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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 21 min read
A Decade of Global Water Cycle Monitoring: NASA Soil Moisture Active Passive Mission
Introduction
The NASA Soil Moisture Active Passive (SMAP) mission, launched in 2015, has over 10 years of global L-band radiometry observations. The low frequency [1.4 GHz frequency or 21 cm (8 in) wavelength] measurements provide information on the state of land surfaces in all weather conditions – regardless of solar illumination. A principal objective of the SMAP mission is to provide estimates of surface soil moisture and its frozen or thawed status. Over the land surface, soil moisture links the water, energy, and carbon cycles. These three cycles are the main drivers of regional climate and regulate the functioning of ecosystems.
The achievement of 10 years in orbit is a fitting time to reflect on what SMAP has accomplished. After briefly discussing the innovative measurement approach and the instrument payload (e.g., a radiometer and a regrettably short-lived L-band radar), a significant section of this article is devoted to describing the mission’s major scientific achievements and how the data from SMAP have been used to serve society (e.g., applied sciences) – including SMAP’s pathfinding role as Early Adopters. This content is followed by a discussion of how SMAP has dealt with issues related to radio frequency interference in the L-Band region, a discussion of the SMAP data products suite, future plans for the SMAP active–passive algorithm, and a possible follow-on L-band global radiometry mission being developed by the European Union’s Copernicus Programme that would allow for data continuity beyond SMAP. This summary for The Earth Observer is excerpted from a longer and more comprehensive paper that, as of this article’s posting, is being prepared for publication in the Proceedings of the Institute of Electrical and Electronics Engineers (IEEE).
SMAP Measurement Approach and Instruments
The SMAP primary and operating instrument is the L-band radiometer, which collects precise surface brightness temperature data. The radiometer includes advanced radio frequency interference (RFI) detection and mitigation hardware and software. The radiometer measures vertical and horizontal polarization observations along with the third and fourth Stokes parameters (T3 and T4) of the microwave radiation upwelling from the Earth. The reflector boom and assembly, which includes a 6 m (20 ft) deployable light mesh reflector, is spun at 14.6 revolutions-per-minute, which creates a 1000 km (621 mi) swath as the SMAP satellite makes its Sun-synchronous orbit of the Earth – see Figure 1. This approach allows coverage of the entire globe in two to three days with an eight-day exact repeat. The radiometer instrument is calibrated monthly by pointing it to the deep sky.
Figure 1. An artist’s rendering of the SMAP Observatory showing both the radiometer and radar. Figure credit: NASA/Jet Propulsion Laboratory/California Institute of Technology The original SMAP instrument design included a companion L-band radar, which operated from April through early July 2015, acquiring observations of co- and cross-polarized radar backscatter at a spatial resolution of about 1 km (0.6 mi) with a temporal revisit of about three days over land. This data collection revealed the dependence of L-band radar signals on soil moisture, vegetation water content, and freeze thaw state. The radar transmitter failed on July 7, 2015. Shortly thereafter, the radar receiver channels were repurposed to record the reflected signals from the Global Navigation Satellite System (GNSS) constellation in August 2015, making SMAP the first full-polarimetric GNSS reflectometer in space for the investigation of land surface and cryosphere.
Scientific Achievements from a Decade of SMAP Data
A decade of SMAP soil moisture observations have led to a plethora of scientific achievements. The data have been used to quantify the linkages of the three main metabolic cycles (e.g., carbon, water, and energy) on land. They have also been used to improve drought assessments and flood prediction as well as the accuracy of numerical weather prediction (NWP) models. They are also used to measure liquid water and thickness of ice sheets, and sea surface salinity. The subsections that follow describe how SMAP data are being put to use in myriad ways that benefit society.
Quantifying Processes that Link the Terrestrial Water, Energy, and Carbon Cycles
The primary SMAP science goal is to develop observational benchmarks of how the water, energy, and carbon cycles link together over land. Soil moisture is the variable state of the land branch of the water cycle. It links the water cycle to the energy cycle through limiting latent heat flux – the change in energy as heat exchanges when water undergoes a phase change, such as evapotranspiration at the land–atmosphere interface. Soil moisture also links the water and carbon cycles, which is evident through plant photosynthesis. SMAP global observations of soil moisture fields, in conjunction with remote sensing of elements of the energy and carbon cycles, can reveal how these three cycles are linked in the real world as a benchmark for weather and Earth system models.
Photosynthesis is down-regulated by both the deficit in water availability and the lack of an adequate amount of photosynthetically active radiation. Global maps reveal how soil moisture and light regulate photosynthesis – see Figure 2. These benchmark observational results can be used to assess how Earth system models link to the three main metabolic cycles of the climate system.
