Enceladus Explorer and TRIPLE
In Enceladus Explorer (EnEx) and TRIPLE we research, develop and test melting probes and navigation systems for these probes.
In the solar system, the icy moons Europa and Enceladus are promising candidates for the search for extraterrestrial life. Under their ice shield, besides liquid water, a thermal energy source is suspected. In addition, cryovolcanoes have been discovered on the surface of Enceladus by the Cassini spacecraft. From these ice fountains are shot into space, in which organic compounds could be detected. Thus according to today's astrobiological conception on Enceladus all basic conditions for the development of life are given. Their relative proximity to Earth makes Europa and Enceladus interesting targets for future exploration missions.
TRIPLE© Marum, Bremen
Within TRIPLE, initiated by the German Space Agency at DLR , Technologies for Rapid Ice Penetration and subglacial Lake Exploration are being researched . The concept was approved by a phase 0 study. The phases A/B are in preparation.
TRIPLE is divided into three major components and aims to explore the subglacial ocean of the Jovian moon Europa. The first component is a melting probe which penetrates the ice shield and navigates to the ocean below. It anchors itself at the ice-water boundary and releases the second component into the water: A small autonomous underwater vehicle will explore the ocean, identify points of interests and take samples. The samples will be delivered to the melting probe and then processed and analyzed by a miniaturized astrobiological laboratory, the third component.
These components will be developed for a terrestrial analog scenario. Several test sites are currently in discussion for a demonstration: Subglacial lakes in the Dome C region, Antarctica or Devon Ice Cap, Canadian Arctic or Upper Taylor Glacier, Antarctica or Vatnajökull , Iceland.
Of those the Dome C region test side is the most challenging, requiring a deep field camp, a high logistical effort and has the highest requirements on the TRIPLE system. At this location, the system needs to penetrate in the order of 4 km of ice and sustain the pressure under the ice cover. The demonstration is aimed to be conducted during one Antarctic season, which requires a rapid melting probe (velocity of approx. 10 m/h).
A melting probe, suitable for this demonstration, is not yet available. As a first step the TRIPLE- IceCraft development aims for an intermediate goal: A drill depth of several hundred meters and a drilling velocity of several meters per hour.
TRIPLE-IceCraft (2019 - today)
The TRIPLE-IceCraft melting probe is currently in development in cooperation with the GSI GmbH from Aachen. This probe will be demonstrated on the Ekström Ice Shelf in Antarctica in Jan/Feb 2022. There it will melt through the 200 m thick ice shelf into the underlying ocean and later return to the surface.
The TRIPLE-IceCraft will be the basis for melting probes for greater ice depths (several kilometres) on the one hand and for extraterrestrial use on the other. TRIPLE-IceCraft will have a modular structure in order to be able to transport any scientific payload. Standardized payload segments can be integrated into TRIPLE-IceCraft. In this way, the nanoAUV will later be deployed in a subglacial lake.
TRIPLE-IceCraft on Twitter: https://twitter.com/TRIPLE_IceCraft
TRIPLE-FRS (2020 - today)
In TRIPLE-FRS, we are developing a forefield reconnaissance system (FRS) in collaboration with FAU Erlangen, GloMic GmbH located in Berlin and BU Wuppertal. Based on radar and sonar technology, the FRS will be integrated into the TRIPLE melting probe in the future. The forefield reconnaissance system located in the head of the probe will have two central tasks. On the one hand, obstacles are to be early identified and located for trajectory planning, and on the other hand, the ice-water transition at which the probe will anchor must be detected. The RWTH Aachen group is responsible for the development of the sonar system.
EnEx Initiative© DLR
The aim of a future Enceladus Explorer space mission is the search for extraterrestrial life on Saturn’s moon Enceladus. To allow for such a mission, new technologies are being developed within the scope of the EnEx initiative of the German Space Agency at DLR.
Saturn’s moon Enceladus is a promising candidate for the search of extraterrestrial life. Its relative proximity to Earth plus the evidence Cassini provided for both the existence of liquid water, which implies the presence of thermal energy, and the existence of organic compounds makes Enceladus an interesting target for a future space mission. Based on present-day astrobiological knowledge all prerequisites for the emergence of life are present on Enceladus.
A maneuverable melting probe will detect and sample a water filled crevasse beneath the ice surface and conduct in-situ analysis of the recovered sample. To reach this goal several research groups work on different topics within the scope of the EnEx initiative.
