Review of Control Methods and Strategies of Space Tether Satellites

Space tether satellites systems are one of the most promising directions in the modern space industry. Such systems consist of two or more spacecraft connected to each other by very long tethers. Great extension and variable configuration of the system in the orbital flight conditions provide some dynamic features, which are not typical of conventional spacecraft. The concept of the tethered satellite system (TSS) promises to revolutionize many aspects of space exploration and exploitation. It provides not only numerous possible and valuable applications, but also challenging and interesting problems related to their dynamics, control, and physical implementation. The overarching theme of the paper is to show various control methods of the tethered satellites system (TSS) that have been undertaken recently, and also to emphasize on the importance of the TSS control method as an important aspect in the tether concepts, design, and missions. This review article presents the historical background and recent hot topics for the space tethers, and introduces the dynamics and control of TSSs in a progressive manner, from basic operating principles to the state-of-the-art achievements. The paper introduces the strategies and methods applied in controlling the TSS not excluding their advantages and disadvantages during the tether satellite deployment, retrieval, and station keeping procedures. At the end of the paper, a conclusion is made about the effectiveness of the control methods in stabilizing the libration and vibration motions of the TSS.