OBSERVER: Copernicus Sentinel-5A to strengthen Europe’s eyes on the atmosphere
evan
Thu, 17/07/2025 – 13:43
2025 is shaping up to be a landmark year for the EU Space Programme, with several satellite launches expanding the capabilities of Copernicus and the other EU space components. Among them is the Sentinel-5A instrument, scheduled for launch in August 2025 from Kourou aboard an Ariane 6 rocket. With this launch, the EU solidifies its position as a space power and global leader in Earth Observation (EO) data provision. Sentinel-5A marks a significant advance in Europe’s ability to monitor air pollution and atmospheric composition. In this Observer, we look at what sets Sentinel-5A apart and what its launch means for the future of atmospheric monitoring.
2025 is a busy year for the EU Space Programme, with several satellite launches taking place across its different components. The pace and scale of launches are a reflection of the continued growth of Europe’s space infrastructure and its strategic investment in the sector. One of the year’s most anticipated launches is Copernicus Sentinel‑5A’s, an evolution of the Sentinel-5Precursor currently in orbit, as this instrument will strengthen the EU’s ability to monitor air pollution and atmospheric composition on a global scale.
This year has already seen the successful launch of Sentinel‑4A, the first geostationary mission for Copernicus, currently undergoing calibration and testing. Operating from a fixed position over Europe and North Africa, Sentinel‑4A provides high-frequency regional measurements of trace gases such as nitrogen dioxide (NO₂), ozone (O₃), and sulphur dioxide (SO₂), which are essential for understanding daily variation and capturing transient peaks of air pollution throughout the day.
To complement this geostationary view, Sentinel‑5A onboard the MetOp-SG A1 satellite will launch in August 2025, from Kourou, French Guiana, aboard an Ariane 6 rocket. Unlike its geostationary counterpart, Sentinel‑5A will fly in a polar orbit, circling the Earth every 100 minutes and delivering full global coverage every 24 hours.
By improving the Copernicus system’s ability to deliver daily global data on air pollutants and other atmospheric trace gases, Sentinel-5A will significantly strengthen what is already considered the world’s most advanced Earth Observation system for air quality and emission monitoring.
The addition of Sentinel‑5A marks an important advancement in Europe’s capacity to track air pollution and atmospheric composition, with its data feeding into the daily forecasts and long-term environmental monitoring delivered by the Copernicus Atmosphere Monitoring Service (CAMS). Together with Sentinel‑4A, it strengthens Copernicus’s atmospheric monitoring capacity, enabling more precise, frequent, and timely insights into greenhouse gases, atmospheric pollutants, and environmental health in Europe and across the globe.
Sentinel-5A: A new phase for operational atmospheric monitoring
While Sentinel‑5P, the precursor mission, is currently fully operational and continues to deliver valuable data, Sentinel‑5A is the beginning of a long-term operational phase in Europe’s atmospheric monitoring.
Rather than flying as a standalone mission, Sentinel‑5A follows the “one satellite, several missions” approach. It is a hosted payload on the MetOp Second Generation-A1 (MetOp-SG A1) meteorological satellite. Operated by EUMETSAT, it is the first in a planned series of three identical Sentinel‑5 instruments which will fly on successive MetOp-SG platforms, ensuring continuity of atmospheric observations into the 2040s. Alongside Sentinel‑5, MetOp-SG A1 carries several other instruments: The Infrared Atmospheric Sounding Interferometer – New Generation (IASI-NG), the Visible Infrared Imager (METImage), the Multi-viewing Multi-channel Multi-polarisation Imager (3MI), the Microwave Sounder (MWS), and the Radio Occultation sounder (RO), making it a versatile, multi-instrument platform supporting multiple missions within both Copernicus and EUMETSAT’s meteorological activities.
Sentinel‑5A will be fully embedded in EUMETSAT’s infrastructure, and its data will be disseminated through established systems, providing reliable access for services such as the Copernicus Atmosphere Monitoring Service (CAMS) and Copernicus Climate Change Service (C3S). These data streams will support air quality forecasting and the long-term tracking of atmospheric composition, helping environmental agencies and public authorities monitor pollution, climate change, and support related decision-making.
