General configuration The general configuration of SPS 2000 has the shape of a triangular prism with a length of 800 m and sides of triangle of 100 m as shown by Figure 1. The prism axis is in the north-south direction, perpendicular to the direction of orbital motion. The transmitting antenna is fixed to the bottom surface facing to the earth, and the other two side surfaces are used to deploy the solar arrays. No energy storage for power transmission during eclipse is provided. FIGURE 1 General configuration of SPS 2000 The reason this configuration is adopted is easiness of construction of the system in orbit as well as of orbital operation under the gravity gradient force which is larger in a low earth orbit (LEO) than in the geosynchronous earth orbit (GEO). On the other hand, the requirements of high efficiencies in terms of power conversion and mass reduction, which have been generally accepted for space system design, arc not considered to have high priority in this study. Structure design A conventional rigid beam structure is assumed for the main structure of pyramid shape. The function of the structure is to deploy the solar array and the phased array antenna, and to provide the subsystems with references of geometrical locations. Since accuracy of shape is not required, the strength of the beam was determined considering the forces caused by off-center-of-gravity forces including gravity gradient torque and the attitude control force. A standard beam of the structure is 100 m long and the cross section is triangular with sides of 3 m. The fundamental element of the structure is
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