No abstract

In recent years international space agencies, and commercial companies have started programming a permanent return to the Moon and future manned missions to Mars. A general consensus for the return to the Moon is the use of a permanent space station in lunar orbit, currently denoted as Lunar Orbital Platform-Gateway (LOP-G), which will serve as a short-term habitation module, science laboratory, and transfer area for rovers and Moon landers.The Human-Enhanced Robotic Architecture and Capability for Lunar Exploration and Science program HERACLES[1], provided a multi-agency baseline study for a lander, whose aim is to collect Moon samples and return them to the Earth using NASA Orion spacecraft, leveraging the LOP-G as a staging point. This space infrastructure will follow a particular type of orbit that has been widely studied in orbital mechanics since the 1960s, but has never been used by now for a real manned space mission: a Near Rectilinear Halo Orbit (NRHO).Such orbits offer long-term stability, with low propellant requirements for orbital station-keeping, by exploiting a balance point in the gravitational field of Earth and Moon [2]. Indeed, the gravitational interaction between our planet and its natural satellite makes possible several highly non-Keplerian orbits, among which the NRHO was selected because of its high eccentricity and orientation, which ensure continuous contact with Earth.Rendezvous and proximity operations with the Gateway will require the development of suitable guidance, navigation, and control (GNC) algorithms, which must take into account the complex dynamic environment. In this work, in particular, the chaser vehicle is assumed to be able to measure relative angles to the target only, which is passive in its NRHO. One of the main reasons for using angular measurements only for rendezvous is the advantage in terms of required power, weight and costs that optical navigation systems can provide [3]. In addition, radio-type relative navigation could not be feasible if the target is uncooperative.The Autonomous Vision Approach Navigation and Target Identification (AVANTI) experiment successfully

The future assembly of the Lunar Orbital Platform Gateway, on a near 9:2 resonant Rectilinear Halo Orbit, requires the necessity of designing safe and reliable strategies to perform rendezvous and docking with the station. The paper describes and tests a strategy to guarantee the safety of an entire rendezvous manoeuvre in the proximity of the Moon L2 Lagrangian point with respect to a specific set of failures. The safety in the far range is guaranteed through the automatic allocation of selected hold-points, whereas during close range rendezvous the safety is actively guaranteed in the presence of selected failures. The main goal of the paper is to contribute to the very limited literature about autonomous design of the guidance for rendezvous in presence of a non negligible third body influence, where safety considerations are paramount. The proposed approach is based on the exploitation of the manifold theory used in the circular restricted three body problem model to guarantee the passive safety in the far-range section, and on an optimal and reliable active collision avoidance manoeuvre to guarantee the safety for the close range approach.