OSCAR: a new airborne instrument to image ocean-atmosphere dynamics at the sub-mesoscale: instrument capabilities and the SEASTARex airborne campaign

<p>OSCAR (Ocean Surface Current Airborne Radar) is a new airborne instrument which provides unique 2D synoptic views of ocean and atmosphere dynamics (currents, waves, winds) below km-scale. OSCAR is the airborne demonstrator of SeaSTAR, an innovative satellite mission concept currently under study in Phase 0 of ESA Earth Explorer 11. SeaSTAR aims to observe ocean submesoscale dynamics and small-scale atmosphere-ocean processes in all coastal, shelf and polar seas by providing simultaneous measurements of current and wind vectors at 1 km resolution with accuracy better than 0.1 m/s and 2 m/s respectively. A key objective of SeaSTAR is to characterize, for the first time, the magnitude, spatial structure, regional distribution and temporal variability of upper ocean dynamics on daily, seasonal and multi-annual time scales, with particular focus on coastal seas, shelf seas and Marginal Ice Zone boundaries.</p><p>OSCAR was flown over the Iroise Sea (West of Brittany, France) in May 2022 during the SEASTARex campaign. The OSCAR operations and products are representative of the spaceborne concept, with geophysical parameters and accuracies that directly relate to those of the SeaSTAR satellite mission. In itself, OSCAR provides a new observing capability that will improve our understanding of microwave Doppler sensing of the ocean thanks to its unique Doppler and scatterometry capabilities in three azimuth directions. OSCAR&#8217;s high-resolution images (8 metres pixels resolution) over a 5km swath provide 2D synoptic views of ocean and atmosphere dynamics below km-scales that are highly relevant to support and complement scientific investigations of fine-scale ocean-atmosphere processes based on in-situ, satellite and model data.</p><p>In this paper, we give an overview of the OSCAR system, of the SEASTARex campaign over the Iroise Sea in May 2022 and present the main preliminary results about the performance and imaging capability of the instrument.</p>