Field testing of a rover guidance, navigation, and control architecture to support a ground-ice prospecting mission to Mars

This paper provides an overview of a rover guidance, navigation, and control (GN&C) architecture being developed to support a ground-ice prospecting mission to Mars. The main contribution of this paper is to detail an integrated field campaign that demonstrates the viability of the key rover GN&C techniques needed to carry out this mission. Tests were conducted on Devon Island in the Canadian High Arctic during the summer of 2009, wherein a large field robot was driven on real polygonal terrain (a landform of interest on Mars). Lessons learned and recommendations for future work are provided.     

Working the Martian night shift - the MER surface operations process

The Mars exploration rover mission has conducted continuous Mars surface operations for over 24 months to date. The operations processes and tools put in place before landing have continued to develop throughout the surface mission, evolving from a capability intended to operate for less than four months to one capable of continuing indefinitely. The MER operations design has been accepted as baseline for the Mars Science Laboratory mission, scheduled for launch in 2009. Our experiences during MER's exciting and unexpectedly extensive surface exploration phase may provide useful insights for other future long duration surface missions.     

Mars Pathfinder Microrover

When the Mars Pathfinder (MPF) spacecraft lands on Mars, the Microrover Flight Experiment (MFEX) will be deployed and perform its mission to conduct technology experiments verifying the engineering design, to deploy an alpha proton x-ray spectrometer (APXS) to measure elemental properties of rocks and soil, and to image the MPF lander. In accomplishing this mission the MFEX rover must determine a safe path to goal locations traversing over a poorly known Martian surface. The rover does this mission with a capable mobile platform executing on-board autonomous functions of navigation and hazard avoidance. In this paper we describe the rover, its operational environment and the implementation of the on-board autonomous functions.     

Mars microrover navigation: Performance evaluation and enhancement

In 1996, NASA will launch the Mars Pathfinder spacecraft, which will carry an 11 kg rover to explore the immediate vicinity of the lander. To assess the capabilities of the rover, as well as to set priorities for future rover research, it is essential to evaluate the performance of its autonomous navigation system as a function of terrain characteristics. Unfortunately, very little of this kind of evaluation has been done, for either planetary rovers or terrestrial applications. To fill this gap, we have constructed a new microrover testbed consisting of the Rocky 3.2 vehicle and an indoor test arena with overhead cameras for automatic, real-time tracking of the true rover position and heading. We create Mars analog terrains in this arena by randomly distributing rocks according to an exponential model of Mars rock size frequency created from Viking lander imagery. To date, we have recorded detailed logs from over 85 navigation trials in this testbed. In this paper, we outline current plans for Mars exploration over the next decade, summarize the design of the lander and rover for the 1996 Pathfinder mission, and introduce a decomposition of rover navigation into four major functions: goal designation, rover localization, hazard detection, and path selection. We then describe the Pathfinder approach to each function, present results to date of evaluating the performance of each function, and outline our approach to enhancing performance for future missions. The results show key limitations in the quality of rover localization, the speed of hazard detection, and the ability of behavior control algorithms for path selection to negotiate the rock frequencies likely to be encountered on Mars. We believe that the facilities, methodologies, and to some extent the specific performance results presented here will provide valuable examples for efforts to evaluate robotic vehicle performance in other applications.     

Self‐reliant rovers for increased mission productivity

Achieving consistently high levels of productivity has been a challenge for Mars surface missions. While the rovers have made major discoveries and dramatically increased our understanding of Mars, they require a great deal of interaction from the operations teams, and achieving mission objectives can take longer than anticipated when productivity is paced by the ground teams' ability to react. We have conducted a project to explore technologies and techniques for creating self‐reliant rovers (SRR): rovers that are able to maintain high levels of productivity with reduced reliance on ground interactions. This paper describes the design of SRR and a prototype implementation that we deployed on a research rover. We evaluated the system by conducting a simulated campaign in which members of the Mars Science Laboratory (Curiosity rover) science team used our rover to explore a geographical region. The evaluation demonstrated the system's ability to maintain high levels of productivity with limited communication with operators.     

