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Calibration and Validation


1 Objectives On June 5 2019, following the UK TechDemoSat-1 mission and the US Cyclone GNSS (CYGNSS) constellation, BuFeng-1 A/B in-orbit demonstration satellites were successfully deployed in orbit by Chinese first-time sea platform launch. Now, it is one of the only two in-orbit operational GNSS-R mission (NASA CYGNSS and BuFeng-1 A/B). After months of full-time operation, the preliminary results reveal that the derived sea surface wind speed is impressively reliable at low-to-moderate wind speed range under fully developed seas condition. As a result, the GNSS-R technique have become a key component for China meteorological satellite observation system for the future numerical weather forecast and typhoon monitoring. The calibration of scattering coefficients for high sea surface wind speeds under heavy precipitation and the validations of the performances for the other GNSS-R applications (such as soil moisture and ocean altimetry) should be further studied, which can guide the design of future ESA and China GNSS-R satellite missions, such as BuFeng constellations, FFScat, G-TERN, Cookie, ORORO and HydroGNSS. The products of ESA SMOS mission, for soil moisture and ocean salinity, can also provide high ocean wind products, and are especially suitable for the calibration and validation of spaceborne GNSS-R measurements. It is noted that the Dragon 5 project can fully cover the life span of the BuFeng-1 A/B satellites. Regarding these requirements, the objectives are summarized as follows: 1) Collocation of integrated ESA-CHINA EO data products and BuFeng-1 data preprocessing 2) Calibration of the BuFeng-1 A/B main observables, including NBRCS, power DDM, and SNR 3) Validation of the calibrated results from BuFeng-1 A/B; 4) Optimization and improvements of future spaceborne GNSS-R instruments. 2 Methods With respect to the objectives, the accumulated first handed BuFeng-1 data from CMA are collected and collocated with other products from ESA and China EO missions, including SMOS, CRYOSAT-2, HY-1/2, and FY series. After that, spaceborne GNSS-R observations and auxiliary data will be analyzed to check the sensitivities of the GNSS-R observables (such as NBRCS, SNR, calibrated power DDM) to different spaceborne GNSS-R applications, such as sea surface winds, inland soil moisture, and sea surface height. Besides EO data, the validation methods also comprise the ECMWF reanalysis products on wind speed, soil moisture content, sea surface height, etc. Based on the preparation of the matchup datasets, the calibration and validation of objectives 2) and 3) will be carried on with the state-of-the-art big data analysis approaches, including Artificial Intelligence and Machine Learning to optimize the models of each application. In order to achieve the objective 4), the error budget of different geophysical measurements will be developed as the functions of different mission and instrumental parameters, which can guide the design of future GNSS-R instruments, such as the data acquisition methods, antennas design, and power calibration algorithms. 3 Deliverables The major deliverables expected from this project include the following: 1) New models, methods, and documents for instrument calibration and performance validation of BuFeng-1 GNSS-R satellite mission are developed and made available to the scientific community. 2) Peer-reviewed journal papers in Remote Sensing of Environment, IEEE TGRS, Remote Sensing, IEEE J-STAR, Geophysical Research Letters, IJRS, etc. 3) Presentations at major international symposium, such as Dragon 5 symposium, ESA Live Planet Symposium and IGARSS. 4) Interim project reports and final project report 5) Ph.D. thesis and M.Sc. thesis 4 Funding Chinese fund: National Major Projects of High-Resolution Earth Observation Systems;European fund: Sensing with Pioneering Opportunistic Techniques, Spanish Ministry of Economy and Competitiveness (RTI2018-099008-B-C22)


PI Europe
Dr. Weiqiang Li, Institute of Space Sciences, CSIC, SPAIN
Co-PIs Europe
Dr. Estel Cardellach, IEEC, SPAIN
Dr. Serni Ribó, IEEC, SPAIN
Prof. Antonio Rius, IEEC, SPAIN
Mr. Yang Nan, IEEC, SPAIN
PI China
Dr. Cheng Jing, China Academy of Space Technology (CAST)-XIAN, CHINA
Co-PIs China
Mr. Guodong Di, DFH satellite, Co., Ltd., CHINA
Prof. Feng Lu, NSMC,CMA, CHINA
Dr. Xinliang Niu, CAST-XIAN, CHINA
Prof. Xiuwan Chen, IRSGIS,PKU, CHINA