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Explore This Section Science Science Activation Sun at the Center: Teacher… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 3 min read
Sun at the Center: Teacher Ambassadors Bring Heliophysics to Classrooms Nationwide
For the fourth year in a row, the American Association of Physics Teachers, a collaborator on the NASA Heliophysics Education Activation Team (HEAT), selected eight new educators to serve as ambassadors for heliophysics education. Meeting in Boulder, CO, from July 14-17, 2025, these teachers met to work through AAPT’s lessons that bring physics content to life in the context of NASA heliophysics missions and the Framework for Heliophysics Education.
The Ambassador program began in 2022 as an effort to identify highly-motivated secondary and tertiary educators who could encourage other educators to integrate NASA content into their teaching. The impact is clear – a handful of Ambassadors in the past few years have joined the program directly as a result of previous educators.
New Jersey high school physics and astronomy teacher Erin Bontempo first learned about the program at the spring meeting of the National Science Teaching Association (NSTA). She attended a workshop led by Hava Turkakin and Francesca Viale, 2023 and 2024 Ambassadors and community college faculty. In a 60-minute interactive session, Hava and Francesca shared brief snapshots of four of AAPT’s lessons, connecting heliophysics to topics traditionally taught in core science courses, such as motion, light, and magnetism.
Erin was intrigued by the lessons she saw: “When I began teaching astronomy eight years ago, I knew little about space. Ever since, I have been an avid student, constantly reading, researching, and in awe of the current NASA missions. I often look for courses to take to further my knowledge, and I feel like this is a perfect fit. When I attended the NSTA conference session on HEAT, it just clicked. The lessons that they brought using real data are the kind of exposure students need.”
Ultimately, Erin was invited to be an Ambassador herself, along with seven other educators, to take part in the summit experience in Boulder. In addition to learning about heliophysics with the AAPT leadership team, the group visited the National Space Weather Prediction Center to hear first-hand how NASA, NOAA, and various federal and international agencies work to understand and respond to our changing Sun.
Since the program began, 32 Ambassadors have been identified and participated in the multi-day professional learning experience, followed by a year of leadership and outreach to other educators. Beyond their own classrooms, they have reached educators across 36 local, state, and national events, holding extended workshops with nearly 500 other teachers.
In addition to AAPT’s lessons, the AAPT/NASA HEAT Resources webpage also provides the names and states for all ambassadors as well as the schedule and topics for the upcoming ‘Physics in an Astronomy Context’ series of free online mini-workshops being planned for the 2025 Fall semester.
NASA HEAT is part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, real content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn/about-science-activation/
Linh Ho and Samuel S. Macintire analyze the motion of a coronal mass ejection from the Sun. Share
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s Psyche captured images of Earth and our Moon from about 180 million miles (290 kilometers) away in July 2025, as it calibrated its imager instrument. When choosing targets for the imager testing, scientists look for bodies that shine with reflected sunlight, just as the asteroid Psyche does.NASA/JPL-Caltech/ASU Headed for a metal-rich asteroid of the same name, the Psyche spacecraft successfully calibrated its cameras by looking homeward.
On schedule for its 2029 arrival at the asteroid Psyche, NASA’s Psyche spacecraft recently looked back toward home and captured images of Earth and our Moon from about 180 million miles (290 million kilometers) away. The images were obtained during one of the mission team’s periodic checkouts of the spacecraft’s science instruments.
On July 20 and July 23, the spacecraft’s twin cameras captured multiple long-exposure (up to 10-second) pictures of the two bodies, which appear as dots sparkling with reflected sunlight amid a starfield in the constellation Aries.
Learn more about the multispectral imager aboard Psyche that will use a pair of identical cameras with filters and telescopic lenses to photograph the surface of the asteroid in different wavelengths of light. NASA/JPL-Caltech/ASU The Psyche multispectral imager instrument comprises a pair of identical cameras equipped with filters and telescopic lenses to photograph the asteroid Psyche’s surface in different wavelengths of light. The color and shape of a planetary body’s spectrum can reveal details about what it’s made of. The Moon and the giant asteroid Vesta, for example, have similar kinds of “bumps and wiggles” in their spectra that scientists could potentially also detect at Psyche. Members of the mission’s science team are interested in Psyche because it will help them better understand the formation of rocky planets with metallic cores, including Earth.
