Initial results from HF propagation studies during solid shield

In May 1981, NRL personnel manned two (2) receiver sites located at Norfolk Virginia and Fort Bragg, North Carolina to obtain 24 hour a day coverage of data available from an oblique sounder network put into operation to support the DoD Solid Shield exercises. The resulting photographic data were scaled to obtain the maximum useable frequency (MUF) vs time for each circuit recorded. One circuit was selected as a control path to provide an update to a model which predicts the MUF. Upon obtaining an update of this model using the control path, the model to compute MUF's for other paths for which data was available. Under the geomagnetically disturbed conditions which prevailed during Solid Shield, the update provided accuracies of about 1 MHz RMS with a new update required about every 3 hours to maintain this accuracy. These results may have profound implications on the design and ultimate operation of automated frequency management systems.