The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organisation created through an international convention agreed by a current total of 30 European Member States.EUMETSAT's primary objective is to establish, maintain and exploit European systems of operational meteorological satellites. EUMETSAT is responsible for the launch and operation of the satellites and for delivering satellite data to end-users as well as contributing to the operational monitoring of climate and the detection of global climate changes.The activities of EUMETSAT contribute to a global meteorological satellite observing system coordinated with other space-faring nations.Satellite observations are an essential input to numerical weather prediction systems and also assist the human forecaster in the diagnosis of potentially hazardous weather developments. Of growing importance is the capacity of weather satellites to gather long-term measurements from space in support of climate change studies.EUMETSAT is not part of the European Union, but became a signatory to the International Charter on Space and Major Disasters in 2012, thus providing for the global charitable use of its space assets.
EUMETSAT successfully launched the first satellite of the EUMETSAT Polar System-Second Generation (EPS-SG), developed as a collaborative program between EUMETSAT and ESA, on 13 August 2025 at 0037:50 (UTC) on an Ariane 62 launcher. EPS-SG is Europe's contribution to the NOAA-EUMETSAT Joint Polar System, continuing and expanding midmorning orbit observations provided by the Metop satellites. EPS-SG comprises three satellites collecting optical imaging and sounding observations (Metop-SGA) and three satellites collecting active and passive microwave observations (Metop-SGB) deployed in pairs, each satellite with a 7.5-yr design lifetime, including 6 months for commissioning. In addition to providing improved legacy observations with the Infrared Atmospheric Sounding Interferometer-New Generation (IASI-NG), Meteorological Imager (METimage), Microwave Sounder (MWS), and Radio Occultation (RO) instruments, the Metop-SGA satellites will carry the Multi-viewing Multi-channel Multi-polarisation Imager (3MI), a passive polarimeter for monitoring atmospheric aerosol and clouds, and the Copernicus Sentinel-5 Ultraviolet (UV)/Visible (Vis)/Near-infrared (NIR)/Shortwave infrared (SWIR) (UVNS) sounding instrument, provided by ESA and the European Commission, measuring trace gases and aerosols. The Metop-SGB satellites will continue observations of ocean vector wind fields with the scatterometer (SCA), also host an RO instrument, and carry the Microwave Imager (MWI) for monitoring precipitation, temperature, clouds, water vapor, sea ice, and snow cover. Metop-SGB will also provide novel observations with the Ice Cloud Imager (ICI), covering submillimeter wavelengths for global observations of ice clouds. Finally, Metop-SGB will in addition carry the Advanced Data Collection System, Argos-4, contributing to the Argos worldwide location and data collection system. This paper describes these instruments, outlines the related products and services, and addresses the evolution of further applications.
Motivated by apparent forecast improvements in the Met Office system with Spire-processed Global Navigation Satellite Systems (GNSS) radio occultation bending-angle observations, various experiments have been run to test the effect of increased vertical smoothing on forecast quality. The initial experiments were run with additional smoothing applied to Spire's observations as part of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) processing. In these experiments it was seen that increasing the smoothing decreased the standard deviation of the observation departures, but also increased the vertical correlation length-scales. These observations with additional smoothing were then ingested within a low-resolution version of the Met Office numerical weather prediction (NWP) system, and the forecast quality was seen to be improved with the observations using additional smoothing compared with the observations using the operational processing. A second set of experiments was run which applied additional smoothing as a pre-processing step within the Met Office system. The smoothing is thus applied to the low-resolution Binary Universal Form for the Representation of meteorological data (BUFR) observations that are normally assimilated operationally. This method has the advantage that it is applied to the whole observation dataset, but the disadvantage that it is applied to the low-resolution observations, which posed some technical challenges. It also meant that it was possible to make the smoothing length-scale proportional to the spacing between vertical levels in the Met Office model. Tests applying the additional smoothing in this way demonstrated improved forecast performance over a wide range of variables. However, using a large smoothing length-scale produced degraded results, and the degradation was seen first in the tropical region, suggesting that less smoothing is beneficial there. Further experimentation is planned, which would demonstrate the impact of additional smoothing on a second NWP system.
