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In those situations, it is useful to use a related quantity called the normalized radar cross-section (NRCS), also known as differential scattering coefficient or radar backscatter coefficient, denoted σ 0 or σ 0 ("sigma nought"), which is the average radar cross-section of a set of objects per unit area:
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The cross-section is the minimum apparent surface area observed in the direction of the radar that must be detectable.. Radar cross section changes with aspect angle. Cross section for anything except a perfect sphere depends upon the aspect angle, which how far the reflector is rotated with respect to the radar pulse.
Optical cross section of a flat mirror with a given reflectivity at a particular wavelength () can be expressed by the formula = Where is the cross sectional diameter of the beam. Note that the direction of the light has to be perpendicular to the mirror surface for this formula to be valid, else the return from the mirror would no longer go ...
For basic considerations of the strength of a signal returned by a given target, the radar equation models the target as a single point in space with a given radar cross-section (RCS). The RCS is difficult to estimate except for the most basic cases, like a perpendicular surface or a sphere.
Pulse-Doppler radar must be multi-mode to handle aircraft turning and crossing trajectory. Once in track mode, pulse-Doppler radar must include a way to modify Doppler filtering for the volume of space surrounding a track when radial velocity falls below the minimum detection velocity.
When it is exactly zero the radar is a monostatic radar, when it is close to zero the radar is pseudo-monostatic, and when it is close to 180 degrees the radar is a forward scatter radar. Elsewhere, the radar is simply described as a bistatic radar. The bistatic angle is an important factor in determining the radar cross section of the target.
These variations can be exploited to estimate the sea surface wind, i.e. its speed and direction. This estimate process is sometimes termed ' wind retrieval' or ' model function inversion' . This is a non-linear inversion procedure based on an accurate knowledge of the GMF (in an empirical or semi-empirical form) that relates the scatterometer ...