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Summary of the 2023 GRACE Follow-On Science Team Meeting

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28 min read

Summary of the 2023 GRACE Follow-On Science Team Meeting

Felix Landerer, NASA/Jet Propulsion Laboratory, felix.w.landerer@jpl.nasa.gov

Introduction

In October 2023, the annual gathering of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On [G-FO] Science Team took place in Boulder, CO, hosted at University Corporation for Atmospheric Research’s (UCAR) Center Green campus. The event had 70 in-person participant and an additional 52 online participants – see Photo. G-FO is a U.S.–German collaboration between NASA and the Helmholtz Centre Potsdam GeoForschungsZentrum (GFZ) [German Research Centre for Geosciences].

GRACE team photo
Photo: Pictured here are the in-person attendees of the 2023 GRACE-FO Science Team. Another 52 people participated online.
Image credit: Felix Landerer/JPL

The meeting agenda featured 15-minute presentations over three days, describing new findings from G-FO observations and the combined GRACE and GRACE-FO [G/G-FO] climate data record that now spans over 21 years (2002–2023). 

The meeting began with the customary G-FO project status session, covering programmatic mission and flight segment technical updates, future mission plans, and descriptions of the latest data released from the GRACE Science Data System (SDS) centers. Subsequent sessions featured more than 53 contributed presentations covering analyses, algorithms, and science results by Science Team members and attendees, totaling 57 oral and 5 poster presentations. Many of the presentations are posted on the GRACE website. While this summary will cover all the content on the agenda of the meeting – it does do so in an exact linear fashion. It begins with a G-FO mission status update, followed by key highlights from the contributed analysis and science presentations.

Status of GRACE Follow-On

Since their launch on May 22, 2018, the twin G-FO satellites have been tracking Earth’s water movements and global surface mass changes that arise from climatic, anthropogenic, and tectonic changes. G-FO also enables new insights into variations of ice sheet and glacier mass, land water storage, as well as changes in sea level and ocean currents. These measurements have important applications and implications for everyday life. The impact of these data is underscored by the publication of over 6000 scientific papers – an average of 5 new publications per week – that have established G/G-FO as a leading Earth Science mission.

In May 2023, G-FO successfully completed its Prime Mission phase that lasted five years after launch. G-FO was among the missions that went through the 2023 NASA Earth Science Senior Review. The NASA project team submitted its response in spring of 2023 to extend mission operations through 2026. The proposal received overall Excellent score, highlighting the unique utility the data provide for Earth Science research and societal applications. However, the G-FO project’s NASA budget will be reduced (compared to the previous baseline) by 15% in fiscal year (FY) 2024 and 24% in FY 2025 and 2026 due to the overall budget constraints that NASA is facing. The G-FO team remains confident in its ability to continue delivering high-value and high-impact science data products – prioritizing science operations management and data latency over data reprocessing campaigns. Both NASA and GFZ had already formally committed to extending their collaboration on G-FO mission operations and data processing through the end of 2026 via a Memorandum of Understanding.

As of December 2023, the G-FO project team has processed and released 62 monthly gravity fields – the most recent being for October 2023 (at the time of this writing). The primary mission objective for G-FO is to provide continuity for the monthly GRACE mass-change observations (2002–2017) via its Microwave Interferometer (MWI) intersatellite range-change observations. G-FO also demonstrated a novel technology demonstration Laser-Ranging Interferometer (LRI) for more accurate satellite-to-satellite ranging observations for future GRACE-like missions. The LRI has been successfully operated in parallel with the MWI for most of the mission, delivering excellent quality data. LRI-based monthly gravity and mass change fields covering the period from mid-2018 to mid-2023 have been made available by the SDS teams for further analysis and study by the science community. 

Programmatic, Mission, and Operations Updates

The meeting began with Frank Flechtner [GFZ–German G-FO Project Manager] and Felix Landerer [NASA/Jet Propulsion Laboratory (JPL)—U.S. G-FO Project Scientist] giving welcoming remarks, followed by detailed assessments of the G-FO mission and operations status from the core SDS centers and flight operations teams.

GRACE Follow-On Project Status

Felix Landerer gave an overview of the G-FO satellites and the science data system performance. He reported that G-FO continues to meet its goal of extending the GRACE mass-change and gravity data record at equivalent precision and spatiotemporal sampling. 

Since the previous STM in October 2022, the overall G-FO science instrument performance has been stable, and the SDS team continued to deliver a gapless monthly data record to users ahead of schedule (on average, within 43 days instead of the 60-day requirement). Improving the data calibrations of the accelerometer measurements – which are noise contaminated on one of the two G-FO spacecraft – remains a core focus of the project SDS team. To this end, an improved calibration approach that reduced data errors by 10–20% has been developed and will be operationalized by the team in the coming months. 

Landerer reported that, as forecasted, the current Solar Cycle 25 has gained in strength through 2023 and will continue to do so through 2024 before subsiding again. The resulting higher non-gravitational forces acting on the satellites need to be properly accounted for in the accelerometer data processing. 

He also noted that small thruster leaks in the satellites cold gas propulsion system have been closely monitored since 2021. To ensure stable data collection and sufficient lifetime margin to achieve continuity with the proposed successor mission GRACE-Continuity, or GRACE-C (which is the new name for the Earth System Observatory Mass Change mission scheduled for launch no earlier than 2028), the G-FO project team, in conjunction with guidance from the satellite manufacturer Airbus and the German Space Operations Center, decided to adjust the operational data collection mode of G-FO to a wide pointing mode – which means that the two spacecraft are allowed to deviate from their relative line-of-sight pointing by up to 2°, whereas the previous pointing angles were 100 times smaller. This operational change necessitates fewer thruster firings, which in turn reduces leaks and improves accelerometer calibrations – and thus leads to better overall science data quality. Due to the wide pointing, the LRI intersatellite ranging data collection has been suspended in this operational mode. However, the LRI instruments are still activated and fully functional. Landerer emphasized that reducing the leak ensures that the GRACE-FO mission will have sufficient fuel to remain operational up until GRACE-C launches.

Despite these operational challenges, Landerer said that the science data delivered by G-FO continues to provide excellent utility and insights into a rapidly changing Earth system. He briefly highlighted a few scientific and decision-support contributions and achievements of G-FO over the last year. These included: 

  • Monitoring California Groundwater. G-FO recorded the largest seasonal total water storage gains over California after the multiple atmospheric rivers made landfall during the 2022/2023 winter. Yet, peak water storage in May was below values observed 15–20 years ago – due to long-term, sustained groundwater declines. Going forward, the data will be invaluable to assess groundwater recharge rates and processes.
  • Tracking Polar Ice Mass Loss. G/G-FO measured net ice mass gains over Antarctica that began around 2021 due to snow accumulation mainly in East Antarctica, which offset the unabated mass loss of the West Antarctic ice sheet.

Subsequent science presentations presented in-depth analyses of these and other findings in the dedicated science sessions, some of which are summarized below. 

Landerer also highlighted the expanding portfolio of open science contributions that the project team is supporting: Jupyter notebooks are part of an expanding GRACE Open Science toolbox with the goal to expand this toolbox with input from the Science Team and user community in the coming years. In addition, easy-to-use browser data portals at JPL and GFZ have been key to expand the science and applications user community that increasingly use the Level-3 and higher data products in decision support contexts (e.g., for drought monitoring and water resources management).

A series of status reports on programmatic G-FO mission operations, science operations, and SDS processing followed the opening presentations. Krzysztof Snopek [GFZ] reported on the ground and mission operations at the German Space Operations Center (GSOC), which is responsible for G-FO spacecraft operations. All essential flight operations, software updates, and planned calibrations were successfully scheduled and carried out by GSOC. Himanshu Save [University of Texas, Center for Space Research (CSR)] provided the science operations assessment. He described the evolving Solar Cycle 25 and its influence on the G-FO spacecraft, the mission’s fuel budget, and adjusted operational procedures and modes (such as the already-mentioned ‘wide’ pointing mode). Christopher McCullough [JPL] reviewed the status of G/G-FO Level 1 processing at JPL, detailing additional improvements made in the accelerometer calibrations. The team is using the noisy accelerometer data on one satellite and retrieving improved science information from it.

