rely upon upper region densities. This effect could extend over a 1000-2000 km region around the launch area depending on the actual launch trajectory. The indicated communications impact would involve many of the same systems indicated in Table 4.8, such as commercial, recreation, and security services. Density variation predictions that imply depletion of the F-layer and the vehicle launch frequency of possibly one per day over a several month period to establish operating power stations could result in several reduced or nonexistent ionosphere channels for the middle and upper frequency operations in the HF spectral regions. To make an assessment of this impact it will be necessary to utilize the theoretical information which will be obtained by studies such as discussed in Appendix 3B to make initial estimates of effects. The initial estimates will then be verified subsequently, observing effects of future launches of the space shuttle on telecommunications systems. 4.2.3 Cause and Effect Relationships Cause and effect relationships are shown graphically in Fig. 4.9. One cause of ionospheric modification that may result from SPS operation is the large amount of energy that will pass through the ionosphere. Although a very small fraction of the energy will be absorbed, the energy densities presently associated with SPS passage (15-25 mW/cm^) may be sufficient to give rise to certain plasma/microwave interaction effects. These include: Fig. 4.9. Effect of the SPS MPTS on Ionosphere and its Consequences
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