In the fall of 2024, the Baie de Monterey in California experienced a disproportionate phytoplankton flower that attracted fish, dolphins, whales, sea birds and – for a few weeks in October – scientists. A team from the NASA Ames Research Center in Silicon Valley, with partners from the University of California in Santa Cruz (UCSC), and the third naval school school spent two weeks on the Californian coast to collect data on the atmosphere and the ocean to verify what the satellites see above. In the spring of 2025, the team returned to collect data under different environmental conditions.
Scientists call for this process validation.
The PACE mission, which means plankton, aerosol, cloud, ocean ecosystem, was launched in February 2024 and designed to transform our understanding of ocean and atmospheric environments. More specifically, the satellite will give scientists a finely detailed look at life near the surface of the ocean and the composition and abundance of aerosol particles in the atmosphere.
Each time NASA launches a new satellite, it sends scientific validation teams around the world to confirm that the data of the instruments in space correspond to what traditional instruments can see on the surface. Airsharp (Airborne assessment of the optical depth of hyperspectral aerosols and performance of reflecting product reflectance for rhythm) is one of these teams, specifically deployed to validate the products of the oceanic instrument of the satellite (OCI).
The OIC spectrometer works by measuring reflected sunlight. While sunlight bounces from the surface of the ocean, it creates specific shades that researchers use to determine what is in the water column below. To validate the OIC data, research teams must confirm that measures directly on the surface correspond to those of the satellite. They also need to understand how the atmosphere changes the color of the ocean while the reflected light returns to the satellite.
In October 2024 and May 2025, the air team led simultaneous campaigns on airborne and conveyed campaigns. Entering the field for different seasons allows the team to collect data under different environmental conditions, validating the range of the instrument as much as possible.
More than 13 days of flights on a twin otter plane, the NASA team used instruments called 4star-B (Spectrometer for the monitoring of the sunshine of atmospheric research B), and the C-AIR (Coastal Air Liaison Radiometer) to collect air data. At the same time, UCSC partners used a multitude of corresponding instruments on board the R / V Shana Rae research ship to collect data from the surface of the water.
The instrument of oceanic colors measures something called water by leaving reflectance, which provides information on the microscopic composition of the water column, including water molecules, phytoplankton and particles such as sand, inorganic materials and even bubbles. The color of the ocean varies depending on how these materials absorb and disperse sunlight. This is particularly useful for determining abundance and types of phytoplankton.
The Airsharp team used radiometers with correspondence technology – C -Air from air and C -OPS (compact optical profiling system) of water – to collect reflectance data leaving the water.
“The C-Air instrument is changed from an instrument that takes place on research ships and takes measures from the surface of the water from very closely,” said NASA Ames researcher Samuel Leblanc. “The problem is that you are very local in an area at a time. What our team has done successfully is to put it on an airplane, which allows us to run all the Baie de Monterey.”
The larger rhythm validation team will compare the OIC measures with the observations made by the sensors much closer to the ocean to ensure that they correspond and make adjustments when they do not.
A factor that can have an impact on OIC data is the presence of aerosols of human and natural origin, which interact with sunlight when it moves in the atmosphere. An aerosol refers to any solid or liquid in suspension in the air, such as the smoke of fires, the salt of the marine spray, the particles of fossil fuel emissions, the dust of the desert and the pollen.
Imagine a tube 420 miles long, with the rhythm satellite at one end and the ocean to the other. All inside the tube is what scientists call the atmospheric column, and it is full of tiny particles that interact with sunlight. Scientists quantify this aerosol interaction with a measure called aerosol optical depth.
“During the air Sharp, we mainly measured, at different wavelengths, how light is changed by the particles present in the atmosphere,” said NASA Ames researcher Kristina Pistone. “The optical depth of aerosols is a measure of the extinction of light, or of the quantity of light dispersed or absorbed by aerosol particles.”
The team has measured the optical depth of aerosols using the 4Star-B spectrometer, which was designed at NASA Ames and allows scientists to identify which aerosols are present and how they interact with sunlight.
Flying these instruments required the use of a twin otter plane, operated by the Naval Postgraduate School (NPS). The twin bout is unique for its ability to make flights at low altitude, making passes to 100 feet above the water in clear conditions.
“It is an intense way to fly. At this low height, the pilots are continuously watching to monitor and avoid birds, large ships and even fauna such as whale violation,” said Anthony Bucholtz, director of the airborne research installation at NPS.
With the phytoplankton flower attracting so many wild animals in an already full of ships, it is not an easy task. “The pilots keep an eye on the radar and fly by hand,” said Bucholtz, “while following meticulous flight plans crisscrossing Monterey bay and making tight spirals on the research ship Shana Rae.”
The data collected from phase 2024 of this campaign is available on two data archive systems. Data from the 4STAR instrument is available in the CAPC data archives and C-AIR data is hosted in basic data archives.
Other data from the NASA validation science team is available on the PACE website: https://pace.ceansciences.org/pvstdoi.htm#
Samuel Leblanc and Kristina Pistone are funded via the Bay Area Environmental Research Institute (Baeri), which is a non -profit organization based on scientists focused on earth and space sciences.
