Characterizing the Impact of Ionospheric Wave Structures on Coordinate Registration.

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 traveling ionospheric disturbances (TID"s) which are underspecified by current methods. Consequently, OTHR target location errors can reach 10s-100 km. The objective of this work is to test the feasibility of a real-time system which will assimilate novel ionospheric measurements capable of fully capturing TID properties in the OTHR signal reflection region, specify fully the perturbed ionosphere and how it modifies OTHR signal propagation, and use that information to improve OTHR coordinate registration. To address this objective we propose to: i) Survey state of the art TID observations and generation mechanisms ii) Establish what OTHR outputs are desired from simulations iii) Demonstrate ingestion of various ionospheric specification models into Raytracing software iv) Use TIDDBIT to specify TID"s as realistic perturbations to ionospheric models v) Demonstrate ability to raytrace HF radio signals through TID perturbed ionospheric model vi) Explore OTHR inversion to obtain TID parameters BENEFIT: At the end of Phase-I, we will deliver a full prototype software system to simulate the effects of TIDs on OTHR signals that could be used to improve coordinate registration (CR). We will have demonstrated the viability of assimilating TIDDBIT and other ionospheric measurements, and shown how the resulting ionospheric specification can be used with raytracing codes to predict how OTHR signals are modified by TID"s. Finally, we will have studied how OTHR itself might be used in such assimilations and the improvements to OTHR CR. The main benefit of this work is the improvement of OTH CR through realistic specification of HF propagation in a perturbed ionosphere. This capability will lead to reductions in OTHR target position and velocity errors. The work complements ASTRA"s existing commercial development of TIDDBIT receivers and expertise in the analysis of TID"s as well as ionospheric modeling, data-analysis, and assimilation methods. The availability of already deployed TIDDBIT systems and their TID databases leads to the added benefit that no hardware development or deployment is required for the success of this Phase-I project. The resulting TID assimilation software can be applied to both commercial and DoD operations.