Navigation technology for exploration of glacier ice with maneuverable melting probes

•The IceMole concept allows oblique melting trajectories and changing the melting direction.•Trilateration of acoustic signals yields the probe's absolute in-ice position.•Combined inertial and magnetometer data allow to track relative changes in attitude and position.•Acoustic reconnaissance provides information about the ice structure in the probe's fore-field.•Multi-sensor fusion combines all available data and provides decision support for the operator.

The Saturnian moon Enceladus with its extensive water bodies underneath a thick ice sheet cover is a potential candidate for extraterrestrial life. Direct exploration of such extraterrestrial aquatic ecosystems requires advanced access and sampling technologies with a high level of autonomy. A new technological approach has been developed as part of the collaborative research project Enceladus Explorer (EnEx). The concept is based upon a minimally invasive melting probe called the IceMole. The force-regulated, heater-controlled IceMole is able to travel along a curved trajectory as well as upwards. Hence, it allows maneuvers which may be necessary for obstacle avoidance or target selection. Maneuverability, however, necessitates a sophisticated on-board navigation system capable of autonomous operations. The development of such a navigational system has been the focal part of the EnEx project. The original IceMole has been further developed to include relative positioning based on in-ice attitude determination, acoustic positioning, ultrasonic obstacle and target detection integrated through a high-level sensor fusion. This paper describes the EnEx technology and discusses implications for an actual extraterrestrial mission concept.