Dinuke Munasinghe [JPL], Sagy Cohen [University of Alabama], and Alexander Handwerger [JPL] Conclusion
HLS is set to continue improving land monitoring efforts across the globe. Meanwhile, the HLS science team is working to improve the algorithms for a more seamless harmonization of Landsat 8 and 9 and Sentinel-2 data. They are also working to improve the cloud-masking algorithm, have recently released vegetation indices, and are working on developing a low-latency (six-hour) HLS surface reflectance product, all while incorporating user feedback.
Looking ahead, the launch of future Sentinel and Landsat satellites will further the development of HLS. The additional data and unique capabilities will continue to meet researchers’ need for more frequent, high-quality satellite observations of Earth’s land surface.
Madeleine Gregory
NASA’s Goddard Space Flight Center/Science Systems and Applications Inc.
madeleine.s.gregory@nasa.gov
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Last Updated Aug 25, 2025 Related Terms
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