Global Navigation Satellite System (GNSS) provides accurate Positioning, Navigation and Timing (PNT) information to the users. Originally, these have been designed to serve terrestrial users, but in the last years the interest in the use of GNSS for autonomous space navigation has significantly increased. These navigation systems, already used at low altitudes, are becoming attractive even for spacecraft navigation at larger distances, as in lunar missions. In fact, exploiting real-time, in-orbit GNSS-based navigation systems would make the spacecraft more autonomous, reducing the costs and the effort of ground operations. However, deploying GNSS receivers all the way to lunar distances is a challenging task due to multiple factors.