Coherent Components of GNSS-R Signal Observed from CYGNSS Raw IF Data

Coherent GPS signal reflections are frequently observed from the raw intermediate frequency (IF) data recorded by CYGNSS. With the coherent GNSS-R carrier phase and high-rate carrier-to-noise ratio (C/N0) measurements, we can potentially achieve centi-meter level altimetry and high-resolution soil moisture monitoring, flood detection, etc. In this paper, we present two approaches, i.e., openloop (OL) and closed-loop (CL), to process the coherently reflected GPS signals. The CL approach is implemented with an adaptive Kalman filter (AKF) tuned by an empirical dynamics noise model and real-time estimated C/N0. Four segments of data, containing coherent reflections from coast area, shallow ocean bank, land, and a lake, are used to evaluate the tracking algorithms performances and the coherent carrier phase and C/N0 measurements.