Spacecraft orbit control using air drag

Air drag can be used in very low Earth orbit to reliably generate moderate orbital control action without need of thrusters and therefore at a reduced cost. This effect can be exploited changing the cross section of the spacecraft by means of deployable appendages or rotating the bus around an axis orthogonal to velocity vector. The paper deals with the use of air drag to control the relative position of two satellites belonging to a formation. The focus is on evaluating optimal strategies which take into account and minimize the orbital decay. An approach which makes use of a recent formulation of the Euler Hill equations modified to include the drag is proposed. A semi analytical solution is provided as input to an optimizer based on genetic algorithms. Advantages of this choice are explained, together with indications on the simulations performed.