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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA Ames research scientist Kristina Pistone monitors instrument data while onboard the Twin Otter aircraft, flying over Monterey Bay during the October 2024 deployment of the AirSHARP campaign. NASA/Samuel Leblanc In autumn 2024, California’s Monterey Bay experienced an outsized phytoplankton bloom that attracted fish, dolphins, whales, seabirds, and – for a few weeks in October – scientists. A team from NASA’s Ames Research Center in Silicon Valley, with partners at the University of California, Santa Cruz (UCSC), and the Naval Postgraduate School, spent two weeks on the California coast gathering data on the atmosphere and the ocean to verify what satellites see from above. In spring 2025, the team returned to gather data under different environmental conditions.
Scientists call this process validation.
Setting up the Campaign
The PACE mission, which stands for Plankton, Aerosol, Cloud, ocean Ecosystem, was launched in February 2024 and designed to transform our understanding of ocean and atmospheric environments. Specifically, the satellite will give scientists a finely detailed look at life near the ocean surface and the composition and abundance of aerosol particles in the atmosphere.
Whenever NASA launches a new satellite, it sends validation science teams around the world to confirm that the data from instruments in space match what traditional instruments can see at the surface. AirSHARP (Airborne aSsessment of Hyperspectral Aerosol optical depth and water-leaving Reflectance Product Performance for PACE) is one of these teams, specifically deployed to validate products from the satellite’s Ocean Color Instrument (OCI).
The OCI spectrometer works by measuring reflected sunlight. As sunlight bounces off of the ocean’s surface, it creates specific shades of color that researchers use to determine what is in the water column below. To validate the OCI data, research teams need to confirm that measurements directly at the surface match those from the satellite. They also need to understand how the atmosphere is changing the color of the ocean as the reflected light is traveling back to the satellite.
In October 2024 and May 2025, the AirSHARP team ran simultaneous airborne and seaborne campaigns. Going into the field during different seasons allows the team to collect data under different environmental conditions, validating as much of the instrument’s range as possible.
Over 13 days of flights on a Twin Otter aircraft, the NASA-led team used instruments called 4STAR-B (Spectrometer for sky-scanning sun Tracking Atmospheric Research B), and the C-AIR (Coastal Airborne In-situ Radiometer) to gather data from the air. At the same time, partners from UCSC used a host of matching instruments onboard the research vessel R/V Shana Rae to gather data from the water’s surface.
Ocean Color and Water Leaving Reflectance
The Ocean Color Instrument measures something called water leaving reflectance, which provides information on the microscopic composition of the water column, including water molecules, phytoplankton, and particulates like sand, inorganic materials, and even bubbles. Ocean color varies based on how these materials absorb and scatter sunlight. This is especially useful for determining the abundance and types of phytoplankton.
Photographs taken out the window of the Twin Otter aircraft during the October 2024 AirSHARP deployment showcase the variation in ocean color, which indicates different molecular composition of the water column beneath. The red color in several of these photos is due to a phytoplankton bloom – in this case a growth of red algae. NASA/Samuel Leblanc
The AirSHARP team used radiometers with matching technology – C-AIR from the air and C-OPS (Compact Optical Profiling System) from the water – to gather water leaving reflectance data.
“The C-AIR instrument is modified from an instrument that goes on research vessels and takes measurements of the water’s surface from very close range,” said NASA Ames research scientist Samuel LeBlanc. “The issue there is that you’re very local to one area at a time. What our team has done successfully is put it on an aircraft, which enables us to span the entire Monterey Bay.”
The larger PACE validation team will compare OCI measurements with observations made by the sensors much closer to the ocean to ensure that they match, and make adjustments when they don’t.
Aerosol Interference
One factor that can impact OCI data is the presence of manmade and natural aerosols, which interact with sunlight as it moves through the atmosphere. An aerosol refers to any solid or liquid suspended in the air, such as smoke from fires, salt from sea spray, particulates from fossil fuel emissions, desert dust, and pollen.
Imagine a 420 mile-long tube, with the PACE satellite at one end and the ocean at the other. Everything inside the tube is what scientists refer to as the atmospheric column, and it is full of tiny particulates that interact with sunlight. Scientists quantify this aerosol interaction with a measurement called aerosol optical depth.
“During AirSHARP, we were essentially measuring, at different wavelengths, how light is changed by the particles present in the atmosphere,” said NASA Ames research scientist Kristina Pistone. “The aerosol optical depth is a measure of light extinction, or how much light is either scattered away or absorbed by aerosol particulates.”
