A STUDY OF LEO CONSTELLATION WITH FIGURE-OF-EIGHT SHAPE RING NETWORK

摘要

In the study of low earth orbit satellite constellation system, the satellite orbit parameters were examined under conditions where at least two satellites were always visible from the user terminal to enable satellite diversity. The parameters to optimize the constellation for dual-satellite accessibility, which maximized the minimum elevation angle was discussed by focusing on the ascending satellite group. The parameter that minimizes the diameter of the circumscribed circle of the spherical triangle composed of two adjacent satellites in the same orbit and one adjacent satellite in an adjacent orbit should be evaluated. Then, the optimum inclination can be evaluated from the combination of the number of orbital planes, the number of satellites per orbital plane, and the phasing factor of the Walker notation. In order to improve the inter-satellite network performance, the bi-directional Manhattan Street Network (MSN) topology was discussed. The relational equations between constellation parameters to achieve a figure-of-eight shape MSN topology were evaluated. The figure-of-eight shape ring network may offer advantages with short connection delays in the north-south direction, and can be applied to regional connections under hierarchical control of the ISL network. Then the parameter sets with the optimum elevation angle which realize the bi-directional MSN topology were derived. In order to evaluate these parameters, the satellite altitude optimization was carried out by using the assumption of the minimum elevation condition for the user terminals. Then, the minimum elevation angle for the user terminal in the latitude area up to 70 degrees was assumed to be 20 degrees for the application of the mobile satellite communication. And finally, the minimum distance between the satellites are evaluated for the candidate parameter sets.