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By NASA
Explore This Section Earth Earth Observer Editor’s Corner Feature Articles Meeting Summaries News Science in the News Calendars In Memoriam Announcements More Archives Conference Schedules Style Guide 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
A member of the space crop production team prepares materials for Veggie seed pillows inside the Space Systems Processing Facility at NASA’s Kennedy Space Center. NASA/Cory S Huston When the Crew-11 astronauts launched to the International Space Station on August 1, 2025, they carried with them another chapter in space farming: the latest VEG-03 experiments, complete with seed pillows ready for planting.
Growing plants provides nutrition for astronauts, as well as psychological benefits that help maintain crew morale during missions.
During VEG-03 MNO, astronauts will be able to choose what they want to grow from a seed library including Wasabi mustard greens, Red Russian Kale, and Dragoon lettuce.
From Seed to Space Salad
The experiment takes place inside Veggie, a chamber about the size of carry-on luggage. The system uses red, blue, and green LED lights to provide the right spectrum for plant growth. Clear flexible bellows — accordion-like walls that expand to accommodate maturing plants — create a semi-controlled environment around the growing area.
Astronauts plant thin strips containing their selected seeds into fabric “seed pillows” filled with a special clay-based growing medium and controlled-release fertilizer. The clay, similar to what’s used on baseball fields, helps distribute water and air around the roots in the microgravity environment.
Crew members will monitor the plants, add water as needed, and document growth through regular photographs. At harvest time, astronauts will eat some of the fresh produce while freezing other samples for return to Earth, where scientists will analyze their nutritional content and safety.
How this benefits space exploration
Fresh food will become critical as astronauts venture farther from Earth on missions to the Moon and Mars. NASA aims to validate different kinds of crops to add variety to astronaut diets during long-duration space exploration missions, while giving crew members more control over what they grow and eat.
How this benefits humanity
The techniques developed for growing crops in space’s challenging conditions may also improve agricultural practices on Earth. Indoor crop cultivation approaches similar to what astronauts do in Veggie might also be adapted for horticultural therapy programs, giving elderly or disabled individuals new ways to experience gardening when traditional methods aren’t accessible.
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NASA’s Biological and Physical Sciences Division pioneers scientific discovery and enables exploration by using space environments to conduct investigations not possible on Earth. Studying biological and physical phenomenon under extreme conditions allows researchers to advance the fundamental scientific knowledge required to go farther and stay longer in space, while also benefitting life on Earth.
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By NASA
Explore Hubble Science Hubble Space Telescope As NASA Missions Study… Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered AI and Hubble Science Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 4 min read
As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI) A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS using the crisp vision of NASA’s Hubble Space Telescope. Hubble is one of many missions across NASA’s fleet of space telescopes slated to observe this comet, together providing more information about its size and physical properties. While the comet poses no threat to Earth, NASA’s space telescopes help support the agency’s ongoing mission to find, track, and better understand near-Earth objects.
Hubble’s observations allow astronomers to more accurately estimate the size of the comet’s solid, icy nucleus. The upper limit on the diameter of the nucleus is 3.5 miles (5.6 kilometers), though it could be as small as 1,000 feet (320 meters) across, researchers report. Though the Hubble images put tighter constraints on the size of the nucleus compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA’s partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 300 million miles from the Sun. This behavior is much like the signature of previously seen Sun-bound comets originating within our solar system.
The big difference is that this interstellar visitor originated in some other solar system elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our solar system at a staggering 130,000 miles (209,000 kilometers) per hour, the highest velocity ever recorded for a solar system visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
“No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second. You can’t project that back with any accuracy to figure out where it started on its path,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations.
The paper will be published in The Astrophysical Journal Letters. It is already available on Astro-ph.
New Evidence for Population of Wandering Space Relics
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.”
This comet was discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on July 1, 2025, at a distance of 420 million miles from the Sun. ATLAS is an asteroid impact early warning system developed by the University of Hawai’i.
In the meantime, other NASA missions will provide new insight into this third interstellar interloper, helping refine our understanding of these objects for the benefit of all. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
To learn more about Hubble, visit: https://science.nasa.gov/hubble
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Comet 3I/ATLAS
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus.