A representative from each of the G-FO mission SDS centers – which includes JPL, GFZ, CSR, and GSFC – summarized the status of the latest gravity-field and mass change data products [RL06.X L2], including an overview of background dealiasing models and the GFZ GravIS portal, the updated JPL mascon data product, new data-processing strategies, e.g., via range acceleration [CSR], and the status of ancillary Satellite-Laser-Ranging (SLR) data processing and dedicated G/G-FO products [GSFC].

Following the project team’s status presentations, there was a 30-minute session to answer questions from the science community and discuss in more detail the mission performance, near-term operations and data processing plans, as well as to gather suggestions and feedback from the community. 

Science Presentations

The remainder of the sessions in the meeting were open-submission science sessions, each of which centered around different thematic topics, including: G/G-FO analysis techniques and next generation gravity mission (NGGM) concept studies, and science analysis of mass-transport data in the fields of glaciology, oceanography, hydrology, and solid-Earth physics. As has been the case in previous years, the presenters underscored the value of interdisciplinary and multi-instrument analyses that utilize the unique complementary value of G/G-FO mass-change observations in combination with other remote sensing data (e.g., satellite altimetry or precipitation observations) and in situ data (e.g., surface deformation or ocean temperature profiles). Such hydrogeodetic combinations yield improved spatial and temporal resolutions that enable advances in Earth system process understanding, which increasingly advance societal applications of science results in support of NASA’s programmatic focus on Earth Science to Action, which seeks to “advance and integrate Earth science knowledge to empower humanity to create a more resilient world.”

Section A: GRACE and GRACE-FO Geodesy

The project status reports presented under the previous heading were part of the first section of the agenda (Session A1) as were two additional sessions: Analysis Techniques and Intercomparisons (Session A2) and NGGM and Bridging the Gap (Session A3), which focused on plans, concepts, and technologies being developed for future gravity missions. Highlights from each of these two sessions follow in the next two subsections. 

Analysis Techniques and Inter-comparisons

This session featured 15 presentations by the SDS centers and ST members on progress in instrument data calibrations and novel data processing algorithms and methods, including data-fusion with other observations.

Representatives from G/G-FO processing centers presented updated gravity-field time-series data, which capitalize on improved parameterizations, better instrument error characterizations (e.g., from star cameras, accelerometers, or ranging instruments) and background models (e.g., for tides) for improved monthly mass change data and uncertainty quantification. The highly accurate LRI data provides further opportunities to identify and characterize measurement system errors, which can be exploited for G-FO data processing but is also informative in the development of the future GRACE-C mission. However, it was also shown that several metrics used in identifying gravitational errors are sensitive to the estimated satellite trajectory, and consequently a sufficient understanding of the orbital trajectory is necessary to make accurate adjustments to the gravity field based on satellite observations.

The G/G-FO data products make use of ground-based geodetic observations, such as satellite laser-ranging (SLR) to a network of dedicated SLR satellites, which can be used to extend the G/G-FO interannual data record back to ~1994 – albeit at a much-reduced spatial resolution. Additionally, SLR data provide an important validation and performance assessment opportunity for G/G-FO observations. In that regard one presenter showed results indicating the recent G-FO accelerometer updates have indeed resulted in better gravity and mass change fields. Other speakers discussed the value and potential for improvement that could be achieved by combining G-FO and SLR observations more formally to exploit the data strengths of the different observation types in an optimal way. Such approaches could reduce uncertainties in global ocean and land ice mass changes. Furthermore, deployment of stable, long-term ocean bottom pressure (OBP) recorders in the Arctic Ocean in 2022 has enabled progress on G/G-FO OBP data validation. The data from these OBP recorders are entirely independent of G/G-FO observations and are thus very valuable to assess the satellite data record. An initial comparison between 1.5 years of OBP data and various G-FO OBP products suggest excellent agreement.

The data collected from G/G-FO has a native resolution of about 300 km (~186 mi). By jointly analyzing these G/G-FO data with higher-resolution surface elevation changes from a multimission synthesis of radar and laser satellite altimeters, net mass changes can be effectively downscaled (within a Bayesian framework) to less than 20 km (~12 mi) resolution, which is sufficiently high resolution to resolve individual ice streams in Antarctica that cannot be separated using G/G-FO data alone.

NGGM and Bridging the Gap 

The presenters in this session provided status-update on the GRACE-C mission, a joint project between NASA and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) [German Aerospace Center], as well as on future instrument developments and mission concepts. 

The 2017 NASA Earth Science Decadal Survey Report highlighted mass-transport monitoring through gravity change as one of five designated observables (i.e., top priorities for study) in Earth observations for the next decade in collaboration with international partners. The GRACE-C project successfully passed the NASA/JPL Mission Concept Review in June 2022, and the NASA Key Decision Point B review in September 2023 and is currently in its Phase B project definition phase. GRACE-C will be a single satellite pair based on a fully redundant LRI (as demonstrated on GRACE-FO) in a polar orbit at 500 km (~311 mi) altitude. To avoid a data gap after GFO, a launch date of no later than 2028 is targeted for GRACE-C.

Similarly, GFZ has been conducting model simulation studies to determine the value of adding a second satellite pair, dubbed Next-Generation Gravity Mission (NGGM) in Europe.  The experiments reveal that advanced parameterization techniques for improved de-aliasing of short-term mass variations can significantly reduce data errors and open the possibility for higher spatial and temporal resolution data products and science applications.

The technology demonstration LRI on G-FO has surpassed its performance requirements. With a LRI expected to be the primary instrument for the GRACE-C mission as well as other future GRACE-like missions, development of a new technique is required to provide long-term laser frequency knowledge to provide a scale correction factor to the geodesy measurement. The LRI-team presented updated results of a so-called scale factor measurement technique that allows the accurate determination of the laser frequency on-orbit that can meet the stringent GRACE-C mission requirements. This was achieved with a dual frequency modulation scheme, and a prototype electronics unit has been developed and tested, demonstrating performance better than the expected mission requirements. 

There were also reports on progress in technology development of low-frequency optomechanical accelerometers for geodetic applications. These highly-sensitive, compact, portable – and cost-effective – optomechanical inertial sensors build upon recent advances in optomechanics to measure accelerations with small form factors. The development of a sensor with lower cost, size, weight, and power – yet with GRACE-like performance – is a major achievement as these could be integrated into cost-effective mission designs, spacecraft miniaturization, simplified architectures, as well as for the deployment of constellations of satellite pairs flying at lower altitudes.

Section B: Geophysics and Climate Science

There were five sessions included in this section of the agenda, which are summarized in the subsections below as follows: Hydrology (Session B4), Cryosphere (Session B2), Solid Earth Sciences (Session B1), Oceanography (Session B3), and Multidisciplinary Science (Session B5). 

Hydrology 

This session, with 12 presentations, highlighted advances in hydrology research and applications using G/G-FO data enabled by the unique value of long, uninterrupted mass change climate data record. 

The topic of terrestrial water storage variations in California came up in several presentations, focusing on the see-saw swings between very wet and very dry years and the early impacts on groundwater recharge after the record-breaking snow accumulation during the 2022/2023 winter. The process of groundwater recharge – an important objective in the 2017 Earth Science Decadal Survey – is not well understood because of the challenges in observing infiltration of new water supply into the ground and the effects of rate of input, amount of input, and various aquifer characteristics. By combining observations of precipitation, snow water equivalent, surface water storage, ground surface deformation, and groundwater storage from G/G-FO, recharge behavior can be characterized in a natural experiment where source inputs are effectively not limited, but recharge capacity is limited. Results of studies shown during the meeting reveal that only a fraction of total available potential recharge can enter the aquifer, and that G/G-FO observations allow us to measure the effective aggregated recharge capacity and how it varies with several predictors. Another paper reported that subsurface water increases in California’s Sierra Nevada by 0.6 m (~2 ft) from October 2022 to June 2023, which represents 43% of the cumulative precipitation. 

