A New Spaceborne Mission Concept for The Monitoring of the Cryosphere : CryoRAD

Over the past decade, the availability of new low-frequency microwave spaceborne data has provided key parameters of the cryosphere and polar ocean that can be assimilated into Earth System Models, enhancing our understanding of fundamental processes. Building on these findings, new initiatives have emerged to explore the potential of using even lower frequencies (with the current lower limit being 1.4 GHz). These lower frequencies can penetrate deeper into ice and have shown greater sensitivity to sea surface salinity in cold waters. Airborne surveys conducted in Greenland and Antarctica have demonstrated the potential of low-frequency wideband radiometers in monitoring polar regions, offering unprecedented capabilities compared to existing and planned spaceborne satellites. The ESA Earth Explorer 12 CryoRad mission candidate aims to fully demonstrate these capabilities and produce key scientific data for advancing cryosphere studies. CryoRad consists of a single satellite equipped with a broadband low-frequency microwave radiometer operating in the range 0.4 to 2 GHz with continuous frequency scanning with frequent revisit and a complete coverage of polar regions. The three main mission objectives are: (i) Better assess the mass balance and stability of ice sheets, by bridging the observation gap for ice sheet  temperature profiles of Antarctic and Greenland ice sheets, extending from surface to base, a dataset previously available only through limited borehole observations or models; (ii) Better assess the freshwater cycle and water mass formation at high latitudes, by bridging the observation gap for sea surface salinity in cold waters enhancing the uncertainty by at least a factor of 2 compared with existing L-band measurements; (iii) Investigate sea ice dynamics and salinity exchange processes in the Arctic and Antarctic, by bridging the observation gap of sea ice thickness in the range 0.5-1 m and deliver the first spaceborne observations of sea ice salinity. Scientific and industrial studies are currently on-going to improve the mission concept and to accurately design the products’ requirements and instrument parameters. The aim of the paper is to present the mission concept to the scientific community, discuss the methodologies for extracting geophysical parameters, and evaluate the potential impact of these new parameters on Earth System Models.