ESA’s first Scout: UK HydroGNSS launches 28 Nov

Two small UK-built satellites are now in orbit. On 28 November 2025, HydroGNSS became the first mission in the European Space Agency’s Scout programme, led by the UK with support from the UK Space Agency. It’s a clear example of space technology being used to study life on Earth.

The pair launched from Vandenberg Space Force Base, California, on a SpaceX Falcon 9 rideshare (Transporter‑15). Liftoff was at 19:44 CET, and Surrey Satellite Technology Ltd confirmed first signals at 22:45 CET the same evening, a key milestone showing both spacecraft are healthy in orbit.

Here’s the simple idea you can share in class: HydroGNSS listens for GPS and Galileo navigation signals after they bounce off Earth’s surface. Those L‑band radio waves pass through cloud and even forest, so the satellites can keep measuring when optical imagers cannot. Scientists call this approach GNSS reflectometry.

What this means on the ground is practical. The mission will map how wet or dry soils are, spot pooling water and floods, and detect when land freezes or thaws. These measurements feed weather forecasts, sharpen flood warnings and support farm planning in the UK and beyond, at a time when severe events are becoming more frequent.

HydroGNSS is designed to sit alongside bigger observatories. ESA’s SMOS and Biomass and NASA’s SMAP already track moisture and vegetation; HydroGNSS adds extra, frequent coverage at low cost, helping to fill gaps between passes and in hard‑to‑see places.

Who built it matters too. Surrey Satellite Technology Ltd in Guildford designed and assembled the pair, with £26 million from the UK Space Agency. For SSTL they count as spacecraft number 75 and 76, delivered in the company’s 40th year-another UK milestone in small‑sat engineering.

Quick explainer for lessons: a navigation satellite sends a steady radio tone. HydroGNSS compares the direct tone with its echo off land, ice or water. A boggy field, a flooded wetland or frozen ground changes the echo in recognisable ways, letting researchers estimate wetness, flooding and seasonal freeze–thaw with a compact sensor in low orbit.

The Scout family exists to test new ideas quickly and affordably, complementing ESA’s larger Earth Explorer missions. By flying small, agile missions on tight schedules and budgets, ESA can try techniques like GNSS reflectometry in space and decide whether to scale up to a wider constellation.

There’s a policy story this week as well. At the ESA Ministerial Council in Bremen on 27 November, the UK confirmed a £1.7 billion package for ESA programmes-taking planned support to about £2.8 billion over the next decade, including funding for launch systems, Earth observation and space weather.

Closer to home, ministers plan to bring the UK Space Agency into the Department for Science, Innovation and Technology on 1 April 2026, creating a single civil space unit to simplify strategy and delivery across research and industry.

For you, this opens ready‑made case studies. Follow HydroGNSS updates and compare them with local rain gauges, river levels and farm reports. It’s a practical way to build media literacy around satellite data: ask what is measured, how often, and what the limits are.

Next steps are standard for any new satellite: commissioning, careful checks and calibration. Once performance is confirmed, science‑quality data will start to flow into forecast models and climate research. With first signals already received, that process is under way.