Fig. 2. Evolution of orbital operations. TABLE 2 ORBITAL OPERATIONS REQUIREMENTS (Operation Modes) MISSION In order to fulfill the mission objectives, various modes of operation can be considered as listed in Table 2. Appropriate operations should be chosen according to the conditions, such as orbit, sunlight, power requirement, produced thrust and distance from MSS, etc. The present mission requires maximizing the solar array output. The operation of the thrusters may be stopped in the eclipse. In this case, thrust verification will be done by the operation mode changing the eccentricity of the orbit effectively. The maximum power operation should be done around the solstice for the orbit with high inclination. Now, it is assumed that the necessary power can be supplied continuously to the system. The continuous long thrusting is simple in the orbit transfer performance to demonstrate the relation between the thrust and the motion of the PF. The features of the orbit transfer are shown in Fig. 3. Both the orbits of the PF and MSS are in the same plane. The PF of 16.5 ton (assumed) is thrusted in the direction parallel to its velocity vector (in the Ascending Mode). The altitude of PF is raised gradually and its angular velocity around the Earth is decreased. while the MSS goes around with a fixed angular velocity. After 700 h operation with about 0.12 N thrust, the PF will be caught up by MSS flying along the inner course. The altitude difference between the two is about 30 km and is high enough to demonstrate the capability of the thrusters. Here, the PF executes a maneuver around its pitch or yaw axis by 180 degrees, and the thrust vector turns to be antiparallel to its velocity vector. A following descending mode operation makes the
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