Towards a family of SAR NRB products

Kurzfassung

The current family of SAR products from Sentinel-1, TerraSAR-X, ERS-1/2 and ENVISAT, primarily contains Level-1 Single Look Complex, Ground Range Detected or ellipsoid and terrain corrected products [1] [2] [3] [4], which inherit their definition from the European heritage Synthetic Aperture Radar (SAR) satellite missions ERS-1/2 and ENVISAT. These products have, over the years, proven to be reliable high-quality data sources. In particular, users largely benefit from the open and free data policy of the ERS-1/2, ENVISAT and Copernicus programme (European space agency, European Commission). This has led to SAR products being routinely used in several operational applications as well as enlarging the user base of SAR data in general. However, the rapid increase of data volume is presenting a challenge to many users who still want to exploit this wealth of information but lack the resources for the processing needed to convert these Level-1 products to interoperable geoinformation. Cloud resources offer opportunities for accelerated data exploitation but require new strategies for data management and provision. As a consequence, the term Analysis Ready Data (ARD) has been coined and several activities have indicated the potential of enlarging the Copernicus product family by such ARD products. With the aim to standardize different categories of ARD, the Committee on Earth Observation Satellites (CEOS) has set up the CEOS Analysis Ready Data initiative (CEOS ARD). Within this framework, ARD was defined as: »satellite data that have been processed to a minimum set of requirements and organized into a form that allows immediate analysis with a minimum of additional user effort and interoperability both through time and with other datasets.« Different SAR product specifications are currently being defined to provide guidelines on how to best process and organize data to serve as many use cases as possible with the respective products [5]. In this context, ESA and DLR decided to collaborate in order to define a family of SAR ARD products for Sentinel-1, ERS-1/2 and ENVISAT, potentially to be extended to other SAR missions. These products should be calibrated the same way (Radiometric Terrain Correction (RTC)), denoised, projected and geolocated in order to allow immediate analysis by the users. The same gridding / tiling system (Military Grid Reference System (MGRS)) and the same Digital Elevation Model (the Copernicus DEM) shall be used in order to allow interoperability of the SAR data from different missions. The use of Cloud-Optimised GeoTIFF (COG) raster files, of VRT files, of XML and STAC metadata will enable efficient exploitation of these datasets into cloud-computing environments. Finally, using open-source code and libraries to generate these new products, processors will represent a considerable step toward Open Science. The status of the development of the ARD products from the different ESA and DLR missions and of the processing experiences will be presented, together will the plans for future missions like Sentinel-1 NG, High Resolution Wide Swath (HRWS), ROSE-L and BIOMASS. In addition, the definition of an Ocean Radar Backscatter (ORB) product for Sentinel-1 will be reported.