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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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Last Updated Aug 18, 2025 Related Terms
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By NASA
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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.
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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
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Editor’s Note: The following is one of three related articles about the NASA Data Acquisition System and related efforts. Please visit Stennis News – NASA to access accompanying articles.
A blended team of NASA personnel and contractors support ongoing development and operation of the NASA Data Acquisition System at NASA’s Stennis Space Center. Team members include, left to right: Andrew Graves (NASA), Shane Cravens (Syncom Space Services), Peggi Marshall (Syncom Space Services), Nicholas Payton Karno (Syncom Space Services), Alex Elliot (NASA), Kris Mobbs (NASA), Brandon Carver (NASA), Richard Smith (Syncom Space Services), and David Carver (NASA)NASA/Danny Nowlin Members of the NASA Data Acquisition System team at NASA’s Stennis Space Center evaluate system hardware for use in monitoring and collecting propulsion test data at the site.NASA/Danny Nowlin NASA software engineer Alex Elliot, right, and Syncom Space Services software engineer Peggi Marshall fine-tune data acquisition equipment at NASA’s Stennis Space Center by adjusting an oscilloscope to capture precise measurements. NASA/Danny Nowlin Syncom Space Services software test engineer Nicholas Payton Karno monitors a lab console at NASA’s Stennis Space Center displaying video footage of an RS-25 engine gimbal test, alongside data acquisition screens showing lab measurements. NASA/Danny Nowlin Just as a steady heartbeat is critical to staying alive, propulsion test data is vital to ensure engines and systems perform flawlessly.
The accuracy of the data produced during hot fire tests at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, tells the performance story.
So, when NASA needed a standardized way to collect hot fire data across test facilities, an onsite team created an adaptable software tool to do it.
“The NASA Data Acquisition System (NDAS) developed at NASA Stennis is a forward-thinking solution,” said David Carver, acting chief of the Office of Test Data and Information Management. “It has unified NASA’s rocket propulsion testing under an adaptable software suite to meet needs with room for future expansion, both within NASA and potentially beyond.”
Before NDAS, contractors conducting test projects used various proprietary tools to gather performance data, which made cross-collaboration difficult. NDAS takes a one-size-fits-all approach, providing NASA with its own system to ensure consistency.
“Test teams in the past had to develop their own software tools, but now, they can focus on propulsion testing while the NDAS team focuses on developing the software that collects data,” said Carver.
A more efficient workflow has followed since the software system is designed to work with any test hardware. It allows engineers to seamlessly work between test areas, even when upgrades have been made and hardware has changed, to support hot fire requirements for the agency and commercial customers.
With the backing and resources of the NASA Rocket Propulsion Test (RPT) Program Office, a blended team of NASA personnel and contractors began developing NDAS in 2011 as part of the agency’s move to resume control of test operations at NASA Stennis. Commercial entities had conducted the operations on NASA’s behalf for several decades.
The NASA Stennis team wrote the NDAS software code with modular components that function independently and can be updated to meet the needs of each test facility. The team used LabVIEW, a graphical platform that allows developers to build software visually rather than using traditional text-based code.
Syncom Space Services software engineer Richard Smith, front, analyzes test results using the NASA Data Acquisition System Displays interface at NASA’s Stennis Space Center while NASA software engineer Brandon Carver actively tests and develops laboratory equipment. NASA/Danny Nowlin NASA engineers, from left to right, Tristan Mooney, Steven Helmstetter Chase Aubry, and Christoffer Barnett-Woods are shown in the E-1 Test Control Center where the NASA Data Acquisition System is utilized for propulsion test activities. NASA/Danny Nowlin NASA engineers Steven Helmstetter, Christoffer Barnett-Woods, and Tristan Mooney perform checkouts on a large data acquisition system for the E-1 Test Stand at NASA’s Stennis Space Center. The data acquisition hardware, which supports testing for E Test Complex commercial customers, is controlled by NASA Data Acquisition System software that allows engineers to view real-time data while troubleshooting hardware configuration.NASA/Danny Nowlin NASA engineers Steven Helmstetter, left, and Tristan Mooney work with the NASA Data Acquisition System in the E-1 Test Control Center, where the system is utilized for propulsion test activities.NASA/Danny Nowlin “These were very good decisions by the original team looking toward the future,” said Joe Lacher, a previous NASA project manager. “LabVIEW was a new language and is now taught in colleges and widely used in industry. Making the program modular made it adaptable.”
During propulsion tests, the NDAS system captures both high-speed and low-speed sensor data. The raw sensor data is converted into units for both real-time monitoring and post-test analysis.
