ADVANCING CRYOSPHERE MONITORING: THE CRYORAD SPACEBORNE MISSION CONCEPT

G. Macelloni¹, T. C. Team²

¹CNR – IFAC, ²ESA

Over the past decade, the availability of new low-frequency microwave spaceborne data at L-band 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. Today, mission proposals are being developed in both the U.S. and Europe. Notably, ESA recently approved the CryoRad mission for Phase-0 studies as a potential candidate for 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 antenna system consists in a feed horn matrix and a large deployable antenna (i.e. around 12 m) that provides a native spatial resolution that ranges from 40 Km at 0.4 Ghz to 10 Km at 2 GHz which could be improved thanks to further studies thanks to enhanced resolution techniques. Measurements are performed in multiple contiguous frequencies over the 0.4 – 2 GHz bandwidth, in order to detect and mitigate radio frequency interference (RFI). Indeed, RFI is a key challenge for CryoRad, due to spectrum allocations in the 0.4 – 2 GHz range, within which measurement of the background Earth thermal emission may be corrupted by manmade transmissions and special effort is devoted in industrial studies on this subject. The three main mission scientific 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. The instrumental preliminary concept and the campaign plan to consolidate the scientific mission readiness will be also presented.