Comet 3I/ATLAS Compass Image
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on July 21, 2025. The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal an angular measurement of 1/3600 of o…
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Last Updated Aug 07, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Contact Media Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
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Science Paper: Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS, PDF (1.57 MB)
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Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA has released a new proposal opportunity for industry to tap into agency know-how, resources, and expertise. The Announcement of Collaboration Opportunity (ACO), managed by the Space Technology Mission Directorate, enables valuable collaboration without financial exchanges between NASA and industry partners. Instead, companies leverage NASA subject matter experts, facilities, software, and hardware to accelerate their technologies and prepare them for future commercial and government use.
On Wednesday, NASA issued a standing ACO announcement for partnership proposals which will be available for five years and will serve as the umbrella opportunity for topic-specific appendix releases. NASA intends to issue appendices every six to 12 months to address evolving space technology needs. The 2025 ACO appendix is open for proposals until Sept. 24.
NASA will host an informational webinar about the opportunity and appendix at 2 p.m. EDT on Wednesday, Aug. 6. Interested proposers are encouraged to submit questions which will be answered during the webinar and will be available online after the webinar.
NASA teaming with industry isn’t new – decades of partnerships have resulted in ambitious missions that benefit all of humanity. But in recent years, NASA has also played a key role as a technology enabler, providing one-of-a-kind tools, resources, and infrastructure to help commercial aerospace companies achieve their goals.
Since 2015, NASA has collaborated with industry on approximately 80 ACO projects. Here are some ways the collaborations have advanced space technology:
Lunar lander systems
Blue Origin and NASA worked together on several ACOs to mature the company’s lunar lander design. NASA provided technical reports and assessments and conducted tests at multiple centers to help Blue Origin advance a stacked fuel cell system for a lander’s primary power source. Other Blue Origin ACO projects evaluated high-temperature engine materials and advanced a landing navigation and guidance system.
Blue Origin’s Blue Moon Mark 1 (MK1) lander is delivering NASA science and technology to the Moon through the agency’s Commercial Lunar Payload Services initiative. In 2023, NASA selected Blue Origin as a Human Landing System provider to develop its Blue Moon MK2 lander for future crewed lunar exploration.
Artist concept of Blue Origin’s Blue Moon Mark 1 (MK1) lander.Blue Origin Blue Origin’s Blue Moon Mark 1 (MK1) lander is delivering NASA science and technology to the Moon through the agency’s Commercial Lunar Payload Services initiative. In 2023, NASA selected Blue Origin as a Human Landing System provider to develop its Blue Moon MK2 lander for future crewed lunar exploration.
Cryogenic fluid transfer
Throughout a year-long ACO, NASA and SpaceX engineers worked together to perform in-depth computational fluid analysis of proposed propellant transfer methods between two SpaceX Starship spacecraft in low-Earth orbit. The SpaceX-specific analysis utilized Starship flight data and data from previous NASA research and development to identify potential risks and help mitigate them during the early stages of commercial development. NASA also provided inputs as SpaceX developed an initial concept of operations for its orbital propellant transfer missions.
Artist’s concept of Starship propellant transfer in space.SpaceX SpaceX used the ACO analyses to inform the design of its Starship Human Landing System, which NASA selected in 2021 to put the first Artemis astronauts on the Moon.
Autonomous spacecraft navigation solution
Advanced Space and NASA partnered to advance the company’s Cislunar Autonomous Positioning System – software that allows lunar spacecraft to determine their location without relying exclusively on tracking from Earth.
Dylan Schmidt, CAPSTONE assembly integration and test lead, installs solar panels onto the CAPSTONE spacecraft at Tyvak Nano-Satellite Systems, Inc., in Irvine, California.NASA/Dominic Hart The CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) spacecraft launched to the Moon in 2022 and continues to operate and collect critical data to refine the software. Under the ACO, Advanced Space was able to use NASA’s Lunar Reconnaissance Orbiter to conduct crosslink experiments with CAPSTONE, helping mature the navigation solution for future missions. The mission’s Cislunar Autonomous Positioning System technology was initially supported through the NASA Small Business Innovation Research program.