During non-test operations, the system monitors the facility and test article systems to help ensure the general health and safety of the facility and personnel.
“Having quality software for instrumentation and data recording systems is critical and, in recent years, has become increasingly important,” said Tristan Mooney, NASA instrumentation engineer. “Long ago, the systems used less software, or even none at all. Amplifiers were configured with physical knobs, and data was recorded on tape or paper charts. Today, we use computers to configure, display, and store data for nearly everything.”
Developers demonstrated the new system on the A-2 Test Stand in 2014 for the J-2X engine test project.
From there, the team rolled it out on the Fred Haise Test Stand (formerly A-1), where it has been used for RS-25 engine testing since 2015. A year later, teams used NDAS on the Thad Cochran Test Stand (formerly B-2) in 2016 to support SLS (Space Launch System) Green Run testing for future Artemis missions.
One of the project goals for the system is to provide a common user experience to drive consistency across test complexes and centers.
Kris Mobbs, current NASA project manager for NDAS, said the system “really shined” during the core stage testing. “We ran 24-hour shifts, so we had people from across the test complex working on Green Run,” Mobbs said. “When the different shifts came to work, there was not a big transition needed. Using the software for troubleshooting, getting access to views, and seeing the measurements were very common activities, so the various teams did not have a lot of build-up time to support that test.”
Following success at the larger test stands, teams started using NDAS in the E Test Complex in 2017, first at the E-2 Test Stand, then on the E-1 and E-3 stands in 2020.
Growth of the project was “a little overwhelming,” Lacher recalled. The team maintained the software on active stands supporting tests, while also continuing to develop the software for other areas and their many unique requirements.
Each request for change had to be tracked, implemented into the code, tested in the lab, then deployed and validated on the test stands.
“This confluence of requirements tested my knowledge of every stand and its uniqueness,” said Lacher. “I had to understand the need, the effort to meet it, and then had to make decisions as to the priorities the team would work on first.”
Creation of the data system and its ongoing updates have transformed into opportunities for growth among the NASA Stennis teams working together.
“From a mechanical test operations perspective, NDAS has been a pretty easy system to learn,” said Derek Zacher, NASA test operations engineer. “The developers are responsive to the team’s ideas for improvement, and our experience has consistently improved with the changes that enable us to view our data in new ways.”
Originally designed to support the RPT office at NASA Stennis, the software is expanding beyond south Mississippi to other test centers, attracting interest from various NASA programs and projects, and garnering attention from government agencies that require reliable and scalable data acquisition. “It can be adopted nearly anywhere, such as aerospace and defense, research and development institutions and more places, where data acquisition systems are needed,” said Mobbs. “It is an ever-evolving solution.”
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Last Updated May 08, 2025 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Dwane Roth (right), a fourth generation grain farmer in Finney County, Kansas, stands with nephew Zion (left) in one of their corn fields. Roth’s farm became one of the first Water Technology Farms in Kansas around 2016, and he has been using OpenET data for the past few years to track evapotranspiration rates and conserve water. Photo courtesy of Dwane Roth A NASA and U.S. Geological Survey (USGS)-supported research and development team is making it easier for farmers and ranchers to manage their water resources.
The team, called OpenET, created the Farm and Ranch Management Support (FARMS) tool, which puts timely, high-resolution water data directly in the hands of individuals and small farm operators. By making the information more accessible, the platform can better support decision-making around agricultural planning, water conservation, and water efficiency. The OpenET team hopes this will help farmers who are working to build greater resiliency in local and regional agriculture communities. build greater resiliency in local and regional agriculture communities.
“It’s all about finding new ways to make satellite data easier to access and use for as many people as possible,” said Forrest Melton, the OpenET project scientist at NASA’s Ames Research Center in Silicon Valley. “The goal is to empower users with actionable, science-based data to support decisions about water management across the West.”
The goal is to empower users with actionable, science-based data to support decisions about water management across the West.
Forrest melton
OpenET Project Scientist
OpenET Data Explorer Tool: The Road to FARMS
The OpenET data explorer tool centers on providing evapotranspiration data. Evapotranspiration (ET) refers to the amount of water leaving Earth’s surface and returning to the atmosphere through evaporation (from soil and surface water) and transpiration (water vapor released by crops and other plants). Evapotranspiration is an important factor in agriculture, water resource management, irrigation planning, drought monitoring, and fire risk evaluation.
