佐伯 孝尚

This paper presents a very high altitude, Sun-Synchronous orbit around the Earth for astronomy satellites. It includes a cart wheel orbit in Hill's motion. Considering the perturbation owing to the Earth gravity, the period of the in-plane motion and out-of-plane motion are different and trajectory becomes Lissajous. The results analytically obtained are examined and compared with those via numerical integration. In addition, it is shown that the fuels amount, which is inquired to keep nominal Cart Wheel orbit properties, decreases as the altitude increases. And, the conclusion is that the Cart Wheel orbit is a kind of sun-synchronous orbit and highly practical with affordable correction velocity increment.

In formation flight missions, it is very important to control the relative positions of satellites. Although there have been many researches on the relative position control for formation flight, most of them assumes the centralized architecture in which an administrator collects every relative position and velocity information about the formation. However, in case the formation consists of many satellites, it takes long time to collect the information of all the satellites and to distribute the command to every satellite. Therefore, the centralized architecture is unsuitable for the control system that requires a rapid response. Beside, if the central control is down, the system loses the formation control functions thoroughly. One strategy that overcomes these flaws is to make each satellite be controlled by using the information on its nearby satellites. This paper discusses the guidance law based on the regional limited information to maintain the formation. In this case, the information structure of the system greatly influences the control law and the control performance. In this study, we discuss how the control laws are designed, first. And how the information structure influence the configuration of the formation is focused on. Copyright © 2004 by The American Astronautical Society.

In formation flying missions, the spacecrafts should keep particular formation, so it is very important to control the relative positions between them. Although there have been many researches on the relative position control, most of them assumes that each satellite use the absolute information about its position and velocity. However, in order to keep the formation strictly and to avoid the collisions, the feedback control with the relative information between the members is effective. In such formation maintenance control, 1) the local control law (control gain, etc.) of each spacecraft and 2) "whose relative information can each spacecraft acquire" (we call this "the information propagation structure") determine the behavior of the formation. Especially, the information propagation structure significantly influences the behavior of the formation. However there are few researches about the information propagation structure. In this study, the information propagation structure of the formation is focused on and how the information propagation structure influences the behavior of the formation is investigated. First, we express the information propagation structure of the formation by a matrix and derive the transfer function matrix of the whole system. Next, from this transfer function matrix, we clarify the relation between the information propagation structure and the stability, the steady-state error and the reactivity of the formation and derive the indexes of these control performances. Finally the method for constructing the information propagation structure by optimizing these indexes is shown.

The paper presents how the formation is controlled to the intended shape by a decentralized control. The formation behaviour is dealt via a z-transformation method and a uniformly convergent strategy that each spacecraft performs is proposed. Not only one-dimensional but tow-dimensional examples are shown. Since the strategy is highly flexible, it is applicable to a variety of the formation flying space missions.