A Low-Cost Mission For Testing In-Orbit A Passive Electrodynamic Tether De-Orbiting System

The need to limit the population of artificial debris in the near-Earth space motivates the development of efficient de-orbiting propulsion systems. Electrodynamic tethers offer a valid and attractive alternative to conventional chemical thrusters since they impose a penalty in terms of de-orbiting time rather than additional launch mass. We have designed a low-cost demonstration mission, where a reduced-scale de-orbiting system will be carried, deployed and controlled by a microsatellite. Numerical simulations show that the proposed configuration of the electrodynamic system allows, even in absence of active tether current control, to maintain a stable tether attitude motion. This is obtained through a careful combination of bare and insulated tether segments. When active current control is applied, the tether libration angles are bounded to within 10 degrees. The closed-loop control laws make use of the in-plane and out-of-plane libration angles and rates, which are estimated through a newly developed extended Kalman filter where the measurements are provided by two three-axis magnetometers mounted on the spacecraft structure and at the lower tether end-point, respectively. We show that this micro system is able to de-orbit a LEO carrier spacecraft in about 2 months, demonstrating salient features of tether technologies and associated electrodynamic effects.