Figure 2. Observed regulation of photosynthesis by water availability [left] and light availability [right]. Blue denotes greater limitation. Photosynthesis rates for both maps determined using solar-induced fluorescence (SIF) measurements (mW/m2 nm sr) from the Tropospheric Ozone Monitoring Instrument (TROPOMI) on the European Union’s Copernicus Sentinel-5P mission. Water availability was determined using soil moisture (SM) measurements from the Soil Moisture Active Passive (SMAP) mission. Light availability was determined using measurements of photosynthetically active radiation (PAR) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua platforms. The resulting maps show the model slope (mW/m2/nm/sr) of the estimated SIF-SM relationship in the water-limited regime [left] and the model slope (10-3/nm/sr) of estimated SIF-PAR relationship in the light-limited regime [right]. Figure credit: Jonard et al (2022) in Biogeosciences Development of Improved Flood Prediction and Drought Monitoring Capability
SMAP products have also been widely used in applied sciences and natural hazard decision-support systems. SMAP’s observation-based soil moisture estimates offer transformative information for managing water-related natural hazards, such as monitoring agricultural drought – defined as a persistent deficit in soil moisture – and flood volumes – defined as the landscape’s water absorption capacity during precipitation events. The SMAP project produces a parallel, near-real-time data stream that is accessed by a number of federal and state agencies in decision-support systems related to drought monitoring, food security, and landscape inundation and trafficability.
Enhancing Weather and Climate Forecasting Skill
SMAP’s enhancement of numerical weather prediction, model skill, and reduction of climate model projection uncertainties is based on the premise of the contribution of solar energy to weather and climate dynamics. Soil moisture has a strong influence on how available solar energy is partitioned into components (e.g., sensible heat flux versus latent heat flux) over land. The influence propagates through the atmospheric boundary layer and ultimately influences the evolution of weather.
To give an example, land surface processes can affect the evolution of the U.S. Great Plains low-level jets (GPLLJs). These jets drive mesoscale convective weather systems. Previous studies have shown that GPLLJs are sensitive to regional soil moisture gradients. Assimilation of SMAP soil moisture data improves forecasts of weakly synoptically forced or uncoupled GPLLJs compared to forecasts of cyclone-induced coupled GPLLJs. For example, the NASA Unified Weather Research and Forecasting Model, with 75 GPLLJs at 9 km (5.6 mi) resolution both with and without SMAP soil moisture data assimilation [SMAP data assimilation (DA) and no-DA respectively], shows how the windspeed mean absolute difference between SMAP DA and no-DA increase approximately linearly over the course of the simulation with maximum differences at 850 hPa (or mb) for the jet entrance and core – see Figure 3.
Figure 3. The impact of adding soil moisture data [SMAP data assimilation (DA) minus no-DA] to a model simulation from theNASA Unified Weather Research and Forecasting Model (NU-WRF)) of the Great Plains Low Level Jet (GPLLJ). The results show the mean over 75 independent GPLLJ events. The plots correspond to wind speed difference with height (y-axis) and time (hours on x-axis). The panels are for jet entrance [left], jet core [middle] and jet exit [right]. Soil moisture data assimilation enhances the intensity of the simulated GPLLJ. The stippling corresponds to 99% statistical confidence. Figure credit: Ferguson (2020) in Monthly Weather Review Measuring Liquid Water Content and Thickness of Ice Sheets
The mass loss of Greenland and Antarctica ice sheets contributes to sea-level rise – which is one of the most impactful and immediate damaging consequences of climate change. The melt rates over the last few years have raised alarm across the globe and impact countries with coastal communities. The cryosphere community has raised a call-to-action to use every observing system and model available to monitor the patterns and rates of land ice melt.
Surface melt affects the ice cap mass loss in many ways: the direct melt outflow from the ablation zone of the Greenland ice sheet, the structural change of the percolation zone of the Greenland ice sheet, changes in the melt water retention and outflow boundaries, changes in the structure of the Antarctic ice shelves, and destabilization of the buttressing of the glacier outflow through various processes (e.g., hydrofracturing and calving). The long-term climate and mass balance models rely on accurate representation of snow, firn, and ice processes to project the future sea level.
The SMAP L-band radiometer has relatively long wavelength [21 cm (8 in)] observations compared to other Earth-observing instruments. It enables the measurement of liquid water content (LWC) in the ice sheets and shelves as it receives the radiation from the deep layers of the snow/firn/ice column. Relatively high LWC values absorb the emission only partially, making the measurement sensitive to different liquid water amounts (LWA) in the entire column. Figure 4 shows the cumulative LWA for 2015–2023 based on SMAP measurements.
Figure 4. Total annual sum of SMAP daily liquid water amount (LWA) for 2015–2023. The black solid line on each map represents grid edges, and the grey color mask inside the ice sheet indicates melt detections by decreasing brightness temperature. Figure Credit: Andreas Colliander [Finnish Meteorological Institute]. The SMAP L-band radiometer has also been used to derive the thickness of thin sea ice [Soil Moisture and Ocean Salinity (SMOS) mission have been recalibrated to SMAP, using the same fixed incidence angle. The data show strong agreement and demonstrate clear benefits of a combined dataset. The L-band thin ice thickness retrievals provide a useful complement to higher-resolution profiles of thicker ice obtained from satellite altimeters (e.g. ESA’s CryoSat-2 and NASA’s Ice, Clouds and land Elevation Satellite–2 missions).
Extending and Expanding the Aquarius Sea Surface Salinity Record
The joint NASA/Argentinian Aquarius/Satélite de Aplicaciones Científicas (SAC)-D (Aquarius), which operated from 2011–2015, used an L-band radiometer and an L-band scatterometer to make unprecedented monthly maps of global sea surface salinity at 150-km (93-mi) resolution. The SMAP L-band radiometer has not only extended the sea surface salinity record in the post-Aquarius period, it has also increased the spatial resolution and temporal frequency of these measurements because of its larger reflector and wider swath. The increased resolution and revisit allow new and unprecedented perspectives into mixing and freshwater events, coastal plume tracking, and other more local oceanic features.
