Retargeting dynamics of a linear tethered interferometer

The study deals with the issue of changing the plane of rotation (retargeting) of a linear kilometer-sized formation of two collectors and one combiner spacecraft connected by two tether arms. A control strategy is proposed that makes use of a pair of electrical thrusters located onboard two of the three spacecraft to redirect the angular momentum of the formation to a new target with an accuracy of a few arcseconds while keeping the angular momentum magnitude constant throughout the maneuver. The thruster profile is optimized to achieve a very smooth but relatively fast maneuver while maintaining the overall fuel consumption at a minimum level. The attitude dynamics of the formation are solved analytically based on a perturbation method, which allows calibrating the thrust profile for high-precision retargeting. A numerical model is employed to test the proposed strategy and to evaluate the influence of massive flexible tethers and external perturbations on the accuracy of the maneuver. Finally, the required propellant mass is evaluated with reference to envisioned space interferometry missions.