RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. The present paper is concerned with sea wave diagnostics by signals from artificial satellites in a bistatic radar scheme using the grazing radio-wave propagation and a diffuse component of the signal reflected off the sea surface. The possibility is considered to expand the range of sea state diagnostics by using satellite emissions in different frequency regions.

Methods and Methodology. The research is based on the data of field experiments using over-the-horizon navigation satellites of the first (Transit) and second (GPS) generations. The data processing is by the methods of moving average and moving mean square deviation adopted because of the dynamic character of the experiments given the moving source presence. The sea surface state in a particular experiment is estimated by the diffuse component extracted from the total experimental signal. A comparative analysis of the diffuse component parameters is carried out by computer modeling at various wavelengths, source elevation angles and root- mean-squared wave heights.

Results. For both satellite systems GPS and Transit, the experimental results show that in the calm and moderate states of the sea surface, the diffuse component intensity of signal fluctuations caused by sea waves differ significantly and fit in with the model upon the Rayleigh Roughness Criterion. On this basis, an advantage can be taken from the satellite emissions in various frequency ranges to expand the scale of sea state diagnostics. The higher-frequency region therewith offers a more accurate yet more limited scale of the sea state measured. The addition of lower-frequency emissions expands the scale of sea state diagnostics towards the severe states.

Conclusions. It has been determined that the range of sea state diagnostics can be expanded by using satellite emissions in different frequency regions.

Keywords: sea disturbance, calm, Transit and GPS navigation satellites, ephemeris, Rayleigh parameter, diffuse component, root-mean-square height of sea waves

Manuscript submitted 02.09.2023

Radio phys. radio astron. 2024, 29(1): 026-037

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