GNSS technology for lunar missions

The use of GNSS signals for navigation, over and beyond the design and application of GNSS constellations, is a challenge that could boost mission autonomy, cut operational costs and improve performance. GNSS-based navigation systems have long been used for GEO missions, and serious consideration is now being given to their beneficial use for highly elliptical orbit (HEO) missions (e.g., PROBA-3) and higher-altitude missions (e.g. moon missions), even if used only partially or as a complement to other navigation sensors.

The European Space Agency’s European Space Research and Technology Centre (ESTEC) has awarded GMV a study for investigating the use of GPS/GNSS (Galileo) weak-signal technology for providing real-time positioning, navigation and timing (PNT) information for various future lunar assets such as automatic landers, rovers, orbiters and earth-moon transportation vehicles.

The study tasks include analysis of the main constraints of current GNSS space receivers in the various moon-mission phases and investigation of synergies between signal processing and other navigation sensors. Due to the weakness of the GNSS signals and the poor signal geometry conditions, a standalone GNSS-Receiver module is unlikely to be able to fulfill all requirements imposed by upcoming lunar exploration missions. Combination or hybridisation with other signal processing systems and other navigation sensors is a common-sense step towards promoting use of GNSS signals at such altitudes.

The study also includes the design and set up of a Proof of Concept as a crucial step towards fully-fledged demonstration equipment or operational demonstration/implementation of the Moon-GNSS navigation receiver system for future Moon missions. It is absolutely essential for the Proof of Concept to be realistic enough to ensure trustworthiness and maturity before moving on to new stages.

GMV is the prime contractor of this activity, with responsibility for definition, analysis and characterization of the moon GNSS scenario, derivation of the requirements of the GNSS navigation receiver, analysis and architecture definition, proof of concept design and set-up, and test campaign.