Development of an HF selection tool based on the Electron Density Assimilative Model near-real-time ionosphere

The Electron Density Assimilative Model (EDAM) has been developed to provide real-time characterization of the ionosphere. A thin-client Web-based ionospheric situational awareness tool, which relies on data from EDAM, has been developed. The tool provides the high-frequency (HF) maximum usable frequency (MUF) and the optimum working frequency (FOT) on the basis of the current ionospheric electron density grid from EDAM. Two validations are reported. First, EDAM has been tested against a set of vertical ionosondes. The results show performance comparable to that of the Utah State University Global Assimilation of Ionospheric Measurements Gauss-Markov Kalman filter model. Second, MUFs estimated from EDAM were compared with those measured on an oblique path from New Zealand to Australia. Although EDAM demonstrates better performance than a monthly median model in some days, over the whole test period EDAM performed no better than the international reference ionosphere. This can be attributed to the lack of input GPS total electron content (TEC) data near the midpoint of the path and a probable TEC bias in the background model.