Ocean Surface Current Airborne Radar (OSCAR) Demonstrator

Monitoring ocean circulation at high resolution in both space and time is of paramount importance for under-standing and modelling the ocean-atmosphere climate system, especially in coastal areas. Spaceborne radar al-timeters have been used to successfully monitor ocean circulation on a global scale ( > 30km) in the deep ocean when the geostrophic approximation is generally valid. The ocean structures seen in high-resolution satellite measurements at meso (10-100km) and sub-mesoscale ( < 10km) are ubiquitous but little is known about their dynamics. During the last two decades, many studies have highlighted the key role played by the ocean sub-mesoscale in air-sea interactions, upper-ocean mixing and ocean vertical transport and the importance of ageo-strophic circulation in these processus. Understanding these smaller currents is critical to drive scientific under-standing of the exchanges of gas, heat, and momentum between the atmosphere and the ocean, and have im-portant implications for forecasting models and climate projections. SEASTAR is an Earth Explorer 11 candidate mission, which aims to observe ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas by providing simultaneous measurements of current and wind vectors at 1km resolution with accuracy of respectively 10cm/s and 2m/s. OSCAR (Ocean Surface Current Airborne Radar) is the demonstrator for this satellite concept, and is in development at the Euro-pean Space Agency (ESA) in the frame of its preparatory activities for ocean surface current retrieval with Meta-sensing as a prime contractor. OSCAR system will be representative of a satellite mission concept, observation parameters and accuracies directly relate to a potential satellite mission. OSCAR is a Ku-band (13.5 GHz) three-look direction SAR system with Along-track Interferometric (ATI) SAR and scatterometric capabilities. It is tailored to the measurement of 2D ocean surface motion and wind retrie