the illumination of the rectenna, and because of adverse geometry, cause large variations in pilot signal parameters. The latter have a strong potential for causing serious ambiguities in control decisions and system stabiity considerations . Current models based on satellite signal data demonstrate ranges of coupling of EM signal characteristics (amplitude, induced frequency modulation and phase) with general meteorological conditions. These satellite signal data allow parametric examination of beam effects and control configurations. Additional study is required to identify variations in refractivity anomaly characteristics and frequencies of occurrence resulting from SPS-induced atmosphere alterations. These data are needed in order to extend the parametric modes of current models. Information regarding the spatial and temporal characteristics of these anomalies would be used to develop signal fluctuation statistics for the cited control decisions. These data are also required to support estimates of sidelobe variations caused by refraction, thus possibly expanding the interference problem for areas outside the rectenna exclusion zone. The panel recommended that the following areas should be addressed during FY 79 and FY 80: (1) Determine meteorological variations in the atmosphere above the rectenna caused by tropospheric absorption and rectenna heating and associated boundary interactions . (2) Determine turbulent flow conditions in the atmosphere with humidity, pressure and temperature gradient ranges to allow development of refraction properties. (3) Predict variations in relations with geographic areas. (4) Modify existing models to provide adequate resolution for parametric analysis. The indicated studies to expand atmospheric physical-parameter definition should include consideration of anomaly events appropriate to higher frequencies in the 10 GHz to 30 GHz range. Since the rectenna area for these frequencies may be smaller than that of the 2.45 GHz system, the smaller anomalies become more directly important to fluctuation components. The higher frequencies would lead to increased atmospheric interactions, greater attenuation losses and refractive and scatter sensitivities. An additional
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