Several presenters reported on efforts to advance concepts to downscale G/G-FO data to bring the information closer to decision-making scales and expand water-related applications, as well as to fill gaps and expand the data record with multisensor observations. One presenter described a new spectral approach that employs wavelet multiresolution analysis to combine seasonal terrestrial water storage change data from G/G-FO with those from global navigation satellite system (GNSS) ground station networks to downscale the observations to smaller hydrological basins and to better separate processes over complex topographical terrain. This method can also be used by fusing G/G-FO and hydrological model data [e.g., from NASA’s Global Land Data Assimilation System (GLDAS) models at continental scales]. Importantly, the method yields trends and long-term signals that match G/G-FO observations – a strength of the observing system. Another approach used a statistical Bayesian framework to incorporate G/G-FO observations and Soil Moisture Change data from different available sources [e.g., NASA’s Soil Moisture Active Passive (SMAP) mission] to obtain nonparametric likelihood functions that allow for downscaling. A statistical technique called cyclostationary empirical orthogonal function (CSEOF) analysis – which is used to interpret space-time variability in a large dataset – allowed researchers to fill short data gaps (~1 year) in G/G-FO record (e.g., between 2017 and 2018 – the gap between GRACE and GRACE–FO) without having any additional data. With the support of physically-related data (e.g., precipitation and temperature), CSEOFs can be used to reconstruct water changes into the past or fill larger data gaps. Such datasets improve understanding of trends and natural variability and anticipate future trends in response to climatic changes. 

Another presenter described a science study that found an apparent abrupt decline in temperate (non-ice) Terrestrial Water Storage (TWS) in 2015 to a new, lower regime that appears to be unique in the past 33 years. The triggering event for this new lower TWS regime appears to be the massive drought in Brazil in 2015. Subsequent droughts around the world (e.g., Europe, the western U.S., Canada, central Africa, and southern Brazil) have helped to keep TWS values depressed. Warm global sea surface temperatures, prevalent since 2015, have decreased rain accumulation over the continents, reducing TWS.

In the European Alps region, a G/G-FO data analysis found that glacier and ice changes are the major contributors to the observed signals. Overall, glaciers here have lost ice mass at rates between 1.4 to 2.2 Gt/year since 2002. Advances in spatial downscaling and data combinations are expected to allow for improved estimates and applications, including geological hazard monitoring.

In Northern Italy, accelerated groundwater loss has been detected using G/G-FO, well measurements, and vertical land motion observations. Since 2015, the groundwater loss has accelerated. Assuming a best-case scenario (conditions similar to 2007–2014), it could take 13–28 years for ground water storage to recover from recent long-term period of decline, thus setting the stage for prolonged drought conditions.

Since a pioneering study in 2014, it is well-established that G/G-FO observations of TWS are an effective means to estimate flood potential and flood risks due to water-saturated soil. Novel G/G-FO data processing schemes that exploit sub-monthly variations of total water storage enabled researchers to delineate basin-specific storage-discharge dynamics more accurately. They found that at submonthly timescales in many global basins, water storage (i.e., saturated soil) has more impact on whether a flood will occur than the amount of precipitation that falls. 

Along the Nile River, G/G-FO data were used to monitor water changes in crucial artificial reservoirs. These data indicate that water losses through underground-seepage over the geologically highly fractured region via a complex network of shear systems, faults, and fractures, are significant and could impact the delicate water balance in the region. A separate study focusing on nearby Southern Arabia found that intense tropical cyclones (wind speeds > 64 kph or ~40 mph) have doubled in the past decade compared to the preceding two, which resulted in significant recharge of the aquifers in the study area. The findings demonstrate the ability of G/G-FO to capture recharge signals and monitor aquifer systems in poorly gauged basins and highlight the significant role of tropical cyclones in recharging aquifers in arid Arabia.

Cryosphere

The five contributions in this session reported on new ice mass balance results of the Earth’s land-ice, as well as on novel data-combinations approaches that can improve the spatial resolution over G/G-FO-only data.

The Antarctica Ice Sheet contributes to the largest sea level rise potential and remains as the largest uncertainty source in the prediction of future sea levels. Data from G-FO and the Ice, Clouds and land Elevation Satellite–2 (ICESat-2) mission have been used to track ice sheet mass and height changes in Greenland and Antarctica, respectively. By combining the strengths of G-FO (gravity or mass change) and ICESat-2, (laser altimetry) data, a more accurate and less uncertain estimate of ice sheet mass changes can be achieved. This combination has led to a proposal for an enhanced iterative algorithm for deriving Antarctic mass balance, incorporating key technologies such as altimetry, gravity measurements, Global Positioning System (GPS) satellite data, and surface mass balance models. The study utilizes an effective density map derived from ICESat-2 and tests the algorithm’s sensitivity and uncertainty with synthetic data, considering realistic physical processes and variability. This approach aims to address discrepancies in estimating ice mass loss in East Antarctica and provides important guidance for optimizing future ground measurements (i.e., GPS station positions). Another presentation focused on understanding the differences in mass change recovered by the G/G-FO and IceSat-2 missions – both in terms of spatial distributions and total magnitudes – to ultimately determine a best combined estimate of ice sheet mass change leveraging the strengths of each mission. 

Temporal gravity field estimates from G/G-FO data reveal that the Antarctic ice sheet contributed approximately 6.1 mm (~0.2 in) to global sea level rise from 2002–2022, with a net loss of ~2150 GT of mass. While mass change accelerated during the GRACE era, it has decelerated during the GRACE-FO era – due to increased mass gain in East Antarctica. The deceleration is attributed to surface mass balance processes: annual precipitation and increased incidences of extreme weather events in East Antarctica, challenging predictions based on correlations with climate indices like Southern Annular Mode and El Niño Southern Oscillation.

A related study confirmed a pause in Antarctica’s mass loss, a non-accelerating mass loss in Greenland, and a steady loss from glaciers and ice caps away from the poles. The use of the LRI observations enabled novel submonthly analysis in key regions (including the Amundsen Sea Embayment of West Antarctica and the Pine Island/Thwaites basins) to gain more understanding of fast ice dynamics and their spatial extent.

While G/G-FO data span two decades, estimates of Earth’s oblateness from other satellite observations that date back to 1976 and provide a much longer data record – albeit at much coarser spatial resolution. This half-century long timeseries provides important constraints on ice mass change prior to the launch of GRACE in 2002. The data suggest that ice mass loss had already begun to accelerate by the 1990s. Recent progress in Earth system models, in conjunction with the long satellite data record, are being used to isolate trends in glacial isostatic adjustment (GIA) – which is the vertical movement of the Earth’s surface after the weight of glaciers is removed from them – and to improved estimates of ice mass loss prior to GRACE.

Solid Earth Sciences

Two presenters in this session described their efforts to evaluate signals in the G/G-FO data record associated with earthquakes. The G/G-FO data provide a unique opportunity to observe the Earth’s response to great earthquakes across diverse tectonic settings at time scales from days to decades. Using 13 earthquakes of magnitude (Mw)>8.0 over the last 20 years, it was found that elastic bulk modulus and viscosity govern large-scale coseismic and postseismic gravimetric changes, respectively. By constraining the solid Earth’s viscosity structure, improved physics-based models of long-term postseismic changes can be developed that incorporate observations from G/G-FO. The portion of the long-term gravity change signal that can be attributed to these earthquakes can then be removed from the G/G-FO data to better quantify processes related to ocean mass and hydrology changes. When physics-based models are not available, alternative statistic-based approaches can be used to remove the co- and post-seismic signature of large earthquakes (e.g., 2004 Andaman-Sumatra and 2011 Tohoku, Japan quakes) from the G/G-FO data. 

As the G/G-FO data record extends into its third decade, the long time series of Earth gravity changes requires careful consideration of the solid-Earth response to contemporary surface mass changes. To isolate the gravity signature of any surface mass signal, it is becoming evident that simple elastic loading corrections are no longer sufficient. Recent advances in mantle rheology – describing and understanding the nature of Earth’s mantle – derived in mineral laboratory experiments, tidal modeling, and seismic imaging provide unequivocal evidence of anelastic contributions to solid-Earth deformation on time-scales ranging from hours to decades. New developments in the solid-Earth capabilities of JPL’s Ice-sheet and Sea-level System Model (ISSM) in the form of viscoelastic solvers for Love numbers and sea-level change was used to implement and explore the so-called Extended Burgers Material (EBM) and so resulting viscoelastic deformations between the seismic and GIA time scales. Preliminary testing with EBM rheology shows potential for a ~15–20% increase in mass change trends for some regions.