Providing New Perspectives on Global Ecology and Plant Water Stress
The L-band vegetation optical depth (VOD) – which is related to water content in vegetation – has been retrieved simultaneously with soil moisture using SMAP’s dual-polarized brightness temperatures and is being used to better understand global ecology. Water in above-ground vegetative tissue attenuates and thus depolarizes surface microwave emission, and VOD quantifies this effect. SMAP can provide global observations of VOD in all weather conditions with a two to three day temporal frequency. Changes in VOD indicate either plant rehydration or growth. Ecologists benefit from this new ecosystem observational data, which augments optical and near-infrared vegetation indices [e.g., leaf area index (LAI)] and has a higher temporal frequency that is not affected by clouds and does not saturate as rapidly for dense vegetation.
Examples of how the data have been used include deciphering the conditions when vegetation uptakes soil water only for rehydration (i.e., VOD increase with no LAI change) compared to plant growth (i.e., increase in both VOD and LAI). The applications of VOD are increasing and the ecology community views this product as a valuable additional perspective on soil–plant water relations.
At the moment, this measurement has no ground-based equivalent. Therefore, field experiments with airborne instruments and ground sampling teams are needed to firmly establish the product as a new observational capability for global ecology.
Applied Science Collaboration: SMAP Observations Serving Society
The SMAP project has worked with the NASA Earth Science Division Applied Sciences Program (now known as Earth Science to Action) and the natural hazards monitoring and forecasting communities for pre- and post-launch implementation of SMAP products in their operations. In some operational applications, for which long-term data continuity is a requirement, the SMAP data are still used for assessment of current conditions, as well as research and development.
The Original Early Adopters
Prior to its launch, the SMAP mission established a program to explore and facilitate applied and operational uses of SMAP mission data products in decision-making activities for societal benefit. To help accomplish these objectives, SMAP was the first NASA mission to create a formal Applications Program and an Early Adopter (EA) program, which eventually became a requirement for all future NASA Earth Science directed satellite missions. SMAP’s EA program increases the awareness of mission products, broadens the user community, increases collaboration with potential users, improves knowledge of SMAP data product capabilities, and expedites the distribution and uses of mission products after launch.
SMAP Data in Action
Several project accomplishments have been achieved primarily through an active continuous engagement with EAs and operational agencies working towards national interests. SMAP soil moisture data have been used by the U.S. Department of Agriculture (USDA) for domestic and international crop yield applications. For example the USDA’s National Agricultural Statistics Service (NASS) conducts a weekly survey of crop progress, crop condition, and soil moisture condition for U.S. cropland. NASS surveys and publishes state-level soil moisture conditions in the NASS Crop Progress Report.
The traditional field soil moisture survey is a large-scale, labor-intensive data collection effort that relies heavily on responses from farmers, agricultural extension agents and/or other domain experts for field observations. One weakness of these observations is that they are based on subjective assessments rather than quantitative measures and can lead to spatial inconsistency based on the human responses from the respective counties. Moreover, the NASS Crop Progress Reports do not provide specific geolocation information for the assessed soil moisture conditions – which are extremely useful metadata to provide to data users. NASS implemented the use of SMAP observations in their weekly reports during the growing period (March–November). SMAP maps estimated root-zone soil moisture for the week of November 14–20, 2022, over NASS Pacific (California and Nevada) and Delta (Arkansas, Mississippi and Louisiana) regional domains—see Figure 5.
Figure 5. SMAP-based soil moisture estimates for California, Nevada, Arkansas, Mississippi, and Louisiana, used by the U.S. Department of Agriculture’s (USDA) National Agricultural Statistics Service (NASS) in their weekly report covering November 14–20, 2022. These data are available for selected states at the NASS website linked in the text. Figure Credit: NASS SMAP Radio Frequency Interference Detection and Mitigation
Although SMAP operates within the protected frequency allocation of 1400–1427 MHz, the radiometer has been impacted by radio frequency interference over the mission lifetime. Unauthorized in-band transmitters as well as out-of-band emissions from transmitters operating adjacent to the allocated spectrum have been observed in SMAP measurements since its launch. The previously launched SMOS and Aquarius radiometers provide evidence of global RFI at L-band. Consequently, SMAP was designed to incorporate a novel onboard digital detector on the back end to enable detection and filtering of RFI. The radiometer produces science data in time and frequency, enabling the use of multiple RFI detection methods in the ground processing software.
On-orbit data demonstrate that the RFI detection and filtering performs well and improves the quality of SMAP brightness temperature measurements. The algorithms are most effective at filtering RFI that is sparse in time and frequency, with minimal impact on the noise equivalent delta temperature (NEDT) – a measure of the radiometer sensitivity. Some areas of the globe remain problematic as RFI that is very high level and persistent results in high percentages of data loss due to removal of contaminated data. A global map of RFI detection rate for January 2025 shows a large contrast between Eastern and Western Hemispheres and between Northern and Southern Hemispheres – see Figure 6. Regions of isolated RFI and severe RFI correspond to populated areas. A detection rate of 100% means all pixels are flagged and removed, resulting in data loss. Analysis of spectral information reveal many sources are likely terrestrial radar systems; however, many wideband, high-level sources and low-level, non-radar sources also persist. Over areas of geopolitical conflict, the time-frequency data show interference covering the entire radiometer receiver bandwidth.
