Sounder Updates for Statistical Model Predictions of Maximum Usable Frequencies on HF Sky Wave Paths

A method is presented for the short-term prediction of maximum usable frequencies (MUFs) in a large communications region. It is shown how ionospheric measurements from a network of ionospherit sounders can be used to update sunspot number or solar 10.7 cm flux inputs to a climatological MUF prediction model, MINIMUF in this case, which is then used to predict MUFs on paths throughout the region. Analysis of mid-latitude oblique-incidence sounder data sets indicates the advantage gained from single-path sounder updates of flux for MUF predictions on adjacent paths. Under specified conditions a further dramatic improvement in MUF prediction accuracy is found from spatial interpolation of sounder-updated flux values. MUF prediction accuracies within 0.5 MHz are obtained for fairly modest sounder network deployments, in which the sounder midpath point distributions and updating frequency satisfy particular requirements.