First Results From the Rotating Fan Beam Scatterometer Onboard CFOSAT

• Published in: IEEE transactions on geoscience and remote sensing Vol. 58; no. 12; pp. 8793 - 8806
• Main Authors: Liu, Jianqiang, Lin, Wenming, Dong, Xiaolong, Lang, Shuyan, Yun, Risheng, Zhu, Di, Zhang, Kuo, Sun, Congrong, Mu, Bo, Ma, Jianying, He, Yijun, Wang, Zhixiong, Li, Xiuzhong, Zhao, Xiaokang, Jiang, Xingwei
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Backscatter; Backscattering; Beams (radiation); Buoys; Calibration; Data analysis; Data processing; Fans; Horizontal polarization; Incidence angle; Information processing; inversion; Noise; Oceanography; Onboard data processing; Physical oceanography; Polar environments; Radar measurements; Rotation; Satellites; scatterometer; Scatterometers; Sea surface; Signal processing; Spaceborne radar; Subtraction; Surface wind; Vectors; Weather forecasting; Wind; wind quality; Wind speed; Wind vectors; Winds
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2020.2990708

The first rotating fan beam scatterometer onboard China-France Oceanography Satellite (CFOSAT) was successfully launched on October 29, 2018. CFOSAT SCATterometer (CSCAT) is dedicated to the monitoring of sea surface wind vectors but also provides valuable data for the applications over land and Polar Regions. This article provides an overview of the relevant procedures of CSCAT data processing, including onboard signal processing and operational ground processing. Then a post-launch analysis is carried out to evaluate the first results of CSCAT L1 and L2 products. It shows that the CSCAT instrument is generally stable in terms of noise measurements and internal calibration, unless there is any important change in the system configuration. Specifically, the CSCAT backscatter (<inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula>) precision and wind quality are studied using a set of collocated ancillary data. The <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> precision degrades as wind speed decreases, and it is relatively low at high incidence angles (e.g., <inline-formula> <tex-math notation="LaTeX">\theta > 46 ^{\circ } </tex-math></inline-formula>). In particular, backscatter estimation of the horizontally polarized beam should be further improved by correcting the noise subtraction factor. The retrieved CSCAT winds are in good agreement with the European Centre for Medium Range Weather Forecasts (ECMWF) winds, the Advanced Scatterometer (ASCAT) winds, as well as the buoy winds. However, due to unresolved calibration and interbeam consistency problems, the wind quality degrades remarkably for the out-swath and the nadir-region wind vector cells, implying that the <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> calibration should be improved in the future updates.