ESA’s first Scout mission, HydroGNSS, led by the UK, is set to lift off on a SpaceX Falcon 9 from Vandenberg, California in November 2025, with launch currently targeted for 10 November on the Transporter‑15 rideshare. The twin satellites promise faster, lower‑cost climate data to aid farm planning, flood preparedness and daily forecasting.

HydroGNSS uses Global Navigation Satellite System reflectometry: the satellites listen to GPS and Galileo signals that bounce off Earth’s surface and compare them with the direct signals. That contrast reveals water‑cycle indicators such as soil moisture, wetland inundation, freeze–thaw over permafrost and above‑ground biomass.

This focus aligns with the Global Climate Observing System framework. The World Meteorological Organization recognises 55 Essential Climate Variables, and UK government guidance notes that around 60% of these can be observed from space-evidence that missions like HydroGNSS can feed both climate science and public‑service operations.

Two identical small satellites will fly in sun‑synchronous orbit about 550 km up, phased 180 degrees apart to speed repeat coverage. At 25 km resolution, the pair can re‑observe more than 80% of land in around 15 days, with expected mission life beyond three years-built for regular, reliable updates rather than once‑in‑a‑while snapshots.

The mission is designed, built and operated in the UK by Surrey Satellite Technology Ltd (SSTL), with science partners including the University of Nottingham and the National Oceanography Centre in the UK, plus teams in Italy, Spain and Finland. SSTL will also distribute processed data to users, keeping latency low for real‑world applications.

HydroGNSS sits within ESA’s FutureEO Scout programme-an agile approach that demonstrates value quickly and affordably. ESA signed a €24 million build contract with SSTL, while earlier UK Centre for Earth Observation Instrumentation funding helped mature key technologies, paving the way for this flight.

The hardware has cleared its final pre‑launch hurdles. After passing Flight Acceptance Review in August, both satellites were shipped to California and integrated onto the launch plate. ESA held a pre‑launch briefing on 3 November, confirming the mission’s November window and readiness for the Falcon 9 rideshare.

For land managers and agritech firms, the gain is practical: L‑band signals used in GNSS‑R work through clouds and tolerate light vegetation, giving consistent, global snapshots of surface wetness. Integrated with local rain gauges and soil sensors, HydroGNSS can sharpen irrigation scheduling, drought tracking and seasonal outlooks.

Coastal agencies and polar researchers also benefit. Beyond land hydrology, the mission derives ocean wind speed and sea‑ice extent as secondary products-useful for maritime safety and high‑latitude operations as sea‑ice seasons shift.

The Scout line originally included CubeMAP, a three‑satellite effort to profile greenhouse gases and aerosols in the tropical upper troposphere and stratosphere with miniaturised spectrometers. ESA halted CubeMAP’s development after it exceeded timeline and budget constraints, but the technical groundwork informs future atmospheric missions.

HydroGNSS now leads ESA’s Scout family into service. If the approach proves its worth in orbit, ESA and partners can scale to a larger GNSS‑R constellation, capturing faster soil‑moisture swings and freeze–thaw cycles that matter to flood teams, farmers and forecasters alike.

Once operational, data will downlink several times a day to ground stations and be processed through SSTL’s payload data system before distribution. That cadence-combined with the mission’s affordable design-helps public agencies and businesses fold space‑borne hydrology into day‑to‑day decisions without waiting months for updates.