A Computer Code for Calculating Tropospheric and Ionospheric Refraction Effects on Radar Systems

We have developed the tropospheric and ionospheric radar refraction (TIRR) code which calculates refraction effects by performing two-dimensional ray tracing through tropospheric and ionospheric specification models. We have performed preliminary tests using the output from a tropospheric model and an ionospheric model that each assimilate actual data to provide near real-time global specifications of their respective atmospheric regions. We present the results of three such runs for the radar system located at Eglin AFB: (1) a baseline run, (2) a run for a nearby hurricane, and (3) a run for a severely disturbed ionosphere. Generally, we find that range error is dominated by the ionosphere, except at low elevation angles where tropospheric refraction becomes more important. We also discuss plans for more extensive tests as well as for augmentation of the model to allow for airborne radar systems and three-dimensional ray tracing.