If at an unstable point initially, a satellite will tend to drift away and never return to the initial point. Since there are only two points where long term stability is achievable, the distribution of geosynchronous satellites about the earth will be limited to these two areas unless station-keeping is permitted. The accumulated delta V requirements for one year for nulling out the ellipticity effects is only one or two feet per second. (4) Conclusions and Recommendations The perturbations on a geosynchronous satellite are due to the luni-solar gravitational forces, the solar pressure, and the gravitational force due to the ellipticity of the earth's equator. The luni-solar effects produce a periodic variation in the inclination of 53 years. By choosing an inclination of 7.3 degrees with a node of zero, an orbital plane fixed in space is obtained. The solar pressure produces a one year periodic variation in the orbital eccentricity e. For e initially zero, the maximum value of e is 0.068. A non-zero e causes a daily oscillation in longitude of +2e (radians). There is some evidence that the perturbation in eccentricity grows with time. Further studies are required in this area. The earth's equator can cause large variations in longitude. Unless placed near one of the two stable libration points, the drifts in longitude can become quite large, but periodic. A detailed analysis for the best approach in correcting these effects is recommended. This analysis should also include perturbations not considered here such as the induced thrust due to the emission of the microwave energy. L. E. Livingston Spacecraft Design Div. b. Non-Ideal Orbits In the ideal case, the SPS would be placed in a stationary (synchronous, zero-eccentricity, zero-inclination) orbit at a longitude equal to that of the rectenna. A synchronous period can be achieved and maintained without difficulty. However, as discussed in the preceding section, eccentricity and inclination can be held at zero, and longitude at any desired value, only by active stationkeeping. This section discusses some of the ramifications of departures from the ideal orbit. Eccentricity The most obvious effect of eccentricity is a daily cyclic variation in the distance from the antenna to the rectenna, which causes
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