GUIBEAR is an on-going activity supported by the European Space Agency aimed at the demonstration of the feasibility of bearings-only (B-O) far-range rendezvous in near rectilinear Halo orbits (NROs). The studied scenario is the far-range rendezvous of the HERACLES Lunar Ascent Element (LAE) with the Lunar Orbital Platform – Gateway (LOP-G) that is orbiting the Moon in an NRO. This activity advances the readiness level of the applicable technologies through a solution based on Computational GNC, structured around a Model Predictive Control framework and tools; and an approach design, development, verification and validation based on iterative prototyping which integrates high-fidelity hosting considerations into the design from a preliminary level: concurrent GNC and software architecture design with hosting, runtime assessment and optical high-fidelity simulations. This paper: presents the context – mission, system and hosting, and algorithm-level challenges and proposed concepts; details and justifies the architecture and design solutions; outlines the methodologies employed for prototyping verification and validation; provides conclusions on the obtained results.