Multi-purpose laser sensing system
Sensuron and NASA matured a miniature, rugged fiber optic sensing system capable of taking thermal and shape measurements for multiple applications. Throughout the ACO, Sensuron benefitted from NASA’s expertise in fiber optics and electrical, mechanical, and system testing engineering to design, fabricate, and “shake and bake” its prototype laser.
NASA’s Armstrong Flight Research Center’s FOSS, Fiber Optic Sensing System, recently supported tests of a system designed to turn oxygen into liquid oxygen, a component of rocket fuel. Patrick Chan, electronics engineer, and NASA Armstrong’s FOSS portfolio project manager, shows fiber like that used in the testing.NASA/Genaro Vavuris Space missions could use the technology to monitor cryogenic propellant levels and determine a fuel tank’s structural integrity throughout an extended mission. The laser technology also has medical applications on Earth, which ultimately resulted in the Sensuron spinoff company, The Shape Sensing Company.
Flexible lunar tires
In 2023, Venturi Astrolab began work with NASA under an ACO to test its flexible lunar tire design. The company tapped into testing capabilities unique to NASA, including heat transfer to cold lunar soil, traction, and life testing. The data validated the performance of tire prototypes, helping ready the design to support future NASA missions.
In 2024, NASA selected three companies, including Venturi Astrolab, to advance capabilities for a lunar terrain vehicle that astronauts could use to travel around the lunar surface, conducting scientific research on the Moon and preparing for human missions to Mars.
Venturi Lab designed and developed a durable, robust, and hyper-deformable lunar wheel.Venturi Lab The Announcement of Collaboration Opportunity (ACO) is one of many ways NASA enables commercial industry to develop, build, own, and eventually operate space systems. To learn more about these technology projects and more, visit: https://techport.nasa.gov/.
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Last Updated Jul 30, 2025 EditorLoura Hall Related Terms
Space Technology Mission Directorate Communicating and Navigating with Missions Small Spacecraft Technology Program Space Communications Technology Technology Technology Transfer & Spinoffs View the full article
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By NASA
NASA’s TRACERS (Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites) mission launched at 2:13 p.m. EDT atop a SpaceX Falcon 9 rocket at Space Launch Complex 4 East at Vandenberg Space Force Base in California. Credit: SpaceX NASA’s newest mission, TRACERS, soon will begin studying how Earth’s magnetic shield protects our planet from the effects of space weather. Short for Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites, the twin TRACERS spacecraft lifted off at 11:13 a.m. PDT (2:13 p.m. EDT) Wednesday aboard a SpaceX Falcon 9 rocket from Space Launch Complex 4 East at Vandenberg Space Force Base in California.
“NASA is proud to launch TRACERS to demonstrate and expand American preeminence in space science research and technology,” said acting NASA Administrator Sean Duffy. “The TRACERS satellites will move us forward in decoding space weather and further our understanding of the connection between Earth and the Sun. This mission will yield breakthroughs that will advance our pursuit of the Moon, and subsequently, Mars.”
The twin satellites will fly one behind the other – following as closely as 10 seconds apart over the same location – and will take a record-breaking 3,000 measurements in one year to build a step-by-step picture of how magnetic reconnection changes over time.
Riding along with TRACERS aboard the Falcon 9 were NASA’s Athena EPIC (Economical Payload Integration Cost), PExT (Polylingual Experimental Terminal), and REAL (Relativistic Electron Atmospheric Loss) missions – three small satellites to demonstrate new technologies and gather scientific data. These three missions were successfully deployed, and mission controllers will work to contact them over the coming hours and days.
Ground controllers for the TRACERS mission established communications with the second of the two spacecraft at 3:43 p.m. PDT (6:43 p.m. EDT), about 3 hours after it separated from the rocket. During the next four weeks, TRACERS will undergo a commissioning period during which mission controllers will check out their instruments and systems.
Once cleared, the twin satellites will begin their 12-month prime mission to study a process called magnetic reconnection, answering key questions about how it shapes the impacts of the Sun and space weather on our daily lives.
“NASA’s heliophysics fleet helps to safeguard humanity’s home in space and understand the influence of our closest star, the Sun,” said Joe Westlake, heliophysics division director at NASA Headquarters in Washington. “By adding TRACERS to that fleet, we will gain a better understanding of those impacts right here at Earth.”