A subdecadal variation of large-scale (i.e., spanning over continental scales) gravity signals with a period of approximately six years has attracted intense interest in the geodesy and geodynamic communities. Earth’s fluid core motions, magnetic field, Earth rotation, and crustal deformations have been invoked as causes for this signal. An analysis of G/G-FO data showed that a significant part of the approximately six-year signals is in fact due to climate-related oscillation of ocean-atmosphere coupling in the Pacific and Atlantic and variations in the land water storage over Africa.

Oceanography

In the oceanography session, five presenters reported on the combination of G/G-FO, satellite altimeters (e.g., from the joint NASA–European Sentinel-6 Michael Freilich mission), and in situ ocean floats (e.g., Argo) to investigate variations in sea level and ocean circulations – e.g., see Figure 1. Other presenters discussed improvements in data processing by reducing errors in atmospheric tides that could lead to spurious trends or double-counting a subset of ocean tides and by incorporating new dedicated ocean data grids that remove geodetic signals not related to ocean dynamics (e.g., global ocean mass; large earthquake signals).

GRACE figure 1
Figure 1. The top row of maps show estimates of individual components of the observed sea level trend in the northwestern Pacific from 2003 to 2016 including contributions from: land ice melt [top row, left], non-ice land water storage [top row, middle], and stereodynamic effects [top row right], which are estimated by directly combining in situ-based steric sea level (i.e., based on Argo ocean profiling floats) with the GRACE-derived ocean mass changes. The bottom row shows the sum of all of the components of sea level trend on the top two rows [bottom row, left], compared the same measurement using satellite-altimetry [bottom row, right]. These data clearly show the strong earthquake-related signature of ocean mass change east of Japan.
Image credit: Felix Landerer/updated from a similar figure published in Nature’s Communications Earth & Environment.

Another presenter described how ocean mass redistribution and regional sea-level rise in the North-West Pacific marginal seas (i.e., around Japan and north of the Philippines) is impacted by seafloor deformation from earthquakes, which alter the ocean bathymetry. G/G-FO data are key to isolating these deformation effects, which in turn allows better sea level projections that can be used for planning purposes.

While long-term sea level trends are of major concern, the seasonal cycle is the dominating climate signal in ocean bottom pressure variability. Accurate representation of seasonal cycle is thus key to efforts to improve observations and models of ocean bottom pressure. Examining differences between models and observations elucidates remaining uncertainty in observations and missing physics in the models (e.g., lack of intrinsic variability due to coarse resolution, no accounting of gravitational and loading effects). This allows researchers to advance the quality of ocean mass change observations and unravel underlying dynamics.

Lastly, ocean bottom pressure observations from G/G-FO have been used to monitor transport variability of deep currents associated overturning circulation in the Northern Hemisphere (the Labrador Current) and Southern Hemisphere (Weddell Sea Bottom Water). This deepwater transport provides an important pathway for the sequestration of excess atmospheric heat and carbon from locations of water mass formation. Continuous observations of deep ocean currents provide valuable insight into Earth’s climate system. However, harsh conditions and complex recirculation transport pathways make in-situ observations of these deep flowing currents challenging.

Interdisciplinary Science

Six presenters contributed to this session. The first study revisited geodetic assumptions about measuring so-called Earth Center-of-Mass (CM) motions that can be traced to planetary-scale seasonal and long-term variations of water cycling between the land the oceans. Differences in SLR and G/G-FO estimates of CM estimates can be helpful to refining global circulation models. In a related study, G/G-FO and SLR data have been used to pin down the causes and origin of polar motion, particularly the mass component related to gravity changes. A novel hybrid SLR/GRACE time-variable gravity approach closely aligned well with the hydrological excitation in independently polar motion.

Errors in GIA corrections impact altimeter estimates of sea level and ocean mass estimates and the so-called sea level budget. Choices in modeling GIA, particularly based on paleoshoreline sites, affect Earth’s viscosity structure and GIA response, influencing global mean sea level (GMSL) budget closure. Even minor Earth model changes can have notable effects on the alignment of GMSL (altimetry), ocean mass (GRACE), and steric sea level change (Argo). Thus, future research needs to focus on accounting for the complex three-dimensional structure of the solid Earth to improve GIA corrections and more accurately isolate contemporary mass change in the G/G-FO data record.

Despite GIA uncertainties, G/G-FO, in combination with sea level measurements from altimetry, provide a unique capability to measure changes in ocean heat content. The ocean takes up nearly 90% of Earth’s current energy imbalance, signifying their important role in overall planetary heating. Two presenters reported consistent findings of ocean heat uptake rates of 0.9 W/m2 based on the indirect geodetic satellite measurements of sea level and ocean mass – a value that is entirely independent of other techniques and thus provides crucial validation – see Figure 2. In addition, the results indicated the overall heating rate over the last decade has increased, which means heat accumulation is accelerating.

GRACE figure 2
Figure 2. This graph shows different estimates of ocean heat uptake (OHU), measured with in-situ ocean floats (orange curve), from top-of-the-atmosphere radiance satellite measurements of Earth energy imbalance (EEi) (black curve), and from geodetic satellites, i.e., G/G-FO and altimeters (blue curve). The satellite measurements agree well and show an increasing energy imbalance over the last 20 years.
Image credit: Felix Landerer/originally in Geophysical Research Letters.

Summary

The hybrid 2023 G-FO STM brought together over 120 international participants and showcased a broad range of science results and applications that are supported and uniquely enabled by the satellite gravimetry-based mass change observations. The G-FO data now span nearly six years and continue to provide crucial insights into how Earth’s hydrosphere, including sea level, ocean currents, and water distribution over land, is changing. The G/G-FO data are extending important climate data records (e.g., the Greenland and Antarctic ice mass time-series, ocean mass sea level data, and TWS over land) into their third decade. The upcoming GRACE-C mission will build on and expand this mature data record, which is increasingly enabling important applications in support of water-related decision making and planning.

The G-FO project team remains focused on providing the mass-change data record at a level of performance consistent with that of GRACE. As the current Solar Cycle 25 increases towards its anticipated maximum in 2024, the team continues to improve the mission’s accelerometer data products in support of that goal. Corresponding data improvements in the monthly gravity and mass change products will be released early 2024.

The next G-FO STM will be held from October 8–10, 2024 in Potsdam, Germany, organized by GFZ. Check the GRACE website for specific details as the date gets closer.

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    • NASA
      Meet the Space Ops Team: Anum Ashraf
      By NASA
      3 min read
      Preparations for Next Moonwalk Simulations Underway (and Underwater)
      For Anum Ashraf, Ph.D., the interconnectedness of NASA’s workforce presents the exciting opportunity to collaborate with a multitude of people and teams. With more than 11 years at the agency, Ashraf has played a fundamental role in leading efforts that actively bridge these connections and support NASA’s mission. 

      Ashraf serves as the mission commitment lead for NASA’s SCaN (Space Communication and Navigation) Program, which is managed through the agency’s Space Operations Mission Directorate. SCaN provides communications and navigation services that are essential to the operation of NASA’s spaceflight missions, including enabling the success of more than 100 NASA and non-NASA missions through the Near Space Network and Deep Space Network. Whether she is supporting missions involving astronauts in space or near-Earth missions monitoring the health of our planet, Ashraf ensures that critical data is efficiently transferred between groups. 
      Near Space Network antennas at the White Sands Complex in Las Cruces, New Mexico.NASA
      “I am the ‘front door’ for all missions that are requesting space communication through the SCaN program,” said Ashraf. “My job is to understand the mission requirements and pair them with the right assets to enable successful back and forth communication throughout their mission life cycle.” 
      Prior to her current role, Ashraf served as the principal investigator for the DEMETER (DEMonstrating the Emerging Technology for measuring the Earth’s Radiation) project at NASA’s Langley Research Center in Hampton, Virginia. DEMETER is the next-generation observational platform for measuring Earth’s radiation. Leading a team of engineers and scientists across NASA’s multifaceted organizations, Ashraf helped develop an innovative solution that will allow future researchers to assess important climate trends affecting the planet.

      Outside of work, Ashraf finds a creative outlet through hobbies like knitting, cross stitching, and playing piano. She brings her ambitious, passionate, and authentic qualities to caring for her two children, who are also her daily source of inspiration.  
      “Inspiration is a two-way street for me; my kids inspire me to be my best, and, in turn, I inspire them,” said Ashraf. “My kids love telling their friends that we are a NASA family.” 