Figure 6. Percentage of pixels on a 0.25° grid for January 2025 that have been flagged for removal by the Soil Moisture Active Passive radio frequency interference detection algorithms. Figure Credit: Priscilla N. Mohammed [GSFC] The RFI challenge is further addressed through official spectrum management channels and formal reports that include the geolocated coordinates of sources, interference levels, frequency of occurrence during the observed period, and spectral information – all of which aid field agents as they work to identify potential offenders. Reports are submitted to the NASA Spectrum office and then forwarded to the country of interest through the Satellite Interference Reporting and Resolution System.
SMAP Science Data Products
The current suite of SMAP science data products is available in the Table. The principal data products are grouped in four levels designated as L1–4. The L1 products are instrument L-band brightness temperature in Kelvin and include all four Stokes parameters (i.e., horizonal and vertical polarization as well as third and fourth Stokes). Both 6:00 AM equatorial crossing (descending) and 6:00 PM equatorial crossing (ascending data) are contained in the products. The user has access to quality flags of the conditions under which measurements are available for each project. The L1B products are time-ordered and include fore and aft measurements. L1C products are on the Equal-Area Scalable Earth V2 (EASE2) grid with polar and global projections. L2 data products are geophysical retrievals (i.e., soil moisture, VOD, and binary freeze/thaw classification on a fixed Earth grid). The L2 half-orbit products are available to the public within a day of acquisition. L3 products are daily composites and include all half-orbits for that day.
The SMAP project also produces L4 data that are the result of data assimilation. The L4 products take advantage of other environmental observations, such as precipitation, air temperature and humidity, radiative fluxes at the land surface, and ancillary land use and soil texture information, to produce estimates of surface [nominally 0–5 cm (0–2 in)] and subsurface (e.g., root-zone up to a meter) soil moisture. The data assimilation system is a merger of model and measurements and hence resolves the diurnal cycle of land surface conditions. The data assimilation system also provides estimates of surface fluxes of carbon, energy, and water, such as evaporation, runoff, gross primary productivity (GPP), and respiration. The difference between GPP and respiration is the net ecosystem exchange, which is the net source/sink of the carbon cycle over land.
The SMAP suite of products also include near-real-time (NRT) brightness temperature and soil moisture products for use in operational weather forecast applications. The NRT product targets delivery to users within three hours of measurement acquisition. The NRT uses predicted SMAP antenna pointing (instead of telemetry) and model predicted ancillary data (soil temperature) in order to support operational centers that require more than three hours of data products for updating weather forecast models. To date SMAP has met its required and target (for NRT) latency requirements.
Two other data projects merge synergistically with other (colocated) satellite measurements. The SPL2SMAP_S merges SMAP L-band radio brightness measurements with C-band synthetic aperture radar (SAR) measurements from the ESA Copernicus Sentinel-1 mission. The SAR data have high resolution and allow the generation of 1 and 3 km (0.62 and 1.8 mi) merged surface soil moisture estimates. The high resolution soil moisture information, however, is only available when there is coincident SMAP and Sentinel-1 measurements. The refresh rate of this product is limited and can be as long as 12 days.
The merged SMOS–SMAP passive L-band radiometry data allows the generation of global, near daily surface soil moisture estimates, which are required to resolve fast hydrologic processes, such as gravity drainage and recharge flux. These parameters are only partially resolved with the SMAP, with a two to three day data refresh rate. This product interpolates the multi-angular SMOS data to the SMAP 40º incident angle and uses all SMAP algorithms, including correction of waterbody impact on SMAP brightness temperature, and ancillary data for geophysical inversions to soil moisture and VOD, ensuring consistency. The combined SMAP–SMOS data product may not be available daily across locations, such as Japan, parts of China, and the Middle East, where RFI affects data collection.
Table. Soil Moisture Active Passive suite of science products are available through the National Snow and Ice Data Center, one of NASA’s Distributed Active Archive Centers.
