Using an S band radio interferometer for measuring the phase shift of radio waves coherently reflected from the sea surface

An analytical study of the interference pattern formed over a sea surface by a coherent source of S band radiation is presented. Results of the theory of wave scattering by rough surfaces are employed to account for the effect of sea state on the interference pattern. The phase of the reflection coefficient for the coherent part of the reflected field is shown to cause a vertical shift of the interference pattern. This shift is utilized to develop interferometric techniques of reflection coefficient phase measurement based on a bistatic transmitter-receiver scheme. Also, a procedure for retrieving sea level information from interferometric measurements is proposed that is based on incorporating the phase shift measurements into a previously developed sea level measurement technique. The measured phase shift precision is estimated to be ±1°, corresponding to a ± 1-cm accuracy in sea level measurements.