Ionospheric factors affecting the performance of HF sky-wave sea-state radars
Abstract
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 technique. The points discussed include the following: (1) The ionospheric propagation modes available will not permit all parts of the ocean which it is desired to investigate to be illuminiated 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. (2) 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. (3) Lack of knowledge of the height of reflection of the sky-wave signals means that the area of ocean probed cannot be located accurately. (4) The azimuthal spreading (arising because of the antenna beam width) and range spreading (caused by ionospheric tilts and corrugations and associated with the finite radar pulse width) both result in Doppler contamination of the returned signals.
- Publication:
-
In AGARD Propagation Factors Affecting Remote Sensing by Radio Waves 10 p (SEE N84-15646 06-43
- Pub Date:
- August 1983
- Bibcode:
- 1983pfar.agar.....B
- Keywords:
-
- Doppler Effect;
- Ionospheric Electron Density;
- Ionospheric Propagation;
- Ocean Currents;
- Radar Measurement;
- Satellite Observation;
- Sea States;
- Backscattering;
- Correlation;
- Mathematical Models;
- Oceanography;
- Radar Attenuation;
- Wave Propagation;
- Wind Direction;
- Wind Velocity Measurement;
- Communications and Radar