The collaborative information portal and NASA's Mars Rover mission

NASA Ames Research Center and the Jet Propulsion Laboratory jointly developed the collaborative information portal for NASA's Mars exploration rover mission. Mission managers, engineers, scientists, and researchers used this Internet-based enterprise software application to view current staffing and event schedules, download data and image files generated by the rovers, send and receive broadcast messages, and get accurate times in various Mars and Earth time zones. This article describes the application's features, architecture, and implementation, and conveys the lessons learned from its deployment.     

Review: The Benefits and Applications of Bioinspired Flight Capabilities

This paper addresses the challenges of flight on Mars that at this time have the same element of novelty as flight on Earth itself was a novelty in the Kitty Hawk era almost 100 years ago, details the scientific need for such flyers, highlights the bioinspired engineering of exploration systems (BEES) flyer development and finally describes a few viable mission architecture options that allow reliable data return from the BEES flyers using the limited telecom infrastructure that can be made available with a lander base to orbiter combination on Mars. Our recent developments using inspiration from biology that are enabling the pathway to demonstrate flight capability for Mars exploration are described. These developments hold substantial spin‐offs for a variety of applications both for NASA and DoD. Unmanned exploration to date suggests that Mars once had abundant liquid water (considered essential for life as we know it). It is not clear what transpired on the Martian climate to have turned the planet into the desert that it is today. Developing a comprehensive understanding of the past and present climatic events for Mars may provide important information relevant to the future of our own planet. Such exploration missions are enabled using the BEES technology. © 2003 Wiley Periodicals, Inc.     

Efficient autonomous navigation for planetary rovers with limited resources

Rovers operating on Mars require more and more autonomous features to fulfill their challenging mission requirements. However, the inherent constraints of space systems render the implementation of complex algorithms an expensive and difficult task. In this paper, we propose an architecture for autonomous navigation. Efficient implementations of autonomous features are built on top of the ExoMars path following navigation approach to enhance the safety and traversing capabilities of the rover. These features allow the rover to detect and avoid hazards and perform significantly longer traverses planned by operators on the ground. The efficient navigation approach has been implemented and tested during field test campaigns on a planetary analogue terrain. The experiments evaluated the proposed architecture by autonomously completing several traverses of variable lengths while avoiding hazards. The approach relies only on the optical Localization Cameras stereo bench, a sensor that is found in all current rovers, and potentially allows for computationally inexpensive long‐range autonomous navigation in terrains of medium difficulty.     

Distributed Control of Multi-Robot Systems Engaged in Tightly Coupled Tasks

NASA mission concepts for the upcoming decades of this century include exploration of sites such as steep cliff faces on Mars, as well as infrastructure deployment for a sustained robotic/manned presence on planetary and/or the lunar surface. Single robotic platforms, such as the Sojourner rover successfully flown in 1997 and the Mars Exploration Rovers (MER) which landed on Mars in January of 2004, have neither the autonomy, mobility, nor manipulation capabilities for such ambitious undertakings. One possible approach to these future missions is the fielding of cooperative multi-robot systems that have the required onboard control algorithms to more or less autonomously perform tightly coordinated tasks. These control algorithms must operate under the constrained mass, volume, processing, and communication conditions that are present on NASA planetary surface rover systems. In this paper, we describe the design and implementation of distributed control algorithms that build on our earlier development of an enabling architecture called CAMPOUT (Control Architecture for Multi-robot Planetary Outposts). We also report on some ongoing physical experiments in tightly coupled distributed control at the Jet Propulsion Lab in Pasadena, CA where in the first study two rovers acquire and carry an extended payload over uneven, natural terrain, and in the second three rovers form a team for cliff access.     

Improved Rover State Estimation in Challenging Terrain

Given ambitious mission objectives and long delay times between command-uplink/data-downlink sessions, increased autonomy is required for planetary rovers. Specifically, NASA's planned 2003 and 2005 Mars rover missions must incorporate increased autonomy if their desired mission goals are to be realized. Increased autonomy, including autonomous path planning and navigation to user designated goals, relies on good quality estimates of the rover's state, e.g., its position and orientation relative to some initial reference frame. The challenging terrain over which the rover will necessarily traverse tends to seriously degrade a dead-reckoned state estimate, given severe wheel slip and/or interaction with obstacles. In this paper, we present the implementation of a complete rover navigation system. First, the system is able to adaptively construct semi-sparse terrain maps based on the current ground texture and distances to possible nearby obstacles. Second, the rover is able to match successively constructed terrain maps to obtain a vision-based state estimate which can then be fused with wheel odometry to obtain a much improved state estimate. Finally the rover makes use of this state estimate to perform autonomous real-time path planning and navigation to user designated goals. Reactive obstacle avoidance is also implemented for roaming in an environment in the absence of a user designated goal. The system is demonstrated in soft soil and relatively dense rock fields, achieving state estimates that are significantly improved with respect to dead reckoning alone (e.g., 0.38 m mean absolute error vs. 1.34 m), and successfully navigating in multiple trials to user designated goals.     

