All Four Sentinel-1 Satellites Are Now Live — and Europe’s Earth Watch Just Got Stronger

Europe’s Copernicus Sentinel-1 radar mission is now operating at full capacity. The fourth and final satellite in the constellation, Sentinel-1D, has completed its in-orbit commissioning phase and entered full operational service, closing a chapter that began when Sentinel-1A launched in 2014.

That first satellite did more than begin a mission. It launched Copernicus itself, the Earth observation arm of the EU’s space programme, and established Europe as a reliable supplier of continuous, high-quality radar data to scientists, governments and emergency services worldwide.

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From Two Satellites to Four, and One Lost Along the Way

The original constellation design called for two identical satellites orbiting 180 degrees apart for maximum coverage. Sentinel-1B joined its partner in 2016. Six years later, a technical anomaly left Sentinel-1B unable to acquire data, and the satellite was decommissioned in August 2022.

Sentinel-1C launched in 2024 to restore the two-satellite configuration. Sentinel-1D followed a year later, lifted into orbit by Ariane 6, completing the expanded four-satellite fleet.

Together, the constellation delivers synthetic aperture radar imagery around the clock, in all weather conditions. The data underpin monitoring of natural disasters, sea ice, land deformation, deforestation and flooding. These are applications that have made the mission indispensable to emergency responders and climate researchers alike.

A 20-Year Data Record Now Within Reach

The mission’s most significant long-term contribution may be its data continuity. The Sentinel-1 series is on course to deliver an unbroken two decades of radar observations, a dataset without precedent in Earth observation history. That record provides the consistency researchers need to track gradual environmental changes and validate climate models.

Sentinel-1C and Sentinel-1D also carry an engineering first: a new separation mechanism designed to reduce the risk of generating space debris, reflecting ESA and the European Commission’s stated commitment to responsible operations in orbit.

ESA’s Sentinel-1 Mission Manager, Nuno Miranda, described the newly commissioned satellite as a turning point. “Sentinel-1 began as a trailblazer,” he said. “With the successful commissioning of Sentinel-1D, it now stands as a cornerstone.”

ESA is already developing Sentinel-1 Next Generation, a follow-on series intended to maintain measurement continuity into the mid-2030s and beyond, with enhanced performance and new capabilities built on the existing mission’s legacy.