The proposed EUMETSAT Polar System (EPS)-Sterna constellation of small satellites comprises passive microwave (MW) sounding instruments with an additional set of novel 325-GHz channels, providing further humidity-sounding capabilities with higher ice cloud sensitivity. These submillimeter channels have only recently become available from cross-track scanners on a space-borne platform. On EPS-Sterna, they complement more traditional temperature-and humidity-sounding channels around 50-60 GHz and 183 GHz. A strategy is developed to simulate and assimilate the 325-GHz channels in an all-sky framework. This includes development of an observation error model based on a new cloud indicator exploiting the cloud signal extracted from the lowest-peaking 325-GHz channel to assign larger observation errors in cloud-affected regions. The new model leads to a more Gaussian distribution of background departures normalized by the assigned observation error, compared to using the same cloud indicator as for the 183-GHz channels. After developing an assimilation strategy, the ensemble of data assimilations (EDA) method is used to evaluate the expected forecast benefit of these new channels. Results show that the 325-GHz channels produce a similar positive impact as the 183-GHz channels when each channel set is added separately to the temperature-sounding channels at 50 GHz. When combined with 50-and 183-GHz sounding channels, the impact of the 325-GHz channels is mostly neutral, with benefits for midtropospheric relative humidity. Inflating the observation errors assigned to the 325-GHz channels is found necessary to achieve this impact. Potential avenues to increase the impact through data assimilation enhancements are discussed (e.g., from better utilizing the ice cloud information).
Since 2014, space agencies have launched advanced meteorological imagers into the geostationary (GEO) orbit encircling Earth's equator, known as the GEO-Ring. JMA, NOAA, and KMA launched imagers measuring 16 spectral bands with thermal resolutions of 2 km and full-disk coverage every 10 min. China Meteorological Administration's (CMA's) Fengyun-4A (FY-4A) series, launched in 2016, observes 14 bands with 4-km thermal resolution and 15-min full-disk scans. In 2022, EUMETSAT introduced the Meteosat Third Generation (MTG) imager, offering 16 channels, 2-km thermal resolution, and 10-min full-disk coverage. Together, these satellites provide near-global coverage with improved capabilities over earlier generations. The 10-12 common channels across the latest imagers enable retrieval of diverse atmospheric variables at high temporal resolution. These data represent a substantial advance beyond the early 1980s when the International Satellite Cloud Climatology Project (ISCCP) was first developed. The challenge facing any new GEO-Ring project, such as one being planned as part of a next generation of ISCCP (ISCCP-NG), is to define a new baseline from these measurements and processing methods to extract meaningful information for the scientific community in the coming decades. This paper outlines the design of a GEO-Ring radiance project to support a future ISCCP-NG and many other applications and emphasizes the benefits compared to the B1 and B3 data used in ISCCP.
The EUMETSAT VICIRS (“VIcarious Calibration tool for MWI and ICI using RadioSoundings”) study developed a vicarious calibration tool for the two conicalscanning radiometers, the MicroWave Imager (MWI) and the Ice Cloud Imager (ICI), planned to fly from 2026 onwards aboard the Metop-SG (Meteorological Operational satelliteSecond Generation) B-satellites as part of the EUMETSAT Polar System (EPS) program. The combined use of MWI and ICI radiometers will provide an unprecedented set of microwave passive measurements, from 18.7 GHz up to 664 GHz, on the same platform. Vicarious calibration using radiosoundings is particularly important for MWI and ICI channels that are unprecedented and therefore cannot be compared with reference observational data from space. The VICIRS tool has been developed to collect clear-sky match-ups between MWI/ICI and radiosoundings from the high-quality, low-density Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) archive, as well as from a more comprehensive, homogenized, higher-density archive, the Radiosounding HARMonization (RHARM) dataset, which also provides estimations of measurement uncertainty at all pressure levels. Numerical Weather Prediction (NWP) profiles are also used to fill gaps in surface parameters and in data above the radiosoundings top levels. The tool provides a statistical analysis of the difference between observed and simulated brightness temperatures, considering the total uncertainty emerging from various sources (e.g., instrumental uncertainties, forward model uncertainties, spatial and temporal mismatches) for each MWI/ICI channel. The VICIRS tool has been tested with the MWI/ICI L1B test data product collocated with RHARM RS, and a dataset of match-ups between observations from NASA's Global Precipitation Measurement (GPM) Microwave Imager (GMI) and GRUAN/RHARM RS.