Perception‐aware autonomous mast motion planning for planetary exploration rovers

Highly accurate real‐time localization is of fundamental importance for the safety and efficiency of planetary rovers exploring the surface of Mars. Mars rover operations rely on vision‐based systems to avoid hazards as well as plan safe routes. However, vision‐based systems operate on the assumption that sufficient visual texture is visible in the scene. This poses a challenge for vision‐based navigation on Mars where regions lacking visual texture are prevalent. To overcome this, we make use of the ability of the rover to actively steer the visual sensor to improve fault tolerance and maximize the perception performance. This paper answers the question of where and when to look by presenting a method for predicting the sensor trajectory that maximizes the localization performance of the rover. This is accomplished by an online assessment of possible trajectories using synthetic, future camera views created from previous observations of the scene. The proposed trajectories are quantified and chosen based on the expected localization performance. In this study, we validate the proposed method in field experiments at the Jet Propulsion Laboratory (JPL) Mars Yard. Furthermore, multiple performance metrics are identified and evaluated for reducing the overall runtime of the algorithm. We show how actively steering the perception system increases the localization accuracy compared with traditional fixed‐sensor configurations.     

Planetary Rover Developments Supporting Mars Exploration, Sample Return and Future Human-Robotic Colonization

We overview our recent research on planetary mobility. Products of this effort include the Field Integrated Design & Operations rover (FIDO), Sample Return Rover (SRR), reconfigurable rover units that function as an All Terrain Explorer (ATE), and a multi-Robot Work Crew of closely cooperating rovers (RWC). FIDO rover is an advanced technology prototype; its design and field testing support NASA's development of long range, in situ Mars surface science missions. Complementing this, SRR implements autonomous visual recognition, navigation, rendezvous, and manipulation functions enabling small object pick-up, handling, and precision terminal docking to a Mars ascent vehicle for future Mars Sample Return. ATE implements on-board reconfiguration of rover geometry and control for adaptive response to adverse and changing terrain, e.g., traversal of steep, sandy slopes. RWC implements coordinated control of two rovers under closed loop kinematics and force constraints, e.g., transport of large payloads, as would occur in robotic colonies at future Mars outposts. RWC is based in a new extensible architecture for decentralized control of, and collective state estimation by multiple heterogeneous robotic platforms—CAMPOUT; we overview the key architectural features. We have conducted experiments with all these new rover system concepts over variable natural terrain. For each of the above developments, we summarize our approach, some of our key experimental results to date, and our future directions of planned development.     

Mars exploration rover surface operations: driving opportunity at Meridiani Planum

Since landing on the Meridiani Planum region of Mars in January 2004, the Mars exploration rover (MER) vehicle named Opportunity has been sending back pictures taken from several different craters that would provide evidence that the region did indeed have a watery past. This paper details the experience of driving Opportunity through this alien landscape during its first 400 days on Mars, from the point of view of the other rover planners, the people who tell the rover where to drive and how to use its robotic arm.     

Mars exploration rover mobility development

The Mars Exploration Rover (MER) Project was launched in mid-2000 to land two mobile exploration platforms at different science targets on the red planet. The centerpiece of each mission is the rover and its scientific payload. Spirit and Opportunity are identical vehicles, and each carries the same science payload and engineering subsystems. NASA's current Mars program is once again focused on missions to the Martian surface to answer fundamental questions of the extent Mars ever supported a liquid water environment on its surface, and hence the planet's ability to have sustained life.     

