Coherent Reflectometry from Space: Sensitivity to Sea-Surface Height and Atmospheric Disturbance

This paper summarizes example results of an ongoing study that focuses on coherent reflectometry data recorded by dedicated GNSS receivers on low Earth orbit (LEO) satellites. The main goal of the study is to assess the overall sensitivity of coherent reflectometry data to changes in sea-surface height and to assess the impact of atmospheric disturbances on respective height retrievals (altimetry). The given example tracks are located in the Caribbean and have grazing incidence with about 15° of elevation angles at the specular point. The results show, in agreement with previous findings, that phase and Doppler residuals derived from the satellite data are sensitive to sea-surface height changes and therefore relevant for altimetry. Apart from the altimetric sensitivity we found further anomalies in the residual Doppler. The standard deviation of Doppler after altimetric correction shows highest values for the track with local time in the evening. We suppose an impact of ionospheric plasma instabilities that are frequent in evening hours at low latitudes. We will extend the analysis for further validation.