Imagine a single mission that could unravel the mysteries of our planet's oceans, clouds, and tiny airborne particles, potentially reshaping how we tackle climate change and protect our ecosystems. That's the thrilling promise of NASA's Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, and the 2025 PAC3 meeting just scratched the surface of its groundbreaking potential. But here's where it gets controversial – could these advanced tools spark debates about how we prioritize environmental research when global challenges like wildfires and algal blooms demand urgent action? Stick around as we dive into the details, and you might discover the part most people miss: the hidden synergies between space tech and everyday science that could change the game for Earth monitoring.
Launched back in February 2024, NASA's PACE mission stands as a pivotal player in Earth system science, aimed at deepening our grasp of how plankton, aerosols, clouds, and oceans interact to shape our climate, carbon cycles, and overall ecosystems. To bolster its efforts, PACE has backed three essential teams: the PACE Postlaunch Airborne eXperiment (PACE–PAX), the third PACE Science and Applications Team (SAT3), and the PACE Validation Science Team (PVST). These groups each bring unique strengths to the table, working hand-in-hand to refine data products and ensure top-notch quality through rigorous testing and development.
Given the overlapping interests among these teams, the organizers smartly merged their individual gatherings into a single, all-encompassing event dubbed the 'PAC3' meeting. This unified conference unfolded from February 18 to 21, 2025, at NASA's Goddard Institute for Space Studies (GISS) in bustling New York City – conveniently timed just 10 days after PACE's first anniversary. Check out Photo 1 and Photo 2 for a glimpse of the excitement.
At its heart, the PACE mission pursues ambitious long-term goals, such as gauging the productivity of ocean and land ecosystems, spotting dangerous algal blooms, and investigating the ties between aerosols and clouds. By weaving these insights into broader Earth system science, the mission boosts both research depth and practical decision-making skills. These objectives come to life through an innovative trio of instruments that complement each other perfectly.
First up is the Ocean Color Instrument (OCI), a hyperspectral radiometer that captures the intricate biological, chemical, and physical features of ocean ecosystems by measuring light across hundreds of precise wavelengths, spanning from deep ultraviolet to infrared. What's more, its wide spectral coverage and fine resolution also empower scientists to analyze aerosols, clouds, land surfaces, and trace gases, offering a versatile toolkit for environmental study.
Then there's the Hyper-Angular Rainbow Polarimeter #2 (HARP2), a wide-swath multiangle polarimeter boasting four visible-to-near-infrared channels and up to 60 viewing angles per channel – that's what gives it its 'hyperangular' edge. HARP2 excels at extracting details about clouds and aerosols, providing critical data for atmospheric research.
Complementing HARP2 is the Spectropolarimeter for Planetary Exploration (SPEXone), another multiangle polarimeter but with its own distinct strengths: a narrower swath, five viewing angles, and sensitivity across 100 bands from ultraviolet to near-infrared. It's finely tuned for pinpointing aerosol properties, rounding out the instrument suite for comprehensive atmospheric probing.
For those eager to learn more, the PACE mission's official website (https://pace.gsfc.nasa.gov/) is a treasure trove of additional details.
The PAC3 meeting kicked off with an in-depth review of PACE's current status and latest advancements. This included progress reports on the OCI, SPEXone, and HARP2 from their lead scientists: Gerhard Meister from NASA's Goddard Space Flight Center (GSFC), Otto Hasekamp from the Netherlands' Space Research Organization (SRON), and Vanderlei Martins from the University of Maryland, Baltimore County (UMBC). The discussion also covered how early mission data is becoming available and accessible, with summaries available on the dedicated PACE data access site (https://pace.oceansciences.org/accesspacedata.htm) and the helpful 'help hub' tutorials (https://oceancolor.gsfc.nasa.gov/resources/docs/tutorials/).
On the OCI front, Meister shared that the instrument has surpassed its radiometric benchmarks, producing ultra-precise hyperspectral data. With the rollout of Version 3 (V3) data reprocessing, calibration now relies solely on in-orbit solar diffuser measurements, boosting long-term consistency. V3 brings key enhancements, like better fixes for atmospheric gas absorption and updated bidirectional reflectance distribution function (BRDF) parameters – think of BRDF as a way to describe how surfaces reflect light from different angles, crucial for accurate Earth observations. Meister pointed out that studies of time-based patterns have uncovered solar diffuser wear in the ultraviolet spectrum, with teams actively applying corrections. For instance, they're leveraging a monthly-exposed diffuser to fine-tune readings from one that's used daily. He also touched on other hiccups, such as banding at around 10° scan angles, diminished precision in the 590–610 nm range, and crosstalk fixes to address wavelength accuracy issues below 340 nm in the ultraviolet. These tweaks ensure data users can trust the results for everything from ocean health to atmospheric clarity.