Product Type Product description Resolution (Gridding) Granule Extent SPL1BTB Geolocated, calibrated brightness temperature in time order 36 km Half Orbit SPL1CTB_E Backus-Gilbert interpolated, calibrated brightness temperature in time order (9 km) Half Orbit SPL1CTB Geolocated, calibrated brightness temperature on Equal-Area Scalable Earth V2 (EASE2) grid 36 km Half Orbit SPL1CTB_E Backus-Gilbert interpolated, calibrated brightness temperature on EASE2 grid (9 km) Half Orbit SPL2SMP Radiometer soil moisture and vegetation optical depth 36 km Half Orbit SPL2SMP_E Radiometer soil moisture and vegetation optical depth based on SPL1CTB (9 km) Half Orbit SPL2SMAP_S SMAP radiometer/Copernicus Sentinel-1 soil moisture 3 km Sentinel-1 SPL3SMP Daily global composite radiometer soil moisture and vegetation optical depth based on SPL1CTB 36 km Daily–Global SPL3SMP_E Daily global composite radiometer soil moisture and vegetation optical depth based on SPL1CTB_E (9 km) Daily–Global SPL3FTP Daily composite freeze/thaw state based on SPL1CTB 36 km Daily–Global SPL3FTP_E Daily composite freeze/thaw state based on SPL1CTB_E (9 km) Daily–Global SPL4SMAU Surface and Root Zone soil moisture 9 km 3 hours – Global SPL4CMDL Carbon Net Ecosystem Exchange 9 km Daily–Global SPL1BTB_NRT Near Real Time Geolocated, calibrated brightness temperature in time order 36 km Half Orbit SPL2SMP_NRT Near Real Time Radiometer soil moisture 36 km Half Orbit L2/L3 SMOS SM SMOS soil moisture and VOD based on SMAP algorithms (9 km) Half Orbit/Daily Global Future Directions for the SMAP Active–Passive Algorithm
Although the SMAP radar failed not long after launch, the data that were collected have been used to advance the development of the SMAP Active–Passive (AP) algorithm, which will be applied to the combined SMAP radiometer data and radar data from the NASA–Indian Space Research Organisation (ISRO) Synthetic Aperture Radar [NISAR] mission, a recently-launched L-Band Synthetic Aperture mission to produce global soil moisture at a spatial resolution of 1 km (0.62 mi) or better. The high resolution product can advance applications of SMAP data (e.g., agricultural productivity, wildfire, and landslide monitoring).
Data Continuity Beyond SMAP
A forthcoming mission meets some – but not all – of the SMAP measurement requirements and desired enhancements. The European Union’s Copernicus Program Copernicus Imaging Microwave Radiometer (CIMR) mission is a proposed multichannel microwave radiometry observatory that includes L-band and four other microwave channels sharing a large mesh reflector. The mesh reflector is similar to the one that is used on SMAP, but larger. The successful SMAP demonstration of rotating large deployable mesh antennas for Earth observations has been useful to the CIMR design.
In terms of RFI detection capability, CIMR will also use an approach that is similar to SMAP. With regard to instrument thermal noise (NEDT) and data latency, CIMR meets or comes close to the next-mission desired characteristics and equals or exceeds SMAP in most of the attributes. The native L-band resolution of CIMR is ~60 km (37 mi); however, the measurements are coincident and higher-resolution measurements in this configuration allow reconstruction of L-band radiometry at higher resolution than CIMR’s L-band. It may be possible to combine the L- and C-bands and achieve a reconstructed ~15 km (9 mi) L-band product based on the coincident and overlapping measurements. A refresh rate of one day is possible with the wide-swath characteristic of CIMR.
CIMR is currently in development; the first version, CIMR-1A, is expected to launch within this decade and the second version, CIMR-1B, in the mid 2030s. Since the Copernicus program supports operational activities (e.g., numerical weather prediction), the program includes plans for follow-on CIMR observatories so that the data record will be maintained without gaps in the future.
Conclusions
The SMAP mission was launched in 2015 and has produced over 10 years of science data. Because of its unique instrument and operating characteristics, the global low-frequency microwave radiometry with the SMAP observatory has resulted in surface soil moisture, vegetation optical depth, and freeze/thaw state estimates that outperform past and current products. The data have been widely used in the Earth system science community and also applied to natural hazards applications.
The Earth system science and application communities are actively using the decade-long, high-quality global L-band radiometry. The intensity and range of SMAP science data usage is evident in the number of peer-reviewed journal publications that contain SMAP or Soil Moisture Active Passive in their title or abstract and use SMAP data in the study (i.e., search: www.webofscience.com data-base). The authors acknowledge that many publications escape this particular query approach. Currently the bibliography includes over 1700 entries and over 20,000 citations spanning several elements of Earth system science, including hydrologic science and regional and global water cycle, oceanic and atmospheric sciences, cryosphere science, global ecology as well as microwave remote sensing technologies.
To Learn More About SMAP
A more comprehensive bibliography of studies published based on SMAP data products, a set of one-page SMAP science and applications highlights in standardized format, and SMAP project documents including assessment reports are all available online via the links provided.
Acknowledgements
The authors wish to acknowledge the contributions of the SMAP Science Team, the SMAP Algorithm Development Team, and the SMAP Project Office engineers and staff. All of these teams contribute to the ongoing SMAP science product generation and uses reported in this article.
Dara Entekhabi
Massachusetts Institute of Technology
darae@mit.edu
Simon Yueh
Jet Propulsion Laboratory/California Institute of Technology
simon.h.yueh@jpl.nasa.gov
Rajat Bindlish
NASA Goddard Space Flight Center
rajat.bindlish@nasa.gov
Mark Garcia
Jet Propulsion Laboratory/California Institute of Technology
mark.d.garcia@jpl.nasa.gov
Jared Entin
NASA Headquarters
jared.k.entin@nasa.gov
Craig Ferguson
NASA Headquarters
craig.r.ferguson@nasa.gov
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By NASA
Credit: NASA NASA has chosen a group of contractors to supply multiple agency facilities with liquid and gaseous helium for at least the next two years.
The NASA Agency-wide Supply of Liquid and Gaseous Helium contract is a fixed-price indefinite-delivery requirements contract with firm-fixed-price delivery orders. The awards have a total estimated value of approximately $105.1 million. The performance period begins Wednesday, Oct. 1, to Sept. 30, 2027, with three one-year option periods that could extend the contract to Sept. 30, 2030.
