AUTHOR=Yan Zhengjie , Zheng Wei , Wu Fan , Wang Cheng , Zhu Huizhong , Xu Aigong 

TITLE=Correction of Atmospheric Delay Error of Airborne and Spaceborne GNSS-R Sea Surface Altimetry

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.730551

DOI=10.3389/feart.2022.730551

ISSN=2296-6463

ABSTRACT=Improving the measurement accuracy is a necessary condition for sea surface altimetry using the Global Navigation Satellite System Reflectometry (GNSS-R).  The influence of the atmospheric environment on GNSS-R altimetry differs from different platforms. By analyzing and sorting out the altimetry data of airborne and spaceborne platforms, this paper studies the variation law of signal delay in the altimetry process from the point of view of mathematical geometry, which provides a example for improving the precision of GNSS-R altimetry measurements. Firstly, in order to facilitate data analysis, this paper constructed an altimetry model with GNSS satellite position, specular reflection point position and receiver position as nodes, and classified direct signals and reflected signals. Secondly, calculate ionospheric puncture point coordinate, and interpolate GIM products provided by IGS using time and puncture point coordinates, to obtain the VTEC value in the vertical direction of the puncture point, the ionospheric delay of each part was obtained in this way. The tropospheric delay of each part is considered along-path component and geometric component, the delay of along-path component was calculated by the UNB3m model. Thirdly, by comparing the sea surface height inversion results with or without atmospheric delay correction with the mean sea surface height provided by DTU15, it is found that the measurement accuracy with atmospheric delay correction is obviously improved, study the influence of atmospheric delay on the altimetry experiments precision error of airborne and spaceborne platforms, the results show that the error magnitude is consistent with the existing literature, in the airborne experiment, the influence of the ionosphere is negligible, and the troposphere has sub-meter influence on altimetry results, among which tropospheric along-path delay component occupies a high proportion, the geometric delay component has a high correlation with the satellite elevation angle, and its influence on the measurement accuracy decreases with the elevation angle increase, and the effect of this factor can be effectively weakened by setting high satellite cutoff angle. In the spaceborne experiment, the effect of atmospheric delay on altimetry results fluctuates in the range of 3~5m when the satellite elevation angle is greater than 60 degree.