For SPEXone, Hasekamp highlighted its delivery of high-quality radiometric and polarimetric information. The team has crafted the Remote Sensing of Trace Gases and Aerosol Products (RemoTAP) algorithm, a sophisticated tool for mapping total atmospheric aerosols, their size distributions, absorbed energy, and layer heights. Initial observations show minimal distortion in size retrievals for low aerosol optical depth (AOD) scenarios, aligning well with ground-based AERONET Sun photometers from the Aerosol Robotic Network (https://aeronet.gsfc.nasa.gov/). Future refinements will tackle calibration mismatches with OCI, ensuring seamless integration across instruments.
Martins reported that HARP2 is performing admirably, capturing detailed polarization data on aerosols and clouds. Upcoming plans involve refining geolocation and calibration, plus cross-checking with OCI and SPEXone to unify all PACE radiometric outputs into a cohesive dataset.
Shifting gears, several talks spotlighted the resources making PACE data readily available to the wider scientific world.
Alicia Scott from GSFC/Science Applications International Corporation (SAIC) showcased the Ocean Biology Distributed Active Archive Center (OB.DAAC) (https://www.earthdata.nasa.gov/centers/ob-daac), which archives and processes data from all PACE sensors. Tools like Earthdata Search (https://search.earthdata.nasa.gov/) and the earthaccess Python libraries (https://github.com/nsidc/earthaccess) simplify data downloads with user-friendly workflows. Plus, training videos and guides (https://oceancolor.gsfc.nasa.gov/resources/docs/tutorials/) help newcomers get up to speed quickly.
Carina Poulin from GSFC/Science Systems and Applications, Inc. (SSAI) walked through the PACE Data Website (https://pace.oceansciences.org/accesspacedata.htm), a central portal for datasets, reprocessing notes, and product guides. The V3 section details calibration tweaks, validation findings, and ways to weave PACE data into research routines.
And this is the part most people miss – the intriguing overlaps with other missions that could redefine our approach to planetary science. Many of PACE's goals mirror those of the Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE), a collaborative effort by the European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA). As a result, EarthCARE teams joined the PAC3 discussions. EarthCARE features four cutting-edge instruments: the Atmospheric LIDar (ATLID), Cloud Profiling Radar (CPR), Multi-Spectral Imager (MSI), and Broad-Band Radiometer (BBR). Their data pairs beautifully with PACE's, enabling cross-verification and richer insights into Earth's complex systems. This partnership extends to validation, where activities for one mission benefit both – for example, PACE-PAX included EarthCARE checks, and vice versa during PACE flyovers. But here's where it gets controversial: Is this international cooperation the key to faster climate solutions, or does it dilute national priorities in an era of rising geopolitical tensions?
Rob Koopman from ESA updated on EarthCARE's strides, including validation prep through ESA-JAXA joint initiatives. ATLID lidar results match up excellently with airborne High Spectral Resolution Lidar (HSRL) data from PACE-PAX, showing strong accuracy for cloud and aerosol detection, though some calibration hurdles remain. Multiple joint validation campaigns are in the works to align PACE and EarthCARE data for consistent scientific outputs.
The conference's opening sessions centered on PACE–PAX, an airborne campaign conducted in California and nearby coasts during September 2024 – take a look at Figure 1. Led by Kirk Knobelspiesse (GSFC, PACE Polarimeter Lead and PACE-PAX Mission Scientist), Ivona Cetinić (GSFC/Morgan State University, PACE Validation Science Team lead and PACE-PAX Deputy Mission Scientist), and Brian Cairns (GISS, PACE Deputy Project Scientist and PACE-PAX Deputy Mission Scientist), the effort drew participants from across NASA, universities like the University of Maryland, Baltimore County, agencies such as the Naval Postgraduate School and NOAA, and international bodies like SRON.
In essence, PACE–PAX supported the PACE Science Data Product Validation Plan (https://pace.oceansciences.org/docs/PACEValidationPlan_14July2020.pdf), encompassing new product validations for PACE and EarthCARE, data collection during satellite passes, measurement verifications, and explorations of local phenomena like layered aerosols and phytoplankton surges.
Operationally, the campaign leveraged a mix of platforms: planes like NASA's ER-2 and the Naval Postgraduate School's CIRPAS Twin Otter, ships including NOAA's R/V Shearwater and the R/V Blissfully sailboat, and ground tools such as Sun photometers and lidars. Highlights include 13 ER-2 flights, 17 Twin Otter sorties, 15 Shearwater cruises, and 9 Blissfully outings, yielding 16 days of PACE overpass data, six for EarthCARE, plus ground calibrations at Ivanpah Playa, CA (https://calval.cr.usgs.gov/apps/ivanpah), and AERONET site flyovers. Bonus discoveries? Intense California wildfires (like the Bridge, Airport, and Line fires in September 2024) and a red tide bloom off Northern California's coast in late September – see Figure 2. PVST members also synced their validations with the campaign.
