Conference Agenda

This research and collaboration project aims at the calibration and validation (Cal/Val) of the European Sentinel-3, Sentinel-6 and the Chinese HY-2B & HY-2C satellite altimeters using two permanent Cal/Val facilities: (1) the Permanent Facility for Altimetry Calibration established by ESA in Crete, Greece and (2) the National Altimetry Calibration Cooperation Plan of China. Other satellites, such as the Guanlan, CryoSat-2, CFOSAT, CRISTAL, etc., could certainly be supported by these Cal/Val infrastructures. Both facilities attain the strategy of Fiducial Reference Measurements (FRM), established by the European Space Agency for reporting calibration of satellite altimeters.

Calibration of satellite altimeters has been accomplished by examining actual satellite observations in open seas against reference ground measurements defined by Cal/Val infrastructures at specific locations in Europe and China.

During this third year of this Dragon-5 collaboration, the following tasks are being carried out:

• An exhaustive analysis of all sources of uncertainties (i.e., water level observations, satellite signal delays, reference surface models, etc.) which each makes a contribution to the final results of satellite altimeter calibrations;
• Reference measurements and all kind of observations on the ground at the Cal/Val infrastructures are connected to the International System of Units (SI) and absolute international standards of reference (speed of light, atomic time, etc.);
• Uncertainties for the results of satellite calibration are reported in a realistic, universal and objective way;
• Independent and diverse techniques for estimating altimeter biases are applied by the European and Chinese teams;
• Final Cal/Val results are reported and intercompared at the two Cal/Val facilities.

The main findings of this joint work are:

• Both European and Chinese Cal/Val sites are operational and implement independent calibrations for European, Chinese and international satellite altimeters (i.e., Sentinel-6A MF, Sentinel-3A/B, HY-2B/C, Jason-3, etc.);
• Operations and data processing are standardized at both Cal/Val reference infrastructures in Europe and China;
• Common procedures are implemented (i.e., tide gauge quality control, GNSS positioning, etc.) towards standardization and unification of operations and data handling and processing.
• The performance of satellite altimeters is continuously monitored by the two Cal/Val infrastructures in China and Europe.

The report we are presenting focuses on the objectives and schedule of our project, providing an update on the ongoing activities and results of Bufeng-1 data processing, calibration workflow, and validation of the calibrated results on hurricane winds, soil moisture, and sea level measurements. This presentation is divided into three parts. Firstly, we will provide a brief introduction about Bufeng-1 and recent Chinese GNSS-R missions, highlighting their significance in the field. Secondly, we will delve into the preliminary results obtained by utilizing the Bufeng-1 Normalized Bistatic Radar Cross Section (NBRCS), earth reflectivity, and range measurements. The preliminary results indicate that Bufeng-1 has a high agreement compared with other observations on severe sea surface winds, soil moisture, and sea level. We will align the measurements of Bufeng-1 with SFMR collected hurricanes, SMAP derived soil moisture, and DTU18 sea level models to provide a comprehensive analysis of the results. We will also analyze the accuracy and correlation coefficients to discuss the limitations and issues for future research. This will be crucial in improving the quality of data and enhancing the accuracy of future measurements. For the last part, we will give the outlook about our future works of the objectives and the future plan of Chinese GNSS-R missions. Our aim is to provide a comprehensive and detailed report that will assist researchers and stakeholders in the field of climate research, weather forecasting, and disaster management in making informed decisions.