A ray tracing based method for coarse coordinate registration in HF skywave OTH radar

Over-the-horizon (OTH) radars use the refractive properties of high-frequency radiowave propagation through the ionosphere for wide-area surveillance at long ranges. Target detection is accomplished by tracking returns in slant range, Doppler and azimuth. Moreover OTH radar performances are affected by several types of frequency dependent factors, mainly due to propagation and ionospheric absorption, but also related to the background noise. Coordinate registration (CR) is the process of localizing the target by converting the slant coordinates R_g into ground coordinates R_gr for all the frequencies used in transmission. The CR method here presented is based on a ray tracing algorithm which provides the ground range distance reached with a specific transmission frequency and elevation angle. The ray tracing approach here adopted uses an electronic density profile estimated by using the latest revision (2007) of IRI (International Reference Ionosphere) model. Errors in the estimated down-range ionospheric parameters introduce as a consequence a degradation of target localization accuracy. The goal of this work is that to show a technique to determine the coordinate registration by jointly using ray tracing and Breit and Tuve theorem.