When choosing targets for the imager testing and calibration, scientists look for bodies that shine with reflected sunlight, just as the asteroid Psyche does. They also look at objects that have a spectrum they’re familiar with, so they can compare previous telescopic or spacecraft data from those objects with what Psyche’s instruments observe. Earlier this year, Psyche turned its lenses toward Jupiter and Mars for calibration — each has a spectrum more reddish than the bluer tones of Earth. That checkout also proved a success.
The Psyche spacecraft is taking a spiral path around the solar system in order to get a boost from a Mars gravity assist in 2026. It will arrive at the asteroid Psyche in 2029. NASA/JPL-Caltech To determine whether the imager’s performance is changing, scientists also compare data from the different tests. That way, when the spacecraft slips into orbit around Psyche, scientists can be sure that the instrument behaves as expected.
“After this, we may look at Saturn or Vesta to help us continue to test the imagers,” said Jim Bell, the Psyche imager instrument lead at Arizona State University in Tempe. “We’re sort of collecting solar system ‘trading cards’ from these different bodies and running them through our calibration pipeline to make sure we’re getting the right answers.”
Strong and Sturdy
The imager wasn’t the only instrument that got a successful checkout in late July: The mission team also put the spacecraft’s magnetometer and the gamma-ray and neutron spectrometer through a gamut of tests — something they do every six months.
“We are up and running, and everything is working well,” said Bob Mase, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Southern California. “We’re on target to fly by Mars in May 2026, and we are accomplishing all of our planned activities for cruise.”
That flyby is the spacecraft’s next big milestone, when it will use the Red Planet’s gravity as a slingshot to help the spacecraft get to the asteroid Psyche. That will mark Psyche’s first of two planned loops around the solar system and 1 billion miles (1.6 billion kilometers) since launching from NASA’s Kennedy Space Center in October 2023.
More About Psyche
The Psyche mission is led by ASU. Lindy Elkins-Tanton of the University of California, Berkeley is the principal investigator.A division of Caltech in Pasadena, JPL is responsible for the mission’s overall management, system engineering, integration and test, and mission operations. Maxar Technologies in Palo Alto, California, provided the high-power solar electric propulsion spacecraft chassis. ASU leads the operations of the imager instrument, working in collaboration with Malin Space Science Systems in San Diego on the design, fabrication, and testing of the cameras.
Psyche is the 14th mission selected as part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. NASA’s Launch Services Program, based at Kennedy, managed the launch service.
For more information about NASA’s Psyche mission go to:
http://www.science.nasa.gov/mission/psyche
Check out the Psyche spacecraft’s trajectory in 3D News Media Contacts
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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
Explore Hubble 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 2 min read
Hubble Examines Low Brightness, High Interest Galaxy
This NASA/ESA Hubble Space Telescope image features a portion of the spiral galaxy NGC 45. ESA/Hubble & NASA, D. Calzetti, R. Chandar; Acknowledgment: M. H. Özsaraç This NASA/ESA Hubble Space Telescope image zooms in on the feathery spiral arms of the galaxy NGC 45, which lies just 22 million light-years away in the constellation Cetus (the Whale).
The portrait uses data drawn from two complementary observing programs. The first took a broad view of 50 nearby galaxies, leveraging Hubble’s ability to observe ultraviolet through visible into near-infrared light to study star formation in these galaxies. The second program examined many of the same nearby galaxies as the first, narrowing in on a particular wavelength of red light called H-alpha. Star-forming nebulae are powerful producers of H-alpha light, and several of these regions are visible across NGC 45 as bright pink-red patches.
These observing programs aimed to study star formation in galaxies of different sizes, structures, and degrees of isolation — and NGC 45 is a particularly interesting target. Though it may appear to be a regular spiral galaxy, NGC 45 is a remarkable type called a low surface brightness galaxy.