The two TRACERS spacecraft will orbit through an open region in Earth’s magnetic field near the North Pole, called the polar cusp. Here, TRACERS will investigate explosive magnetic events that happen when the Sun’s magnetic field – carried through space in a stream of solar material called the solar wind – collides with Earth’s magnetic field. This collision creates a buildup of energy that causes magnetic reconnection, when magnetic field lines snap and explosively realign, flinging away nearby particles at high speeds.
Flying through the polar cusp allows the TRACERS satellites to study the results of these magnetic explosions, measuring charged particles that race down into Earth’s atmosphere and collide with atmospheric gases – giving scientist the tools to reconstruct exactly how changes in the incoming solar wind affect how, and how quickly, energy and particles are coupled into near-Earth space.
“The successful launch of TRACERS is a tribute to many years of work by an excellent team,” said David Miles, TRACERS principal investigator at the University of Iowa. “TRACERS is set to transform our understanding of Earth’s magnetosphere. We’re excited to explore the dynamic processes driving space weather.”
Small Satellites Along for Ride
Athena EPIC is a pathfinder mission that will demonstrate NASA’s use of an innovative and configurable commercial SmallSat architecture to improve flexibility of payload designs, reduce launch schedule, and reduce overall costs in future missions, as well as the benefits of working collaboratively with federal partners. In addition to this demonstration for NASA, once the Athena EPIC satellite completes its two-week commissioning period, the mission will spend the next 12 months taking measurements of outgoing longwave radiation from Earth.
The PExT demonstration will test interoperability between commercial and government communication networks for the first time by demonstrating a wideband polylingual terminal in low Earth orbit. This terminal will use software-defined radios to jump between government and commercial networks, similar to cell phones roaming between providers on Earth. These terminals could allow future missions to switch seamlessly between networks and access new commercial services throughout its lifecycle in space.
The REAL mission is a CubeSat that will investigate how energetic electrons are scattered out of the Van Allen radiation belts and into Earth’s atmosphere. Shaped like concentric rings high above Earth’s equator, the Van Allen belts are composed of a mix of high-energy electrons and protons that are trapped in place by Earth’s magnetic field. Studying electrons and their interactions, REAL aims to improve our understanding of these energetic particles that can damage spacecraft and imperil astronauts who pass through them.
The TRACERS mission is led by David Miles at the University of Iowa with support from the Southwest Research Institute in San Antonio, Texas. NASA’s Heliophysics Explorers Program Office at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, manages the mission for the Heliophysics Division at NASA Headquarters in Washington. The University of Iowa, Southwest Research Institute, University of California, Los Angeles, and the University of California, Berkeley, all lead instruments on TRACERS.
The Athena EPIC mission is led by NASA’s Langley Research Center in Hampton, Virginia, and is a partnership between National Oceanic and Atmospheric Administration, U.S. Space Force, and NovaWurks. Athena EPIC’s launch is supported by launch integrator SEOPS. The PExT demonstration is managed by NASA’s SCaN (Space Communications and Navigation) program in partnership with Johns Hopkins Applied Physics Laboratory, with launch support by York Space Systems. The REAL project is led by Dartmouth College in Hanover, New Hampshire, and is a partnership between Johns Hopkins Applied Physics Laboratory, Montana State University, and Boston University. Sponsored by NASA’s Heliophysics Division and CubeSat Launch Initiative, it was included through launch integrator Maverick Space Systems.
NASA’s Launch Services Program, based at the agency’s Kennedy Space Center in Florida, manages the VADR (Venture-class Acquisition of Dedicated and Rideshare) contract.
To learn more about TRACERS, visit:
https://nasa.gov/tracers
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Abbey Interrante / Karen Fox
Headquarters, Washington
301-201-0124 / 202-358-1600
abbey.a.interrante@nasa.gov / karen.c.fox@nasa.gov
Sarah Frazier
Goddard Space Flight Center, Greenbelt, Maryland
202-853-7191
sarah.frazier@nasa.gov
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Last Updated Jul 23, 2025 LocationNASA Headquarters Related Terms
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