The Copernicus Sentinel-1 mission is soon get its fourth satellite after having undergone the checks and functional tests prior to its integration with Ariane 6. Plans for the launch are on Tuesday, 4 November 2025. The Copernicus Sentinel-1 mission is based on a constellation of two identical satellites flying in the same orbit but 180° apart, to optimise global coverage and data delivery for Copernicus.
Functional checks have been performed on the spacecraft to confirm the spacecraft is in working order after being transported to Kourou.
These tests started with a pressurization and leak check before the spacecraft was switched on. Afterwards several tests were performed to assess the spacecraft’s health status and the correct functionality of all sub-systems. The AIS antenna assemblies, which were transported to the launch site in separate containers, have also been integrated onto the spacecraft and the final connectivity test to ensure their correct electrical connection concluded the spacecraft functional testing.
The spacecraft is now ready for the next steps, including spacecraft finalization before fueling.
Sentinel-1A was the first satellite in the series, launched in April 2014, followed by the launch of Sentinel-1B in 2016. The Sentinel-1B mission came to an end in August 2022 after experiencing a technical fault that rendered it unable to acquire data. The satellite has been successfully de-orbited and will re-enter Earth’s atmosphere within 25 years. Sentinel-1C was launched in December 2024 to take over the role of Sentinel-1B.
The launch of Copernicus Sentinel-1D will provide a much-needed replacement to Sentinel-1A, which has been in orbit for 11 years now, well beyond its planned lifetime. Sentinel-1C was placed in orbit in December 2024, Sentinel-1D will significantly enhance the capabilities of the Copernicus Earth observation program.
Ramón Torres, Sentinel-1 Satellite Mission Director at ESA, commented, “This time we are launching the fourth Sentinel-1 satellite, and last of the first generation, on an Ariane 6, which will be an important moment for the whole of our space community. To see this mission, the first of the Copernicus programme family and a cornerstone of the Earth observation component of Europe’s space programme, be lifted into orbit on Europe’s newest heavy lift rocket, feels quite momentous. I would like to thank and congratulate all Sentinel-1 team members and our partners who have worked so diligently to make this milestone a huge success.”
Sentinel-1C has been fully commissioned and currently operates with Sentinel-1A to deliver radar images of Earth’s surface, performing in all weathers, day-and-night. This service is vital for disaster response teams, environmental agencies, maritime authorities, climate scientists — and other users who depend on frequent updates of critical data.
Having two satellites in operation at any one time is essential for providing timely data and can mean a significant difference between a late warning and a critical early warning. The arrival of Sentinel-1D will enhance the Sentinel-1 mission’s performance in several ways:
- Better revisit time and coverage: With two satellites in the same orbit 180° apart, the revisit rate over any location on Earth improves. This means more frequent imaging, faster change detection, better monitoring.
- Enhanced features working in synergy: Both satellites have a C-band Synthetic Aperture Radar (SAR) instrument on board, which allows it to capture high-resolution imagery of Earth’s surface. They are also equipped with an Automatic Identification System (AIS) instrument to improve detection and tracking of ships. When both are operational, more frequent AIS observations are possible.
- Streamlined operations and cost savings: Because Sentinel-1C has just gone through commissioning, lessons learned can be applied to Sentinel-1D, reducing time and risk.
- GNSS compatibility: There are other improved onboard capabilities for Sentinel-1. For example, while Sentinel-1A and -1B were compatible only with the Global Positioning System (GPS), Sentinel-1C and -1D are compatible with the whole Global Navigation Satellite System (GNSS), including Galileo.
Sentinel-1 interferogram of Myanmar earthquake
Meanwhile, the Sentinel-1 mission will continue to deliver a supply of radar images of Earth’s surface, performing in all weathers, day-and-night. It makes a key contribution to Europe’s Copernicus program by supporting a broad range of applications that help manage the environment, understand and tackle the effects of climate change and safeguard everyday lives.
Simonetta Cheli, Director of Earth Observation Programs at ESA, added, “It is really a credit to the strong partnership between ESA and the European Commission that we are now preparing to launch another satellite for the Copernicus program. Sentinel-1 has provided vital radar data that has been used in emergency responses, in scientific studies and in climate observation — a range of use-cases that highlights just how invaluable Copernicus is to our society.”
The Sentinel-1 mission has contributed data to scientific studies on a wide range of topics, including these recent examples:
