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The mission

HydroGNSS is the first ESA Scout mission. The two-satellite mission uses a technique called Global Navigation Satellite System reflectometry to measure hydrological climate variables, including soil moisture, freeze–thaw state over permafrost, inundation and wetlands, and biomass.

Embracing the concept of New Space, Scout missions pave the way to innovative science in a quick and agile fashion, and complement ESA’s Earth Explorer research missions.


The launch

Date: 28 November 2025
Site: Vandenberg, California, US
Rocket: Falcon 9

1st Scout mission
2 identical satellites
550 km altitude
25 km resolution

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[ HydroGNSS ]
ÁBHAR CARTLAINNE: 28 SAMH. 2025

ESA’s HydroGNSS mission launched to ‘scout’ for water

The European Space Agency’s first Scout mission, HydroGNSS, was launched today, 28 November, marking a significant step in advancing global understanding of water availability and the effects of climate change on Earth’s water cycle.The two twin HydroGNSS satellites were carried into orbit at 19:44 CET aboard a SpaceX Falcon 9 rocket, as part of the Transporter-15 rideshare flight from the Vandenberg Space Force Base in California.
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[ HydroGNSS ]
ÁBHAR CARTLAINNE: 26 SAMH. 2025

Watch: HydroGNSS, IRIDE and Greek mission satellites launch

Update 26 November: The launch is now targeted for 28 November. The European Space Agency’s HydroGNSS, a twin-satellite mission to gather data on Earth’s water cycle, is now scheduled to launch on 28 November at 19:44 CET (10:44 Pacific Time). Live coverage of the launch will be shown on ESA Web TV.
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[ HydroGNSS ]
ÁBHAR CARTLAINNE: 06 SAMH. 2025

ESA’s HydroGNSS Scout satellites ready for launch

After arriving at the California launch site at the end of September, the two HydroGNSS satellites have been carefully prepared for liftoff, scheduled this month.HydroGNSS – a twin-satellite mission – marks the European Space Agency’s first ‘Scout’ venture. By harnessing signals from navigation satellites, HydroGNSS will help scientists gain new insights into key climate variables linked to water.
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[ HydroGNSS ]
ÁBHAR CARTLAINNE: 06 MÁRT. 2023

HydroGNSS twice as good

ESA’s HydroGNSS mission will now comprise two identical satellites to halve the time it takes to revisit the same place on Earth’s surface and re-measure various climate variables such soil moisture. Having two satellites in orbit will significantly improve the science that this exciting new Scout mission will yield.
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HydroGNSS videos

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HydroGNSS mission kit

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[ HydroGNSS ]
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HydroGNSS documents and publications

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[ HydroGNSS ]
04 DEAI. 2025

Introducing HydroGNSS

The HydroGNSS Scout mission comprises two identical satellites that were launched on 28 November 2025.
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[ HydroGNSS ]
04 DEAI. 2025

HydroGNSS: ESA’s first Scout

HydroGNSS is ESA’s first Scout mission. Developed within ESA’s Earth Observation FutureEO programme, Scouts are small satellite missions that pave the way to innovative science in a quick and agile fashion, and complement ESA’s larger Earth Explorer research missions.
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[ HydroGNSS ]
07 DEAI. 2025

Scouting for water

Changes in Earth’s water cycle pose a serious risk to the ecosystems, the environment and to communities.
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[ HydroGNSS ]
09 DEAI. 2025

Satellites and mission

The HydroGNSS mission consists of two identical microsatellites orbiting the Earth on opposite sides of the planet, 180 degrees apart, to provide maximum global coverage.Each satellite weighs around 75 kilograms and measures 45 × 45 × 70 centimetres, built on the compact and reliable SSTL-21 platform.
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