The awardees include:
Messer, LLC in Bridgewater, New Jersey Linde, Inc. in Danbury, Connecticut Airgas USA, LLC in Tulsa, Oklahoma, and Long Beach, California Under this contract, contractors will supply about 2.6 million liters of liquid helium and 90.6 million standard cubic feet of gaseous helium for multiple NASA centers and their respective facilities. These include Goddard Space Flight Center in Greenbelt, Maryland, Glenn Research Center in Cleveland, Jet Propulsion Laboratory in Southern California, Johnson Space Center in Houston, Kennedy Space Center in Florida, Langley Research Center in Hampton, Virginia, Marshall Space Flight Center in Huntsville, Alabama, and Stennis Space Center in Bay St. Louis, Mississippi.
For information about the agency and its programs, visit:
https://www.nasa.gov
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Tiernan Doyle
Headquarters, Washington
202-358-1600
tiernan.doyle@nasa.gov
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA instruments and aircraft are helping identify potential sources of critical minerals across vast swaths of California, Nevada, and other Western states. Pilots gear up to reach altitudes about twice as high as those of a cruising passenger jet.NASA NASA and the U.S. Geological Survey have been mapping the planets since Apollo. One team is searching closer to home for minerals critical to national security and the economy.
If not for the Joshua trees, the tan hills of Cuprite, Nevada, would resemble Mars. Scalded and chemically altered by water from deep underground, the rocks here are earthly analogs for understanding ancient Martian geology. The hills are also rich with minerals. They’ve lured prospectors for more than 100 years and made Cuprite an ideal place to test NASA technology designed to map the minerals, craters, crusts, and ices of our solar system.
Sensors that discovered lunar water, charted Saturn’s moons, even investigated ground zero in New York City were all tested and calibrated at Cuprite, said Robert Green, a senior research scientist at NASA’s Jet Propulsion Laboratory in Southern California. He’s honed instruments in Nevada for decades.
One of Green’s latest projects is to find and map rocky surfaces in the American West that could contain minerals crucial to the nation’s economy and security. Currently, the U.S. is dependent on imports of 50 critical minerals, which include lithium and rare earth elements used in everything from rechargeable batteries to medicine.
Scientists from the U.S. Geological Survey (USGS) are searching nationwide for domestic sources. NASA is contributing to this effort with high-altitude aircraft and sensors capable of detecting the molecular fingerprints of minerals across vast, treeless expanses in wavelengths of light not visible to human eyes.
The hills of Cuprite, Nevada, appear pink and tan to the eye (top image) but they shine with mica, gypsum, and alunite among other types of minerals when imaged spectroscopically (lower image). NASA sensors used to study Earth and other rocky worlds have been tested there.USGS/Ray Kokaly The collaboration is called GEMx, the Geological Earth Mapping Experiment, and it’s likely the largest airborne spectroscopic survey in U.S. history. Since 2023, scientists working on GEMx have charted more than 190,000 square miles (500,000 square kilometers) of North American soil.
Mapping Partnership Started During Apollo
As NASA instruments fly in aircraft 60,000 feet (18,000 meters) overhead, Todd Hoefen, a geophysicist, and his colleagues from USGS work below. The samples of rock they test and collect in the field are crucial to ensuring that the airborne observations match reality on the ground and are not skewed by the intervening atmosphere.
The GEMx mission marks the latest in a long history of partnerships between NASA and USGS. The two agencies have worked together to map rocky worlds — and keep astronauts and rovers safe — since the early days of the space race.
For example, geologic maps of the Moon made in the early 1960s at the USGS Astrogeology Science Center in Flagstaff, Arizona, helped Apollo mission planners select safe and scientifically promising sites for the six crewed landings that occurred from 1969 to 1972. Before stepping onto the lunar surface, NASA’s Moon-bound astronauts traveled to Flagstaff to practice fieldwork with USGS geologists. A version of those Apollo boot camps continues today with astronauts and scientists involved in NASA’s Artemis mission.
Geophysicist Raymond Kokaly, who leads the GEMx campaign for USGS, is pictured here conducting ground-based hyperspectral imaging of rock in Cuprite, Nevada, in April 2019.USGS/Todd Hoefen The GEMx mission marks the latest in a long history of partnerships between NASA and USGS. The two agencies have worked together to map rocky worlds — and keep astronauts and rovers safe — since the early days of the space race.
Rainbows and Rocks
To detect minerals and other compounds on the surfaces of rocky bodies across the solar system, including Earth, scientists use a technology pioneered by JPL in the 1980s called imaging spectroscopy. One of the original imaging spectrometers built by Robert Green and his team is central to the GEMx campaign in the Western U.S.
About the size and weight of a minifridge and built to fly on planes, the instrument is called AVIRIS-Classic, short for Airborne Visible/Infrared Imaging Spectrometer. Like all imaging spectrometers, it takes advantage of the fact that every molecule reflects and absorbs light in a unique pattern, like a fingerprint. Spectrometers detect these molecular fingerprints in the light bouncing off or emitted from a sample or a surface.
In the case of GEMx, that’s sunlight shimmering off different kinds of rocks.
