Observing Sea Surface Current by Gaofen-3 Satellite Along-Track Interferometric SAR Experimental Mode

Abstract

Sea surface current is a research hotspot in oceanography. Space-borne along-track interferometric Synthetic Aperture Radar (along-track InSAR, ATI) is a promising sensor for measuring high-resolution sea surface current field, and there is no operational system in orbit yet. To support future spaceborne ATI systems, based on the ATI experimental mode of the Gaofen-3 (GF-3) satellite, the first sea surface current observing experiment was conducted in the Jiaozhou Gulf in China in 2019. Meanwhile, SAR observations and in-situ instrument measurements of the current are obtained in the experiments. The data is firstly preprocessed by a processor specially developed for the GF-3 ATI data. Then, the current is extracted based on the M4S mode. The retrieved current of the Jiaozhou Gulf is compared with ground-based High Frequency Surface Wave Radar (HFSWR) data. The results show that the root mean square error (RMSE) of the surface current observed by the GF-3 satellite is less than 0.2 m/s.

Maximum a Posteriori Based Ocean Surface Current Inversion for Doppler Scatterometer

“…The refined ocean current speed and direction can be estimated by maximizing J M AP in (7) or maximizing both J M AP V and J M AP φ in (8) and (9). Taking the MAP-II based method as an example, the proposed ocean surface current inversion method is illustrated in Fig.…”

“…Step 4: The final current speed V is employed to update f si and J M LE in (4), then the simplex search algorithm is used to solve (9) to obtain the final current direction φ.…”

“…Satellite altimeters [8] can observe ocean circulation on a large scale (>200 km), but their capability of current inversion in small and medium scales is limited. Synthetic aperture radar (SAR) [9], [10] can realize global current observation with high spatial resolution, but a monostatic radar can only estimate radial current speeds rather than vector current fields. Moreover, it cannot achieve continuous observation due to its revisit period.…”

Integrating SBAS-InSAR and AT-LSTM for Time-Series Analysis and Prediction Method of Ground Subsidence in Mining Areas

“…Furthermore, the selection of SAR data is an important aspect influencing ground settlement monitoring outcomes. The key data sources in the analysis are presently ENVISAT [19], TerraSAR-X [20], COSMO-SkyMed [21], TanDEM-X [22], Sentinel-1 [23], ALOS [24], and Gaofen-3 [25]. Combining the features of Sentinel-1A data such as large observation range, high temporal resolution, and free access [26], this study uses Sentinel-1A data for SBAS-InSAR processing.…”