The European Space Agency (ESA) has reported progress on two separate satellite missions, involving the completion of one first-generation constellation and experimental trials on another satellite nearing the end of its lifespan.
Sentinel-1D Becomes Operational
The Sentinel-1D satellite has completed its commissioning phase and entered full operational service. Launched on 4 November 2025, it is the fourth and final spacecraft in the first-generation Sentinel-1 constellation.
According to ESA, Sentinel-1D will replace Sentinel-1A, which has been in orbit since 2014. It will operate alongside Sentinel-1C. The Sentinel-1 mission was originally designed for dual-spacecraft operation in the same orbit, with satellites separated by 180 degrees. This dual-satellite configuration was disrupted when Sentinel-1B ended operations in 2022 due to an equipment malfunction. Sentinel-1C replaced Sentinel-1B in 2024.
Satellite Specifications
Sentinel-1D measures 21 meters long, 2.5 meters wide, and 4 meters high, with a mass of approximately 2,180 kg. It has a minimum design life of 7 years.
The primary instrument is a C-band synthetic aperture radar operating at 5.405 GHz. A secondary instrument, an Automatic Identification System, is present on Sentinel-1C and Sentinel-1D.
Imaging modes include:
- Interferometric wide-swath: 250 km swath, resolution of 5 x 20 meters.
- Wave mode: 20 x 20 km images at 5 x 5 meter resolution, taken at 100 km intervals.
- Strip map: 80 km swath, resolution of 5 x 5 meters.
- Extra wide-swath: 400 km swath, resolution of 20 x 40 meters.
Future Plans
ESA is developing a follow-on mission, Sentinel-1 Next Generation, intended to ensure continuity of measurements into the mid-2030s and beyond. Nuno Miranda, ESA’s Sentinel-1 Mission Manager, has stated that future satellites are expected to provide enhanced performance and new capabilities.
Sentinel-2A Night Vision Trials
Separately, the Sentinel-2A satellite, launched in 2015, is undergoing experimental tests as it nears the end of its operational life. ESA is testing the satellite beyond its original design parameters, including nighttime operations.
Sentinel-2A was designed to provide high-resolution multispectral optical images of Earth's surface for land and coastal area monitoring. All Sentinel-2 satellites feature a 13-band multispectral imager that relies on reflected sunlight. Historically, these imagers were deactivated during night passes.
ESA reports that the night imaging experiment successfully captured images of gas flares from oil production in the Middle East, a wildfire in India, and fishing boats off the coast of South Korea during nighttime conditions.
The current generation of Sentinel-2 satellites was not built for night imaging. The upcoming Sentinel-2 Next Generation mission is planned to include this capability for specific regions.
Simon Proud, ESA’s Sentinel-2 Next Generation Mission Scientist, stated that the results inform the design of the next-generation mission, which aims for higher-resolution imagery and night imaging capabilities. The experiments are intended to establish key features for the next-generation mission and assess the technical feasibility of night imaging. Nighttime imagery is considered useful for security and monitoring urban growth through city lights.
Ferran Gascon, ESA’s Sentinel-2 Mission Manager, noted that the experiment placed a demanding strain on Sentinel-2A, requiring significant energy. Gascon added that the satellite performed well and remains in good health, continuing to deliver data for a range of applications.