Compared to a standard digital camera, which “sees” three color channels (red, green, and blue), imaging spectrometers can see more than 200 channels, including infrared wavelengths of light that are invisible to the human eye.
NASA spectrometers have orbited or flown by every major rocky body in our solar system. They’ve helped scientists investigate methane lakes on Titan, Saturn’s largest moon, and study Pluto’s thin atmosphere. One JPL-built spectrometer is currently en route to Europa, an icy moon of Jupiter, to help search for chemical ingredients necessary to support life.
“One of the cool things about NASA is that we develop technology to look out at the solar system and beyond, but we also turn around and look back down,” said Ben Phillips, a longtime NASA program manager who led GEMx until he retired in 2025.
The Newest Instrument
More than 200 hours of GEMx flights are scheduled through fall 2025. Scientists will process and validate the data, with the first USGS mineral maps to follow. During these flights, an ER-2 research aircraft from NASA’s Armstrong Flight Research Center in Edwards, California, will cruise over the Western U.S. at altitudes twice as high as a passenger jet flies.
At such high altitudes, pilot Dean Neeley must wear a spacesuit similar to those used by astronauts. He flies solo in the cramped cockpit but will be accompanied by state-of-the-art NASA instruments. In the belly of the plane rides AVIRIS-Classic, which will be retiring soon after more than three decades in service. Carefully packed in the plane’s nose is its successor: AVIRIS-5, taking flight for the first time in 2025.
Together, the two instruments provide 10 times the performance of the older spectrometer alone, but even by itself AVIRIS-5 marks a leap forward. It can sample areas ranging from about 30 feet (10 meters) to less than a foot (30 centimeters).
“The newest generation of AVIRIS will more than live up to the original,” Green said.
More About GEMx
The GEMx research project will last four years and is funded by the USGS Earth Mapping Resources Initiative. The initiative will capitalize on both the technology developed by NASA for spectroscopic imaging, as well as the agency’s expertise in analyzing the datasets and extracting critical mineral information from them.
Data collected by GEMx is available here.
News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
Karen Fox / Elizabeth Vlock
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / elizabeth.a.vlock@nasa.gov
Written by Sally Younger
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Last Updated Jul 10, 2025 Related Terms
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Explore Webb Webb News Latest News Latest Images Webb’s Blog Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Deployment Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 5 Min Read Another First: NASA Webb Identifies Frozen Water in Young Star System
For the first time, researchers confirmed the presence of crystalline water ice in a dusty debris disk that orbits a Sun-like star, using NASA’s James Webb Space Telescope. The full artist’s concept illustration and full caption is shown below. Credits:
NASA, ESA, CSA, Ralf Crawford (STScI) Is frozen water scattered in systems around other stars? Astronomers have long expected it is, partially based on previous detections of its gaseous form, water vapor, and its presence in our own solar system.
Now there is definitive evidence: Researchers confirmed the presence of crystalline water ice in a dusty debris disk that orbits a Sun-like star 155 light-years away using detailed data known as spectra from NASA’s James Webb Space Telescope. (The term water ice specifies its makeup, since many other frozen molecules are also observed in space, such as carbon dioxide ice, or “dry ice.”) In 2008, data from NASA’s retired Spitzer Space Telescope hinted at the possibility of frozen water in this system.
“Webb unambiguously detected not just water ice, but crystalline water ice, which is also found in locations like Saturn’s rings and icy bodies in our solar system’s Kuiper Belt,” said Chen Xie, the lead author of the new paper and an assistant research scientist at Johns Hopkins University in Baltimore, Maryland.
All the frozen water Webb detected is paired with fine dust particles throughout the disk — like itsy-bitsy “dirty snowballs.” The results published Wednesday in the journal Nature.
Astronomers have been waiting for this definitive data for decades. “When I was a graduate student 25 years ago, my advisor told me there should be ice in debris disks, but prior to Webb, we didn’t have instruments sensitive enough to make these observations,” said Christine Chen, a co-author and associate astronomer at the Space Telescope Science Institute in Baltimore. “What’s most striking is that this data looks similar to the telescope’s other recent observations of Kuiper Belt objects in our own solar system.”
Water ice is a vital ingredient in disks around young stars — it heavily influences the formation of giant planets and may also be delivered by small bodies like comets and asteroids to fully formed rocky planets. Now that researchers have detected water ice with Webb, they have opened the door for all researchers to study how these processes play out in new ways in many other planetary systems.
Image: Debris Disk Around Star HD 181327 (Artist’s Concept)
For the first time, researchers confirmed the presence of crystalline water ice in a dusty debris disk that orbits a Sun-like star, using NASA’s James Webb Space Telescope. All the frozen water detected by Webb is paired with fine dust particles throughout the disk. The majority of the water ice observed is found where it’s coldest and farthest from the star. The closer to the star the researchers looked, the less water ice they found. NASA, ESA, CSA, Ralf Crawford (STScI) Rocks, Dust, Ice Rushing Around
The star, cataloged HD 181327, is significantly younger than our Sun. It’s estimated to be 23 million years old, compared to the Sun’s more mature 4.6 billion years. The star is slightly more massive than the Sun, and it’s hotter, which led to the formation of a slightly larger system around it.