The FARMS resource is the third phase of OpenET’s Data Explorer tool, launched in 2021, which uses satellite data to quantify evapotranspiration across the western U.S.
It starts with using Landsat data to measure patterns in land surface temperature and key indicators of vegetation conditions. The satellite data is combined with agricultural data, such as field boundaries, and weather data, such as air temperature, humidity, solar radiation, wind speed, and precipitation. All of these factors feed into a model, which calculates the final evapotranspiration data.
The new FARMS interface was designed to make that data easier to access, with features that meet specific needs identified by users.
“This amount of data can be complicated to use, so user input helped us shape FARMS,” said Jordan Harding, app developer and interface design leader from HabitatSeven. “It provides a mobile-friendly, map-based web interface designed to make it easy as possible to get automated, regular reports.”
Top: A section of the 2024 annual report Roth submits to the Farm Service Agency, with hand-written annotations marking which crop will be grown that year. Bottom: Those same fields in the new OpenET FARMS interface, with a dashboard on the left displaying evapotranspiration data over the course of 2024 at monthly intervals. Each color line corresponds to the same color field on the map, showcasing how much evapotranspiration rates can differ between different crops in the same vicinity. The unique shape of the purple field (forage sorghum), is an example of a case where FARMS’ custom shape feature is helpful. Once the initial report is set up, Roth can re-run reports for the same fields at any time. NASA/OpenET “The FARMS tool is designed to help farmers optimize irrigation timing and amounts, simplify planning for the upcoming irrigation season, and automate ET and water use reporting,” said Sara Larsen, CEO of OpenET. “All of this reduces waste, lowers costs, and informs crop planning.”
Although FARMS is geared towards agriculture, the tool has value for other audiences in the western U.S. Land managers who evaluate the impacts of wildfire can use it to evaluate burn scars and changes to local hydrology. Similarly, resource managers can track evapotranspiration changes over time to evaluate the effectiveness of different forest management plans.
New Features in FARMS
To develop FARMS, the OpenET team held listening sessions with farmers, ranchers, and resource managers. One requested function was support for field-to-field comparisons; a feature for planning irrigation needs and identifying problem areas, like where pests or weeds may be impacting crop yields.
The tool includes numerous options for drawing or selecting field boundaries, generating custom reports based on selected models and variables, and automatically re-running reports at daily or monthly intervals.
The fine spatial resolution and long OpenET data record behind FARMS make these features more effective. Many existing global ET data products have a pixel size of over half a mile, which is too big to be practical for most farmers and ranchers. The FARMS interface provides insights at the scale of a quarter-acre per pixel, which offers multiple data points within an individual field.
“If I had told my father about this 15 years ago, he would have called me crazy,” said Dwane Roth, a fourth-generation farmer in Kansas. “Thanks to OpenET, I can now monitor water loss from my crops in real-time. By combining it with data from our soil moisture probes, this tool is enabling us to produce more food with less water. It’s revolutionizing agriculture.”
The FARMS mobile interface displays a six-year evapotranspiration report of a pear orchard owned by sixth-generation California farmer Brett Baker. The purple line in the dashboard report (left) corresponds with the field selected in purple on the map view (right), which users can toggle between using the green buttons in the top right corners. Running multi-year reports allows farmers to review historical trends.NASA/OpenET For those like sixth-generation California pear farmer Brett Baker, the 25-year span of ET data is part of what makes the tool so valuable. “My family has been farming the same crop on the same piece of ground for over 150 years,” Baker said. “Using FARMS gives us the ability to review historical trends and changes to understand what worked and what didn’t year to year: maybe I need to apply more fertilizer to that field, or better weed control to another. Farmers know their land, and FARMS provides a new tool that will allow us to make better use of land and resources.”
According to Roth, the best feature of the tool is intangible. “Being a farmer is stressful,” Roth said. “OpenET is beneficial for the farm and the agronomic decisions, but I think the best thing it gives me is peace of mind.”
Being a farmer is stressful. OpenET is beneficial for the farm and the agronomic decisions, but I think the best thing it gives me is peace of mind.
Dwane Roth
Fourth-Generation Kansas Grain Farmer
Continuing Evolution of FARMS
Over the coming months, the OpenET team plans to present the new tool at agricultural conferences and conventions in order to gather feedback from as many users as possible. “We know that there is already a demand for a seven-day forecast of ET, and I’m sure there will be requests about the interface itself,” said OpenET senior software engineer Will Carrara. “We’re definitely looking to the community to help us further refine that platform.”
