Exploration Rover Research Articles

LiDAR-Inertial SLAM with DEM-driven Global Constraints for Planetary Rover Exploration

LiDAR-Inertial SLAM with DEM-driven Global Constraints for Planetary Rover Exploration

Method for Underground Motion Using Vibration-Induced Ground Resistance Changes for Planetary Exploration

Exploration rovers have difficulty moving underground because the drag force from the ground restricts their movement; this hinders underground exploration. This study aimed to address this challenge. We posit a hypothesis that the rover can move underground by imparting vibration to the ground and changing the drag force. To validate this hypothesis, a testbed that moves underground was developed, and the drag force when imparting vibration was investigated. The results revealed that the drag force while imparting vibration is smaller than that after imparting vibration, and we accordingly devised the operation for moving underground. The proposed operation causes bias of the drag force by imparting vibration to make the testbed move in the direction of the small drag force. The effectiveness of the proposed method was assessed through an experiment wherein the testbed was set to move underground. The experimental results demonstrate the superiority of the proposed method, as the movement distance achieved with vibration is considerably greater than that without vibration. The findings validate the hypothesis that using vibration for underground motion is effective in improving mobility and provides valuable insights into the design of robots for underground motion.

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

ABSTRACT This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context.

An Automated Wayfinding Algorithm to Find Rovers' Path on the Lunar South Pole

As a part of the upcoming Artemis mission, NASA released a large satellite dataset (latitude, longitude, height, and slope) of the lunar south pole, around the area of the lunar module landing site and rover exploration site near the Shackleton Crater. While designing the rover, it’s important to understand the minimum power the rover needs (the amount of slope it can overcome) to navigate the terrain. Our goal was to process the data, visualize the data in 2-D and 3-D, and develop an algorithm that would automatically map the shortest possible path (or no possible path) between two coordinates according to the lunar terrain and rover parameters. To accomplish that, we processed a large unorganized dataset into an equally spaced and sequential matrix of latitude, longitude, height, and slope. The matrix was then converted into a go/no-go maze of the terrain and the Breadth First Search (BSF) and A* algorithms were applied to the maze to find the optimal path. The terrain and the optimal path were plotted in 2-D using Matplotlib and interactively displayed in 3D using Plotly. We developed a Jupyter Notebook web-based app that will allow a user to interactively use the algorithm and visualize the lunar terrain. The results identify the minimum rover slope and various paths depending on higher rover slopes. The algorithm and the rover paths were validated by the NASA SCaN (Satellite Communication and Navigation) team of engineers and the application can be used for design, validation, and training purposes.

DROD: bio-robotic drill/sampler for planetary subterranean exploration: experiments and challenges

Key features for space exploration equipment, and in particular drills and sampling mechanisms, are low weight, small size, and energy efficiency. These characteristics are substantially required not only in reducing the spaceship flight cost, but also in extending the exploration time on the extraterrestrial bodies. This article experimentally investigates the feasibility of a novel drill bioinspired by wood-wasp and sand-fish lizard as an integrated robotic solution for rover exploration tasks. A new penetration depth of 820 mm in terms of reciprocation drilling technique has been achieved by the proposed dual reciprocation and oscillation drill (DROD), especially with the new enhancements such as miniature sample compartment and toothed stems. Additionally, a first sampling experiment with DROD has been performed and a sample amount of 20 g and size of 30 cm3 has been collected successfully. Finally, the article provides developments for integration of DROD with rovers for future exploration missions and potentials for horizontal drilling for subterranean applications.

Near-infrared signature of hydrothermal opal: a case study of Icelandic silica sinters

Abstract. Silica minerals constitute a main target to assess the origin of life or the possibility of its emergence. On Earth, ancient hydrothermal silica deposits have preserved the oldest forms of life. Beyond Earth, such silica-rich hydrothermal systems have been observed on Mars by orbital near-infrared (NIR) remote sensing and in situ rover exploration. This work investigates the variations of texture and NIR properties of opal with temperature, within a single geological context of hot springs. Silica sinters have been sampled in Icelandic hot-spring fields, in the Reykholt region, and at the Hveravellir site, with water temperature ranging from 14 to 101 ∘C. Variations in the NIR spectral features (concavity ratio criteria, CRC) vary with fluid temperature, lithofacies, and microtexture. Only high-temperature samples display high CRC values (CRC5200>0.85), but low CRC values (CRC5200 < 0.75) are measured for any temperature. Hence, temperature is not the only parameter controlling spectral properties of opal. Several other parameters such as the hydrodynamic context, the microbial activity, silica micro-textures, and porosity may also affect silica precipitation, the incorporation and speciation of water in it, and thus its NIR signature. The observations suggest a limitation in the use of NIR spectral features for the interpretation of the geological context of fossil opal on Earth or Mars: only opal with high CRC values can be inferred as being formed by hydrothermal activity. Low CRC values can be attributed to either low-temperature hydrothermal activity (< 50–60 ∘C) or to continental weathering.

