Spacecraft fast fly-around formations design using the parallelogram configuration

In this paper, for observing the target spacecraft from many viewpoints, we propose a parallelogram fly-around formation design with practical maintenance strategies. First, we present the concept of the parallelogram fly-around formation and analyze the relative motion along a side of the parallelogram formation. Then, the impulse-control algorithms are presented for establishing the parallelogram fly-around formation theoretically, and a rapid method is presented to estimate the range of the multi-loop parallelogram fly-around formation. Furthermore, we present double-stage finite-thrust control strategy that is easily realized in applications for maintaining the fly-around formation. Finally, we verified the effectiveness of the proposed fly-around design and maintenance strategies with numerical simulations. The proposed impulse-control strategy and double-stage finite-thrust control strategy successfully achieved the single- and multi-loop fly-around formation, which provide a practical way for establishing flexible 360° monitor for target spacecraft at an elliptical orbit.