      Anum Ashraf, Ph.D., mission commitment lead for NASA’s Space Communications and Navigation Program


      Looking toward the future, Ashraf is excited to see a collaboration between NASA, industry, academia, and international space enthusiasts working together towards a common goal of space exploration. As a devoted and collaborative leader, Ashraf will continue to play an important role in advancing the agency’s missions of space research and exploration. 


      NASA’s Space Operations Mission Directorate maintains a continuous human presence in space for the benefit of people on Earth. The programs within the directorate are the hub of NASA’s space exploration efforts, enabling Artemis, commercial space, science, and other agency missions through communication, launch services, research capabilities, and crew support.

      To learn more about NASA’s Space Operation Mission Directorate, visit:  
      https://www.nasa.gov/directorates/space-operations
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      Last Updated Mar 27, 2025 Related Terms
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      3 min read NASA Successfully Acquires GPS Signals on Moon 
      Article 3 weeks ago 2 min read More Than 400 Lives Saved with NASA’s Search and Rescue Tech in 2024
      Article 2 months ago 3 min read Meet the Space Ops Team: Lindsai Bland
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    • NASA
      NASA’s Parker Solar Probe Team Wins 2024 Collier Trophy
      By NASA
      The innovative team of engineers and scientists from NASA, the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, and more than 40 other partner organizations across the country that created the Parker Solar Probe mission has been awarded the 2024 Robert J. Collier Trophy by the National Aeronautic Association (NAA). This annual award recognizes the most exceptional achievement in aeronautics and astronautics in America with respect to improving the performance, efficiency, and safety of air or space vehicles in the previous year.   
      “Congratulations to the entire Parker Solar Probe team for this well-earned recognition,” said NASA acting Administrator Janet Petro. “This mission’s trailblazing research is rewriting the textbooks on solar science by going to a place no human-made object has ever been and advancing NASA’s efforts to better understand our solar system and the Sun’s influence, with lasting benefits for us all. As the first to touch the Sun and fastest human-made object ever built, Parker Solar Probe is a testament to human ingenuity and discovery.”
      An artist’s concept of NASA’s Parker Solar Probe. NASA On Dec. 24, 2024, Parker Solar Probe made its closest approach to the Sun, passing deep within the Sun’s corona, just 3.8 million miles above the Sun’s surface and at a top speed of close to 430,000 mph, ushering in a new era of scientific discovery and space exploration.
      “This award is a recognition of the unrelenting dedication and hard work of the Parker Solar Probe team. I am so proud of this team and honored to have been a part of it,” said Nicky Fox, associate administrator, Science Mission Directorate, NASA Headquarters in Washington. “By studying the Sun closer than ever before, we continue to advance our understanding of not only our closest star, but also stars across our universe. Parker Solar Probe’s historic close approaches to the Sun are a testament to the incredible engineering that made this record-breaking journey possible.”
      Three novel aerospace technology advancements were critical to enabling this record performance: The first is the Thermal Protection System, or heat shield, that protects the spacecraft and is built to withstand brutal temperatures as high as 2,500 degrees Fahrenheit. The Thermal Protection System allows Parker’s electronics and instruments to operate close to room temperature.
      Additional Parker innovations included first-of-their-kind actively cooled solar arrays that protect themselves from overexposure to intense solar energy while powering the spacecraft, and a fully autonomous spacecraft system that can manage its own flight behavior, orientation, and configuration for months at a time. Parker has relied upon all of these vital technologies every day since its launch almost seven years ago, in August 2018.
      “I am thrilled for the Parker Solar Probe team on receiving this well-deserved award,” said Joe Westlake, director of the Heliophysics Division at NASA Headquarters. “The new information about the Sun made available through this mission will improve our ability to prepare for space weather events across the solar system, as well as better understand the very star that makes life possible for us on Earth.”
      Parker’s close-up observations of solar events, such as coronal mass ejections and solar particle events, are critical to advancing our understanding of the science of our Sun and the phenomena that drive high-energy space weather events that pose risks to satellites, air travel, astronauts, and even power grids on Earth. Understanding the fundamental physics behind events which drive space weather will enable more reliable predictions and lower astronaut exposure to hazardous radiation during future deep space missions to the Moon and Mars.
      “This amazing team brought to life an incredibly difficult space science mission that had been studied, and determined to be impossible, for more than 60 years. They did so by solving numerous long-standing technology challenges and dramatically advancing our nation’s spaceflight capabilities,” said APL Director Ralph Semmel. “The Collier Trophy is well-earned recognition for this phenomenal group of innovators from NASA, APL, and our industry and research partners from across the nation.”
      First awarded in 1911, the Robert J. Collier Trophy winner is selected by a group of aviation leaders chosen by the NAA. The Collier Trophy is housed in the Smithsonian’s National Air and Space Museum in Washington.
      “Traveling three times closer to the Sun and seven times faster than any spacecraft before, Parker’s technology innovations enabled humanity to reach inside the Sun’s atmosphere for the first time,” said Bobby Braun, head of APL’s Space Exploration Sector. “We are all immensely proud that the Parker Solar Probe team will join a long legacy of prestigious aerospace endeavors that redefined technology and changed history.”
      “The Parker Solar Probe team’s achievement in earning the 2024 Collier is a shining example of determination, genius, and teamwork,” said NAA President and CEO Amy Spowart. “It’s a distinct honor for the NAA to acknowledge and celebrate the remarkable team that turned the impossible into reality.”
      Parker Solar Probe was developed as part of NASA’s Living With a Star program to explore aspects of the Sun-Earth system that directly affect life and society. The Living With a Star program is managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington. The Applied Physics Laboratory designed, built, and operates the spacecraft and manages the mission for NASA.
      By Geoff Brown
      Johns Hopkins University Applied Physics Laboratory
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      Details
      Last Updated Mar 25, 2025 Editor Sarah Frazier Contact Abbey Interrante abbey.a.interrante@nasa.gov Location Goddard Space Flight Center Related Terms
      Heliophysics Goddard Space Flight Center Heliophysics Division Parker Solar Probe (PSP) The Sun Explore More
      5 min read NASA’s Parker Solar Probe Makes History With Closest Pass to Sun


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      11 min read NASA Enters the Solar Atmosphere for the First Time, Bringing New Discoveries
      A major milestone and new results from NASA’s Parker Solar Probe were announced on Dec.…


