High Frequency (HF) Over the Horizon Radar (OTHR) Metric Accuracy
ABSTRACT: Over-the-Horizon radar (OTHR) uses ionospheric reflection to propagate HF transmissions to long range (~500-5000 km). The ionosphere is a dynamic"mirror"that varies diurnally, seasonally, and with the solar cycle. Geolocation of targets observed by OTHR, (Coordinate Registration; CR), requires accurate real-time ionospheric modeling and HF propagation calculations to convert radar-measured target signal delays and beam steers to geographical position. In Phase I NWRA merged the backscatter ionogram (BI) leading edge inversion algorithm CREDO with NWRA"s more advanced ionospheric data assimilation capability, GPSII. In Phase II we will incorporate additional CREDO capabilities into GPSII, including using multi-hop leading and trailing edge BI data. CREDO"s ability to utilize radar returns from Known Reference Points (KRPs) will be extended to allow utilization of forward oblique ionograms. This extended version of GPSII will be validated against real data. For this validation, we intend to use a comprehensive Australian set of ionospheric measurements (the DINIS data) provided to us through the US/Australian Radar Agreement. This set includes multiple vertical, oblique, and backscatter ionograms. Finally, we will develop an implementation package for the new CR capability that is user friendly and on a par with those we have previously developed for CREDO and GPSII. BENEFIT: The incorporation of additional ionospheric data beyond conventional OTHR vertical and oblique backscatter soundings is expected to improve the fidelity of real-time ionosphere models, resulting in improved OTHR Coordinate Registration metric accuracy. The Next Generation OTH Radar (NGOTHR) is expected to have the additional benefit of elevation information in its backscatter soundings, and this can be incorporated in our solution method for additional fidelity. Furthermore, because GPSII uses a non-radar-centric coordinate system, a single self-consistent ionosphere model can be developed for multiple OTH radars in the same region. This will result in consistent CR of targets in overlapping coverage areas and ensure smooth track continuity as targets move from one radar"s coverage to another. Improved CR metric accuracy will enhance the applicability of OTHR as a wide area surveillance asset for Air Force and Homeland Security applications with dramatic cost savings over alternative microwave radar solutions.
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Sr. Research Scientist
NorthWest Research Associates, Inc.
P.O. Box 3027 Bellevue, WA -
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