“I think there are many applications we haven’t even thought of yet,” Baker added. “The FARMS interface isn’t just a tool; it’s an entirely new toolbox itself. I’m excited to see what people do with it.”
FARMS was developed through a public-private collaboration led by NASA, USGS, USDA, the non-profit OpenET, Inc., Desert Research Institute, Environmental Defense Fund, Google Earth Engine, HabitatSeven, California State University Monterey Bay, Chapman University, Cornell University, University of Nebraska-Lincoln, UC Berkeley and other universities, with input from more than 100 stakeholders.
To use FARMS, please visit: https://farms.etdata.org/
For additional resources/tutorials on how to use FARMS, please visit: https://openet.gitbook.io/docs/additional-resources/farms
About the Author
Milan Loiacono
Science Communication SpecialistMilan Loiacono is a science communication specialist for the Earth Science Division at NASA Ames Research Center.
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Last Updated Mar 04, 2025 Related Terms
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Artist concept highlighting the novel approach proposed by the 2025 NIAC awarded selection of SUPREME-QG: Space-borne Ultra-Precise Measurement of the Equivalence Principle Signature of Quantum GravityNASA/Selim Shahriar Selim Shahriar
Northwestern University, Evanston
Progress in physics has largely been driven by the development and verification of new theories that unify different fundamental forces of nature. For example, Maxwell revolutionized physics with his unified theory of electricity and magnetism, and the Standard Model of particle physics provides a consistent description of all fundamental forces (electromagnetic, strong, and weak) except for gravity. The major barrier to completing the quest for unification is that General Relativity (GR), the current theory of gravity, cannot be reconciled with QM. Theories of Quantum Gravity (TQG), which are yet untested, prescribe modifications of both GR and QM in a manner that makes them consistent with each other. Tests of TQG represent arguably the greatest challenge facing our understanding of the Universe. The most promising way to test TQG is to search for violation of the Equivalence Principle (EP), a fundamental tenet of GR which states that all objects experience the same acceleration in a gravitational field. Violation of EP is characterized by a nonzero Eotvos parameter, Eta, defined as the ratio of the relative acceleration to the mean acceleration experienced by two objects with different inertial masses in a gravitational field. EP violations at the level of Eta < 10^(-18) arise in many versions of TQG (e.g., string theory). The most precise test of the EP to date has been carried out under the space-borne MICROSCOPE experiment employing classical accelerometers, constraining the value of Eta to <1.5×10^(-15). We propose to investigate the use of a radically new method that leverages quantum entanglement to test the EP with extreme precision, at the level of Eta ~ 10^(-20), using a space-borne platform. This method is described in a recent paper by us (PRD 108, 024011, ’23). It makes use of simultaneous Schroedinger Cat (SC) state atom interferometers (AIs) with two isotopes of Rb. Consisting of N=10^6 atoms, the SC state, which is a maximally entangled quantum state generated via spin-squeezing of cold atoms in an optical cavity, acts as a single particle, in a superposition of two collective states, enhancing the sensitivity by a factor of ~root(N)=10^3. Such large-N SC states are difficult to create and have not been observed yet, let alone leveraged for precision metrology. In another recent paper, we described a novel protocol, namely the generalized echo squeezing protocol (GESP), to overcome the challenges of creating such a state (PRA 107, 032610, ’23). We will demonstrate the functionality of this method in a testbed to enable a follow-on space-borne mission capable of testing the EP at the level of Eta ~ 10^(-20). If EP violation is observed, the version of TQG that agrees most closely with the result would form the foundation for a complete theory governing the universe, including its birth: the Big Bang. A null result would force physicists to conceive an entirely new approach to addressing the irreconcilability of GR and QM, fundamentally altering the course of theoretical physics. Either outcome would represent one of the greatest developments in our quest for understanding nature. The SC-state AI (SCAI), also holds the promise of revolutionary improvements in the precision of gravitational cartography and inertial navigation, when configured for simultaneous accelerometry and rotation sensing. The sensitivity of such a sensor, for one second averaging time, would be ~0.9 femto-g for accelerometry, and ~0.5 pico-degree/hour for rotation sensing. This would represent an improvement by a factor of ~10^5 over the best conventional accelerometer, and a factor of ~10^4 over the best conventional gyroscopes. As such, the SCAI would find widespread usage in defense as well as non-defense sectors, including deep-space exploration, for inertial navigation. A space-borne SCAI would be able to carry out gravitational cartography with a resolution far greater than that achieved using the GRACE-FO satellites.
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Last Updated Jan 10, 2025 EditorLoura Hall Related Terms
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