Low surface brightness galaxies are fainter than the night sky itself, making them incredibly difficult to detect. They appear unexpectedly faint because they have relatively few stars for the volume of gas and dark matter they carry. In the decades since astronomers serendipitously discovered the first low surface brightness galaxy in 1986, researchers have learned that 30–60% of all galaxies may fall into this category. Studying these hard-to-detect galaxies is key to understanding how galaxies form and evolve, and Hubble’s sensitive instruments are equal to the task.
Text Credit: ESA/Hubble
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Last Updated Aug 14, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Astrophysics Astrophysics Division Galaxies Galaxies, Stars, & Black Holes Hubble Space Telescope Spiral Galaxies Star-forming Nebulae Stars The Universe Keep Exploring Discover More Topics From Hubble
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By NASA
NASA Honor Award recipients are shown with their award plaques, alongside NASA Stennis Space Center Director John Bailey and Deputy Director Christine Powell, following the ceremony at NASA Stennis on Aug. 13. Pictured (left to right) is Andrew Bracey, Briou Bourgeois, Jared Grover, Robert Simmers, Robert Williams, Richard Wear, Tom Stanley, Alison Dardar, Marvin Horne, Cary Tolman, Tim Pierce, Rebecca Mataya, Bailey, Powell, Gina Ladner, and Brittany Bouche. NASA/Danny Nowlin NASA Stennis Space Center Director John Bailey speaks to employees during the NASA Honor Awards ceremony at NASA Stennis on Aug. 13. NASA/Danny Nowlin NASA Stennis Space Center Director John Bailey and Deputy Director Christine Powell presented NASA Honor Awards to employees during an onsite ceremony Aug. 13.
One NASA Stennis employee received NASA’s Outstanding Leadership Medal. The medal is awarded to government employees for notable leadership accomplishments that have significantly influenced the NASA mission.
Marvin Horne of Fulton, Maryland, received the NASA Outstanding Leadership Medal for his work in the Office of Procurement that has resulted in significant cost savings for the agency. Among his accomplishments, Horne designed, implemented, and led an integrated contract management office between NASA Stennis, NASA’s Michoud Assembly Facility in New Orleans, and NASA’s Marshall Space Flight Center in Huntsville, Alabama. The office transformed facility services from independent models to a shared model. The innovative solution was the first joint contract management office at NASA Stennis comprised of procurement, finance, and technical personnel designed to implement effective and efficient business processes. Horne currently serves as the NASA acting administrator for procurement.
Three NASA Stennis employees received NASA’s Exceptional Service Medal. The medal is awarded to government employees for sustained performance that embodies multiple contributions to NASA projects, programs, or initiatives.
Jared Grover of Diamondhead, Mississippi, received the NASA Exceptional Service Medal for his contributions to the success of the NASA Stennis E Test Complex through his dedication and technical expertise. As a NASA mechanical operations engineer, he has led various testing and facility preparation efforts, worked with challenging propellants, and trained new personnel. His work has supported numerous NASA and commercial aerospace projects Grover is also active in community outreach, promoting NASA’s mission and inspiring future engineers.
Tim Pierce of Long Beach, Mississippi, received the NASA Exceptional Service Medal following 26 years with NASA and 41 years working at NASA Stennis as a contractor and civil servant in the Center Operations Directorate. Through Pierce’s contributions, NASA Stennis became a leader in drafting agreements with external agencies, streamlining administrative procedures, and enhancing partnerships. In one notable instance, he led efforts to collaborate with county officials on a sewer treatment project that will save costs and optimize underused infrastructure. Pierce retired from NASA in January 2025.
Barry Robinson of Slidell, Louisiana, received the NASA Exceptional Service Medal in absentia for service to the nation’s space program and achievement across multiple propulsion test programs and projects. Robinson joined NASA in 1994 and worked on the space shuttle main engine test project, eventually becoming a test operations consultant. Over the years, Robinson held various roles, including chief of the NASA Stennis Mechanical Engineering Branch and project manager for projects supporting NASA’s SLS (Space Launch System) rocket for Artemis missions to the Moon and beyond. Robinson retired from NASA in December 2024.