Vision-Based Virtual Simulation Platform for Planetary Rovers

In order to evaluate the feasibility of planetary exploration missions, it is imperative to construct planetary terrain environments on the ground. Nevertheless, the implementation of this method is characterized by time-consuming and challenging factors. By contrast, resorting to simulation approaches represents a cost-effective and high-efficiency alternative, which can facilitate the simulation validation of planetary rover exploration missions in an effective manner. In this paper, a modular planet rover simulation platform is proposed; by building and overlaying multiple feature layers corresponding to the surface of the planet, we realize the simulation of high-resolution fine terrain and through adjusting the terrain parameters to meet the needs of different simulated terrain. The experimental results show that we have built a scene to satisfy the requirements of visual effects and physically realistic characteristics of simulation. Using an improved PatchMatch stereomethod to recover images captured real time by a planetary rover navigation camera in a virtual environment provided more complete three-dimensional terrain data for subsequent simulation validation of local path planning. Finally, a simulation environment that combines high-fidelity visual effects and kinematic characteristics supports visualizing the simulation platform: we propose a path planning method using global planning combined with local obstacle avoidance, and we obtain the optimal path that satisfies the kinematic constraints.

MIT Zero-G outreach initiative: Using experiment design and virtual reality to inspire the next generation of space scientists and engineers

MIT's Space Exploration Initiative offers a course on project development, prototyping, and deployment readiness for parabolic flights, culminating in an annually chartered research flight with Zero-G. MIT's Resource Exploration and Science of our Cosmic Environment (RESOURCE) team participated in the course in the fall of 2021 with a Zero-G flight in May of 2022 testing technology for a virtual reality platform to enable science on Lunar rover exploration missions. In parallel with the scientific effort, the team developed the MIT Zero-G Outreach Initiative (0G-OI), an outreach program to engage with the Cambridge Public School's (CPS) grade 7 classes to teach them about research in microgravity, parabolic flight, and experiment design. The goal of the outreach program is to inspire the next generation of space scientists and engineers using virtual reality.The CPS grade 7 curriculum covers ‘Mysteries of the Universe’ where students consider the role of gravity in the solar system. They also complete a unit on roller coasters in which they learn about key ideas of force, motion, and energy through the context of roller coasters. The 0G-OI Initiative ties these two units together through five videos covering: 1) an overview of the initiative, 2) the basics of parabolic flight and how we perceive gravity, 3) an overview of gravity and its function in the universe, 4) why and what we can study in microgravity and 5) how to design an experiment for microgravity. The students then design their own experiments for microgravity. These are down-selected to the top 5 experiments that are reviewed by an astronaut to select one experiment to fly on the MIT chartered Zero-G parabolic flight. The flight and the experiment are filmed in VR video by the MIT RESOURCE team. Each participating school is provided with an Oculus Quest 2 VR headset and a flight day is held at each school where the students experience the Zero-G flight and see the results of their experiment in an immersive VR environment. Using this initial setup, the 0G-OI can be run annually in parallel with MIT's SEI parabolic flight course.Some key development parameters included keeping the educational videos under 10 min, that having an astronaut select the winning experiment provided incentive and finally, using VR, as this technology is commonly associated with gaming and entertainment. Lessons learned focused on improvements to scheduling and coordination with Zero-G, in-person programming and classroom experience optimization. The 0G-OI aims to develop a lasting relationship with the CPSs and make the exciting experience of parabolic flight and space exploration an accessible experience.

