Seeing beyond the visible
Catherine Prigent will draw insights from microwave instruments on Metop-SG satellites that will help to improve life-saving forecasts
During the Crimean War in 1854, a violent storm swept across the Black Sea and struck the allied fleet at Balaklava, wrecking ships and killing hundreds of people. At the Paris Observatory, astronomer Urbain Le Verrier – renowned for correctly predicting Neptune’s existence – gathered weather reports from across Europe and noticed something striking: the storm had followed a trackable path.
29 July 2025
29 July 2025
Le Verrier’s insight helped spur the creation of a coordinated network of international observatories supported by the newly-emerging telegraph system, laying the foundation for modern weather forecasting.
More than 150 years later, Dr Catherine Prigent carries the Paris Observatory’s meteorological legacy forward, drawing insights not from ground-based reports, but from space. Her work focuses on the analysis of satellite data from microwave instruments, such as those aboard EUMETSAT’s Metop series, that can help to improve life-saving forecasts and monitor the impacts of the climate crisis.
Photo: Courtesy of Catherine Prigent
“Most scientists at the Paris Observatory are astronomers studying the cosmos – we are the only group focused on the Earth,” says Prigent, whose office in downtown Paris overlooks the Eiffel Tower and the Sacré-Cœur. “But we actually have a lot in common: microwave instruments developed for radio astronomy have turned out to be incredibly useful for observing our own planet from space.
“Microwave imaging and sounding instruments on weather satellites work like radio receivers, tuning into specific frequencies to pick up signals. But instead of music, these signals can provide a wealth of vital information about our planet, relevant for monitoring temperature and humidity throughout the atmosphere, ocean winds, sea ice, snow cover, and even moisture below the Earth’s surface.”
Image: Sylvain Cnudde/Bibliothèque de l’Observatoire de Paris
A golden age of microwave meteorology
As Europe prepares to launch the first of its next-generation Metop satellites, Metop Second Generation A1 (Metop-SGA1), the signals Prigent studies are about to get much clearer. Part of the EUMETSAT Polar System – Second Generation (EPS-SG), Metop-SGA1 carries advanced instruments that will span the electromagnetic spectrum – including a Microwave Sounder that delivers temperature and humidity profiles by measuring microwave brightness temperatures at different altitudes, in all weather.
The spacecraft’s counterpart, Metop-SGB1, will be launched next year with a complementary payload that (amongst others) includes a Microwave Imager that will deliver data relevant for monitoring precipitation, clouds, and surface conditions; an Ice Cloud Imager to observe high-altitude cirrus clouds; and a Scatterometer to gauge ocean surface roughness and estimate wind speed, direction, and soil moisture.
“In many respects we are at the start of a golden age of microwave meteorology in Europe.”
“Instruments on board Metop-SG satellites and other exciting new European missions span a much broader frequency range than we have had so far. By bridging gaps between the microwave and infrared parts of the electromagnetic spectrum, we can build a more complete picture of the Earth’s atmosphere, land, water, and ice – data that are essential for enhancing the numerical prediction models behind weather forecasts.
“Lower microwave frequencies penetrate clouds to reveal surface conditions like soil moisture, snow cover, and sea ice – data often inaccessible to infrared and optical sensors, as we live on a very cloudy planet! Higher frequencies can be used to detect tiny ice particles in high-altitude clouds, helping refine how these clouds are represented in weather and climate models. And combined with infrared sounder data, microwave observations can also offer very detailed insights into atmospheric humidity and temperature, the two most important variables in weather forecasts.”
Image: EUMETSAT
Making the data count
But collecting data is only the beginning. Making sense of microwave signals means correcting for instrument biases, accounting for how radiation is absorbed, scattered or reflected, and carefully calibrating measurements across different satellites and missions – an ongoing international effort involving many institutes, teams and scientists.
“Our job is to turn those signals into something useful,” says Prigent, who previously worked at NASA’s Goddard Institute for Space Studies. “The microwave spectrum is incredibly rich, but using it effectively means understanding both the physics and the noise.”
To do this, her team builds physical models that simulate how microwave signals interact with gases, clouds and the Earth’s surface. These help decode raw satellite measurements so they can be fed into numerical weather prediction systems and improve forecast accuracy.
Image: EUMETSAT/Copernicus Sentinel-3
They also contribute to long-term climate monitoring. In collaboration with EUMETSAT’s Satellite Application Facility on Climate Monitoring, Prigent’s group helps create climate data records stretching back to the late 1970s.
“We develop algorithms to extract climate-relevant variables from microwave data – like wetland extent, land surface temperature, sea ice concentration,” she explains. “By carefully building these time series, we can show clearly how the planet is changing. This kind of data is essential for helping societies make informed decisions as the climate crisis intensifies.”
Image: EUMETSAT
Prigent originally trained as a telecommunications engineer, but was quickly drawn to the challenge of interpreting signals. “I have always been interested in what data can tell us – not just collecting observations, but understanding the story behind them. And I have been lucky to work with brilliant colleagues around the world.”
With new tools and missions, that global effort is only gaining momentum. “Machine learning is opening up new ways to explore the data. And with instruments on Metop-SG and upcoming missions like EPS-Sterna and the Copernicus Imaging Microwave Radiometer, there is still much more to uncover. It is a really exciting time to be in this field – especially for younger scientists just starting out.
“If you listen carefully, microwave signals can tell you incredible things about our world,” she adds. “The key is to stay grounded in the physics.”
Author:
Adam Gristwood
Main video: Adobe Stock
