1 METHOD OF TETHERED SYSTEM CONTROL FOR DEORBITING OBJECTS USING EARTH’S ATMOSPHERE Yury N. Razoumny * , Sergei A. Kupreev † and Arun Misra # A space tethered system used as an atmospheric braking device for deorbiting small satellites from low orbits is considered. A simplified mathematical model of a small space tethered system that takes into account aerodynamic drag of the upper layers of the atmosphere and tether mass has been developed. A mathemat- ical tool of dynamic systems qualitative theory and bifurcation theory is used for the given model analysis. The feasible modes of tethered system motion during descent in the upper layers of the atmosphere are defined. The most rational mode of tethered system is singled out relying on the stated efficiency factors. Based on CubeSat-type spacecraft, the application of different tethered system design op- tions have been reviewed. Tethered systems of approximately 2 km long are proved to be efficient for deorbiting small satellites from low near-circular orbits. INTRODUCTION Space tethered systems (STS) are new non-traditional space structures capable of addressing problems that are impossible, inexpedient or uneconomical to handle using existing space aids. 1, 2 Interest in these systems is confirmed by experiments conducted regularly in the world. 3, 4 Ac- cording to many experts, further development of rocket and space technology is tied to the use of STS technology. 5, 6, 7, 8, 9, 10. In recent decades, there have been trends to widen the rational applications of small-size spacecraft capable of addressing applied research, engineering and technological problems. A short active lifetime is considered a technical limitation of these spacecraft. At the same time, in the operation of a satellite network, the problem of deorbiting post- mission satellites followed by their destructive re-entry has become urgent. To this end, it is pro- posed to use STS that can act as an atmospheric braking device. The purpose of this paper is to analyze the feasibility of using a tethered system for atmos- pheric braking of satellites in circular and elliptic orbits. In the dynamics analysis, it is assumed that the tethered system is designed on the basis of small space vehicle and the tether length is between 0.5 to 2 km. Only the in-plane motion, accounting for the effect of aerodynamic forces, is considered. * PhD, Prof., Peoples’ Friendship University of Russia (RUDN University), Academy of Engineering, Department of Mechanics and Mechatronics, Head of the Department, address: 6, Mikluho-Maklaya Str., Moscow, Russia, 117198 † PhD, Peoples’ Friendship University of Russia (RUDN University), Academy of Engineering, Deputy Director, ad- dress: 6, Mikluho-Maklaya Str., Moscow, Russia, 117198 # PhD, McGill University, Department of Mechanical Engineering, Thomas Workman Professor, address: Montreal, QC,Canada, H3A 0C3 IAA-AAS-DyCoSS3-152