HydroGNSS-the first of the European Space Agency’s rapid, low‑cost Scout missions-reached orbit on 28 November 2025 aboard a SpaceX Falcon 9 from Vandenberg. Both satellites separated cleanly, with first signals confirmed the same evening.

Built by Surrey Satellite Technology Ltd in Guildford and backed by £26 million from the UK Space Agency, the UK‑led mission is designed to put climate‑relevant measurements into use quickly, showcasing Britain’s small‑satellite strengths in service of Earth observation.

Instead of carrying a traditional radar, HydroGNSS listens for GPS and Galileo signals after they bounce off Earth’s surface-a method known as GNSS reflectometry. Operating at L‑band, it keeps working through cloud, rain and moderate vegetation. The twin spacecraft fly in polar orbit at roughly 550 km altitude, spaced 180 degrees apart, and are designed to deliver about 25 km resolution snapshots of land surface conditions.

The mission zeroes in on soil moisture, inundation and wetlands, the freeze–thaw state over permafrost, and above‑ground biomass. These are recognised by the Global Climate Observing System as Essential Climate Variables that underpin climate services and guide practical adaptation decisions.

For flood managers, frequent, cloud‑immune soil moisture and inundation maps sharpen the starting point of river models. Europe’s EFAS and GloFAS early‑warning systems combine satellite observations with hydrological models to highlight flood risk up to 15 and 30 days ahead, respectively-a lead time that depends on reliable ground wetness. England’s Environment Agency says richer data will strengthen warnings and operational response.

The approach already has a track record. NASA’s CYGNSS constellation-originally built to measure hurricane winds-has been repurposed by researchers to monitor inland flooding. Peer‑reviewed work on the 2021 Henan, China floods shows daily GNSS‑R can map flood extent and evolution at actionable scales.

HydroGNSS adds to, rather than replaces, existing satellites. ESA’s SMOS provides global soil moisture at about 50 km resolution and NASA’s SMAP maps soil moisture and freeze–thaw every two to three days; GNSS‑R brings low‑cost, frequent snapshots that keep working under cloud, improving blended products used by forecasters, farmers and conservation teams.

Access is set up for practical use. After a short, free registration, standard HydroGNSS products are released with a nominal latency of around 30 days, while a fast‑data option can deliver files within roughly 48 hours-useful for operational pilots and rapid research.

The timing aligns with a wider UK push on space for climate and public services. On 27 November, ministers agreed a £1.7 billion package at ESA’s ministerial in Bremen, taking the UK’s ESA support to £2.8 billion over the next decade, including Earth observation lines. The UK space sector supports about 55,550 jobs and generated £18.6 billion in 2022/23.

What matters next is turning signal into service: commissioning and calibration, then integration into weather, flood and drought workflows. Soil moisture and freeze–thaw are pivotal in land–atmosphere exchange, agriculture and habitat health; more consistent observations mean earlier warnings, smarter irrigation and better tracking of permafrost change.