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Ionospheric Factors Affecting the Performance of HF (High Frequency) Sky-Wave Sea-State Radars,
RUTHERFORD AND APPLETON LABS CHILTON (ENGLAND)
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This paper contains an assessment, partly theoretical and partly based on observations, of the impact of various ionospheric factors on the usefulness of the HF sky-wave sea-state radar techniques. The points discussed include the following a The ionospheric propagation modes available will not permit all parts of the ocean which it is desired to investigate to be illuminated at all times in such a way that good-quality Doppler spectra are obtained. Es-mode propagation generally results in good-quality Doppler spectra from which information about the sea waves can be inferred, but F-mode propagation yields poor spectra which can only be used to deduce the surface wind direction, b Doppler shifts associated with vertical ionospheric motions give spectral contamination which limits the amount of information that can be derived. Spectral contamination also arises under conditions of multi-mode propagation and when high- and low-angle rays are present, and c Lack of knowledge of the height of reflection of the sky-wave signals means that the area of ocean probed cannot be located accurately.
APPROVED FOR PUBLIC RELEASE