Europe now has a full set of four radar eyes in the sky. The Copernicus Sentinel-1D satellite, launched last November from French Guiana, has passed its in-orbit commissioning tests and is fully operational. That means the entire Sentinel-1 constellation is finally deployed, a milestone more than a decade in the making.
A constellation rebuilt after a 2022 failure
The Sentinel-1 mission was originally designed as a pair of identical satellites orbiting Earth 180 degrees apart. Sentinel-1A launched in 2014, and Sentinel-1B followed in 2016. But in August 2022, Sentinel-1B suffered a technical anomaly that left it unable to collect data. That gap forced a rebuild. Sentinel-1C launched in 2024 to restore the constellation, and Sentinel-1D joined it in orbit a year later. Now both slots are filled again.
Seeing through clouds, day and night
Each satellite carries a synthetic aperture radar that can image Earth's surface in all weather conditions, day or night. That capability makes the constellation indispensable for monitoring natural disasters, sea ice, land deformation, and deforestation. Emergency responders, scientists, and policymakers around the world rely on the data. The satellites have tracked floods in Australia, oil spills off Portugal, earthquake deformation in Myanmar, and ice movement in Antarctica.
Two decades of continuous radar watch
The Sentinel-1 series is on track to deliver an uninterrupted two decades of radar observations. That long dataset strengthens Europe's role in Earth observation. The mission began as the cornerstone of Copernicus, the European Union's space-based environmental monitoring program. With all four satellites now active, the system provides more frequent coverage and greater resilience against future failures.
