Abstract
Sentinel-1A and -1B are twin spaceborne synthetic aperture radar (SAR) sensors developed and operated by the European Space Agency under the auspices of the Copernicus Earth observation programme. Launched in April 2014 and April 2016, Sentinel-1A and -1B are currently operating in tandem, in a common orbital configuration to provide an increased revisit frequency. In-orbit commissioning was completed for each unit within months of their respective launches, and level-1 SAR products generated by the operational SAR processor have been geometrically calibrated. In order to compare and monitor the geometric characteristics of the level-1 products from both units, as well as to investigate potential improvements, products from both satellites have been monitored since their respective commissioning phases. In this study, we present geolocation accuracy estimates for both Sentinel-1 units based on the time series of level-1 products collected thus far. While both units were demonstrated to be performing consistently, and providing SAR data products according to the nominal product specifications, a subtle beam- and mode-dependent azimuth bias common to the data from both units was identified. A method for removing the bias is proposed, and the corresponding improvement to the geometric accuracies is demonstrated and quantified.
Highlights
The Sentinel-1 (S-1) Mission, as part of the space component of Copernicus, is based on a constellation of two satellites that fulfil revisit and coverage requirements, providing robust datasets for Copernicus services
We present geolocation accuracy estimates for both Sentinel-1 units based on the time series of level-1 products collected far
As partAsofpart the of ongoing cooperation between the the Geoscience Australia (GSA), thethe suitability test site for geometric calibration purposes was assessed, and comparisons made with the corner reflector (CR) test site for geometric calibration purposes was assessed, and comparisons made with the Swisssites
Summary
The Sentinel-1 (S-1) Mission, as part of the space component of Copernicus, is based on a constellation of two satellites that fulfil revisit and coverage requirements, providing robust datasets for Copernicus services. High quality geolocation is required for SAR interferometric processing, such as during image co-registration using the annotated timing information and orbital data [4]. The improved orbit state vector quality is reflected in the small residual 2baseline fringes in interferograms [10]. Given the rapidly growing dense time series from S-1 and other sensors, accurate product the small residual baseline fringes in interferograms [10]. High accuracy modern SAR assensors using such products as geodetic references for S-1 less[7,8,9]. SAR-GNSS (SAR-Global Navigation Satellite Systems) geodetic networks for Beyond applications such as interferometric SAR (InSAR), an improved geolocation accuracy deformation monitoring [15]. (DLR) TSX/TanDEM-X constellation [3,11,12,13,15]
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