The team measured aerosol optical depth using the 4STAR-B spectrometer, which was engineered at NASA Ames and enables scientists to identify which aerosols are present and how they interact with sunlight.
Twin Otter Aircraft
AirSHARP principal investigator Liane Guild walks towards a Twin Otter aircraft owned and operated by the Naval Postgraduate School. The aircraft’s ability to perform complex, low-altitude flights made it the ideal platform to fly multiple instruments over Monterey Bay during the AirSHARP campaign. NASA/Samuel Leblanc
Flying these instruments required use of a Twin Otter plane, operated by the Naval Postgraduate School (NPS). The Twin Otter is unique for its ability to perform extremely low-altitude flights, making passes down to 100 feet above the water in clear conditions.
“It’s an intense way to fly. At that low height, the pilots continually watch for and avoid birds, tall ships, and even wildlife like breaching whales,” said Anthony Bucholtz, director of the Airborne Research Facility at NPS.
With the phytoplankton bloom attracting so much wildlife in a bay already full of ships, this is no small feat. “The pilots keep a close eye on the radar, and fly by hand,” Bucholtz said, “all while following careful flight plans crisscrossing Monterey Bay and performing tight spirals over the Research Vessel Shana Rae.”
Campaign Data
Data gathered from the 2024 phase of this campaign is available on two data archive systems. Data from the 4STAR instrument is available in the PACE data archive and data from C-AIR is housed in the SeaBASS data archive.
Other data from the NASA PACE Validation Science Team is available through the PACE website: https://pace.oceansciences.org/pvstdoi.htm#
Samuel LeBlanc and Kristina Pistone are funded via the Bay Area Environmental Research Institute (BAERI), which is a scientist-founded nonprofit focused on supporting Earth and space sciences.
About the Author
Milan Loiacono
Science Communication SpecialistMilan Loiacono is a science communication specialist for the Earth Science Division at NASA Ames Research Center.
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Last Updated Jun 26, 2025 Related Terms
Ames Research Center's Science Directorate Ames Research Center Earth Earth Science Earth Science Division PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) Science Mission Directorate Explore More
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By European Space Agency
While satellites have revolutionised our ability to measure sea level with remarkable precision, their data becomes less reliable near coasts – where accurate information is most urgently needed. To address this critical gap, ESA’s Climate Change Initiative Sea Level Project research team has reprocessed almost two decades of satellite data to establish a pioneering network of ‘virtual’ coastal stations. These stations now provide, for the first time, reliable and consistent sea-level measurements along coastlines.
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By NASA
A new online portal by NASA and the Alaska Satellite Facility maps satellite radar meas-urements across North America, enabling users to track land movement since 2016 caused by earthquakes, landslides, volcanoes, and other phenomena.USGS An online tool maps measurements and enables non-experts to understand earthquakes, subsidence, landslides, and other types of land motion.
NASA is collaborating with the Alaska Satellite Facility in Fairbanks to create a powerful web-based tool that will show the movement of land across North America down to less than an inch. The online portal and its underlying dataset unlock a trove of satellite radar measurements that can help anyone identify where and by how much the land beneath their feet may be moving — whether from earthquakes, volcanoes, landslides, or the extraction of underground natural resources such as groundwater.
Spearheaded by NASA’s Observational Products for End-Users from Remote Sensing Analysis (OPERA) project at the agency’s Jet Propulsion Laboratory in Southern California, the effort equips users with information that would otherwise take years of training to produce. The project builds on measurements from spaceborne synthetic aperture radars, or SARs, to generate high-resolution data on how Earth’s surface is moving.
The OPERA portal shows how land is sinking in Freshkills Park, which is being built on the site of a former landfill on Staten Island, New York. Landfills tend to sink over time as waste decomposes and settles. The blue dot marks the spot where the portal is showing movement in the graph.Alaska Satellite Facility Formally called the North America Surface Displacement Product Suite, the new dataset comes ready to use with measurements dating to 2016, and the portal allows users to view those measurements at a local, state, and regional scales in a few seconds. For someone not using the dataset or website, it could take days or longer to do a similar analysis.
“You can zoom in to your country, your state, your city block, and look at how the land there is moving over time,” said David Bekaert, the OPERA project manager and a JPL radar scientist. “You can see that by a simple mouse click.”
