@proceedings {849,
	title = {On the ray tracing block of a sky wave over-the-horizon radar simulation tool},
	year = {2024},
	month = {03/2024},
	publisher = {HamSCI},
	address = {Cleveland, OH},
	abstract = {<p>A simulation tool of a sky wave over-the-horizon radar performance and detection process includes many stages based on different models, which creates a synthetic searching scenario as a first step followed by a digital signal processing to detect and locate a potential target. The whole process involves several concatenated physical mechanisms which depend on OTHR specific properties. They can be modeled as quasi-independent blocks to analyze synthetic scenarios in order to define the radar{\textquoteright}s characteristics and range of operation which are essential when selecting radar{\textquoteright}s operating parameters in order to achieve the best performance. In this work a sensitivity analysis of the ray tracing block is performed. This block is implemented as an independent block in the simulation tool and estimates the signal propagation path with an adapted Jones \&amp; Stephenson ray tracing code. This code has options for: (1) the electron density profile, which can be chosen from analytical models or the IRI-2016 model, (2) the Earth{\textquoteright}s magnetic field from the IGRF-12 model, which can be turned on and off, and (3) collision frequencies, which can also be turned on and off. From this ray tracing we obtain the two-way delay of the signal travelling between the transmitter and the target, the ground range distance and azimuth relative to the transmitter. The sensitivity analysis is carried out analyzing this block output{\textquoteright}s\&nbsp;variation as a consequence of changes in its main input factors. This study is useful to dimension features and elements of a real radar, and also to determine the needs of in-situ ionosphere sounding.</p>
},
	author = {Zenon Saavedra and Ana G. Elias}
}
@proceedings {848,
	title = {Sensitivity analysis of ray-tracing techniques to ionospheric electron density profiles},
	year = {2024},
	month = {03/2024},
	publisher = {HamSCI},
	address = {Cleveland, OH},
	abstract = {<p>The Earth{\textquoteright}s ionosphere, a weakly ionized plasma embedded in a magnetic field, constitutes an anisotropic and dispersive medium for the propagation of HF radio waves. Ray-tracing is a powerful and useful technique, included in several radar simulation codes, that allows determining the path of these radio waves through the ionosphere in order, for example, to locate and track a target. Depending on the degree of precision needed, ray-tracing requires more or less precise knowledge of ionospheric conditions along the propagation path. A sensitivity analysis is performed in this work to determine the effect of different electron density height profiles in ray path features considering a fully analytical approach and two ray-tracing algorithms. The analytical approach is based on the quasi-parabolic electron density height distribution which allows for the derivation of exact equations for ray path parameters. The first ray-tracing algorithm consists of Snell-law application to a two-dimensional ionosphere which is layered into thin homogeneous slabs with a constant refractive index. The second algorithm implements the code of Jones and Stephenson, introduced in 1975, and numerically solves Haselgrove ray equations to trace ray paths through an anisotropic medium whose refractive index varies in three dimensions. The three methodologies used to assess an HF signal ray path must assume an electron density height profile which strongly affects any output parameter that depends on the signal traveling path. In particular, the analytical approach, even though it is less accurate, it is considerably faster than any numerical ray-tracing technique. This sensitivity analysis approach allows estimating the percentage variation of ray-tracing outputs which may serve to analyze the errors introduced by ionospheric transient disturbances which cannot be easily included in models considered in ray-tracing algorithms.</p>
},
	author = {Ana G. Elias and Mariano Fagre and Zenon Saavedra and Adrian Llanes and Blas F. de Haro Barbas}
}
