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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Instruments in space are helping scientists map wastewater plumes flowing into the Pacific Ocean from the heavily polluted Tijuana River, seen here with the San Diego sky-line to the north. NOAA Proof-of-concept results from the mouth of the Tijuana River in San Diego County show how an instrument called EMIT could aid wastewater detection.
An instrument built at NASA’s Jet Propulsion Laboratory to map minerals on Earth is now revealing clues about water quality. A recent study found that EMIT (Earth Surface Mineral Dust Source Investigation) was able to identify signs of sewage in the water at a Southern California beach.
The authors of the study examined a large wastewater plume at the mouth of the Tijuana River, south of Imperial Beach near San Diego. Every year, millions of gallons of treated and untreated sewage enter the river, which carries pollutants through communities and a national reserve on the U.S.-Mexico border before emptying into the Pacific Ocean. Contaminated coastal waters have been known to impact human health — from beachgoers to U.S. Navy trainees — and harm marine ecosystems, fisheries, and wildlife.
For decades scientists have tracked water quality issues like harmful algal blooms using satellite instruments that analyze ocean color. Shades that range from vibrant red to bright green can reveal the presence of algae and phytoplankton. But other pollutants and harmful bacteria are more difficult to monitor because they’re harder to distinguish with traditional satellite sensors.
A plume spreads out to sea in this image captured off San Diego by the Sentinel-2 satellite on March 24, 2023. Both a spectroradiometer used to analyze water samples (yellow star) and NASA’s EMIT identified in the plume signs of a type of bacterium that can sicken humans and animals.SDSU/Eva Scrivner That’s where EMIT comes in. NASA’s hyperspectral instrument orbits Earth aboard the International Space Station, observing sunlight reflecting off the planet below. Its advanced optical components split the visible and infrared wavelengths into hundreds of color bands. By analyzing each satellite scene pixel by pixel at finer spatial resolution, scientists can discern what molecules are present based on their unique spectral “fingerprint.”
Scientists compared EMIT’s observations of the Tijuana River plume with water samples they tested on the ground. Both EMIT and the ground-based instruments detected a spectral fingerprint pointing to phycocyanin, a pigment in cyanobacteria, an organism that can sicken humans and animals that ingest or inhale it.
‘Smoking Gun’
Many beachgoers are already familiar with online water-quality dashboards, which often rely on samples collected in the field, said Christine Lee, a scientist at JPL in Southern California and a coauthor of the study. She noted the potential for EMIT to complement these efforts.
“From orbit you are able to look down and see that a wastewater plume is extending into places you haven’t sampled,” Lee said. “It’s like a diagnostic at the doctor’s office that tells you, ‘Hey, let’s take a closer look at this.’”
Lead author Eva Scrivner, a doctoral student at the University of Connecticut, said that the findings “show a ‘smoking gun’ of sorts for wastewater in the Tijuana River plume.” Scrivner, who led the study while at San Diego State University, added that EMIT could be useful for filling data gaps around intensely polluted sites where traditional water sampling takes a lot of time and money.
EMIT’s Many Uses
The technology behind EMIT is called imaging spectroscopy, which was pioneered at JPL in the 1980s. Imaging spectrometers developed at JPL over the decades have been used to support areas ranging from agriculture to forest health and firefighting.
When EMIT was launched in July 2022, it was solely aimed at mapping minerals and dust in Earth’s desert regions. That same sensitivity enabled it to spot the phycocyanin pigments off the California coast.
Scrivner hadn’t anticipated that an instrument initially devoted to exploring land could reveal insights about water. “The fact that EMIT’s findings over the coast are consistent with measurements in the field is compelling to water scientists,” she said. “It’s really exciting.”