Numerical Simulation of the Lunar Polar Environment: Implications for Rover Exploration Challenge

The lunar polar regions are key areas for future exploration due to the long-term continuous illumination and persistently shadowed regions that can cold trap abundant water and other volatiles. However, the complex terrain, dynamic lighting, and solar wind-induced electric-field environment present multiple challenges for polar investigation and sampling missions. China’s Chang’E-7 (CE-7) will explore the Moon’s south polar region in 2026. One of the scientific goals is to drill samples in a wide area with a rover for in situ analysis. This study analyzes the engineering constraints of the polar illumination condition, slopes, and electric field for landing and sampling-site selection. Then, we create a 3D model of CE-7’s lunar rover in three operating environments by employing the Spacecraft Plasma Interaction Software, with the rover sampling (i) on a flat surface, (ii) in a shadow, and (iii) near a meter-scale crater under different solar altitude angles. The results show that the rover can be charged to different potentials under the combined effects of solar wind incident angles and surrounding terrains. We find that a favorable traversing and/or sampling site of the rover for future polar exploration is in the upwind direction of a bulge (positively elevated terrains, such as the lander or boulders) or crater, which will cause a minimum charging effect on the rover. Our results have important implications for minimizing the risk of charging effects and guiding the lunar polar region exploration.

Numerical analysis of wheel locomotion on soft soil using the extended terramechanics model based on cellular automata

The evaluation of the traveling performance of moon/planetary exploration rovers is the primary aspect of scientific missions and human exploration in space. However, conventional models lack the detailed description of mechanical interaction between the wheels and soft soil. Therefore, in this study, the effectiveness of an extended terramechanics (xTerramechanics) model was investigated by considering the soil deformation actions based on cellular automata for the evaluation of rover traveling performance. First, the results of single-wheel traveling analysis were compared with the experimental results under the forced-slip condition, and it was shown that drawbar-pull and sinkage were represented with good accuracy (mean absolute errors less than 5.5 N and 3.2 mm). Next, we applied the xTerramechanics model under the self-propelled traveling condition at a constant towing load and slope climbing. The model successfully reproduced the well-known “difference in traveling performance depending on traveling conditions.” Furthermore, we used the model for the multibody dynamics analysis of a simple rover, and its applicability to the examination of the overall vehicle performance and multipath effects was demonstrated.

The Curiosity Rover's Exploration of Glen Torridon, Gale Crater, Mars: An Overview of the Campaign and Scientific Results.

The Mars Science Laboratory rover, Curiosity, explored the clay mineral-bearing Glen Torridon region for 1 Martian year between January 2019 and January 2021, including a short campaign onto the Greenheugh pediment. The Glen Torridon campaign sought to characterize the geology of the area, seek evidence of habitable environments, and document the onset of a potentially global climatic transition during the Hesperian era. Curiosity roved 5km in total throughout Glen Torridon, from the Vera Rubin ridge to the northern margin of the Greenheugh pediment. Curiosity acquired samples from 11 drill holes during this campaign and conducted the first Martian thermochemolytic-based organics detection experiment with the Sample Analysis at Mars instrument suite. The lowest elevations within Glen Torridon represent a continuation of lacustrine Murray formation deposits, but overlying widespread cross bedded sandstones indicate an interval of more energetic fluvial environments and prompted the definition of a new stratigraphic formation in the Mount Sharp group called the Carolyn Shoemaker formation. Glen Torridon hosts abundant phyllosilicates yet remains compositionally and mineralogically comparable to the rest of the Mount Sharp group. Glen Torridon samples have a great diversity and abundance of sulfur-bearing organic molecules, which are consistent with the presence of ancient refractory organic matter. The Glen Torridon region experienced heterogeneous diagenesis, with the most striking alteration occurring just below the Siccar Point unconformity at the Greenheugh pediment. Results from the pediment campaign show that the capping sandstone formed within the Stimson Hesperian aeolian sand sea that experienced seasonal variations in wind direction.

An Approach to Science and Risk-Aware Planetary Rover Exploration

This work grapples with the challenge of directing autonomous decision making by planetary rovers conducting science investigations. Most of the related work addresses obstacle avoidance and traversabilty, while less work seeks to directly improve science yield. This research develops a comprehensive approach for planetary rovers that accounts for both science investigation and mobility risk. We present a probabilistic framework that quantifies these two attributes of rover exploration and generates paths that constrain risk while increasing science return. Specifically, science productivity is measured and improved using formal principles from information theory and statistical learning for decision making. Risk is estimated using a probabilistic model that predicts rover wheel slippage based on geometric and semantic information. Our method is evaluated in a simulation study using real Mars surface data that is relevant for both science and terrain investigations. Experimental analysis verifies the effectiveness of our approach.