EnEx-RANGE (2015 - 2019)© EnEx
EnEx-RANGE is part of the EnEx initiative. RANGE is an acronym for „ robust autonomous acoustic navigation in glacier ice “ (German: „ R obuste autonome Akustische Navigation in Gletscher-Eis “ ). Participating RWTH institutes are the Physics Institute III B and Institute Cluster IMA/ZLW & IfU.
Intelligent acoustic sensor network
EnEx-RANGE aims to develop an intelligent acoustic sensor network which allows for the navigation of an autonomous probe within an ice volume, e.g. an alpine glacier.
The intelligent acoustic sensor network will consist of separate Autonomous Pinger Units (APU), which are equipped with matched acoustic emitter and low noise acoustic receiver units. The APU carrier system includes a melting system enabling the APU to melt downwards into the glacier. A sophisticated, high performance data system records and processes the sensor data and controls the actuating elements. Furthermore, a reasoning system will carry out a distributed optimization of the sensor network based on its evaluation of current sensor data. Both, automated positioning via two-way acoustic signal exchange and autonomous evaluation of the signal quality is conducted. The latter information is used to determine the accuracy of the positioning and to assure an uniform acoustic coverage of the test area.
Navigation of the EnEx probe
Both the acoustic positioning as well as reconnaissance system developed within the former collaborative EnEx project will be enhanced within EnEx-RANGE.
The acoustic positioning system was developed to determine the absolute position of the EnEx probe based on trilateration. This system is to be adapted to the APU network and will be improved by an increase in sensitivity of the sensor technology. This improved performance will be achieved by the reuse of technology developed for the APU network. Overall this permits a reduction of measurement time while increasing the measurement accuracy. Furthermore, the degree of autonomy will be increased to enable the EnEx probe to act independently. This includes trajectory planning based upon the expected signal quality as well as autonomously initiated re-positioning in case of exceeded error tolerances.
The acoustic reconnaissance system acquires information about the surroundings of the EnEx probe based on sonography. The system emits directive acoustic signals and records the echoes from structural transitions such as obstacles (e.g rock fragments) or regions of interest (e.g. water-fille d crevasses). The data provided by the acoustic reconnaissance system allows generating a map of the fore-filed of the EnEx probe, which can be used for navigation purposes. The sensor technology of the acoustic reconnaissance system is to be optimized to achieve a higher sensitivity as well as an expanded range. Furthermore, a performance enhancement of the electronics will enable an extension of local data processing.
System tests in water and glacier ice
System tests in water and glacier ice are carried out to review the accomplished improvements as well as the self-optimization of the APU network. Since glacier expeditions present a great logistic effort, measurements are conducted in water if possible. Measurements requiring water volumes up to about three cubic meters can be performed in the Aachen acoustic laboratory which is part of the Physics Institute III B. The swimming pool of the Ulla-Klinger-Halle as well as at the Rur Lake at RWTH Aachen Wildenhof venue can be used for e xperiments that require larger test environments. Especially the latter allows for spacious test scenarios similar to the ones planned for the glacier expedition in summer 2017. In summer 2018 the functionality of the intelligent acoustic sensor network in combination with the EnEx probe is to be demonstrated within the ice of an alpine glacier.
EnEx project (2012 - 2015)© EnEx
The Enceladus Explorer collaborative research project was the foundation of the EnEx initiative. The EnEx project was a research and development project consisting of six German universities cooperating to develop basic principles for a future space mission.
A scenario similar to the one on Enceladus was tested in Antarctica by probing a water filled crevasse originating from a subglacial water reservoir. Hence an in-ice navigation system was developed which allows tracking of the probe as well as imaging of the fore-field. The so called IceMole, which is a combined drilling and melting probe, served as maneuverable in-ice probe.
For this mission, two acoustic navigation systems were developed alongside conventional navigation solutions. First a positioning system based on trilateration and second a sonographic reconnaissance system based on phased ultrasonic arrays.
In November 2014, the EnEx probe succeeded in taking the first contamination-free water sample from the subglacial lake at Blood Falls in Antarctica. Press release of RWTH, article in the journal Countdown (DLR) and press release of DLR regarding the successful sample taking (press release by RWTH, article in magazin COUNTDOWN by DLR).
Article on the DLR funding of the Eceladus Explorer Projects.
Cassini-Huygens mission is a mission for the exploration of Saturn and its moons. Detailed information can be found at DLR and NASA.
Information for IceMole development, especially before the time of Enceladus Explorer project are available on Wikipedia.