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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 8 min read
ICESat-2 Applications Team Hosts Satellite Bathymetry Workshop
Introduction
On September 15, 2018, the NASA Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission launched from Vandenberg Air Force Base and began its journey to provide spatially dense and fine precision global measurements of our Earth’s surface elevation. Now in Phase E of NASA’s project life cycle (where the mission is carried out, data is collected and analyzed, and the spacecraft is maintained) of the mission and with almost six years of data collection, the focus shifts to looking ahead to new applications and synergies that may be developed using data from ICESat-2’s one instrument: the Advanced Topographic Laster Altimetry System (ATLAS) – see Figure 1.
Figure 1. The ATLAS instrument onboard the ICESat-2 platform obtains data using a green, photon-counting lidar that is split into six beams. Figure credit: ICESat-2 Mission Team Satellite-derived bathymetry (SDB) is the process of mapping the seafloor using satellite imagery. The system uses light penetration and reflection in the water to make measurements and estimate variations in ocean floor depths. SDB provides several advantages over other techniques used to map the seafloor (e.g., cost-effectiveness, global coverage, and faster data acquisition). On the other hand, SDB can be limited by water clarity, spatial resolution of the remote sensing measurement, and accuracy, depending on the method and satellite platform/instrument. These limitations notwithstanding, SDB can be used in a wide variety of applications, e.g., coastal zone management, navigation and safety, marine habitat monitoring, and disaster response. ICESat-2 has become a major contributor to SDB, with over 2000 journal article references to this topic to date. Now is the time to think about the state-of-the-art and additional capabilities of SDB for the future.
To help stimulate such thinking, the NASA ICESat-2 applications team hosted a one-day workshop on March 17, 2025. The workshop focused on the principles and methods for SDB. Held in conjunction with the annual US-Hydro meeting on March 17–20, 2025 at the Wilmington Convention Center in Wilmington, NC, the meeting was hosted by the Hydrographic Society of America. During the workshop the applications team brought together SDB end-users, algorithm developers, operators, and decision makers to discuss the current state and future needs of satellite bathymetry for the community. The objective of this workshop was to provide a space to foster collaboration and conceptualization of SDB applications not yet exploited and to allow for networking to foster synergies and collaborations between different sectors.
Meeting Overview
The workshop provided an opportunity for members from government, academia, and private sectors to share their SDB research, applications, and data fusion activities to support decision making and policy support across a wide range of activities. Presenters highlighted SDB principles, methods, and tools for SDB, an introduction of the new ICESat-2 bathymetric data product (ATL24), which is now available through the National Snow and Ice Data Center (NSIDC). During the workshop, the ICESat-2 team delivered a live demonstration of a web service for science data processing. Toward the end of the day, the applications team opened an opportunity for attendees to gather and discuss various topics related to SDB. This portion of the meeting was also available to online participation via Webex Webinars, which broadened the discussion.
Meeting Goal
The workshop offered a set of plenary presentations and discussions. During the plenary talks, participants provided an overview of Earth observation and SDB principles, existing methods and tools, an introduction to the newest ICESat-2 bathymetry product ATL24, a demonstration of the use of the webservice SlideRule Earth, and opportunities for open discission, asking questions and developing collaborations.
Meeting and Summary Format
The agenda of the SDB workshop was intended to bring together SDB end-users, including ICESat-2 application developers, satellite operators, and decision makers from both government and non-governmental entities to discuss the current state and future needs of the community. The workshop consisted of six sessions that covered various topics of SDB. This report is organized according to the topical focus of the plenary presentations with a brief narrative summary of each presentation included. The discussions that followed were not recorded and are not included in the report. The last section of this report consists of conclusions and future steps. The online meeting agenda includes links to slide decks for many of the presentations.
Welcoming Remarks
Aimee Neeley [NASA’s Goddard Space Flight Center (GSFC)/Science Systems and Applications Inc. (SSAI)—ICESat-2 Mission Applications Lead] organized the workshop and served as the host for the event. She opened the day with a brief overview of workshop goals, logistics, and the agenda.
