Abstract
Global navigation satellite system reflectometry (GNSS-R) has found many applications in the field of Earth observation including ocean wind-speed detection, ice altimetry, soil moisture monitoring, and more. The main focus of GNSS-R research to date has been on forward-scattered reflections, but theoretical work has proposed a backscattering regime and associated new application opportunities, including marine target detection. This article discusses the methods and results of processing the U.K. TechDemoSat-1 raw data collections in a backscattering regime for the first time, with initial results from sea ice datasets presented. The research has also identified a key problem with the backscatter method-for certain geometries the power from the specular point (forward scattered) may contaminate the data. The theory behind this and a method for predicting such occurrences is also discussed.
Highlights
G LOBAL navigation satellite system reflectometry (GNSSR), a passive bistatic L-band system using navigation satellites as transmitters of ‘signals of opportunity” (SoOP), has achieved great success in the field of ocean wind speed sensing
It should be noted that the current study has only considered the global positioning system (GPS) coarse acquisition (C/A) signals but work is ongoing on processing Galileo reflections from the raw data, both in forward and backscattering modes
The Global navigation satellite system reflectometry (GNSS-R) software receiver used, developed alongside the SGR-ReSI reflectometry payload [8] which flew on TDS-1, works in the conventional sense by predicting an specular point (SP) using the positions of transmitter and receiver and a quasi-spherical Earth model, using this position and relative velocities to generate the predicted delay and Doppler of a signal reflected from that point
Summary
G LOBAL navigation satellite system reflectometry (GNSSR), a passive bistatic L-band system using navigation satellites as transmitters of ‘signals of opportunity” (SoOP), has achieved great success in the field of ocean wind speed sensing Missions such as UK-DMC (launched in 2003) and TechDemoSat-1 ( U.K., launched in 2014) proved that the technique was viable on a space-borne platform and opened the door for the NASA CYGNSS mission (constellation of 8 satellites, launched in 2016), as well as providing valuable data in their own right. The unprocessed nature of the data allows the cross-correlation process between the reflected signal and a clean copy of the transmitted signal to be targeted at delays and Dopplers from nonspecular directions This is in contrast with the processed Level 1B delay-Doppler maps (DDMs) which have been made available by Surrey Satellite Technology Ltd. She received financial and technical support through partnership with Surrey Satellite Technology Ltd. (Corresponding author: Lucinda King.)
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