Guidance, Navigation and Control for Autonomous Cooperative Docking of CubeSats

Is it possible to dock CubeSats in Low Earth Orbit? The challenges are mainly associated with the level of miniaturisation. A docking mechanism was designed, built and tested in the laboratory. Results show that a relative precision better than 1 cm and 2 degrees is required for the docking. The docking mechanism and metrology system, composed of a monocular camera and sets of light- emitting diodes, are contained within 0.5U volume and can thus be used on nano-satellites. The chaser and target satellites have a complete 3-axis attitude pointing capability and are equipped with available CubeSats attitude sensors and actuators. The chaser is further equipped with a 6 degrees of freedom low-thrust cold gas propulsion system. Different robust control schemes have been investigated and their stability and performance assessed. Non-linear Monte Carlo simulations have been performed to assess the Guidance, Navigation and Control (GNC) performance and fuel consumption. Results show that the proposed GNC is robust to the various sources of uncertainties and that a lateral accuracy better than 5 mm is obtained at docking. Furthermore, it is not affected by the loss of the star trackers or by illumination conditions and can thus take place on a variety of orbits.