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    • NASA
      NASA’s SpaceX Crew-9 Astronauts to Discuss Science Mission
      By NASA
      NASA astronaut Butch Wilmore, left, Roscosmos cosmonaut Aleksandr Gorbunov, second from left, and NASA astronauts Nick Hague, second from right, and Suni Williams, right, are seen inside a SpaceX Dragon spacecraft shortly after splashing down off the coast of Florida, Tuesday, March 18, 2025. NASA’s SpaceX Crew-9 mission returned from a long-duration science expedition aboard the International Space Station. Photo Credit: (Credit: NASA).NASA/Keegan Barber After completing a long-duration stay aboard the International Space Station, NASA’s SpaceX Crew-9 astronauts will discuss their science mission during a postflight news conference at 2:30 p.m. EDT Monday, March 31, from the agency’s Johnson Space Center in Houston. Following the news conference, the crew will be available for a limited number of individual interviews at 3:30 p.m.
      NASA astronauts Nick Hague, Suni Williams, and Butch Wilmore will answer questions about their time in space. The three NASA crew members and Roscosmos cosmonaut Aleksandr Gorbunov returned to Earth on March 18. Gorbunov will not participate in the news conference because of his travel schedule.
      Watch live coverage on NASA+. Learn how to watch NASA content through a variety of additional platforms, including social media.
      Media are invited to attend in person or virtually. U.S. media requesting in-person attendance or media seeking an interview with the crew must contact the NASA Johnson newsroom no later than 5 p.m. on Friday, March 28, at 281-483-5111 or jsccommu@mail.nasa.gov. A copy of NASA’s media accreditation policy is available on the agency’s website. Media participating by phone must dial into the news conference no later than 10 minutes before the start of the event to ask questions. Questions also may be submitted on social media using #AskNASA.
      Hague and Gorbunov lifted off at 1:17 p.m. Sept. 28, 2024, on a SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida. The next day, they docked to the forward-facing port of the station’s Harmony module. Williams and Wilmore launched aboard Boeing’s Starliner spacecraft and United Launch Alliance Atlas V rocket on June 5, 2024, from Space Launch Complex 41 as part of the agency’s Boeing Crew Flight Test. The duo arrived at the space station on June 6. In August, NASA announced the uncrewed return of Starliner to Earth and integrated Wilmore and Williams as part of the space station’s Expedition 71/72 for a return on Crew-9.
      Williams and Wilmore traveled 121,347,491 miles during their mission, spent 286 days in space, and completed 4,576 orbits around Earth. Hague and Gorbunov traveled 72,553,920 miles during their mission, spent 171 days in space, and completed 2,736 orbits around Earth.
      Hague, Williams, and Wilmore completed over 900 hours of research, conducting more than 150 unique experiments. During their time in orbit, the crew studied plant growth and development, tested stem cell technology to improve patient outcomes on Earth, and participated in research to understand how the space environment affects material degradation. They also performed a spacewalk and collected samples from the station’s exterior, studying the survivability of microorganisms in space. Additionally, the crew supported 30 ham radio events with students worldwide and conducted a student-led genetic experiment, helping to inspire the next generation of explorers.
      NASA’s Commercial Crew Program has delivered on its goal of safe, reliable, and cost-effective transportation to and from the International Space Station from the United States through a partnership with American private industry. This partnership is changing the arc of human spaceflight history by opening access to low Earth orbit and the International Space Station to more people, more science, and more commercial opportunities. The space station remains the springboard to NASA’s next great leap in space exploration, including future missions to the Moon and, eventually, to Mars.
      Find more information on NASA’s Commercial Crew Program at:
      https://www.nasa.gov/commercialcrew
      -end-
      Joshua Finch / Jimi Russell
      Headquarters, Washington
      202-358-1100
      joshua.a.finch@nasa.gov / james.j.russell@nasa.gov
      Courtney Beasley
      Johnson Space Center, Houston
      281-483-5111
      courtney.m.beasley@nasa.gov
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      Last Updated Mar 24, 2025 LocationNASA Headquarters Related Terms
      Humans in Space International Space Station (ISS) Missions View the full article
    • NASA
      Meet the Johnson CLPS Team Supporting NASA’s Lunar Exploration Goals
      By NASA
      As part of NASA’s Artemis campaign, the Commercial Lunar Payload Services (CLPS) initiative, managed out of Johnson Space Center in Houston, is paving the way for conducting lunar science for the benefit of humanity.

      Through CLPS, NASA teams worked closely with commercial companies to develop a new model for space exploration, enabling a sustainable return to the Moon. These commercial missions deliver NASA science and technology to the lunar surface, providing insights into the environment and demonstrating new technologies that will support future astronauts—on the Moon and, eventually, on Mars.
      Carrying a suite of NASA science and technology, Firefly Aerospace’s Blue Ghost Mission 1 successfully landed at 3:34 a.m. EST on Sunday, March 2, 2025, near a volcanic feature called Mons Latreille within Mare Crisium, a more than 300-mile-wide basin located in the northeast quadrant of the Moon’s near side.Firefly Aerospace Intuitive Machines’ IM-2 captured an image March 6, 2025, after landing in a crater from the Moon’s South Pole. The lunar lander is on its side about 820 feet from the intended landing site, Mons Mouton. In the center of the image between the two lander legs is the Polar Resources Ice Mining Experiment 1 suite, which shows the drill deployed.Credit: Intuitive Machines 2025: A Year of Lunar Firsts

      This year has already seen historic milestones. Firefly Aerospace’s Blue Ghost Mission 1 successfully delivered 10 science and technology instruments to the Moon on March 2, 2025. It touched down near a volcanic feature called Mons Latreille within Mare Crisium, a basin over 300 miles wide in the northeast quadrant of the Moon’s near side. Intuitive Machines’ IM-2 Mission, landed near the Moon’s South Pole on March 6, marking the southernmost lunar landing ever achieved.

      The lunar deliveries for NASA have collected valuable insights and data to inform the next giant leap in humanity’s return to the Moon, helping scientists address challenges like lunar dust mitigation, resource utilization, and radiation tolerance.

      Meet the Johnson employees contributing to lunar innovations that are helping to shape the future of human presence on the Moon.

      Mark Dillard: Pioneering Payload Integration
      Official NASA portrait of CLPS Payload Integration Manager Mark Dillard. NASA/James Blair Mark Dillard, Blue Ghost Mission 1 payload integration manager, has been at the forefront of space exploration for more than 40 years, including 28 years with the International Space Station Program. Beyond ensuring all NASA payloads are integrated onto the lunar landers, he oversees schedules, costs, and technical oversight while fostering strong partnerships with CLPS vendors and NASA science teams.

      “I believe NASA is about to enter its next Golden Age,” said Dillard. “The enthusiasm of Firefly’s engineering team is contagious, and it has been a privilege to witness their success.”

      Dillard’s career includes five years as NASA’s resident manager in Torino, Italy, where he oversaw the development of International Space Station modules, including three logistics modules, the European Space Agency’s Columbus module, and two space station nodes.
      Mark Dillard in the clean room with Firefly Aerospace’s Blue Ghost Mission 1 lander behind him. “Like Apollo, Shuttle, and the International Space Station Programs, Artemis will add the next building block for space exploration,” said Dillard. “The CLPS initiative is a significant building block, aiming to establish reliable and long-term access to the lunar surface.”

      Susan Lederer: Guiding Science in Real Time
      Official portrait of CLPS Project Scientist Susan Lederer.NASA/Bill Stafford Susan Lederer, IM-2 project scientist, has spent years ensuring all the NASA instruments are fully prepared for lunar operations. She oversees real-time science operations from IM’s Nova Control Center, working to maximize the mission’s scientific return and prepare for the next generation of astronauts to explore the Moon, Mars, and beyond.

      “We have done our best with remote data, but the only way to truly understand the Moon—how to drill for resources, how to live on another celestial body—is to go there and do the experiments,” she said. “Now, we get to do that.”

      Lederer’s path to CLPS was shaped by a background in space exploration, astrophysics, and planetary science. She has contributed to multiple spacecraft missions, including NASA’s Deep Impact mission, which sent a projectile into Comet Tempel 1, and a separate mission that retrieved a sample from asteroid Itokawa.

      On Ascension Island, a remote joint U.S. Air Force and Royal Air Force base, she co-led the construction of a 20,000-pound optical telescope to study space debris. Her work spans collaborations with the Defense Advanced Research Projects Agency, a tenure as a physics professor, and the design of impact experiments at NASA’s Experimental Impact Lab, where she used a vertical gun firing projectiles at speeds exceeding those of sniper rifles to study asteroid and comet collisions.

      Lederer has logged hundreds of hours conducting observing runs at professional observatories worldwide, where she refined both her scientific precision and her ability to repair instruments while working alone on remote mountaintops.

      As a private pilot and SciComm (the science equivalent of Capsule Communicator) for NASA’s Desert Research and Technology Studies, she honed her mission communication skills. She was also part of an international team that discovered two extrasolar planetary systems—one with a single Earth-sized planet and another with seven—orbiting ultracool red dwarf stars.

      Her expertise has uniquely prepared her to oversee real-time science operations for lunar missions in high-intensity environments.
      NASA and Intuitive Machines IM-1 lunar lander mission status press briefing. From left to right: Steve Altemus, Intuitive Machines’ chief executive officer and co-founder; Dr. Joel Kearns, NASA’s deputy associate administrator, Exploration, Science Mission Directorate; Dr. Tim Crain, Intuitive Machines’ chief technology officer and co-founder; and CLPS Project Scientist Susan Lederer. NASA/Robert Markowitz Lederer emphasizes the importance of both scientific discovery and the practical realities of living and working on another world—a challenge NASA is tackling for the first time in history.

      “Honestly, it’s when things don’t go as planned that you learn the most,” she said. “I’m looking forward to the surprises that we get to solve together as a team. That’s our greatest strength—the knowledge and teamwork that make this all happen.”

      Lederer credits the success of CLPS lunar deliveries to the dedication of teams working on payloads like Polar Resources Ice Mining Experiment-1 and Lunar Retroreflector Array, as well as peers within NASA’s Science Mission Directorate, Space Technology Mission Directorate, and Intuitive Machines.

