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The Surface Water and Ocean Topography (SWOT) satellite, developed by the National Aeronautics and Space Administration (NASA, USA) and Centre National d’Études Spatiales (CNES, France), with contributions from the Canadian Space Agency (CSA, Canada) and UK Space Agency (UKSA, United Kingdom), is a groundbreaking mission aimed at providing the first comprehensive global survey of Earth’s surface water. By measuring fine details of ocean surface topography and monitoring changes in water bodies over time, SWOT will enhance our understanding of global hydrological and oceanic processes. For SWOT to fulfill its primary mission, precise orbit determination is essential. To achieve this, the satellite is equipped with a DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) instrument, enabling highly accurate positioning and geodetic measurements. This study presents the first results of SWOT DORIS data processing by the IDS IGN-IPGP/JPL Analysis Center (IGN AC), focusing on orbit quality and its impact on geodetic products.We assess the accuracy of SWOT orbit solutions through internal consistency checks (overlap analysis) and external comparisons with SSALTO Precise Orbit Determination (POD) products, developed by CNES in collaboration with Collecte Localisation Satellites (CLS, France), for precise orbit computation and altimetry data processing. After verifying the quality of SWOT DORIS data processing through these orbit comparisons, we further evaluated the impact of including or excluding SWOT data in the multi-satellite solutions generated by the IGN AC and delivered to the IDS. This assessment provides insights into the contribution of SWOT to the robustness of combined geodetic products and highlights its potential role in future IDS solutions. The results show that SWOT significantly improves the weighted root mean square (WRMS) of station coordinates, with reductions of about 15 \(\%\) for East and Up components and 25 \(\%\) for North, compared to solutions without SWOT. Improvements are also observed for Earth Orientation Parameters, with WRMS reductions of approximately 7.5 \(\%\) for both X-pole and Y-pole. SWOT further contributes to the definition of the terrestrial reference frame, particularly along the X-origin, although slight degradations are noted in the Z-origin and scale (around 0.2 ppb). These findings highlight the positive contribution of SWOT to IDS geodetic products, while also pointing to potential calibration issues related to the antenna Phase Center Offset that warrant further investigation.

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First Assessment of SWOT DORIS Data by the IDS IGN-IPGP/JPL Analysis Center

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  • 出版模式：

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  • 发表日期：

    2026年

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  • Arnaud Pollet,
  • Samuel Nahmani,
  • Willy Bertiger

摘要

The Surface Water and Ocean Topography (SWOT) satellite, developed by the National Aeronautics and Space Administration (NASA, USA) and Centre National d’Études Spatiales (CNES, France), with contributions from the Canadian Space Agency (CSA, Canada) and UK Space Agency (UKSA, United Kingdom), is a groundbreaking mission aimed at providing the first comprehensive global survey of Earth’s surface water. By measuring fine details of ocean surface topography and monitoring changes in water bodies over time, SWOT will enhance our understanding of global hydrological and oceanic processes. For SWOT to fulfill its primary mission, precise orbit determination is essential. To achieve this, the satellite is equipped with a DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) instrument, enabling highly accurate positioning and geodetic measurements. This study presents the first results of SWOT DORIS data processing by the IDS IGN-IPGP/JPL Analysis Center (IGN AC), focusing on orbit quality and its impact on geodetic products.We assess the accuracy of SWOT orbit solutions through internal consistency checks (overlap analysis) and external comparisons with SSALTO Precise Orbit Determination (POD) products, developed by CNES in collaboration with Collecte Localisation Satellites (CLS, France), for precise orbit computation and altimetry data processing. After verifying the quality of SWOT DORIS data processing through these orbit comparisons, we further evaluated the impact of including or excluding SWOT data in the multi-satellite solutions generated by the IGN AC and delivered to the IDS. This assessment provides insights into the contribution of SWOT to the robustness of combined geodetic products and highlights its potential role in future IDS solutions. The results show that SWOT significantly improves the weighted root mean square (WRMS) of station coordinates, with reductions of about 15 \(\%\) for East and Up components and 25 \(\%\) for North, compared to solutions without SWOT. Improvements are also observed for Earth Orientation Parameters, with WRMS reductions of approximately 7.5 \(\%\) for both X-pole and Y-pole. SWOT further contributes to the definition of the terrestrial reference frame, particularly along the X-origin, although slight degradations are noted in the Z-origin and scale (around 0.2 ppb). These findings highlight the positive contribution of SWOT to IDS geodetic products, while also pointing to potential calibration issues related to the antenna Phase Center Offset that warrant further investigation.