Webb’s observations confirm a significant gap between the star and its debris disk — a wide area that is free of dust. Farther out, its debris disk is similar to our solar system’s Kuiper Belt, where dwarf planets, comets, and other bits of ice and rock are found (and sometimes collide with one another). Billions of years ago, our Kuiper Belt was likely similar to this star’s debris disk.
“HD 181327 is a very active system,” Chen said. “There are regular, ongoing collisions in its debris disk. When those icy bodies collide, they release tiny particles of dusty water ice that are perfectly sized for Webb to detect.”
Frozen Water — Almost Everywhere
Water ice isn’t spread evenly throughout this system. The majority is found where it’s coldest and farthest from the star. “The outer area of the debris disk consists of over 20% water ice,” Xie said.
The closer in the researchers looked, the less water ice they found. Toward the middle of the debris disk, Webb detected about 8% water ice. Here, it’s likely that frozen water particles are produced slightly faster than they are destroyed. In the area of the debris disk closest to the star, Webb detected almost none. It’s likely that the star’s ultraviolet light vaporizes the closest specks of water ice. It’s also possible that rocks known as planetesimals have “locked up” frozen water in their interiors, which Webb can’t detect.
This team and many more researchers will continue to search for — and study — water ice in debris disks and actively forming planetary systems throughout our Milky Way galaxy. “The presence of water ice helps facilitate planet formation,” Xie said. “Icy materials may also ultimately be ‘delivered’ to terrestrial planets that may form over a couple hundred million years in systems like this.”
The researchers observed HD 181327 with Webb’s NIRSpec (Near-Infrared Spectrograph), which is super-sensitive to extremely faint dust particles that can only be detected from space.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
To learn more about Webb, visit:
https://science.nasa.gov/webb
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Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Claire Blome – cblome@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
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View Webb images of other debris disks around Vega, Fomalhaut, Beta Pictoris, and AU Microscopii
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
The C-20A aircraft, based at NASA’s Armstrong Flight Research Center in Edwards, California, flies over the Sierra Nevada Mountains in California for the Dense UAVSAR Snow Time (DUST) mission on Feb. 28, 2025. The DUST mission collected airborne data about snow water to help improve water management and reservoir systems on the ground.NASA/Starr Ginn As part of a science mission tracking one of Earth’s most precious resources – water – NASA’s C-20A aircraft conducted a series of seven research flights in March that can help researchers track the process and timeline as snow melts and transforms into a freshwater resource. The agency’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) installed on the aircraft collected measurements of seasonal snow cover and estimate the freshwater contained in it.
“Seasonal snow is a critical resource for drinking water, power generation, supporting multi-billion dollar agricultural and recreation industries,” said Starr Ginn, C-20A project manager at NASA’s Armstrong Flight Research Center in Edwards, California. “Consequently, understanding the distribution of seasonal snow storage and subsequent runoff is essential.”
The Dense UAVSAR Snow Time (DUST) mission mapped snow accumulation over the Sierra Nevada mountains in California and the Rocky Mountains in Idaho. Mission scientists can use these observations to estimate the amount of water stored in that snow.
Peter Wu, radar operator from NASA’s Jet Propulsion Laboratory in Southern California, observes data collected during the Dense UAVSAR Snow Time (DUST) mission onboard NASA’s C-20A aircraft on Feb. 28, 2025. The C-20A flew from NASA’s Armstrong Flight Research Center in Edwards, California, over the Sierra Nevada Mountains to collect data about snow water.NASA/Starr Ginn “Until recently, defining the best method for accurately measuring snow water equivalent (SWE) – or how much and when fresh water is converted from snow – has been a challenge,” said Shadi Oveisgharan, principal investigator of DUST and scientist at NASA’s Jet Propulsion Laboratory in Southern California. “The UAVSAR has been shown to be a good instrument to retrieve SWE data.”
Recent research has shown that snow properties, weather patterns, and seasonal conditions in the American West have been shifting in recent decades. These changes have fundamentally altered previous expectations about snowpack monitoring and forecasts of snow runoff. The DUST mission aims to better track and understand those changes to develop more accurate estimates of snow-to-water conversions and their timelines.
“We are trying to find the optimum window during which to retrieve snow data,” Oveisgharan said. “This estimation will help us better estimate available fresh snow and manage our reservoirs better.”
The Dense UAVSAR Snow Time (DUST) mission team assembles next to the C-20A aircraft at NASA’s Armstrong Flight Research Center in Edwards, California, on Feb. 28, 2025. From left, radar operator Adam Vaccaro, avionics lead Kelly Jellison, C-20A project manager Starr Ginn, pilot Carrie Worth, pilot Troy Asher, aircraft mechanic Eric Apikian, and operations engineer Ian Elkin.NASA/Starr Ginn The DUST mission achieved a new level of snow data accuracy, which is partly due to the specialized flight paths flown by the C-20A. The aircraft’s Platform Precision Autopilot (PPA) enables the team to fly very specific routes at exact altitudes, speeds, and angles so the UAVSAR can more precisely measure terrain changes.
“Imagine the rows made on grass by a lawn mower,” said Joe Piotrowski Jr., operations engineer for NASA Armstrong’s airborne science program. “The PPA system enables the C-20A to make those paths while measuring terrain changes down to the diameter of a centimeter.”
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