2025 is another milestone year for the EU Space Programme.
Following the successful expansion of Copernicus with the launch of Sentinel-5A and Sentinel-4A earlier in the year, on 4 November 2025, Sentinel-1D will lift off from Europe’s Spaceport in Kourou, French Guiana, ensuring the continuity of services on which a wide range of end users rely worldwide.
Sentinel-1D joins Sentinel-1C, launched in December 2024.
Both satellites are equipped with Galileo-enabled receivers for more accurate in-orbit positioning and carry an Automatic Identification System (AIS) payload which detects signals from ships, supporting maritime domain awareness and the detection of unauthorised activities at sea.
Sentinel-1D’s launch aboard Ariane 6 reflects Europe’s growing capacity to put its satellites into orbit on its own terms, strengthening the resilience of Copernicus Services and the EU’s strategic autonomy.
In this Observer, we look at the upcoming launch and the benefits the Sentinel-1 mission delivers.
When Sentinel-1A launched in 2014, it marked the start of routine, operational monitoring under Copernicus.
Building on Europe’s earlier SAR heritage with missions such as Envisat, it transformed access to radar data by making it routinely available on a free and open basis.
Sentinel-1’s radar sensor makes it possible to track changes to land, oceans, and ice regardless of cloud cover or darkness.
Over the past decade, this data has supported emergency responses to floods, mapped shifting coastlines, detected oil spills and illegal activities at sea, and helped monitor forests, vegetation, and agricultural activity.
As in-orbit servicing and repair are not yet a reality for most satellite missions, satellites are designed with a nominal lifetime in mind.
Sentinel-1A’s nominal lifetime was seven years, yet it has continued its mission for more than a decade.
While Sentinel-1A remains functional, Sentinel-1D will gradually assume the role of 1A in the constellation.
This will ensure the satellite mission’s full operational capacity and continuity of service, with uninterrupted radar data provision to end users worldwide.
This animation shows the Thwaites Glacier in Antarctica from January 2023 to 20 September 2025.
Credit: European Union, Copernicus Sentinel-1.
Eyes that never closeUnlike most high-resolution optical satellites which require daylight and clear skies to acquire usable images, Sentinel-1 satellites are equipped with a C-band Synthetic Aperture Radar (SAR) instrument, which can see through clouds, rain, and smoke, providing all-weather, day-and-night observations of the Earth’s surface.
Sentinel-1D, like its predecessors, will operate in a sun-synchronous orbit at an altitude of around 700 kilometres.
Each Sentinel-1 satellite follows a 12-day repeat cycle, meaning it retraces the same ground track every 12 days.
The effective revisit time, or the time it takes to observe the same location under any orbit pass, is much shorter because the radar instrument has a wide swath and collects data on both ascending and descending passes.
For a single satellite, the revisit time is typically around three days at the equator, about two days over Europe, and less than a day in the Arctic.
In a two-satellite configuration, the constellation achieves a six-day repeat cycle and revisit times of about a day in most regions, and even less at higher latitudes.
This means that Europe can benefit from timely, reliable observations no matter the season or the conditions on the ground.
Sentinel-1D will join Sentinel-1C, which was launched in December 2024 and is already fully operational.
Together, the two satellites will maintain the six-day revisit cycle of the Sentinel-1 mission, ensuring continuous radar coverage for Copernicus Services.
Both satellites are equipped with Galileo-enabled receivers, which make in-orbit positioning more robust and accurate.
Moreover, if GPS signals become unavailable, the satellites can continue operating independently using Galileo.
Both Sentinel-1C and Sentinel-1D carry an Automatic Identification System (AIS) payload which detects maritime vessel signals, supporting maritime domain awareness by helping to monitor ship traffic, identify dark vessels, and detect unauthorised or illegal activities at sea.
Revisit times for the Sentinel-1 satellite constellation in days per revisit.
Credit: European Union.
From data to operational servicesData from Sentinel-1 satellites flows directly into Copernicus Services.
It underpins the
Copernicus Emergency Management Service (CEMS) for flood mapping, the
Copernicus Maritime Surveillance (CMS) Service for oil spill and vessel detection, and the
Copernicus Marine Service (CMEMS) for monitoring icebergs and sea ice concentration to support safe navigation.
