Orbiting Earth 180 degrees apart, the Scout mission uses a technique called Global Navigation Satellite System (GNSS) reflectometry to measure important climate variables such as soil moisture, freeze–thaw state over permafrost, inundation and biomass – all of which are linked to Earth’s water cycle. The mission comprises two identical satellites orbiting 180 degrees apart. Each satellite weighs around 60 kg.

Embracing the New Space concept, HydroGNSS is one of ESA’s new Scout missions being developed within the Earth Observation FutureEO programme.