future. The SPS also would be located at GEO altitudes. The U.S. INTELSAT satellite has been analyzed as a "worst case" example of potential SPS interference with other GEO satellites. The microwave power which could be delivered to INTELSAT by a solar power satellite was computed and compared with the calculated interference threshold for INTELSAT. The comparison showed that, under maximum-interference conditions, the power delivered by the power satellite would be more than five times lower than that required for interference to occur. Interference thresholds for other commercial GEO satellites are similar to that for INTELSAT, so it can be inferred that the SPS would not be likely to interfere with commercial satellites in GEO. Military satellites are now being analyzed. Low earth orbit also is occupied by satellites, such as LANDSAT, which is used to monitor earth resources management, and GPS, which is used as a global navigation and position-fixing system. LANDSAT traverses the continental United States six to eight times each day, so it conceivably could encounter an SPS microwave beam. The transit time through the beam would be approximately four seconds; sensor and communications interference could occur during transit. Modifications to the resource satellite to prevent interference appear to be feasible. The GPS satellite is in a higher orbit than LANDSAT and therefore would be.exposed to more intense SPS electromagnetic energy and consequently would experience more severe interference. Mitigation strategies are currently being studied for GPS. Both radio and optical astronomy are used to study the weakest measurable sky signals. Since the satellite power system would contribute power to the radio, infrared, and optical spectrums, there would be significant potential for limiting capabilities for astronomical observations. Radioastronomy could be affected by SPS microwave power beams at distances of hundreds of kilometers from rectenna sites. Additional studies are required to develop a quantitative assessment of these effects. Power satellites in space would be expected to reflect substantial amounts of light. Even with a coefficient of reflectivity as low as four percent, each power satellite would appear to be brighter than all but the brightest bodies in the sky (the sun and the moon) and-would be about as bright as Venus when it is most visible. Multiple satellites would brighten the sky considerably. For example, 60 satellites would provide as much light as the moon between its new and quarter phases across a band 40° long and 10° wide. Earth-based optical observations would be hindered under these conditions. REFERENCES 1. Satellite Power System Concept Development and Evaluation Program Reference System Report3 Department of Energy Report DOE/ER-0023 (October 1978).
RkJQdWJsaXNoZXIy MTU5NjU0Mg==