It also supports the
Copernicus Land Monitoring Service (CLMS) for vegetation, forest, and agricultural monitoring.
Notably, Sentinel-1 radar data processed with interferometry is used in the
European Ground Motion Service (EGMS), part of CLMS, to detect and track ground motion from subsidence, landslides, volcanic activity and earthquakes.
Together, these services turn Sentinel-1 data into operational information which has tangible societal benefits: better disaster response, safer seas, improved land and agricultural management, and greater resilience to natural hazards.
Thanks to the open and free data policy of Copernicus, this operational information is widely accessible to public authorities, industry, researchers and service providers, who can build further applications on top of the core Copernicus products and data.
As a matter of fact, Sentinel-1 is the only satellite mission in the world which provides data on a full, free and open basis.
A larger system built on reliable launchesSentinel-1 is not an isolated satellite mission but part of Copernicus, the world’s most advanced Earth Observation system.
Each Sentinel satellite mission carries different instruments with complementary capabilities: Sentinel-2 delivers high-resolution multispectral imagery for land and environmental monitoring, supporting applications from agriculture and forestry to disaster mapping; Sentinel-3 carries a suite of instruments, including a radiometer for sea and land surface temperature (SLSTR), a radar altimeter (SRAL) for sea-surface height and ice topography, and an ocean and land colour instrument (OCLI), providing data on the state of the oceans, inland waters, vegetation, and the cryosphere; Sentinel-5, equipped with the Tropospheric Monitoring Instrument (TROPOMI), provides measurements of atmospheric composition, including ozone, nitrogen dioxide, carbon monoxide, methane and aerosols, supporting air quality monitoring and climate studies; and Sentinel-6, carrying the Poseidon-4 radar altimeter and a microwave radiometer, provides high-precision measurements of global sea level.
Sentinel-1, with its C-band radar, contributes a distinct capability within Copernicus, complementing the optical, ocean, and atmospheric missions by providing data that is independent of weather or daylight.
The launch of Sentinel-1D aboard Ariane 6, following the successful deployment of Sentinel-5A on Ariane 6 in August 2025, underscores Europe’s commitment to autonomous access to space.
This independence ensures that European missions can reach orbit on Europe’s terms, providing continuity of service for Copernicus users worldwide without reliance on external launch providers.
Ariane 6 also embodies Europe’s commitment to sustainability in spaceflight.
Its upper stage is designed to perform controlled de-orbit manoeuvres, preventing the creation of persistent space debris and keeping orbital pathways safe for future missions.
Even its journey to the launch site reflects this ethos, whereby Ariane 6 components are shipped across the Atlantic aboard Canopée, a purpose-built wind-powered hybrid industrial sailing vessel specifically designed to ship Ariane 6 components to the launch site while significantly reducing emissions compared to conventional transport.
By coupling mission continuity with European launch capacity, the EU strengthens the resilience of its space infrastructure.
The result is a robust, long-term system which delivers continuous, high-quality data in support of public authorities, services, science, and society at large, enabling safer communities, cleaner seas, and stronger climate preparedness.
Copernicus Sentinel-1D manoeuvred into place.Credit: ESA.
Continuity for the next decade
Sentinel-1D is designed to operate well into the 2030s, ensuring the continuity of the Copernicus radar mission.
This confirms Europe’s commitment to open and free access to high-quality Earth Observation data which supports science, innovation, security, and climate action.
Its launch underscores the EU’s role as a leader in Earth Observation and highlights the practical value of European investment in space for safer communities, maritime security, disaster response, and long-term resilience.
On 4 November 2025 at 6:03 p.m.local time in Kourou (9:03 p.m. UTC, 10:03 p.m.CET), Sentinel-1D will lift off aboard Ariane 6 from Europe’s Spaceport in Kourou, French Guiana.
After about 30 minutes, it will be placed into orbit, ready to begin its commissioning phase, during which the radar instrument will be calibrated and validated before being declared fully operational.
Links :
Ariane 6 upper stage.
This early chart depicts the waters around New York Harbor.
This nautical chart from 1854 shows an artistic rendering of the headlands of Anacapa Island, off the coast of California.
These three charts depict the same area near San Francisco at three different times—1859, 1974, and 2006.
Hydrographic surveying techniques and procedures have changed over time with evolving technology.