One NASA Stennis employee received NASA’s Exceptional Engineering Achievement Medal. The medal is awarded to both government and non-government individuals for exceptional engineering contributions toward achievement of NASA’s mission.
Richard Wear of Slidell, Louisiana, received the NASA Exceptional Engineering Achievement Medal for his contributions to the NASA Stennis Engineering and Test Directorate. Wear serves as the subject matter expert in thermal and fluid systems analysis. In that role, he has greatly contributed to facilitating the use of liquid natural gas propellant in testing onsite, including by developing a Cryogenics in Propulsion Testing training course to support future test projects and programs. His contributions have significantly enhanced NASA’s support for commercial partners at NASA Stennis.
Eight NASA Stennis employees received NASA’s Exceptional Achievement Medal. This medal is awarded to any government employee for a significant specific achievement or substantial improvement in operations, efficiency, service, financial savings, science, or technology which contributes to the mission of NASA.
Leslie Anderson of Picayune, Mississippi, received the NASA Exceptional Achievement Medal in absentia for leadership and customer service as the lead accountant in the Office of the Chief Financial Officer at NASA Stennis. Anderson has successfully managed critical financial activities with technical expertise, project management, and strong customer service skills. Her efforts help maintain federal partnerships worth approximately $70 million annually and contribute to the success of NASA Stennis, demonstrating NASA’s core values of integrity, teamwork, excellence, and inclusion.
Alison Dardar of Diamondhead, Mississippi, received the NASA Exceptional Achievement Medal for innovation in improving financial and technical processes associated with the $1 billion-plus consolidated operations and maintenance contract for NASA Stennis and NASA’s Michoud Assembly Facility in New Orleans. As senior budget analyst in the NASA Stennis Office of the Chief Financial Officer, Dardar led in identifying and addressing key reporting and accounting issues related to the contract. Her innovations resulted in a 55% improvement in cost reporting accuracy and $20 million in savings to the contract.
Gina Ladner of Diamondhead, Mississippi, received the NASA Exceptional Achievement Medal for management, problem solving, and leadership during a year-long detail as chief of the NASA Stennis Facilities Services Division. During the year, Ladner led the division team through numerous changes and tackled unexpected challenges, including a severe weather event that featured confirmed tornados onsite and a contractor work stoppage activity, to ensure ongoing site operations. She also led in numerous infrastructure investments, including repairs to roadways, fire systems, and communications equipment.
Rebecca Mataya of Carriere, Mississippi, received the NASA Exceptional Achievement Medal for service as a budget analyst in the NASA Stennis Office of the Chief Financial Officer in improving processes and operations. As an analyst on the procurement development team for a new operations, services, and infrastructure contract, Mataya identified creative methods to increase cost savings and maximize facility projects. She also has helped secure over $408 million for facility improvements, enhancing water systems, power generation, and more.
Tom Stanley of Biloxi, Mississippi, received the NASA Exceptional Achievement Medal for contributions to improve NASA’s technology transfer process. As the NASA Stennis technology transfer officer, he developed a tool to standardize and automate evaluation of software usage agreements, reducing costs by 10 times and evaluation time by 75%. The changes led to record numbers of agreements awarded. Stanley also created a tool for contract closeouts, which has contributed to cost savings for the agency.
Cary Tolman of Fort Walton Beach, Florida, received the NASA Exceptional Achievement Medal for work in the NASA Office of the General Counsel. Beyond her role as procurement attorney, Tolman established a software and management audit review team to provide consistent and timely legal advice on software licenses and terms. Tolman’s work has helped NASA save $85 million and simplified legal support for software issues while reducing cybersecurity and financial risk.
