Advantages and capabilities of an in-space navigation infrastructure in Moon and Mars missions

Future space activities are likely to include frequent missions toward Moon and Mars. The exploitation of these missions will require extensive navigation and guidance, and limited and expensive ground-based assets could be advantageously integrated or substituted by autonomous capabilities. The paper investigates two possible approaches to provide these capabilities by means of a navigation infrastructure. The first approach deals with exploiting at their limit the possibilities of the Global Navigation Satellite Systems (GNSSs) that, while primarily directed to serve the Earth and the low altitude orbits, are also able to extend their serviced volume at higher altitudes. By means of advanced use of the GNSS signals and a special architecture of the on-board navigation subsystem it would be possible to guide autonomously a complete mission to the Moon. The second approach is based on a local satellite-based navigation system devoted to a celestial body which is going to become the target of a number of missions. Such a kind of infrastructure, also able to provide data relay and communication services, could be of interest in the frame of an intense Mars exploration as a significant help in Martian operations. This system should be far simpler than current GNSS, providing the service to the areas of interest without a continuity requirement. A very quick reminder of alternative techniques that may have some role in the medium future – and therefore should be taken into account in the analysis of the problem - completes the paper.