What’s new in Sentinel-5A
Sentinel‑5A carries a next-generation Ultraviolet Visible Near-infrared Short-wave infrared (UVNS) spectrometer, building on the heritage of the TROPOMI instrument flown on Sentinel‑5P. Covering seven spectral bands from 270 to 2385 nm, the instrument is designed to acquire data in support of a broad range of applications, covering ozone and surface UV, air quality, and climate applications. Specifically, Sentinel-5A will monitor trace gases, including nitrogen dioxide (NO₂), ozone (O₃), sulphur dioxide (SO₂), carbon monoxide (CO), methane (CH₄), glyoxal (CHOCHO), formaldehyde (HCHO), aerosols, and cloud properties. It will perform these atmospheric measurements at a high spatial, spectral, and temporal resolution. Beyond measuring total column concentrations, the instrument’s spectral resolution allows it to retrieve vertical profiles for selected parameters.
With a wide swath of 2670 km and a spatial resolution of approximately 7 km, Sentinel‑5A will provide daily global coverage at a scale suitable for tracking city-wide air pollution trends, wildfire plumes, and the long-range transport of dust and aerosols.
Sentinel‑5A also benefits from its co-location with other instruments aboard MetOp-SG A1, particularly the IASI-NG and the MWS. Together, these sensors provide a more complete picture of the atmosphere by observing it in different parts of the electromagnetic spectrum. Sentinel‑5A acquires from ultraviolet to shortwave infrared, while IASI-NG observes in the thermal infrared. By combining these complementary measurements, scientists can retrieve gas concentrations more accurately, distinguish between similar atmospheric signals, and validate results across instruments.
A system of systems: complementarity in atmospheric monitoring
The relationship between Sentinel-5 and Sentinel-4 exemplifies the Copernicus approach to complementarity. Sentinel-4A, in geostationary orbit, focuses on capturing hourly changes over Europe, such as morning rush-hour pollution spikes. Sentinel-5A, meanwhile, will provide a daily global snapshot, useful for tracking transboundary air pollution and placing regional phenomena in a wider, global context.
Together, they allow for multi-scale analysis of atmospheric dynamics, supporting everything from city-level air quality forecasts to global assessments of pollutant transport.
While Sentinel-5 is primarily an atmospheric chemistry mission, it also contributes to Europe’s broader climate monitoring strategy. It forms part of a wider “system of systems” for tracking climate-relevant gases and pollutants from space, with Sentinel-5 offering wide-area context and long time series, and upcoming missions such as CNES’s MicroCarb and the Copernicus CO2M expansion mission providing targeted, high-precision measurements of CO₂ and CH₄ emissions. Alongside Sentinel-4 and the soon-to-be-launched CO2M, Sentinel-5 will secure Copernicus’s position as the most trusted and accurate Earth Observation source for atmospheric monitoring in the world.
Turning data into action
The impacts of Sentinel-5A will extend beyond research and modelling. Access to frequent, authoritative data from Sentinel-5A will directly underpin EU policies including the Zero Pollution Action Plan, the Ambient Air Quality Directive, and the EU Methane Strategy, support early warnings for air pollution events, and provide valuable information to a wide range of sectors.
Public health agencies, for instance, will be able to issue more accurate pollution alerts, and solar energy providers will benefit from improved aerosol forecasts. Additionally, Sentinel‑5A’s measurements of sulphur dioxide and aerosols can also support volcanic plume monitoring during eruptions.
Thanks to the Copernicus open data policy, all of this information will be freely available, not just to European users, but to users around the world.
The CAMS Methane Hotspot Explorer is a practical example of how satellite-based atmospheric data, such as those from Sentinel-5A, support EU policy and decision-making on emissions. Credit: European Union, Copernicus Atmosphere Monitoring Service.
Looking ahead
Sentinel-5A marks the transition from demonstration to a long-term operational series designed to ensure continuity in atmospheric monitoring at both European and global scales.
Whether helping policymakers track progress on climate goals, supporting air quality alerts for cities, or contributing to international environmental monitoring efforts, Sentinel-5A will bring tangible societal benefits.
Thu, 17/07/2025 – 12:00