The portal currently includes measurements for millions of pixels across the U.S. Southwest, northern Mexico, and the New York metropolitan region, each representing a 200-foot-by-200-foot (60-meter-by-60-meter) area on the ground. By the end of 2025, OPERA will add data to cover the rest of the United States, Central America, and Canada within 120 miles (200 kilometers) of the U.S. border. When a user clicks on a pixel, the system pulls measurements from hundreds of files to create a graph visualizing the land surface’s cumulative movement over time.
Land is rising at the Colorado River’s outlet to the Gulf of California, as indicated in this screenshot from the OPERA portal. The uplift is due to the sediment from the river building up over time. The graph shows that the land at the blue dot has risen about 8 inches (20 centimeters) since 2016.Alaska Satellite Facility “The OPERA project automated the end-to-end SAR data processing system such that users and decision-makers can focus on discovering where the land surface may be moving in their areas of interest,” said Gerald Bawden, program scientist responsible for OPERA at NASA Headquarters in Washington. “This will provide a significant advancement in identifying and understanding potential threats to the end users, while providing cost and time savings for agencies.”
For example, water-management bureaus and state geological surveys will be able to directly use the OPERA products without needing to make big investments in data storage, software engineering expertise, and computing muscle.
How It Works
To create the displacement product, the OPERA team continuously draws data from the ESA (European Space Agency) Sentinel-1 radar satellites, the first of which launched in 2014. Data from NISAR, the NASA-ISRO (Indian Space Research Organisation) Synthetic Aperture Radar mission, will be added to the mix after that spacecraft launches later this year.
The OPERA portal shows that land near Willcox, Arizona, subsided about 8 inches (20 centimeters) since between 2016 and 2021, in large part due to groundwater pumping. The region is part of an area being managed by state water officials.Alaska Satellite Facility Satellite-borne radars work by emitting microwave pulses at Earth’s surface. The signals scatter when they hit land and water surfaces, buildings, and other objects. Raw data consists of the strength and time delay of the signals that echo back to the sensor.
To understand how land in a given area is moving, OPERA algorithms automate steps in an otherwise painstaking process. Without OPERA, a researcher would first download hundreds or thousands of data files, each representing a pass of the radar over the point of interest, then make sure the data aligned geographically over time and had precise coordinates.
Then they would use a computationally intensive technique called radar interferometry to gauge how much the land moved, if at all, and in which direction — towards the satellite, which would indicate the land rose, or away from the satellite, which would mean it sank.
“The OPERA project has helped bring that capability to the masses, making it more accessible to state and federal agencies, and also users wondering, ‘What’s going on around my house?’” said Franz Meyer, chief scientist of the Alaska Satellite Facility, a part of the University of Alaska Fairbanks Geophysical Institute.
Monitoring Groundwater
Sinking land is a top priority to the Arizona Department of Water Resources. From the 1950s through the 1980s, it was the main form of ground movement officials saw, as groundwater pumping increased alongside growth in the state’s population and agricultural industry. In 1980, the state enacted the Groundwater Management Act, which reduced its reliance on groundwater in highly populated areas and included requirements to monitor its use.
The department began to measure this sinking, called subsidence, with radar data from various satellites in the early 2000s, using a combination of SAR, GPS-based monitoring, and traditional surveying to inform groundwater-management decisions.
Now, the OPERA dataset and portal will help the agency share subsidence information with officials and community members, said Brian Conway, the department’s principal hydrogeologist and supervisor of its geophysics unit. They won’t replace the SAR analysis he performs, but they will offer points of comparison for his calculations. Because the dataset and portal will cover the entire state, they also could identify areas not yet known to be subsiding.
“It’s a great tool to say, ‘Let’s look at those areas more intensely with our own SAR processing,’” Conway said.
The displacement product is part of a series of data products OPERA has released since 2023. The project began in 2020 with a multidisciplinary team of scientists at JPL working to address satellite data needs across different federal agencies. Through the Satellite Needs Working Group, those agencies submitted their requests, and the OPERA team worked to improve access to information to aid a range of efforts such as disaster response, deforestation tracking, and wildfire monitoring.
NASA-Led Project Tracking Changes to Water, Ecosystems, Land Surface News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
2025-076
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Last Updated Jun 06, 2025 Related Terms
Earth Science Earth Science Division Earthquakes Jet Propulsion Laboratory Natural Disasters Volcanoes Explore More
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By European Space Agency
Satellite observations show that sea-surface temperatures over the past four decades have been getting warmer at an accelerated pace.
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By European Space Agency
Image: The Copernicus Sentinel-2 mission shows us what is left of the Aral Sea, once the fourth largest lake in the world. View the full article
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