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Sentinel-1 GRD preprocessing workflow
1  Institute for Environmental Protection and Research (ISPRA)


The establishment of the Copernicus Programme by the European Commission created a new paradigm in the availability and accessibility of data information, offering services based on satellite Earth Observation and in situ data under 6 thematic Copernicus services. The Copernicus Programme became the world largest space data provider, providing complete, free and open access to satellite data, mainly acquired by Sentinel satellites. Main advantages offered by Sentinel data are the improved spatial resolution and high revisit frequency, that makes them useful for a wide range of applications.
Sentinel-1 satellites constellation acquires SAR data in single or dual polarization with a revisit time of 6 days. Sentinel-1 Level 1 data are distributed by the Copernicus Open Access Hub under two product types: Ground Range Detected (GRD) and Single Look Complex (SLC). While few research applications need Sentinel-1 GRD data with few corrections applied, the wider part of the users needs products with a standard set of corrections applied. In order to facilitate the exploitation of Sentinel-1 GRD products, there is the need to standardise procedures to preprocess SAR data to a higher processing level.
A standard generic workflow to preprocess Copernicus Sentinel-1 GRD data is here presented. The workflow aims to apply a series of standard corrections, and precisely to apply precise orbit of acquisition, remove thermal and image border noise, perform radiometric calibration, apply range doppler and terrain correction. Additionally, the workflow allows to spatially snap Sentinel-1 GRD products to Sentinel-2 MSI data grids, in order to promote the use of satellite virtual constellations by means of data fusion techniques.
The presented workflow allows to produce a set of preprocessed Sentinel-1 GRD data, offering a benchmark for the development of new products and operational downstreaming services based on Copernicus Sentinel-1 GRD data, with the aim of providing reliable information of interest to a wide range of communities.

Keywords: Sentinel-1;Synthetic Aperture Radar;preprocessing;radiometric calibration;terrain correction