Initial Pose Acquisition Phase for Active Debris Removal Missions

Space debris is one of the biggest challenges in space exploration.Without any actions, a situation called a Kessler syndrome might occur, which would forbid humankind's access to space.To avoid this situation, the generation of new debris needs to be reduced to a minimum, which means that we have to actively remove old, uncooperative space objects from the orbits they occupy.This requires a dedicated mission to rendezvous with the object, capture, and de-orbit it.Navigating near the satellite presents a serious challenge for the Guidance, Navigation, and Control (GNC) system, especially when a priori information on the state of the object is not known.The system has to be initialised with a pose that the tracking algorithms could then use to perform the mission.In this paper, the initial pose acquisition phase is analyzed, in particular using a previously developed Perspective Principal Line (PPL) method.This method employs a specific version of the Perspective-n-Line (PnL) methods, where the pose is estimated from the projected and 3D line correspondence.In the PPL case, these lines are the principal (reference frame) axes.It is a computationally inexpensive algorithm that can run on a dedicated hardware in real-time and deliver sufficient accuracy, however, it requires certain conditions to be met.This paper addresses the constraints that this algorithm puts on the mission, e.g.initial distance, illumination conditions, and certain properties of the target satellite.Furthermore, the design of this phase is presented and it is shown that if an appropriate scenario is chosen, the PPL method could be a reliable tool for initial pose acquisition.