SECTION 3 ENVIRONMENTAL EFFECTS - PROPAGATION 3. 1 INTRODUCTION In the Satellite Power Station concept a large amount of microwave power is transmitted to the earth from a large phased array antenna. It is received and rectified by a large ground antenna. Control of the high power beam is maintained by both a command system and a self-phasing system. The command system senses deviations from the desired power density distribution on the ground and telemeters phase corrections to the array. The self-phasing or adaptive system uses a pilot signal or control beam radiated from the ground to adjust the array phase distribution to focus the power on the receiving antenna. This section describes the effects of the atmosphere and ionosphere on the transmission and control of the high power beam. It also identifies possible effects of the high power beam on the natural environment of the ionosphere and atmosphere. The physics of molecular absorption by oxygen and water vapor and the theory of scattering and absorption by hydrometeors, such as rain, cloud droplets, snow and hail, are reviewed in Paragraph 3. 2 and applied to estimating the atmospheric transmission efficiency as a function of frequency from 1 to 30 GHz and for various meteorological conditions. Paragraph 3. 3 deals with the power beam displacement and dispersion due to refraction and ionospheric irregularities as well as the control beam phase and amplitude noise due to ambient and self-induced electron density fluctuations. Paragraph 3.4 provides a brief discussion of ionospheric modification due to microwave heating. Additional in-depth work will be required in this area to determine the effects of power fluxes in excess of 20 mW/cm . Detailed derivations and discussions of the various ionospheric propagation factors are provided in Appendices A, B and C. The effects of atmospheric absorption are to attenuate the transmitted power significant but limited amounts which are minimal for frequencies below 3 GHz (2 percent attenuation nominally and 4 percent in most severe cloud and rain conditions).
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