Overview of Principles of SDB
Ross Smith [TCarta—Senior Geospatial Scientist] provided an overview of the principles of space-based bathymetry, including the concepts, capabilities, limitations, and methods. Smith began by relaying the history of satellite-derived bathymetry, which began with a collaboration between NASA and Jacques Cousteau in 1975, in which Cousteau used Landsat 1 data, as well as in situ data, to calculate bathymetry to a depth of 22 m (72 ft) in the Bahamas. Smith then described the five broad methodologies and their basic concepts for deriving bathymetry from remote sensing: radar altimetry, bottom reflectance, wave kinematics, laser altimetry, and space-based photogrammetry – see Figure 2. He then introduced the broad methodologies, most commonly used satellite sensors, the capabilities and limitations of each sensor, and the role of ICESat-2 in satellite bathymetry.
Figure 2. Satellite platforms commonly used for SDB. Figure credit: Ross Smith Review of SDB Methods and Tools
In this grouping of plenary presentations, representatives from different organizations presented their methods and tools for creating satellite bathymetry products.
Gretchen Imahori [National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey, Remote Sensing Division] presented the NOAA SatBathy (beta v2.2.3) Tool Update. During this presentation, Imahori provided an overview of the NOAA SatBathy desktop tool, example imagery, updates to the latest version, and the implementation plan for ATL24. The next session included more details about ATL24.
Minsu Kim [United States Geological Survey (USGS), Earth Resource and Observation Center (EROS)/ Kellogg, Brown & Root (KBR)—Chief Scientist] presented the talk Satellite Derived Bathymetry (SDB) Using OLI/MSI Based-On Physics-Based Algorithm. He provided an overview of an SDB method based on atmospheric and oceanic optical properties. Kim also shared examples of imagery from the SDB product – see Figure 3.
Figure 3. Three-dimensional renderings of the ocean south of Key West, FL created by adding SDB Digital Elevation Model (physics-based) to a Landsat Operational Land Imager (OLI) scene [top] and a Sentinel-2 Multispectral Imager (MSI) scene [bottom]. Figure credit: Minsu Kim Edward Albada [Earth Observation and Environmental Services GmbH (EOMAP)—Principal] presented the talk Satellite Lidar Bathymetry and EoappTM SLB-Online. The company EOMAP provides various services, including SDB, habitat mapping. For context, Albada provided an overview of EoappTM SDB-Online, a cloud-based software for creating SDB. (EoappTM SDB-online is one of several Eoapp apps and is based on the ICESat-2 photon data product (ATL03). Albada also provided example use cases from Eoapp – see Figure 4.
Figure 4.A display of the Marquesas Keys (part of the Florida Keys) using satellite lidar bathymetry data from the Eoapp SLB-Online tool from EOMAP. Figure credit: Edward Albada Monica Palaseanu-Lovejoy [USGS GMEG—Research Geographer] presented on a Satellite Triangulated Sea Depth (SaTSeaD): Bathymetry Module for NASA Ames Stereo Pipeline (ASP). She provided an overview of the shallow water bathymetry SaTSeaD module, a photogrammetric method for mapping bathymetry. Palaseanu-Lovejoy presented error statistics and validation procedures. She also shared case study results from Key West, FL; Cocos Lagoon, Guam; and Cabo Rojo, Puerto Rico – see Figure 5.
Figure 5. Photogrammetric bathymetry map of Cabo Roja, Puerto Rico displayed using the SatSeaD Satellite Triangulated Sea Depth (SaTSeaD): Bathymetry Module for NASA Ames Stereo Pipeline (ASP) module. Figure credit: Monica Palaseanu-Lovejoy Ross Smith presented a presentation on TCarta’s Trident Tools: Approachable SDB|Familiar Environment. During this presentation, Smith provided an overview of the Trident Tools Geoprocessing Toolbox deployed in Esri’s ArcPro. Smith described several use cases for the toolbox in Abu Dhabi, United Arab Emirates; Lucayan Archipelago, Bahamas; and the Red Sea.
Michael Jasinski [GSFC—Research Hydrologist] presented on The ICESat-2 Inland Water Along Track Algorithm (ATL13). He provided an overview of the ICESat-2 data product ATL13 an inland water product that is distributed by NSIDC. Jasinski described the functionality of the ATL13 semi-empirical algorithm and proceeded to provide examples of its applications with lakes and shallow coastal waters – see Figure 6.
