Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors
Interactions between ocean surface currents, winds and waves at the atmosphere-ocean interface are key controls of lateral and vertical exchanges of water, heat, carbon, gases and nutrients in the global Earth System. The SeaSTAR satellite mission concept proposes to better quantify and understand t...
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MDPI AG
2024-09-01
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| author | Adrien C. H. Martin Christine P. Gommenginger Daria Andrievskaia Petronilo Martin-Iglesias Alejandro Egido |
| author_facet | Adrien C. H. Martin Christine P. Gommenginger Daria Andrievskaia Petronilo Martin-Iglesias Alejandro Egido |
| author_sort | Adrien C. H. Martin |
| collection | DOAJ |
| description | Interactions between ocean surface currents, winds and waves at the atmosphere-ocean interface are key controls of lateral and vertical exchanges of water, heat, carbon, gases and nutrients in the global Earth System. The SeaSTAR satellite mission concept proposes to better quantify and understand these important dynamic processes by measuring two-dimensional fields of total surface current and wind vectors with unparalleled spatial and temporal resolution (1 × 1 km<sup>2</sup> or finer, 1 day) and unmatched precision over one continuous wide swath (100 km or more). This paper presents a comprehensive numerical analysis of the expected performance of the Earth Explorer 11 (EE11) SeaSTAR mission candidate in the case of idealised and realistic 2D ocean currents and wind fields. A Bayesian framework derived from satellite scatterometry is adapted and applied to SeaSTAR’s bespoke inversion scheme that simultaneously retrieves total surface current vectors (TSCV) and ocean surface vector winds (OSVW). The results confirm the excellent performance of the EE11 SeaSTAR concept, with Root Mean Square Errors (RMSE) for TSCV and OSVW at 1 × 1 km<sup>2</sup> resolution consistently better than 0.1 m/s and 0.4 m/s, respectively. The analyses highlight some performance degradation in some relative wind directions, particularly marked at near range and low wind speeds. Retrieval uncertainties are also reported for several variations around the SeaSTAR baseline three-azimuth configuration, indicating that RMSEs improve only marginally (by ∼0.01 m/s for TSCV) when including broadside Radial Surface Velocity or broadside dual-polarisation data in the inversion. In contrast, our results underscore (a) the critical need to include broadside Normalised Radar Cross Section data in the inversion; (b) the rapid performance degradation when broadside incidence angles become steeper than 20° from nadir; and (c) the benefits of maintaining ground squint angle separation between fore and aft lines-of-sight close to 90°. The numerical results are consistent with experimental performance estimates from airborne data and confirm that the EE11 SeaSTAR concept satisfies the requirements of the mission objectives. |
| format | Article |
| id | doaj-art-109986d848ee44ea9c5958850bee133c |
| institution | OA Journals |
| issn | 2072-4292 |
| language | English |
| publishDate | 2024-09-01 |
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| series | Remote Sensing |
| spelling | doaj-art-109986d848ee44ea9c5958850bee133c2025-08-20T01:47:34ZengMDPI AGRemote Sensing2072-42922024-09-011619355610.3390/rs16193556Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind VectorsAdrien C. H. Martin0Christine P. Gommenginger1Daria Andrievskaia2Petronilo Martin-Iglesias3Alejandro Egido4National Oceanography Centre, Southampton SO14 3ZH, UKNational Oceanography Centre, Southampton SO14 3ZH, UKNOVELTIS, 31670 Labège, FranceEuropean Space Research and Technology Centre (ESTEC), European Space Agency, 2201 AZ Noordwijk, The NetherlandsEuropean Space Research and Technology Centre (ESTEC), European Space Agency, 2201 AZ Noordwijk, The NetherlandsInteractions between ocean surface currents, winds and waves at the atmosphere-ocean interface are key controls of lateral and vertical exchanges of water, heat, carbon, gases and nutrients in the global Earth System. The SeaSTAR satellite mission concept proposes to better quantify and understand these important dynamic processes by measuring two-dimensional fields of total surface current and wind vectors with unparalleled spatial and temporal resolution (1 × 1 km<sup>2</sup> or finer, 1 day) and unmatched precision over one continuous wide swath (100 km or more). This paper presents a comprehensive numerical analysis of the expected performance of the Earth Explorer 11 (EE11) SeaSTAR mission candidate in the case of idealised and realistic 2D ocean currents and wind fields. A Bayesian framework derived from satellite scatterometry is adapted and applied to SeaSTAR’s bespoke inversion scheme that simultaneously retrieves total surface current vectors (TSCV) and ocean surface vector winds (OSVW). The results confirm the excellent performance of the EE11 SeaSTAR concept, with Root Mean Square Errors (RMSE) for TSCV and OSVW at 1 × 1 km<sup>2</sup> resolution consistently better than 0.1 m/s and 0.4 m/s, respectively. The analyses highlight some performance degradation in some relative wind directions, particularly marked at near range and low wind speeds. Retrieval uncertainties are also reported for several variations around the SeaSTAR baseline three-azimuth configuration, indicating that RMSEs improve only marginally (by ∼0.01 m/s for TSCV) when including broadside Radial Surface Velocity or broadside dual-polarisation data in the inversion. In contrast, our results underscore (a) the critical need to include broadside Normalised Radar Cross Section data in the inversion; (b) the rapid performance degradation when broadside incidence angles become steeper than 20° from nadir; and (c) the benefits of maintaining ground squint angle separation between fore and aft lines-of-sight close to 90°. The numerical results are consistent with experimental performance estimates from airborne data and confirm that the EE11 SeaSTAR concept satisfies the requirements of the mission objectives.https://www.mdpi.com/2072-4292/16/19/3556total surface current vectorocean surface vector windSARDoppleralong-track interferometryBayesian inversion |
| spellingShingle | Adrien C. H. Martin Christine P. Gommenginger Daria Andrievskaia Petronilo Martin-Iglesias Alejandro Egido Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors Remote Sensing total surface current vector ocean surface vector wind SAR Doppler along-track interferometry Bayesian inversion |
| title | Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors |
| title_full | Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors |
| title_fullStr | Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors |
| title_full_unstemmed | Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors |
| title_short | Performance of the Earth Explorer 11 SeaSTAR Mission Candidate for Simultaneous Retrieval of Total Surface Current and Wind Vectors |
| title_sort | performance of the earth explorer 11 seastar mission candidate for simultaneous retrieval of total surface current and wind vectors |
| topic | total surface current vector ocean surface vector wind SAR Doppler along-track interferometry Bayesian inversion |
| url | https://www.mdpi.com/2072-4292/16/19/3556 |
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