Modeling Impacts of Coherent and Random TID Structures on OTHR Performance

ABSTRACT:The DoD requires accurate real-time knowledge of ionospheric variability in order to reduce one of the biggest error sources inherent in the use of critical systems such as Over the Horizon Radar (OTHR). OTHR is particularly susceptible to TIDs which are underspecified by current methods. In the proposed work, we will develop physics-based models for generation of 3D coherent and random density irregularities with long range spatial correlation properties associated with and driven by Traveling Ionospheric Disturbances. We will study the feasibility of a numerical toolbox for evaluation of TID impacts on the performance of NGOTH radars. This work will leverage ASTRAs existing coordinate registration software tool (CRICKET) by augmenting the ionospheric specification with electron density structures from a physics-based model and measured TID characteristics. We will also augment an existing ray tracing capability by adding a wave-optics approach. A preliminary wave-optics-based HF propagation model will be developed to investigate the importance of diffractive effects compared to refractive ray tracing for radio waves propagating through the plasma structures.BENEFIT:At the conclusion of our proposed Phase I effort, we will have investigated all of the critical technology areas necessary for successfully developing a fully mature software environment and validated user toolkit. The benefits of the proposed effort are that it uses a physics-based model of the ionosphere (PBMOD). This model permits not only the simulation of coherent TID wave structures, but also for the first time the coupling of the TIDs to bulk, field-aligned structures in the ionosphere, and the cascading of random plasma turbulence to scale sizes smaller than the mesoscale TID waves themselves. The work also benefits from the inclusion of wave-optics solutions to HF oblique propagation through these structured plasma volumes versus the standard ray tracing methods that have several shortcomings discussed in the proposal. By the end of Phase-I, we will have integrated the new plasma structure and propagation models into a prototype user support tool for improving OTHR coordinate registration and reducing geolocation errors. Potential commercial applications include DoD for OTHR and other applications, other agencies such as IARPA for geolocation, as well as commercial HF operators.