Figure 6. A graphic of the network of lakes and rivers in North America that are measured by ICESat-2. Figure credit: Michael Jasinski ATL24 Data Product Update
Christopher Parrish [Oregon State University, School of Civil and Construction Engineering—Professor] presented on ATL24: A New Global ICESat-2 Bathymetric Data Product. Parrish provided an overview of the recently released ATL24 product and described the ATL24 workflow, uncertainty analysis, and applications in shallow coastal waters. Parrish included a case study where ATL24 data were used for bathymetric mapping of Kiriwina Island, Papua New Guinea – see Figure 7.
Figure 7. ATL24 data observed for Kiriwina Island, Papua New Guinea. Figure credit: Christopher Parrish SlideRule Demo
J. P. Swinski [GSFC—Computer Engineer] presented SlideRule Earth: Enabling Rapid, Scalable, Open Science. Swinski explained that SlideRule Earth is a public web service that provides access to on-demand processing and visualization of ICESat-2 data. SlideRule can be used to process a subset of ICESat-2 data products, including ATL24 – see Figure 8.
Figure 8. ATL24 data observed for Sanibel, FL as viewed on the SlideRule Earth public web client. Figure credit: SlideRule Earth SDB Accuracy
Kim Lowell [University of New Hampshire—Data Analytics Research Scientist and Affiliate Professor] presented on SDB Accuracy Assessment and Improvement Talking Points. During this presentation, Lowell provided examples of accuracy assessments and uncertainty through the comparison of ground measurement of coastal bathymetry to those modeled from satellite data.
Conclusion
The ICESat-2 Satellite Bathymetry workshop fostered discussion and collaboration around the topic of SDB methods. The plenary speakers presented the state-of-the-art methods used by different sectors and organizations, including government and private entities. With the release of ATL24, ICESat-2’s new bathymetry product, it was prudent to have a conversation about new and upcoming capabilities for all methods and measurements of satellite bathymetry. Both in-person and online participants were provided with the opportunity to learn, ask questions, and discuss potential applications in their own research. The ICESat-2 applications team hopes to host more events to ensure the growth of this field to maximize the capabilities of ICESat-2 and other Earth Observing systems.
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Last Updated Jun 05, 2025 Related Terms
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
What happens when the universe’s most magnetic object shines with the power of 1000 Suns in a matter of seconds? Thanks to NASA’s IXPE (Imaging X-ray Polarimetry Explorer), a mission in collaboration with ASI (Italian Space Agency), scientists are one step closer to understanding this extreme event.
Magnetars are a type of young neutron star – a stellar remnant formed when a massive star reaches the end of its life and collapses in on itself, leaving behind a dense core roughly the mass of the Sun, but squashed down to the size of a city. Neutron stars display some of the most extreme physics in the observable universe and present unique opportunities to study conditions that would otherwise be impossible to replicate in a laboratory on Earth.
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Illustrated magnetar flyby sequence showing magnetic field lines. A magnetar is a type of isolated neutron star, the crushed, city-size remains of a star many times more massive than our Sun. Their magnetic fields can be 10 trillion times stronger than a refrigerator magnet's and up to a thousand times stronger than a typical neutron star's. This represents an enormous storehouse of energy that astronomers suspect powers magnetar outbursts.NASAs Goddard Space Flight Center/Chris Smith (USRA) The magnetar 1E 1841-045, located in the remnants of a supernova (SNR Kes 73) nearly 28,000 light-years from Earth, was observed to be in a state of outburst by NASA’s Swift, Fermi, and NICER telescopes on August 21, 2024.
A few times a year, the IXPE team approves requests to interrupt the telescope’s scheduled observations to instead focus on unique and unexpected celestial events. When magnetar 1E 1841-045 entered this brighter, active state, scientists decided to redirect IXPE to obtain the first-ever polarization measurements of a flaring magnetar.
Magnetars have magnetic fields several thousand times stronger than most neutron stars and host the strongest magnetic fields of any known object in the universe. Disturbances to their extreme magnetic fields can cause a magnetar to release up to a thousand times more X-ray energy than it normally would for several weeks. This enhanced state is called an outburst, but the mechanisms behind them are still not well understood.
Through IXPE’s X-ray polarization measurements, scientists may be able to get closer to uncovering the mysteries of these events. Polarization carries information about the orientation and alignment of the emitted X-ray light waves; the higher the degree of polarization, the more the X-ray waves are traveling in sync, akin to a tightly choreographed dance performance. Examining the polarization characteristics of magnetars reveals clues about the energetic processes producing the observed photons as well as the direction and geometry of the magnetar magnetic fields.
