From Radar System Performance Modeling, Second Edition
The radar environment includes terrain and sea surfaces, the atmosphere (including precipitation), and the ionosphere. These may degrade radar observations and performance by producing clutter and other spurious returns, signal attenuation, and bending of the radar-signal path. Radar techniques that may avoid or minimize the impact of many of these effects are available.
This chapter addresses these environmental effects and potential mitigation techniques:
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Terrain and sea surfaces, which may produce target masking, radar clutter, and multipath interference;
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Precipitation, principally rain, which may produce signal attenuation and clutter returns;
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The troposphere, which may produce refraction that bends the radar signal path, signal attenuation, and a lens loss;
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The ionosphere, which may produce refraction that bends the radar signal path, signal fluctuation and attenuation, waveform dispersion, and rotation of signal polarization.
9.1 Terrain and Sea-Surface Effects
The Earth's surface may affect radar operation in three ways:
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The Earth may block the LOS to the target, making radar observations impossible.
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Radar energy may be scattered from the Earth's surface back to the radar receive antenna. When this energy interferes with the target signal, it is called surface, terrain, or sea clutter.
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Radar energy may be forward-scattered from the Earth's surface and reach the target by this indirect path. This is called multipath propagation.
Terrain may block the radar LOS to low-altitude targets, preventing their observation. While ground-based radar is usually sited to minimize terrain blockage, the effects still may be significant. Terrain blockage is less serious for airborne or space- based radar, but...
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