In this work, measurements and a method for analyzing flight-dynamic effects on radar cross-section models for aircraft are presented. Flight-dynamic effects need to be considered when designing combat aircraft and creating target models for radar simulators. The work is based on flight data from three different types of aircraft: Piper PA-28 Archer II, Boeing 737, and Saab JAS 39 Gripen. Using inertial navigation and global-positioning systems, the motions of the three aircraft are recorded in flight. From the data, aspect angles toward a radar station located in the extension of the intended flight path are generated using a simulator. It is found that the major contribution to perturbations in aspect angles is due to the rotational degrees of freedom and that bivariate normal distributions are a good candidate for approximating the uncertainty in aspect angles for all three aircraft types. It is also found that each rotational degree of freedom is close to a normal distribution but that the parameter values of the distribution vary with altitude and aircraft type.
NomenclatureAz = azimuth aspect angle, deg a = major axis of confidence ellipse, deg b = minor axis of confidence ellipse, deg El = elevation aspect angle, deg E i = incident electric vector field, V∕m E s = scattered electric vector field, V∕m G = antenna gain h r = radar antenna height, m h t = target altitude, m P t = transmitted power, W R = range between radar and target, m R h = range to radar horizon, m R max = maximum detection range, m r e = effective radius of Earth, m S min = minimum detectable signal, W α = alpha risk θ = eigenvalue of Σ λ = radiation wavelength, m σ = radar cross-section, m 2 μ = mean value, deg ρ = correlation coefficient Σ = covariance matrix σ Az = azimuth standard deviation, deg σ El = elevation standard deviation, deg χ 2 2 α = upper αth percentile of chi-squared distribution with two degrees of freedom
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