Rapid EDP and TID specifications for OTHR applications.

ABSTRACT: Over the horizon radar (OTHR) systems survey large areas searching for targets several thousand kilometers away by using ionospherically reflected high frequency (HF) radio waves. Accurate coordinate-registration (CR) of the targets requires detailed knowledge of the electron density profile (EDP) of the ionosphere between the radar and the targets. Our proposal outlines a realistic path toward providing in near real-time the specification of the ionospheric electron density distribution including wave modulations caused by traveling ionospheric disturbances (TIDs). The International Reference Ionosphere (IRI) model is used as a background model. Digisondes are proposed for the measurement of the ionospheric characteristics for real-time assimilation into the IRI model: foF2, foF1, foE, hmF2, hmF1, hmE, B0, B1, and D1. This real-time procedure will create the IRI Real-Time Assimilative Model (IRTAM). The Digisondes also measure the Doppler frequencies and arrival angles of ionospherically reflected HF signals from which the TID wave parameters are derived in real-time. The detected TID electron density waves can then be superimposed on the IRTAM electron distribution. The Huang-Reinisch2006 raytracing algorithm will be used to calculate the ray path through IRTAM. A computer simulation of this process will be conducted under Phase-I. BENEFIT: The rapid EDP and TID specifications technique proposed can be directly integrated into the existing Digisonde GIRO network in support of OTHR operations. The GIRO network can also easily be expanded by deploying additional commercially available Digisondes.