Flyaround orbit design and control for observing spacecraft

This paper investigates the design and maintenance method of flyaround orbit for spacecraft relative motion. At first, based on the analytical solution of linear dynamics, a new set of relative orbit elements is presented to describe intuitively geometrical characteristics such as the size, location and orientation of the relative flyaround orbit. The initial relative orbit elements of flyaround orbit are designed according to the requirements of spacecraft observation. Then, the flyaround trajectory control is investigated. The nonlinear relative motion equations, in which the relative motion is decoupled from chaser's attitude, are derived under the constraints of chaser's desired attitude. Considering the on-off characteristic of engine's thrust, the nonlinear predictive control based on Fliess expansion is utilized to design the flyaround orbit maintenance control law to track the desired flyaround trajectory. Finally, the control algorithm is validated by simulation results and the control precision is satisfied.