Design of ADCS system for Earth Observation using a 3-unit CubeSat

GWSat is a project led by George Washington University in collaboration with the Costa Rica Institute of Technology and the United States Naval Academy. It uses a 3U CubeSat to test GWU’s Micro-Cathode Arc Thruster technology developed at GWU’s Micro-Propulsion and Nanotechnology Laboratory. This CubeSat will have two advanced attitude control systems. The first system consists of a pointing mode that will allow the satellite to orientate its camera to Palo Verde National Park, Costa Rica, for remote monitoring purposes. The second system, the station-keeping mode, will contribute by extending the life of the mission. The attitude orbit and determination system control of GWSat is based on the combination of the thrusters and magnetometers only. In this paper, the design of the ADCS for Earth observation of GWSat is described. Here, simulations show how different control methodologies, from simple proportional-derivative controllers to a method designed using the port-Hamiltonian framework, influence the performance of the system. Perturbations, such as atmospheric drag and gravity gradient, are considered in the dynamics of the satellite. This performance is of outmost importance in this mission, given that the energy efficiency is directly correlated with the use of propellant of the thrusters.