3. Radio Interference - see section IV-C-2 Radio noise produced by the microwave beam may cause interference to users of frequencies near that of the beam. These could include radio astronomers, and certain radar and communication frequencies. The extent of that interference will depend on the microwave frequency used as well as the size of the band that can be set aside for energy transmission. b. SPS Effects 1. Magnetosphere Each SPS will require a significant amount of propellant in order to maintain attitude and position in orbit. Although this amount will be less than that of the orbital transfer vehicle, it will be consistently released, and should be looked at farther. 2. Reflected and Emitted Light In addition to microwaves, the SPS will reflect sunlight, and emit thermal, IR, radiation which could interfere with astronomical observations. From Earth, the reflected sunlight will cause an SPS to normally appear as a stellar object, about as bright as the planet Venus. However, if the SPS is allowed to drift a few degrees from its solar attitude, as is expected in order to conserve propellant, then there will be times that light will be specularly reflected to areas on Earth. This would be observed from these areas as a large increase in brightness, to that of a full moon, or brighter. This brightness wculd last for several minutes to about an hour. Both the intensity and duration of brightness would depend on the "flatness" of the solar cells and mirror surfaces. c. Rectenna Site A 10 G watt solar power station can expect to dump about 0.5 G watt of heat into the atmosphere at the 5GW rectenna site. Although this is less than that of a conventional power station, or that of a large city, it should be studied. It has been shown that minor local changes in meteorology take place as a result of heat islands of larger magnitudes. If the effect exist at this lower level, a complete understanding can help to minimize it, or produce desirable results. (4) Summary of SPS Environmental Effects The following outline summarizes the SPS environmental effects Each effect is followed by a "priority number" (1, 2 or 3) to designate its relative level of importance.
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