Ground test technology for the Tianwen-1 Mars Probe

<p indent="0mm">The mission characteristics of Tianwen-1 Mars Probe, and the complicated environment during the entry descent and landing (EDL) and the rover exploration put forward a high demand for ground validation technology. At the research and development stage, in addition to conventional spacecraft tests, many special tests for the mission goals and the Mars environment characteristics are carried out. The adequacy of the ground test ensures the successful implementation of the mission. After the introduction of ground verification requirements, the system-level special test planning, implementation, and test results are thoroughly described. Finally, the ground test methods and test technology of the Tianwen-1 Mars probe are summarized. It has an important reference for future ground verification of deep space landing probes.

Learning State-Variable Relationships in POMCP: A Framework for Mobile Robots.

We address the problem of learning relationships on state variables in Partially Observable Markov Decision Processes (POMDPs) to improve planning performance. Specifically, we focus on Partially Observable Monte Carlo Planning (POMCP) and represent the acquired knowledge with a Markov Random Field (MRF). We propose, in particular, a method for learning these relationships on a robot as POMCP is used to plan future actions. Then, we present an algorithm that deals with cases in which the MRF is used on episodes having unlikely states with respect to the equality relationships represented by the MRF. Our approach acquires information from the agent’s action outcomes to adapt online the MRF if a mismatch is detected between the MRF and the true state. We test this technique on two domains, rocksample, a standard rover exploration task, and a problem of velocity regulation in industrial mobile robotic platforms, showing that the MRF adaptation algorithm improves the planning performance with respect to the standard approach, which does not adapt the MRF online. Finally, a ROS-based architecture is proposed, which allows running the MRF learning, the MRF adaptation, and MRF usage in POMCP on real robotic platforms. In this case, we successfully tested the architecture on a Gazebo simulator of rocksample. A video of the experiments is available in the Supplementary Material, and the code of the ROS-based architecture is available online.

Study on lunar/planetary exploration rovers considering on characteristics of loose soil and its application

Study on lunar/planetary exploration rovers considering on characteristics of loose soil and its application

Development of a New Pressure-Sinkage Model for Rover Wheel-Lunar Soil Interaction based on Dimensional Analysis and Bevameter Tests

A rover is a planetary surface exploration device designed to move across the ground on a planet or a planetary-like body. Exploration rovers are increasingly becoming a vital part of the search for scientific evidence and discoveries on a planetary satellite of the Sun, such as the Moon or Mars. Reliable behavior and predictable locomotion of a rover is important. Understanding soil behavior and its interaction with rover wheels—the terramechanics—is of great importance in rover exploration performance. Up to now, many researchers have adopted Bekker’s semiempirical model to predict rover wheelsoil interaction, which is based on the assumption that soil is deformable when a pressure is applied to it. Despite this basic assumption of the model, the pressure-sinkage relation is not fully understood, and it continues to present challenges for rover designers. This article presents a new pressure-sinkage model based on dimensional analysis (DA) and results of bevameter tests. DA was applied to the test results in order to propose a new pressure-sinkage model by reducing physical quantitative parameters. As part of the work, a new bevameter was designed and built so that it could be successfully used to obtain a proper pressure-sinkage relation of Korean Lunar Soil Simulant (KLS-1). The new pressure-sinkage model was constructed by using three different sizes of flat plate diameters of the bevameter. The newly proposed model was compared successfully with other models for validation purposes.

SegVisRL: development of a robot's neural visuomotor and planning system for lunar exploration

In this paper, we present an approach for the learning of a visuomotor system for a robotic rover using reinforcement learning (RL) within a simulation that combines both proprioceptive and exteroceptive information. With a rising interest in private lunar exploration, compact, power-efficient and cost-efficient rover concepts are becoming numerous. Many of these still use LIDARs for obstacle avoidance, however, using a camera could help achieve a more optimal system. Visual data contains structured information that can be used for understanding texture, localization and object recognition. That said, it is hard to use RL with raw high-resolution visual data due to the dimensional size, with over 6 million inputs in an image alone. By preprocessing the images to be segmented and down sampling to reduce size, we are able to achieve stable learning, and to teach a robot to understand footage to avoid obstacles and reach its goals. This method combines exteroceptive data from the camera and the goal location information along with proprioceptive information, such as the robot”s angular rotation. Moreover, whereas most approaches feed the RL output to a motion controller or trajectory generator, our RL agent is able to directly control the actuator outputs of the rover.

