Advanced Sentinel-1 Analysis Ready Data for Africa (SAR-4-Africa)

Sentinel-1 is the operational C-band synthetic aperture radar (SAR) satellite mission of the European Copernicus Program providing weather and sunlight independent radar imagery of the whole Earth on a consistent 12-day repeat cycle. However, there is a strong reluctance to use SAR data because of its complexity in regard to sensor-specific noise, topographic effects, (pre-)processing requirements, and unfamiliar appearance for interpretation. These technical and human capacity requirements as well as the vast amount of data makes it out of reach for most non-technical user groups that could benefit from its monitoring potential in general and especially in persistently cloud-covered areas as the tropics. This project aims to overcome these technical challenges and subjective reluctance by providing attractive, easy-to-use “Advanced Sentinel-1 Analysis Ready Data” (ASARD) image products with a focus on African users. Such imagery needs to be timely accessible, visually attractive and easier interpretable without losing essential information for the users monitoring needs and potential further numerical analysis. To a large extent, such information can be conserved by statistical analysis of dense time series and providing noise-reduced mosaics instead of single satellite images. By a demand-driven approach and user assessment involving five African countries (D.R. Congo, Ethiopia, Ghana, Malawi and South Africa), we standardize such ASARD products to a set of monthly and yearly averaged Sentinel-1 mosaic [RGB = [VV,VH,NDI] and yearly statistical analysis images representing, mean, median, variance, minimum, maximum, number of acquisitions and an accumulated SAR shadow/overlay mask for each SAR polarization. The aim of providing such easy-to-use imagery is to boost the use of Sentinel-1 data for operations to a wider user community, including the non-technical community and policy makers, in order to support the United Nations Sustainable Development Goals. The user’s ASARD service and product assessments showed high general satisfaction; products generally exceeded the quality of their in-house processed S1 data, are easy to understand and use and satisfy general operational requirements. The users concluded that it would be highly beneficially if such ASARD data would be available operationally on a national and global scale. Finally, the ASARD processing line was successfully tested to run in a cloud environment on CreoDIAS, one of Copernicus’ Data and Information Access Services. Ghana data was also ingested directly in the African Regional Data Cube (ARDC).