3.1 SCOPE All levels of the Earth’s atmosphere will be affected at least to some extent by the construction and operation of the satellite power system. The objective of this portion of the program is to identify which effects are important with respect to their consequences for the environment. Figure 3.1 shows a schematic diagram of the natural atmosphere that indicates the various levels referred to in the following text and the most commonly used terms. Some terms, such as troposphere and exosphere, refer to the general atmosphere dominated by electrically neutral constituents. Coexisting with the neutral atmosphere, above an altitude of about 60 km, are ionized constituents that make up the various regions of the ionosphere and plasmasphere. The magnetosphere, which extends from about 150 km out to about 10 Earth radii on the sunlight side and far beyond that on the dark side, is defined as that region in which the motion of the ions is dominated by the Earth’s magnetic field (i.e., ion-ion and ion-neutral collisions are much less important). For a more detailed discussion of the natural atmosphere the reader should refer to the Handbook of Geophys ics and Space Environments (Ref. 3.1). The variety of processes that occur naturally in the atmosphere is very large and many of these processes can be influenced by various aspects of the SPS. Figure 3.2 illustrates some of the disturbances that may result from the deposition of propulsion system effluents in various levels of the atmosphere. Below are listed some of the more obvious sources of atmospheric disturbance associated with the SPS: • Thruster effluents in the lower and upper atmosphere (including neutral and ionized chemical species as well as thermal acoustic energy); e Other effluents released into the upper atmosphere including waste heat and effluents from gas leaks, surface weathering, space manufacturing operations, debris, etc. (sometimes referred to as ’’fugitive emissions”); e Presence of large metal structures in orbit (source of reflected light, wake effects, etc.); ® Presence of large metal structure (rectenna) near the ground surface (change in surface roughness, surface albedo, atmospheric electric effects); and e Microwave-related phenomena in the troposphere.
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