Casey Wheeler of Gulfport, Mississippi, received the NASA Exceptional Achievement Medal for leadership and innovation in replacing the high pressure water industrial water system that supports crucial testing facilities at NASA Stennis. As project manager in the NASA Stennis Center Operations Directorate, Wheeler showcased his planning and coordination skills by completing the complex project without delaying rocket engine testing. His work restored the system to full design pressure in an area that directly supports NASA’s SLS (Space Launch System) rocket through RS-25 engine testing, and other critical projects.
Dale Woolridge of Slidell, Louisiana, received the NASA Exceptional Achievement Medal in absentia for contributions as project manager in the NASA Stennis Center Operations Directorate. Woolridge successfully led multiple construction projects, completing them on time and within budget. One notable project was the refurbishment of the miter gates at NASA Stennis’ navigational lock, which supports NASA’s rocket engine testing operations. The team completed the refurbishment ahead of schedule and within budget, ensuring minimal disruption to NASA operations.
Four NASA Stennis employees received NASA’s Early Career Achievement Medal. The medal is awarded to government employees for unusual and significant performance during the first 10 years of an individual’s career in support of the agency.
Briou Bourgeois of Pass Christian, Mississippi, received the NASA Early Career Achievement for his contributions in the NASA Stennis Engineering and Test Directorate. Bourgeois joined NASA in 2017 and has worked on various projects, including the SLS (Space Launch System) core stage Green Run test series and RS-25 engine testing for Artemis missions. Bourgeois played a key role in modifying the liquid oxygen tanking process during the SLS core stage series. He has since become test director in the NASA Stennis E Test Complex and a leader in commercial test projects at NASA Stennis.
Brandon Ladner of Poplarville, Mississippi, received the NASA Early Career Achievement Medal for contributions to the Exploration Upper Stage Test Project on the Thad Cochran Test Stand at NASA Stennis. As the NASA lead mechanical design engineer for the project, Ladner has significantly contributed to the design and build-up of the B-2 position of the Thad Cochran Test Stand in preparation for Green Run testing of the new SLS (Space Launch System) upper stage. He has led in completion of numerous large design packages and provided valuable engineering oversight to improve construction schedule.
Robert Simmers of Slidell, Louisiana, received the NASA Early Career Achievement for his expertise and versatility since joining NASA in 2015 as a member of the NASA Stennis Safety and Mission Assurance Directorate team. He serves as the safety point of contact for the Thad Cochran Test Stand (B-2). In that role, he supported all operations during Green Run testing of NASA’s SLS (Space Launch System) core stage. Simmers also has supported safety audits at various NASA centers. In 2020, he became the NASA Stennis explosive safety officer responsible for explosive safety and compliance.
Robert Williams of Gulfport, Mississippi, received the NASA Early Career Achievement for his work in the NASA Stennis Engineering and Test Directorate. Williams has worked with NASA for eight years, serving as a lead mechanical design engineer for several commercial test projects. Williams is recognized as a subject matter expert in structural systems and has contributed to various NASA Stennis projects, providing technical and modeling expertise.
Two NASA Stennis employees received NASA’s Silver Achievement Medal. The medal is awarded to any government or non-government employee for a stellar achievement that supports one or more of NASA’s core values, when it is deemed to be extraordinarily important and appropriate to recognize such achievement in a timely and personalized manner.
Brittany Bouche of Slidell, Louisiana, received the NASA Silver Achievement Medal for contributions in the NASA Stennis Center Operations Directorate. Bouche has held multiple key roles in the Facilities Services Division, including acting deputy, maintenance and operations lead, and project manager for several construction projects. She has successfully led various design and construction projects, completing them on time and within budget. These include a $9.1 million sewage system and treatment repair project, successfully completed with minimal service impact.
Andrew Bracey of Picayune, Mississippi, received the NASA Silver Achievement Medal for contributions as a NASA electrical design engineer at NASA Stennis. He has provided critical design support for work related to Green Run testing of the new SLS (Space Launch System) exploration upper stage. Bracey also has been crucial to the NASA Stennis vision of supporting commercial aerospace testing, leading preliminary design reviews for multiple projects onsite.
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Last Updated Aug 14, 2025 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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