The IXPE results, aided by observations from NASA’s NuSTAR and NICER telescopes, show that the X-ray emissions from 1E 1841-045 become more polarized at higher energy levels while still maintaining the same direction of propagation. A significant contribution to this high polarization degree comes from the hard X-ray tail of 1E 1841-045, an energetic magnetospheric component dominating the highest photon energies observed by IXPE. “Hard X-rays” refer to X-rays with shorter wavelengths and higher energies than “soft X-rays.” Although prevalent in magnetars, the mechanics driving the production of these high energy X-ray photons are still largely unknown. Several theories have been proposed to explain this emission, but now the high polarization associated with these hard X-rays provide further clues into their origin.
This illustration depicts IXPE’s measurements of X-ray polarization emitting from magnetar 1E 1841-045 located within the Supernova Remnant Kes 73. At the time of observation, the magnetar was in a state of outburst and emitting the luminosity equivalent to 1000 suns. By studying the X-ray polarization of magnetars experiencing an outburst scientists may be able to get closer to uncovering the mysteries of these events. Michela Rigoselli/Italian National Institute of Astrophysics The results are presented in two papers published in The Astrophysical Journal Letters, one led by Rachael Stewart, a PhD student at George Washington University, and the other by Michela Rigoselli of the Italian National Institute of Astrophysics..
“This unique observation will help advance the existing models aiming to explain magnetar hard X-ray emission by requiring them to account for this very high level of synchronization we see among these hard X-ray photons,” said Stewart. “This really showcases the power of polarization measurements in constraining physics in the extreme environments of magnetars.”
Rigoselli, lead author of the companion paper, added, “It will be interesting to observe 1E 1841-045 once it has returned to its quiescent, baseline state to follow the evolution of its polarimetric properties.”
IXPE is a space observatory built to discover the secrets of some of the most extreme objects in the universe. Launched in December 2021 from NASA’s Kennedy Space Center on a Falcon 9 rocket, the IXPE mission is part of NASA’s Small Explorer series.
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.
Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
Media Contact
Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845
Lane Figueroa
Marshall Space Flight Center, Huntsville, Ala.
lane.e.figueroa@nasa.gov
256.544.0034
About the Author
Beth Ridgeway
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Last Updated Jun 05, 2025 EditorBeth RidgewayContactLane FigueroaElizabeth R. Landauelizabeth.r.landau@nasa.govLocationMarshall Space Flight Center Related Terms
IXPE (Imaging X-ray Polarimetry Explorer) Astrophysics Astrophysics Division Marshall Astrophysics Marshall Science Research & Projects Marshall Space Flight Center The Universe Explore More
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By NASA
NASA NASA astronaut Ed White, pilot of the Gemini IV mission, floats in space on June 3, 1965, while performing the first spacewalk by an American. As White floated outside the spacecraft, he used a Hand-Held Maneuvering Unit, informally called a “zip gun.” The device, seen in White’s right hand in this image, expelled pressurized oxygen to provide thrust for controlling his movements outside the capsule.
“You look beautiful, Ed,” remarked fellow crew member astronaut James A. McDivitt, who remained inside the spacecraft, as he began taking pictures of White tumbling around outside his window. “I feel like a million dollars,” White said. “This is the greatest experience. It’s just tremendous.”
Watch video of the first American spacewalk.
Image credit: NASA
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By NASA
Two NASA-developed technologies are key components of a new high-resolution sensor for observing wildfires: High Operating Temperature Barrier Infrared Detector (HOT-BIRD), developed with support from NASA’s Earth Science Technology Office (ESTO), and a cutting-edge Digital Readout Integrated Circuit (DROIC), developed with funding from NASA’s Small Business Innovation Research (SBIR) program.
NASA’s c-FIRST instrument could provide high resolution data from a compact space-based platform in under an hour, making it easier for wildfire managers to detect and monitor active burns. Credit: NASA/JPL A novel space-based sensor for observing wildfires could allow first responders to monitor burns at a global scale, paving the way for future small satellite (SmallSat) constellations dedicated entirely to fire management and prevention.
