Abstract:
Error rate data obtained for a high latitude transionospheric earth-space VHF communications channel are presented. Interpretation of these data with respect to certain ionospheric indicators has resulted in qualitative as well as quantitative correlation between the observed error rate data and F-region irregularities. Amplitude scintillation has been found to be of the most critical importance to data channel efficiency and reliability. Indications of extra-terrestriaI (i.e., solar) control have also been documented. Transionospheric propagation phenomena have been shown to give rise to adverse channel carrier/noise ratios, while waveform distortion and timing instability remain essentially unaffected. Information on channel reliability during extreme geomagnetic storms has shown that fading margins in excess of 20 dB are necessary in order to maintain channel error rates of 10⁻⁵ or better at VHF over a transionospheric channel at high latitudes.
