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.