Developed with support from NASA’s Earth Science Technology Office (ESTO), the “Compact Fire Infrared Radiance Spectral Tracker” (c-FIRST) is a small, mid-wave infrared sensor that collects thermal radiation data across five spectral bands. Most traditional space-based sensors dedicated to observing fires have long revisit times, observing a scene just once over days or even weeks. The compact c-FIRST sensor could be employed in a SmallSat constellation that could observe a scene multiple times a day, providing first responders data with high spatial resolution in under an hour.
In addition, c-FIRST’s dynamic spectral range covers the entire temperature profile of terrestrial wild fires, making it easier for first-responders to detect everything from smoldering, low-intensity fires to flaming, high intensity fires.
“Wildfires are becoming more frequent, and not only in California. It’s a worldwide problem, and it generates tons of by-products that create very unhealthy conditions for humans,” said Sarath Gunapala, who is an Engineering Fellow at NASA’s Jet Propulsion Laboratory (JPL) and serves as Principal Investigator for c-FIRST.
The need for space-based assets dedicated to wildfire management is severe. During the Palisade and Eaton Fires earlier this year, strong winds kept critical observation aircraft from taking to the skies, making it difficult for firefighters to monitor and track massive burns.
Space-based sensors with high revisit rates and high spatial resolution would give firefighters and first responders a constant source of eye-in-the-sky data.
“Ground-based assets don’t have far-away vision. They can only see a local area. And airborne assets, they can’t fly all the time. A small constellation of CubeSats could give you that constant coverage,” said Gunapala.
c-FIRST leverages decades of sensor development at JPL to achieve its compact size and high performance. In particular, the quarter-sized High Operating Temperature Barrier Infrared Detector (HOT-BIRD), a compact infrared detector also developed at JPL with ESTO support, keeps c-FIRST small, eliminating the need for bulky cryocooler subsystems that add mass to traditional infrared sensors.
With HOT-BIRD alone, c-FIRST could gather high-resolution images and quantitative retrievals of targets between 300°K (about 80°F) to 1000°K (about 1300°F). But when paired with a state-of-the-art Digital Readout Integrated Circuit (DROIC), c-FIRST can observe targets greater than 1600°K (about 2400°F).
Developed by Copious Imaging LLC. and JPL with funding from NASA’s Small Business Innovation Research (SBIR) program, this DROIC features an in-pixel digital counter to reduce saturation, allowing c-FIRST to capture reliable infrared data across a broader spectral range.
Artifical intelligence (AI) will also play a role in c-FIRST’s success. Gunapala plans to leverage AI in an onboard smart controller that parses collected data for evidence of hot spots or active burns. This data will be prioritized for downlinking, keeping first responders one step ahead of potential wildfires.
“We wanted it to be simple, small, low cost, low power, low weight, and low volume, so that it’s ideal for a small satellite constellation,” said Gunapala.
Gunapala and his team had a unique opportunity to test c-FIRST after the Palisade and Eaton Fires in California. Flying their instrument aboard NASA’s B-200 Super King Air, the scientists identified lingering hot spots in the Palisades and Eaton Canyon area five days after the initial burn had been contained.
Now, the team is eyeing a path to low Earth orbit. Gunapala explained that their current prototype employs a standard desktop computer that isn’t suited for the rigors of space, and they’re working to incorporate a radiation-tolerant computer into their instrument design.
But this successful test over Los Angeles demonstrates c-FIRST is fit for fire detection and science applications. As wildfires become increasingly common and more destructive, Gunapala hopes that this tool will help first responders combat nascent wildfires before they become catastrophes.
“To fight these things, you need to detect them when they’re very small,” said Gunapala.
A publication about c-FIRST appeared in the journal “Society of Photo-Optical Instrumentation Engineers” (SPIE) in March, 2023.
For additional details, see the entry for this project on NASA TechPort.
To learn more about emerging technologies for Earth science, visit ESTO’s open solicitations page.
Project Lead: Sarath Gunapala, NASA Jet Propulsion Laboratory (JPL)
Sponsoring Organization: NASA ESTO
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Last Updated Jun 03, 2025 Related Terms
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By European Space Agency
Japanese lunar exploration company ispace will attempt to land its RESILIENCE spacecraft on the Moon no earlier than 5 June (CEST) 2025.
The European Space Agency’s (ESA) global network of ground stations is facilitating communication between the spacecraft and ispace mission control.
Click here to watch the ispace landing livestream in English.
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