HydroGNSS set for 10 Nov launch as ESA halts CubeMAP

Imagine listening for GPS and Galileo echoes to read Earth’s water story. That’s HydroGNSS: the European Space Agency’s first “Scout” mission, led by the UK, using two small satellites to gather fast, affordable measurements that help us understand a warming planet. ESA frames Scouts as quick, agile missions designed to prove bold Earth observation ideas.

Here’s the when and where. HydroGNSS is planned to launch on 10 November 2025 from Vandenberg Space Force Base in California on a SpaceX Falcon 9 rideshare (Transporter‑15). ESA held a pre‑launch briefing on 3 November, and Surrey Satellite Technology Ltd (SSTL) says both satellites are integrated at the launch site and awaiting liftoff.

Quick explainer: GNSS‑Reflectometry. Navigation satellites beam constant L‑band radio signals. HydroGNSS will record both the direct signal and the same signal after it bounces off Earth’s surface. The shape and delay of that reflection change with surface roughness and wetness, so with careful processing we can estimate things like soil moisture and flood extent.

What HydroGNSS will measure. ESA lists four primary targets linked to Essential Climate Variables (ECVs): soil moisture, permafrost freeze–thaw, inundation and wetlands, and above‑ground biomass. It will also provide secondary measurements of ocean wind speed and sea‑ice extent. In climate science, ECVs are the agreed “vital signs” (there are currently 55) and about 60% can be observed from space.

Why this matters for you. Better readings of how wet the ground is, where water is pooling, and when frozen ground thaws feed into weather and climate models, crop planning and flood preparedness. ESA’s Climate Office and mission pages stress that these datasets help decision‑makers act earlier and more precisely.

Let’s size this up. Each HydroGNSS satellite is roughly 45 × 45 × 70 cm and about 75 kg-think washing‑machine class. The pair will fly in near‑polar orbit around 550 km up, separated by 180°, with a typical measurement resolution near 25 km. Together they can observe more than 80% of land every 15 days.

Who’s building and operating it. SSTL in Guildford is ESA’s prime and will also operate the satellites and distribute the data. The UK Space Agency has supported the mission through ESA’s FutureEO programme (about €30 million), and UK/European science teams include partners from Sapienza and Tor Vergata (Italy), IFAC‑CNR (Italy), FMI (Finland), ICE/IEEC (Spain), the National Oceanography Centre (UK) and the University of Nottingham.

How you’ll access the data. SSTL hosts an ESA data portal for HydroGNSS. Users register for access; standard products are typically released after a short delay and a “fast data” option (around 48 hours) is available for specific users, subject to terms. If you teach, that means near‑real‑time case studies are firmly within reach.

About Scout missions. Scouts are deliberately small and speedy: build‑to‑launch in roughly three years with a tight budget-ESA documents cite about €30–35 million covering development, launch and commissioning. The idea is to prove new observing techniques quickly and then scale up if they work.

A real‑world lesson in constraints. ESA has terminated development of the CubeMAP Scout mission after it exceeded timeline and budget boundaries, even though the underlying science case and instruments (HIROS and HSDI) were considered promising. ESA says the know‑how will be carried into future efforts outside the Scout framework.

Teacher note: use HydroGNSS as a data‑literacy exercise. Ask students to predict where soil will be driest or wettest after a local weather event, then compare with satellite‑derived soil moisture once products are online. Discuss what satellites can and can’t “see” and why ground truth still matters.

What to watch next. After launch and early checkouts, expect calibration, initial “first light” results and then regular data releases via the portal. Two more Scouts are in the pipeline: NanoMagSat to track Earth’s magnetic field and ionospheric environment, and Tango to monitor greenhouse‑gas plumes over major emitters.