The effects of increasing velocity on the tractive performance of planetary rovers

An emerging paradigm is being embraced in the conceptualization of future planetary exploration missions. Ambitious objectives and increasingly demanding mission constraints stress the importance associated with faster surface mobility. Driving speeds approaching or surpassing 1 m/s have been rarely used and their effect on performance is today unclear. This study presents experimental evidence and preliminary observations on the impact that increasing velocity has on the tractive performance of planetary rovers. Single-wheel driving tests were conducted using two different metallic, grousered wheels-one rigid and one flexible-over two different soils, olivine sand and CaCO3-based silty soil. Experiments were conducted at speeds between 0.01-1 m/s throughout an ample range of slip ratios (5-90%). Three performance metrics were evaluated: drawbar pull coefficient, wheel sinkage, and tractive efficiency. Results showed similar data trends among all the cases investigated. Drawbar pull and tractive efficiency considerably decreased for speeds beyond 0.2 m/s. Wheel sinkage, unlike what published evidence suggested, increased with increasing velocities. The flexible wheel performed the best at 1m/s, exhibiting 2 times higher drawbar pull and efficiency with 18% lower sinkage under low slip conditions. Although similar data trends were obtained, a different wheel-soil interactive behavior was observed when driving over the different soils. Overall, despite the performance reduction experienced at higher velocities, a speed in the range of 0.2-0.3 m/s would enable 5-10 times faster traverses, compared to current rovers driving capability, while only diminishing drawbar pull and efficiency by 7%. The measurements collected and the analysis presented here lay the groundwork for initial stages in the development of new locomotion subsystems for planetary surface exploration. At the same time...Comment: 15th International Society for Terrain Vehicle Systems (ISTVS) Conference, Prague, Czech Republic, 201

A Goal-Oriented Autonomous Controller for Space Exploration

The Goal-Oriented Autonomous Controller (GOAC) is the envisaged result of a multi-institutional effort within the on-going Autonomous Controller R&D activity funded by ESA ESTEC. The objective of this effort is to design, build and test a viable on-board controller to demonstrate key concepts in fully autonomous operations for ESA missions. This three-layer architecture is an integrative effort to bring together four mature technologies; for a functional layer, a verification and validation system, a planning engine and a controller framework for planning and execution which uses the sense-plan-act paradigm for goal oriented autonomy. GOAC as a result will generate plans in situ, deterministically dispatch activities for execution, and recover from off-nominal conditions

SAFER: The promising results of the Mars mission simulation campaign in Atacama, Chile

The SAFER project (Sample Acquisition Field Experiment with a Rover), led by RAL Space and sponsored by the European Space Agency, was successfully concluded by a Mars Mission Simulation campaign in the Atacama Desert in October 2013. The objectives of SAFER were manifolds: Firstly, bring three ExoMars instruments prototypes together on a rover platform. Secondly, perform field trials in a Mars analogue in order to acquire valuable insight on the strategies for approaching a science target, investigating it, and sampling it to investigate possible traces of life. Lastly, the SAFER project targeted to implement a highly realistic scenario with a dual team, one with the rover system in a Mars analogue location, while all navigation and science investigation decisions would be taken remotely by a separate team, fully isolated from the field. The Atacama Desert in Chile was selected during the study as suitable Mars analogue for SAFER: Its extent, variety of landscapes, high quality Mars analogue and geological characteristics are all of high relevance for a Mars mission simulation. SAFER used an early version of ESA’s 2018 ExoMars rover, provided by Astrium, fitted with a trio of ExoMars prototype instruments, including the AUPE-2 PANCAM prototype from Aberystwyth University, the WISDOM ground penetrating radar prototype from LATMOS, and a CLUPI prototype provided by Space-X. All three instruments were used to identify promising sites for subsurface excavation. During the Mars mission simulation a field trials team composed of instruments engineers, geologists, and field trials engineers was on location in the Atacama Desert in Chile. The remote control team was in parallel overseeing the rover operations from the Satellite Applications Catapult facility in Harwell, UK. The remote control team was composed of instrument operators, key members of the ExoMars programme team, ExoMars instruments principal investigators and a geologist. The controllers used a video wall to combine data from the rover’s instruments with their own 3D planning maps to help the remote team to analyse instruments data, elaborate a science strategy, and produce plans of activities for each sol, as it would be performed during a Mars exploration mission. Each plan was dispatched to the local team in the field who then uploaded it to the rover, while trying to remain as ‘invisible’ as possible for the remote operators. The SAFER campaign was a success and its results are opening the way to successful, safe, and optimized planetary exploration for the European Space Agency: Firstly, remote operations with an average of two Martian sols per day were achieved, including the acquisition of valuable instruments data. Drilling down to more than a meter was achieved by manual operation, and the samples obtained are being documented to help cross calibrating the ground penetrating instrument data and support future Mars exploration missions. Secondly, SAFER unique outcomes and lessons learnt will be transmitted to the European Space Agency’s planetary exploration teams; a key outcome has been the importance of well-defined interfaces between the rover and instruments, the importance of the remote operations team composition, and valuable operations lessons learnt demonstrating feasible activities to be achieved in a single Martian sol. Valuable instruments operations feedback was also acquired and will be presented in the final paper. Finally, SAFER opens the way to efficient, easy, and cost effective future field trials activities; an extensive expertise in the organization of such trials has been developed, as well as a detailed knowledge of the Atacama region which has proven to be a highly representative analogue for Mars mission simulations

Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover

International audienceThe second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth down to 2 m. This subsurface sampling capability will provide the best chance yet to gain access to chemical biosignatures. Using the powerful Pasteur payload instruments, the ExoMars science team will conduct a holistic search for traces of life and seek corroborating geological context informatio