ESA GNC Conference Papers Repository

The future interplanetary exploration missions envisaged by ESA, like Mars re-entry and precision landing, small body sample return missions, or Jovian system science, call for ever higher guidance, navigation and control system performances either to satisfy mission scientific and programmatic needs, or to reduce propellant costs and enable complex mission scenarios with current launcher capability. Autonomous navigation, in particular based on vision techniques, is being demonstrated in the ESA Innovative Autonomous Navigation Techniques study (IANT) and in phases A and assessment studies to be a very efficient way to enhance the overall efficiency of a GNC system dedicated to such missions. In particular, for Mars re-entry missions, it is expected that landmark matching techniques used up to a few hours before encounter with the red planet could help significantly reduce delivery errors at entry interface point (EIP), due to the fine knowledge of Mars surface and referencing of its features. These EIP errors being an important contributor to final landing accuracy after guided re-entry, precision landing is thus facilitated, which is the main goal for missions like ESA’s Mars Precision Lander (MPL). Following the guided re-entry phase, autonomous relative vision based navigation can ensure soft landing and absolute vision based navigation using multi-scale matching image processing is a promising solution for pinpoint landing. On a mission like Jupiter Icy Moon Explorer (JUICE), the same techniques cannot be directly applied because the surface of the Galilean moons is not as accurately known and referenced as Mars and Jupiter’s atmosphere appearance is permanently varying. Still, it is possible to increase the realization accuracy of encounters with the moons and of the ensuing gravity assists by observation and extraction of the moon sunlit limb and derivation of the Moon centre line of sight, which permits a very significant reduction of the stochastic ?V associated with the correction of those fly-bys. The relative navigation thus performed is, unlike ground traditional RF tracking, independent from ephemeris errors and can allow partial mitigation of the ?V contributor associated with the latter. Large ephemeris knowledge errors also exist for small bodies like asteroids and comets, due to their faint magnitude and the difficulty to observe them from Earth. This implies that the same kind of relative navigation as for JUICE is also desirable for mission performing rendezvous with such targets like MarcoPolo-R aiming at returning a sample from the primitive asteroid 2008 EV5. Used autonomously with the ensuing guidance, the relative navigation is expected to allow rendezvous propellant cost reduction, which is always useful to lighten system constraints in order to reach remote targets in the solar system. In addition to the rendezvous phase, most of the missions targeted at small bodies currently or formerly envisaged by ESA (MarcoPolo-R as a former Cosmic Vision M3 candidate and Phootprint as a possible future MREP mission) are sample return missions and require the S/C to descend to the small body surface to allow the sampling. The time constraints for the descent require an autonomous GNC, and recent studies have proven the efficiency of relative vision based navigation to ensure both soft and accurate landing. For each of the mentioned mission cases, this article recalls the mission context, specifies the GNC challenges originating from mission constraints and describes the GNC strategies considered in the currently on-going IANT study and the mission assessment and phase A studies. The way the autonomous functions can be inserted in a non autonomous baseline while mitigating risk and optimizing on-board/ground task sharing is clearly detailed. As the IANT study is still ongoing, the efficiency and expected performance of these strategies are then assessed based the results of JUICE phase A study, MarcoPolo-R assessment study, and Phootprint pre-phase A study, as well as the MREP EDLS and other internal studies on the Mars case following the MPL phase 0. This article is more meant as an overview of future intended European missions and the various innovative GNC technologies of relevance to them than as a detailed description of a particular technology actually implemented on an existing mission. Each technology and mission description will therefore be synthetic as required by the vastness of the paper panorama.