Space missions involving proximity operations among spacecraft have gained increasing importance over the years. Indeed, they enable complex objectives that would be impossible, or at least very difficult, to achieve with a single spacecraft. These kinds of missions require a very high level of precision in maintaining relative distances among satellites throughout their operational lifespan. The challenge is heightened by the need for fully autonomous operation, as communication with ground stations becomes impractical or impossible (e.g., deep space missions). For these reasons, a robust and reliable Guidance, Navigation, and Control (GNC) system is essential for the success of spacecraft proximity operations.