To learn more about EMIT, visit:
https://earth.jpl.nasa.gov/emit/
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
Written by Sally Younger
2025-078
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Last Updated Jun 12, 2025 Related Terms
EMIT (Earth Surface Mineral Dust Source Investigation) Earth Earth Science Technology Office Human Dimensions International Space Station (ISS) Oceans Water on Earth Explore More
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By NASA
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
This image shows a simulated observation from NASA’s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument’s field of view. More than 20 gravitational lenses, with examples shown at left and right, are expected to pop out in every one of Roman’s vast observations. A journal paper led by Bryce Wedig, a graduate student at Washington University in St. Louis, Missouri, estimates that of those Roman detects, about 500 from the telescope’s High-Latitude Wide-Area Survey will be suitable for dark matter studies. By examining such a large population of gravitational lenses, the researchers hope to learn a lot more about the mysterious nature of dark matter.Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI) A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal led by Bryce Wedig, a graduate student at Washington University in St. Louis. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
“The current sample size of these objects from other telescopes is fairly small because we’re relying on two galaxies to be lined up nearly perfectly along our line of sight,” Wedig said. “Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.”
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Roman will not only significantly increase our sample size — its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,” said Tansu Daylan, the principal investigator of the science team conducting this research program. Daylan is an assistant professor and a faculty fellow at the McDonnell Center for the Space Sciences at Washington University in St. Louis. “Ultimately, both the alignment and the brightness of the background galaxies need to meet a certain threshold so we can characterize the dark matter within the foreground galaxies.”
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This video shows how a background galaxy’s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA’s Roman Space Telescope. Light from the background galaxy is distorted, curving around the foreground galaxy and appearing more than once as warped arcs and crescents. Researchers studying these objects, known as gravitational lenses, can better characterize the mass of the foreground galaxy, which offers clues about the particle nature of dark matter.Credit: NASA, Joseph Olmsted (STScI) What Is Dark Matter?
Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy’s mass is made up of dark matter, so called because it doesn’t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.
When the gravity of a foreground galaxy bends the path of a background galaxy’s light, its light is routed onto multiple paths. “This effect produces multiple images of the background galaxy that are magnified and distorted differently,” Daylan said. These “duplicates” are a huge advantage for researchers — they allow multiple measurements of the lensing galaxy’s mass distribution, ensuring that the resulting measurement is far more precise.
Roman’s 300-megapixel camera, known as its Wide Field Instrument, will allow researchers to accurately determine the bending of the background galaxies’ light by as little as 50 milliarcseconds, which is like measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches.
The amount of gravitational lensing that the background light experiences depends on the intervening mass. Less massive clumps of dark matter cause smaller distortions. As a result, if researchers are able to measure tinier amounts of bending, they can detect and characterize smaller, less massive dark matter structures — the types of structures that gradually merged over time to build up the galaxies we see today.
With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. “Finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, we can cast a wide net and expect to get lucky often,” Wedig said. “We won’t see dark matter in the images — it’s invisible — but we can measure its effects.”
“Ultimately, the question we’re trying to address is: What particle or particles constitute dark matter?” Daylan added. “While some properties of dark matter are known, we essentially have no idea what makes up dark matter. Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature.”
Preparations Continue
Before Roman launches, the team will also search for more candidates in observations from ESA’s (the European Space Agency’s) Euclid mission and the upcoming ground-based Vera C. Rubin Observatory in Chile, which will begin its full-scale operations in a few weeks. Once Roman’s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what’s known about these galaxies.
“We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter,” Daylan said.
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 in Southern California; Caltech/IPAC in Pasadena, 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 Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Claire Blome
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Jun 12, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research The Universe Explore More
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By Space Force
The Air Force Aid Society, AFAS, announced a series of bold changes aimed at better supporting the evolving needs of Airmen, Guardians, and their families.
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By European Space Agency
Video: 00:02:00 ESA project astronaut Sławosz Uznański-Wiśniewski is heading to the International Space Station on his first mission as part of Axiom Mission 4 (Ax-4). He is the second ESA project astronaut from a new generation of Europeans to fly on a commercial human spaceflight mission with Axiom Space.
Sponsored by the Polish government and supported by ESA, the Polish Ministry of Economic Development and Technology (MRiT), and the Polish Space Agency (POLSA), the mission—called Ignis—features an ambitious technological and scientific programme. It includes several experiments proposed by the Polish space industry and developed in cooperation with ESA, along with additional ESA-led experiments.
Follow Sławosz's journey on the Ignis mission website and discover more about the next mission patch to be hung on the walls of the Columbus Control Centre.
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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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