Hybrid concept for a forefield reconnaissance system for melting probes capable of moving through terrestrial and extraterrestrial cryospheres

The most promising places for the development of extraterrestrial life are the ocean worlds of our Solar system such as the icy moons Europa or Enceladus and their subglacial oceans.  Space mission concepts are being developed to explore the moons’ chemical composition, investigate their habitability, and search for biosignatures.
The TRIPLE Project, initiated by the German Space Agency at DLR, involves the development of technologies for rapid ice penetration and subglacial lake exploration. It consists of three components: (i) a melting probe that travels safely through the ice and carries (ii) an autonomous nano-scale underwater vehicle that explores the ocean and takes samples to be delivered to (iii) an astrobiological laboratory. The entire system will be tested in an analogue scenario in Antarctica as a demonstration for a future space mission. To ensure the success of the test, a retrievable melting probe is needed that can safely penetrate several kilometers of ice. The melting probe should also be able to detect the transition between the ice and the water body to stop at this boundary. 

The Forefield Reconnaissance System (FRS) for such a melting probe developed in the project TRIPLE-FRS combines radar and sonar techniques to benefit from both sensor principles inside the ice. The radar antennas as well as a piezoelectric acoustic transducer will be directly integrated into the melting head. This integration into the head should leave the melting capability of the melting probe as unaffected as possible. An in-situ permittivity sensor will also be developed to account for the propagation speed of electromagnetic waves, which is dependent on the surrounding ice structure. The goal of this system is to detect obstacles or other interference bodies to guarantee a safe transition through the ice. Damage-free melting must be secured to allow all other scientific exploration. In order to prove the functionality and performance of the system, several field tests on alpine glaciers are performed during the project. In this contribution, we describe the main ideas behind the system and show how it could serve as a baseline design for the future development of space missions to ocean worlds like Europa.