      “What we do every day in CLPS creates a new world for exploration that is efficient in schedule, cost, and gaining science and technology knowledge in these areas like we’ve never done before,” said Lederer. “It feels very much like being a trailblazer for inspiring future generations of explorers – at least that’s my hope, to keep the next generation inspired and engaged in the wonders of our universe.”
      View the full article
    • NASA
      The NASA DC-8 Retires: Reflections on its Contributions to Earth System Science
      By NASA
      Explore This Section Earth Home Earth Observer Home Editor’s Corner Feature Articles Meeting Summaries News Science in the News Calendars In Memoriam More Archives 13 min read
      The NASA DC-8 Retires: Reflections on its Contributions to Earth System Science
      Introduction
      Since 1987, a highly modified McDonnell Douglas DC-8 aircraft has been a workhorse in NASA’s Airborne Science Program (ASP)—see Photo 1. The aircraft, located at NASA’s Armstrong Flight Research Center (AFRC) in California, flew countless missions as a science laboratory, producing science data that supports projects serving the world’s scientific community, particularly the NASA Earth science community. NASA recently decided to retire the venerable DC-8 aircraft, which made its last science flight in April 2024. The DC-8 is being replaced with a similarly refurbished Boeing 777 aircraft, which will be even more capable than the DC-8.
      Photo 1. NASA’s DC-8 flying laboratory flew Earth science missions for NASA’s. Airborne Science Program (ASP) from 1987–2024. The versatile aircraft was used to conduct a variety of research experiments that spanned all seven continents. Photo credit: Lori Losey [NASA’s Armstrong Flight Research Center (AFRC)] More information is available about the full history of ASP, its primary objectives, and its many achievements in an archived article: see “Flying in the ‘Gap’ Between Earth and Space: NASA’s Airborne Science Program” [The Earth Observer, September–October 2020, 32:5, 4–14].
      Workshop Overview
      The NASA History Office and NASA Earth Science Division cohosted a workshop, titled “Contributions of the DC-8 to Earth System Science at NASA,” on October 24–25, 2024 at the Mary W. Jackson NASA Headquarters (HQ) Building in Washington, DC – see Photo 2.
      The agenda included not just the DC-8’s contributions to Earth Science at NASA, but also its role supporting the Aeronautics Research Mission Directorate and work in space science. Many DC-8 veterans – including several who are now retired – attended the event in person or online. The program consisted of six panels and roundtables, each calling attention to a unique aspect of the DC-8 story.
      Photo 2. Group photo of the in person and remote participants of the workshop on “Contributions of the DC-8 to Earth System Science at NASA,” which took place October 24–25, 2024 at the Mary W. Jackson NASA Headquarters (HQ) Building in Washington, DC. Photo credit: Rafael Luis Méndez Peña [NASA’s Ames Research Center, Earth Science Program Office] The event featured 38 individuals (speakers, panelists, and moderators) from NASA HQ, five NASA centers, eight universities, the Search for Extraterrestrial Intelligence Institute, and the National Oceanic and Atmospheric Administration. In addition, Spanish filmmaker Rafael Luis Méndez Peña debuted a trailer for his documentary film, NASA-817, on October 24 and took photographs during the workshop. The ??? agenda a workshop recording ???, and other related materials are available through the NASA History Office.
      The Tale of the NASA DC-8
      The article follows the outline of the workshop that places the DC-8 in the context of the overall history of NASA aircraft observations, science campaigns, community, and international collaboration, education and outreach activities.
      A History in Context: the DC-8 and NASA’s Airborne Science Program
      NASA’s involvement in airborne science extends to the agency’s inception. The National Aeronautics and Space Act of 1958 states that NASA’s first objective shall be “the expansion of human knowledge of phenomena in the atmosphere and space.” Subsequent legislation expanded NASA’s role in atmospheric and Earth system science. To fulfill this objective, NASA maintains a fleet of airborne platforms through ASP – see Figure –to study the environment, develop new technologies, verify satellite data, and monitor space vehicle activity.
      Figure. The DC-8 was but one aircraft is NASA’s sizeable Airborne Science Fleet – which is maintained and operated by ASP. Note that in addition to a variety of piloted aircraft operating at different altitudes shown in this drawing, NASA also operates uncrewed aircraft systems and even uses kites to conduct Earth observations. Figure credit: NASA Science Suborbital Platforms, NASA’s Goddard Space Flight Center, Science Support Office NASA operated two large flying laboratories prior to the DC-8 Airborne Science Laboratory. Both aircraft were converted Convair (CV) 990s. Regrettably, both aircraft succumbed to catastrophic accidents. The first, known as Galileo, collided with a U.S. Navy P-3 Orion near Moffett Field, CA, in April 1973, killing 11 NASA personnel. Its replacement, Galileo II, crashed on takeoff at March Air Force Base in July 1985. While there were no fatalities in the second accident, the ensuing fire consumed the aircraft and its instruments. The loss of Galileo II left a gaping hole in NASA’s ability to conduct essential scientific and engineering research.
      In January 1986, after months of bureaucratic scrambling, NASA finalized the purchase of former commercial airliner (DC-8-72) for $24 million, which included costs to modify the aircraft to carry a science payload and crew. The modified DC-8 Airborne Science Laboratory—shown in Photo 2— arrived at NASA Ames Research Center during the Summer of 1987.
      Overview Presentations on Airborne Science
      Jack Kaye [NASA Headquarters—Associate Director for Research of the Earth Science Division] gave the meeting’s opening remarks, where he placed the DC-8’s activities in a larger perspective. He noted that one of the features that makes airborne science so unique at NASA is the combination of platforms, sensors, systems, people, and opportunities. The DC-8 was able to carry a large number of people as well as instruments to carry out long-range operations under diverse conditions.
      “[The DC-8 offered] a really versatile, flexible platform that’s allowed for lots of science,” said Kaye.
      Later in the meeting, Karen St. Germain [NASA Headquarters—Director of the Earth Science Division] built upon Kaye’s comments. She noted that while NASA’s satellite missions receive most of the public’s attention, airborne science is an essential part of the NASA mission.
      “This is the grassroots of science,” she stressed. “It’s where a lot of the great ideas are born. It’s where a lot of the fledgling sensor technologies are demonstrated.”
      First Flight for the DC-8
      NASA routinely conducts field campaigns – where ground observations are timed and coordinated with aircraft flights (often at more than one altitude) and with satellite overpasses to gain a comprehensive (multilayered, multiscale) picture of the atmosphere over a certain area. A more detailed account of two NASA field campaigns from the 1980s and 1990s, and their follow-up missions, is available in an archived article: see “Reflections on FIFE and BOREAS: Historical Perspective and Meeting Summary” [The Earth Observer, January–February 2017, 29:1, 6–23]. The article illustrates scaled observations as they were conducted during FIFE and BOREAS.
      Researchers first used the DC-8 Airborne Science Laboratory on a high-profile interagency field campaign – Antarctic Airborne Ozone Expedition (AAOE), the first airborne experiment to study the chemistry and dynamics of the Antarctic ozone hole. The scientific data collected during AAOE produced unequivocable evidence that human-made chemicals were involved in the destruction of ozone over the Antarctic. This data served as a major impetus toward the enactment of amendments to the Montreal Protocol, which banned the manufacture of chlorofluorocarbons.
      Estelle Condon [NASA’s Ames Research Center (ARC), emeritus] was a program manager for AAOE. During the meeting, she shared her memories of the hectic days leading up to the DC-8’s first mission.
      “There was an enormous task in front of [the aircraft team] – just a huge task – to get all the relay racks, all the wiring, all the ports for the windows designed and built so that when the scientists finally came, all that instrumentation could actually be put on the aircraft,” said Condon. She added that the ARC staff worked day and night and every weekend to make the plane ready.
      “It’s a miracle that they were able to put everything together and get it to the tip of South America in time for the mission,” she said.
      Other Noteworthy Field Campaigns Involving the DC-8
      The DC-8 would go on to be used in many other field campaigns throughout its 37-year history
      and was central to several of NASA’s research disciplines. For example, Michael Kurylo [NASA Headquarters—Atmospheric Composition Program Scientist] was the manager of NASA’s Upper Atmosphere Research Program, where he developed, promoted, and implemented an extramural research program in stratospheric and upper tropospheric composition and directed its advanced planning at a national and international level. Kurylo summarized the DC-8’s many flights to study stratospheric chemistry beyond the AAOE missions.
