The two satellites lifted off at 10:44am local time from Vandenberg Space Force Base, California, on a SpaceX Falcon 9 as part of the Transporter-15 mission. Deployment was scheduled for just over an hour after launch but, in true space fashion, there was a brief moment of tension as the expected call-out for satellite separation passed without immediate confirmation due to a comms drop-pit. A few minutes later the launch director confirmed that both HydroGNSS satellites had in fact deployed safely - prompting a collective exhale from the SSTL launch team watching from Guildford.
At approximately three hours after liftoff, well into the dark autumn evening in the UK, SSTL’s Mission Control received first signals from both HydroGNSS spacecraft, completing a successful “acquisition of signal”. Subsequent early passes confirmed that both satellites have deployed their solar panels and are healthy, safe and operating nominally on orbit.
Pete Garner, SSTL HydroGNSS Project Manager, added:
“Those first few passes are always special – and it’s a huge relief to confirm both spacecraft are healthy and that their solar panels are out and generating power. A great moment for the team, and a brilliant start to the mission.”
About the HydroGNSS Mission
HydroGNSS is the first mission in ESA’s Scout programme - a new family of rapid, lower-cost, quick-turnaround Earth observation missions designed for agility, innovation and scientific impact. SSTL served as prime contractor, designing, building and delivering both satellites on an accelerated development schedule.
Using GNSS reflectometry, HydroGNSS measures faint GPS and Galileo signals reflected off Earth’s surface. By analysing these reflections, the mission will retrieve key hydrological variables that shape the global water cycle, including Soil moisture, Freeze–thaw state, Biomass, Wetlands, inundation and flooding, Snow and ice properties.
These data will support climate science, environmental modelling, disaster monitoring and improved understanding of changing land-surface processes.
HydroGNSS-1 and -2 also mark an internal milestone for SSTL – the company’s 75th and 76th spacecraft, launched during its 40th anniversary year.
Simonetta Cheli, Director of Earth Observation Programmes, ESA
“As the first of ESA’s Scout missions to launch, HydroGNSS marks an important milestone for this new family of rapid, low-cost Earth observation missions, and we extend our thanks to the mission’s prime contractor, SSTL. The launch also represents a key step in the evolution of our FutureEO programme, where the Scouts embody a fast, agile, innovative and cost-efficient approach – complementing our larger Earth Explorer missions. We now look forward to seeing how HydroGNSS will employ GNSS reflectometry to deliver valuable insights into key hydrological variables that shape Earth’s water cycle.”
Andrew Cawthorne, Managing Director, Surrey Satellite Technology Ltd
“Watching the HydroGNSS satellites lift off and then hearing those first signals never loses its magic. It’s the moment years of hard work turn into something real orbiting overhead. These two small spacecraft mean a lot to us: they’re our 75th and 76th satellites, launched in our 40th anniversary year, and the very first in ESA’s innovative Scout programme. HydroGNSS captures so much of what defines SSTL – agility, collaboration and technical excellence – and we’re incredibly proud of the whole team who delivered it at pace. We can’t wait to see the mission start returning meaningful data for ESA and the wider Earth observation community.”
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