NASA installs forest fluorescence instrument in Puerto Rico to support satellite checks

NASA researchers have installed an instrument at the Guánica Dry Forest tower in Puerto Rico to measure light emitted by plants, the agency reported on 29 September 2026. The ground observations are intended to help check satellite measurements of forest activity, but NASA has reported preliminary field measurements rather than analyzed results.

Natalia L. Quinteros Casaverde, a postdoctoral researcher at NASA Goddard’s Biospheric Sciences Laboratory and the Southeastern Universities Research Association, described the work after ten days in southwestern and central Puerto Rico with Petya Campbell. Campbell is a research professor at the University of Maryland Baltimore County and a research scientist at the Goddard laboratory. She leads the project to monitor fluorescence from the Guánica canopy from 2026 to 2028.

How the Guánica tower will measure plant fluorescence

The team installed a fluorescence box, or FloX, dual spectrometer on a tower in the forest. Its measurements will track solar-induced fluorescence: a faint glow plants emit as they interact with sunlight. Researchers use the signal to gain insight into photosynthetic activity and how efficiently plants use sunlight. NASA says studying how the canopy signal changes during the day and across seasons should help improve the accuracy of satellite observations.

NASA plans to compare the new fluorescence observations with environmental measurements from instruments on the same tower. That comparison will give researchers a ground reference when assessing satellite data, including products from the European Space Agency’s Fluorescence Explorer, or FLEX, mission. The installation establishes a way to collect the observations; NASA has not said that the Guánica data have already validated a FLEX product.

Why Guánica matters to the FLEX mission

Guánica offers a dry forest setting for the comparison. NEON describes its field site as a 34.9-square-kilometre reserve on Puerto Rico’s southern coast, managed by the Commonwealth’s Department of Natural and Environmental Resources. It contains more than 700 plant species across upland deciduous forest, semi-evergreen forest and coastal scrub. Those distinct types of vegetation form the setting in which the new instrument will observe changes in the canopy signal.

The European Space Agency says FLEX is its first satellite designed specifically to measure photosynthetic activity from space. Its instrument detects the faint fluorescence plants emit during photosynthesis. ESA says the mission’s measurements are intended to help scientists assess plant health, ecosystem productivity and the effects of environmental stress and climate change. Those are goals for the satellite mission, not findings from NASA’s Puerto Rico fieldwork.

FLEX launched with Copernicus Sentinel-3C aboard a Vega-C rocket from French Guiana on 15 September 2026. ESA reported receiving a first signal from each satellite after deployment and identified commissioning the spacecraft and instruments as the next phase. The launch is recent context for NASA’s ground work; the agency’s field account does not report completed comparisons with operational FLEX products.

ESA plans to combine FLEX fluorescence measurements with near-simultaneous Sentinel-3 observations. Those observations include information about clouds, aerosols and water vapour, as well as surface temperature and land cover. The combined observations are intended to give scientists more context for interpreting the faint signal from vegetation.

What NASA measured during its Puerto Rico visit

Alongside the instrument installation, the NASA researchers measured tree height, trunk diameter and crown leaf cover. These measurements describe the forest’s structure and will help prepare for a future Puerto Rico campaign using NASA Goddard’s LiDAR, Hyperspectral and Thermal Imager, or G-LiHT. NASA describes G-LiHT as an airborne system that maps the composition, structure and function of land ecosystems.

The field trip extended beyond Guánica. Quinteros Casaverde and Campbell visited Maricao State Forest in the mountains and agricultural sites near the coast. NASA says Campbell has also installed similar instruments on NEON towers in Alaska, Kansas and Maryland. Comparing the new Guánica observations with measurements from those other ecosystems is among the team’s planned next steps.

What remains to be established

NASA says it left Puerto Rico with preliminary measurements and now needs to process the FloX data, compare Guánica with other ecosystems and prepare for the airborne G-LiHT work. Its account gives no date for that deployment or for the release of processed fluorescence results. It also reports no measured improvement in satellite monitoring performance from this field campaign so far.

The distinction matters for interpreting the project: the tower installation and tree measurements are completed field activities, while the satellite validation they are designed to support remains ahead. NASA’s report establishes how the team is gathering a ground reference in a tropical dry forest; it does not yet show what the comparison with FLEX will find.