Early highlights from PACE-PAX sessions underscored:
- Checking EarthCARE and PACE aerosol/cloud data against HSRL2 on the ER-2,
- Validating PACE cloud info via ER-2 polarimeters and Twin Otter sensors,
- Successful matches between OCI hyperspectral data and ship-measured chlorophyll-a levels, and
- Captures of varied events, like marine stratocumulus clouds and wildfire smoke over clouds, aiding new algorithm tests.
These initial outcomes underline how such field efforts act as vital links between space-based science and real-world ground truth, potentially accelerating breakthroughs in environmental monitoring.
Next, the SAT3 sessions, blending pure science with practical applications, formed the meeting's vibrant second act. As previously covered in The Earth Observer's 2023 piece on the PACE Applications Workshop (https://assets.science.nasa.gov/content/dam/science/esd/earth-observer/2023/EO%20Nov-Dec%202023-Digital%20508.pdf), SAT3 explored ways PACE data can advance research and societal benefits. Focused discussions updated on NASA-backed projects for novel geophysical data retrieval, better data assimilation, and improved product pipelines.
SAT3 presentations revealed promising early findings, such as using OCI for specific pigment absorption reads, diatom biomass estimates, and chlorophyll counts – tools that help track individual phytoplankton like diatoms and cyanobacteria, essential for ecosystem studies and bloom dynamics. Talks also covered models for spotting harmful algal blooms (HABs), enhancing early alert systems to safeguard public health and economies in coastal zones and the Great Lakes. Additionally, new aerosol absorption/scattering insights from polarimeters like SPEXone and HARP2 are feeding into aerosol-cloud interaction models, while machine learning is integrating PACE data into Earth system simulations for sharper global climate tracking.
Overall, SAT3 underscored PACE's broad influence, from oceanography to climate modeling, sparking ideas for transformative applications.
Finally, PVST sessions stressed the team's role in verifying PACE data reliability, precision, and stability. Key areas included algorithm creation and testing, inter-mission collaborations, field campaign ties, and cloud product validations.
Presenters updated on pipelines for radiometric and polarimetric validations, comparing against trusted sources like AERONET photometers, HSRL, and the Pan-and-Tilt Hyperspectral Radiometer (PANTHR) from Belgium's Flanders Marine Institute – installed on a 30-meter tower in Chesapeake Bay (https://umbc.edu/stories/panthyr-in-chesapeake-bay/) in May 2024 as part of the WATERHYPERNET network (https://waterhypernet.org/), which delivers time-series hyperspectral water data for satellite validation across 400–900 nm wavelengths. Reports showed how PACE-PAX and overpass data refine pre-launch error estimates and uncertainty analyses. Other talks detailed cloud property validations, including thickness, height, and droplet sizes, bolstered by EarthCARE inputs. Ocean validations covered optical and biological retrievals, validating advanced phytoplankton and productivity products.
PVST's efforts build the trust needed for PACE data's global scientific use.
Wrapping up, the PAC3 meeting at GISS celebrated the unified push from PACE's teams to tackle wide-ranging Earth science puzzles. By merging PACE–PAX, SAT3, and PVST discussions, attendees fostered stronger partnerships, aligned projects, and paved paths for upcoming research and validations.
Interactive roundtables and updates emphasized PACE's role in long-standing questions, like aerosol impacts on cloud formation and ocean changes' effects on biogeochemical cycles. Action items emerged for sustained calibration, streamlined data flows, and algorithm improvements.
Notably, this was among the final major events at GISS before its closure in May 2025. PAC3's insights continue to fuel PACE's mission, amplifying its value in deciphering our planet's intricacies.
Kirk Knobelspiesse
NASA’s Goddard Space Flight Center
kirk.d.knobelspiesse@nasa.gov
Cecile S. Rousseaux
NASA’s Goddard Space Flight Center
cecile.s.rousseaux@nasa.gov
Ivona Cetinić
NASA’s Goddard Space Flight Center/Morgan State University
ivona.cetinic@nasa.gov
Andrew Sayer
NASA’s Goddard Space Flight Center
andrew.sayer@nasa.gov
What do you think? With missions like PACE revealing so much about our changing Earth, should we be investing more in international collaborations to combat climate threats, or might that spread resources too thin? And could the data from these instruments challenge existing climate models in ways that surprise us – for better or worse? Drop your thoughts in the comments; I'd love to hear if you agree, disagree, or have your own take on the future of planetary science!