      Kurylo also discussed the DC-8’s role in tropospheric chemistry investigations, especially through the many field campaigns that were conducted as part of the Global Troposphere Experiment (GTE). He also touched on the culture of NASA airborne science and the dynamic that existed between scientists and those who operated and maintained the aircraft.  “The scientists were always referred to [by NASA pilots and groundcrew] as ‘coneheads’…. Too much college, not enough high school,” Kurylo explained. But he and his colleagues have such fond memories of their time spent working together onboard the DC-8. 
      James Crawford [NASA’s Langley Research Center], a project scientist for many of the GTE campaigns, explained that from 1983–2001 16 GTE aircraft-based missions, each with its own name and location, took place. Each mission collected a rich set of data records of atmospheric observations and on many occasions the data were used as baselines for subsequent campaigns. The DC-8 was one of several NASA aircraft involved, the others being the Corvair-990, Electra, and P-3B.
      Joshua Schwarz [NOAA’s Chemical Sciencc Laboratory] discussed the airplane’s role in global atmospheric monitoring.  He recall thinking, after his first experience with the DC-8 that this flying airborne laboratory, “…was going to make things possible that wouldn’t otherwise be possible,” Schwarz concluded after his first encounter with the DC-8.
      Other workshop participants went on to describe how – for nearly four decades – investigators used data collected by instruments on the DC-8 to conduct research and write papers on important scientific and engineering topics.
      The People Behind the Aircraft: The DC-8 Community
      The DC-8 was a large and durable aircraft capable of long-range flights, which made it ideal for conducting scientific research. Around these research efforts a strong community emerged. Over three decades, the DC-8 accommodated many investigators from NASA, interagency offices, U.S. universities, and international organizations on extended global missions. Agency officials also moved the DC-8 base of operations several times between 1986 and 2024, thereby demanding tremendous cross-center cooperation.
      “Looking around the room, it’s clear that what brought us together [for the workshop] is more than just an aircraft,” said Nickelle Reid [NASA’s Armstrong Flight Research Center]. “It’s been a shared commitment, decades of passion and dedication from scientists, yes, but also mechanics, technicians, integration engineers, project managers, mission planners, operations engineers, flight engineers, mission directors, mission managers, logistics technicians and, of course, pilots. This village of people has been the beating heart of the DC-8 program.”
      This DC-8 community was well represented at this workshop and played a key role in its success.
      The DC-8 as a Means of International Engagement
      The DC-8 community expanded beyond the U.S., opening unique opportunities for international engagement. The campaigns of the DC-8 Airborne Science Laboratory routinely involved foreign students, institutions, and governments. For example, the Korea–U.S. Air Quality (KORUS-AQ) campaign, an international cooperative air quality field study in Korea, took place in 2016. For more information about this campaign, see the archived Earth Observer article, “Flying in the ‘Gap’ Between Earth and Space: NASA’s Airborne Science Program” [The Earth Observer, September–October 2022, 32:5, 4–14].
      Yunling Lou [NASA/Jet Propulsion Laboratory] spoke to the workshop audience about the value of international collaboration.
      “I think [international collaboration] really helped – not just doing the collaboration [to accomplish a specific mission] but doing the training, the capacity building in these countries to build the community of global scientists and engineers,” said Lou.
      Trina Dryal [LaRC—Deputy Director] continued that the DC-8 and NASA’s other airborne assets are more than just science laboratories.
      “[They] are opportunities for science, diplomacy, international collaboration, cross learning, educational inspiration, and goodwill,” said Dryal—see Photo 3.
      Photo 3. International collaborations included educational endeavors.  Here, Walter Klein [AFRC—DC-8 Mission Manager] poses with a group of Chilean students onboard the DC-8 Airborne Science Laboratory in Punta Arenas, Chile, March 2004. Photo credit: Jim Closs [NASA’s Langley Research Center] Student Investigations on the DC-8
      Closer to home, the flying scientific laboratory affected the lives of many U.S. students and early career professionals. NASA’s Student Airborne Research Program (SARP), is an eight-week summer internship for rising-senior undergraduates that takes place annually on the East and West coasts of the U.S – see Photo 4. During the program, students gain hands-on experience conducting all aspects of a scientific campaign. They conduct field research, analyze the data, and gain access to one or more of NASA’s ASP flying science laboratories.  Since 2009, this program alone has provided hands on experience in conducting NASA Earth science research to XXXX students.
      Berry Lefer [NASA Headquarters—Tropospheric Composition Program Manager] pointed out that SARP helped to integrate American students into DC-8 scientific missions.
      “I want to make sure the NASA historians understand that the DC-8 is the premier flying laboratory on the planet, bar none,” said Lefer. “You’ve seen over the whole three-decade life of the DC-8 that education and outreach, student involvement has been a hallmark of the DC-8 [program].”
      Yaitza Luna-Cruz [NASA Headquarters—Program Executive] was one among several SARP alumni who delivered testimony on the impact of the SARP program at the workshop.
      “SARP unleashed my potential in ways that I cannot even describe,” said Luna-Cruz. “You never know what a single opportunity could do to shape the career of a student or early career researcher.
      Luna-Cruz hopes these efforts continue with the coming of NASA’s new Boeing 777 airborne laboratory.
      Photo 4. One of the most popular student investigations flown on the DC-8 (and other ASP aircraft) was (is) the Student Airborne Research Program (SARP), in which upper-level undergraduate students can gain valuable hands-on experience conducting field research.  Students taking part in SARP and their mentors posed with the DC-8 at AFRC in 2019 [top] and in 2022 [bottom]. The 2022 SARP group flew flights over California’s Central Valley to study air quality. Photo credit: [Top] NASA; [bottom] Lauren Hughes [ARC] Final Flight and Retirement of the DC-8
      The DC-8 Airborne Science Laboratory flew its last science flight during the international Airborne and Satellite Investigation of Asian Air Quality mission (ASIA-AQ) in April 2024. Since its final flight, the aircraft has been retired to Idaho State University (ISU). Today, students in ISU’s aircraft maintenance program work on the airplane to develop real-world technical skills – continuing the DC-8’s mission as an educational platform. According to Gerald Anhorn [ISU—Dean of College of Technology], ISU students have a unique opportuning to gain experience working on a legendary research aircraft.
      “Our students have that opportunity because of [NASA’s] donation” to the school, said Auborn.
      Conclusion: Flying Toward the Future – From DC-8 to Boeing 777
      While the DC-8 is retiring from active service, airborne observations continue to be a vital part of NASA’s mission. The agency recently acquired a Boeing 777and will modify it to support its ongoing airborne scientific research efforts. This new addition expands beyond the capacity of the DC-8 by allowing for even longer flights with larger payloads and more researchers to gather data. Several members of the Boeing 777 team from NASA’s Langley Research Center (LaRC) attended the workshop.
       “I mentioned I was in charge of the ‘replacement’ for the DC-8,” said Martin Nowicki [LaRC—Boeing 777 Lead]. “Over the last two days, here, it’s become pretty apparent that there’s no ‘replacing’ the DC-8. It’s carved out its own place in history. It’s just done so much.”
      Nowicki looks forward to working with workshop participants to identify useful lessons of the past for future operators. He concluded that the Boeing 777 will carry the legacy of the DC-8 and continue with capturing the amazing science of ASP.
      Acknowledgments
      The authors wish to thank Jack Kaye [NASA HQ—Associate Director of Research for the Earth Science Division] for his helpful reviews of the article draft.  The first author also wishes to thank Lisa Frazier [NASA Headquarters—Strategic Events and Engagement Lead] for providing support and assistance throughout for the in-person workshop participants. and to the Earth Science Project Office team from NASA’s Ames Research Center, who performed essential conference tasks, such as website construction, audio-visual support, and food service management. This article is an enhanced version of the first author’s summary, which appeared in the Spring 2025 issue of News & Notes – The NASA History Office’s newsletter.
      Bradley L. Coleman
      NASA’s Marshall Space Flight Center, NASA History Office
      bradley.l.coleman@nasa.gov
      Alan B. Ward
      NASA’s Goddard Space Flight Center/Global Science & Technology Inc.
      alan.b.ward@nasa.gov
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      Last Updated Mar 11, 2025 Related Terms
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