The Lake St. Martin impact structure (Manitoba, Canada): A simulated rover exploration of a sulfate-bearing impact crater

The exploration of Mars can benefit from rover-like exploration of terrestrial analogue sites. We undertook such a study of the Lake St. Martin (LSM) impact structure in Manitoba, Canada. The site consists of intracrater evaporite/gypsum deposits, a granitic impact-melted and -shocked central uplift, carbonate-rich impact melt rocks, and poorly-stratified fluvio-lacustrine conglomerates (“red beds”) that contain clasts of all of these lithologies. LSM may be relevant to Jezero crater landing site on Mars because it is also characterized by intra-crater fluvio-lacustrine activity. Exploration of the site was driven by prioritized science goals and undertaken using, initially, panoramic color imaging of two landing sites from which a heterogeneous science team, consisting of undergraduates and grade 10–12 high school students under the supervision of a senior mentor, selected regions and targets of interest for more detailed investigation and sample triage (in the context of sample return) using close-up imagery, reflectance, and Raman spectroscopy. Targets of interest were subsequently analyzed off-site using X-ray diffractometry, X-ray fluorescence, wet chemistry and additional reflectance and Raman spectroscopy. It was found that reflectance spectroscopy and Raman spectroscopy were complementary because they generally identified different minerals and phases. Reflectance spectra of the surfaces of whole rocks often differed from bulk powders of the same samples in terms of spectral influence of Fe oxyhydroxides, overall reflectance, and absorption band depths. Powdering of samples generally reduced the spectral contributions of the weathered surface and Fe oxyhydroxide grain coatings, allowing the identity of the “bulk rock” to be better determined. Raman spectra of powdered bulk samples were often able to identify one or more specific mineral phases, but induced fluorescence reduced the number of identifiable Raman peaks. The deployment also provided valuable operational experience for current and next-generation planetary researchers. Evidence consistent with impact cratering and associated hydrothermal alteration was suggested by the field data. Overall, the deployment demonstrated that multiple analytical techniques are highly complementary in exploring and characterizing an impact crater hosting evaporites, conglomerates, and impact melt/shock products.

Evidence for a Diagenetic Origin of Vera Rubin Ridge, Gale Crater, Mars: Summary and Synthesis of Curiosity's Exploration Campaign.

This paper provides an overview of the Curiosity rover's exploration at Vera Rubin ridge (VRR) and summarizes the science results. VRR is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mount Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray‐colored patches concentrated toward the upper elevations of VRR, and these gray patches also contain small, dark Fe‐rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric‐related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars' rock record.

A simulated rover exploration of a long-lived hypersaline spring environment: The East German Creek (MB, Canada) Mars analogue site

We undertook a Mars rover-like deployment at a terrestrial analogue site consisting of active and relict perennial hypersaline springs at the East German Creek site in west-central Manitoba, Canada. This site serves as an analogue for possible long-lived springs on Mars. The deployment consisted of landing site-type investigations involving panoramic imagery from which regions of interest and targets of interest were selected for subsequent analysis by close-up imagery, and reflectance and Raman spectroscopy. These data were then used to prioritize samples for caching in the context of sample return. It was found that reflectance spectroscopy and Raman spectroscopy were complementary because they generally identified different minerals and phases. Reflectance spectra of the surfaces of whole rocks often differed from bulk powders of the same samples. Powdering of samples generally reduced the spectral contributions of the surface and grain coatings, allowing the identity of the “bulk rock” to be better determined. Raman spectra of powdered bulk samples were generally featureless due to induced fluorescence. Both spectroscopic techniques were equally effective at detecting biology at the site (cyanobacteria/chlorophyll). Biological activity could also be inferred from the crenulated texture of cyanobacterial mats. Post-deployment analysis of the samples was used to confirm and expand mineral identities, largely by X-ray diffraction (XRD) and elemental analysis. Mineral abundances, presence of phases undetectable by spectroscopy and XRD, and the pervasive presence of Fe oxyhydroxides could be addressed by X-ray fluorescence and wet chemistry. The deployment also provided valuable operational experience for current and next-generation planetary researchers. Overall, the results suggest that multiple analytical techniques, being the XRD, XRF, reflectance and Raman spectroscopy are highly complementary in exploring and characterizing a biology-hosting hypersaline springs environment. This work provides a framework for the value of different instruments for exploring similar sites on Mars, as the instrument from our field campaign have equivalents on the Perseverance and Rosalind Franklin rovers.