Aerodynamic attitude control of very-low-earth-orbit satellites: simulative analysis and insights into nonlinear system properties

Abstract Satellites operating in the Very-Low-Earth-Orbit regime, that is, at altitudes where the residual atmosphere significantly impacts spacecraft dynamics, encounter notable aerodynamic forces, which are traditionally considered disturbances in spacecraft attitude control design. Instead, active control methods seek to harness these forces using the torques generated by adjustable aerodynamic surfaces as an additional means of external actuation. In this work, we examine the nonlinear structure of the control problem for a satellite featuring a reference geometry in a feathered configuration with four rotatable surfaces. We argue that challenges for the control design include uncertainty in aerodynamic and atmospheric models as well as time-varying parameters such as density and thermospheric temperature. Furthermore, our work emphasizes that low lift-to-drag ratios not only reduce control authority around the roll axis but also significantly restrict the region of validity of the linearized system, complicating actuator allocation procedures. To highlight the effects on control performance, we introduce a custom simulation tool designed for testing rotatable panel geometries under VLEO conditions and present a case study that illustrates the limitations of linear control design methods. Finally, we discuss potential nonlinear control strategies and the need for stability guarantees to further advance the field of aerodynamic attitude control in VLEO.