Mars Science Laboratory Curiosity Rover Megaripple Crossings up to Sol 710 in Gale Crater

After landing in Gale Crater on August 6, 2012, the Mars Science Laboratory Curiosity rover traveled across regolith‐covered, rock‐strewn plains that transitioned into terrains that have been variably eroded, with valleys partially filled with windblown sands, and intervening plateaus capped by well‐cemented sandstones that have been fractured and shaped by wind into outcrops with numerous sharp rock surfaces. Wheel punctures and tears caused by sharp rocks while traversing the plateaus led to directing the rover to traverse in valleys where sands would cushion wheel loads. This required driving across a megaripple (windblown, sand‐sized deposit covered by coarser grains) that straddles a narrow gap and several extensive megaripple deposits that accumulated in low portions of valleys. Traverses across megaripple deposits led to mobility difficulties, with sinkage values up to approximately 30% of the 0.50 m wheel diameter, resultant high compaction resistances, and rover‐based slip up to 77%. Analysis of imaging and engineering data collected during traverses across megaripples for the first 710 sols (Mars days) of the mission, laboratory‐based single‐wheel soil experiments, full‐scale rover tests at the Dumont Dunes, Mojave Desert, California, and numerical simulations show that a combination of material properties and megaripple geometries explain the high wheel sinkage and slip events. Extensive megaripple deposits have subsequently been avoided and instead traverses have been implemented across terrains covered with regolith or thin windblown sand covers and megaripples separated by bedrock exposures.     

Introducing a globally consistent orbital‐based localization system

In spite of the good performance of space exploratory missions, open issues still await to be solved. In autonomous or composite semi‐autonomous exploration of planetary land surfaces, rover localization is such an issue. The rovers of these missions (e.g., the MER and MSL) navigate relatively to their landing spot, ignoring their exact position on the coordinate system defined for the celestial body they explore. However, future advanced missions, like the Mars Sample Return, will require the localization of rovers on a global frame rather than the arbitrarily defined landing frame. In this paper we attempt to retrieve the absolute rover's location by identifying matching Regions of Interest (ROIs) between orbital and land images. In particular, we propose a system comprising two parts, an offline and an onboard one, which functions as follows: in advance of the mission a Global ROI Network (GN) is built offline by investigating the satellite images near the predicted touchdown ellipse, while during the mission a Local ROI Network (LN) is constructed counting on the images acquired by the vision system of the rover along its traverse. The last procedure relies on the accurate VO‐based relative rover localization. The LN is then paired with the GN through a modified 2D DARCES algorithm. The system has been assessed on real data collected by the ESA at the Atacama desert. The results demonstrate the system's potential to perform absolute localization, on condition that the area includes discriminative ROIs. The main contribution of this work is the enablement of global localization performed on contemporary rovers without requiring any additional hardware, such as long range LIDARs.     

火星车沉陷机理与脱困策略研究

以“祝融号”火星车为研究对象,基于车辆地面力学理论分析了火星车发生沉陷的机理,基于滑转率、电流、沉陷深度等给出沉陷判别方法,制定了不同条件下“祝融号”火星车的沉陷判别准则及脱困策略。验证试验结果表明：临界沉陷时滑转率为61.25%、驱动电流为1.90 A,达到沉陷临界值后“祝融号”火星车将无法直接驶离,而“祝融号”火星车主动悬架的蠕动是实现脱困的有效方法。研究成果可为“祝融号”火星车在轨使用策略提供试验数据和参考。     

Driving on Mars with RSVP

The rover sequencing and visualization program (RSVP) suite of tools has been a critical factor in the success of the Mars exploration rover (MER) missions. It would be impossible to prepare the large command loads each sol without the capabilities that it possesses. It has proven to be robust and easy to use and capable of answering key questions about sequence validity and constraints. Certainly, training is required to use RSVP, but this is primarily in the general area of command sequencing and rover operations. Once these concepts are understood, RSVP feels natural for building sequences. RSVP has met its prime requirements of supporting rapid assimilation and understanding of the terrain and operational constraints, rapid sequence generation and validation, and production of documentation and archival products. This can be seen in the very limited number of sols lost due to errors in the command sequences. The success of the MER mission and the tremendous amount of science data collected attest to the capability of RSVP.     

Seeker—Autonomous Long‐range Rover Navigation for Remote Exploration

Under the umbrella of the European Space Agency (ESA) StarTiger program, a rapid prototyping study called Seeker was initiated. A range of partners from space and nonspace sectors were brought together to develop a prototype Mars rover system capable of autonomously exploring several kilometers of highly representative Mars terrain over a three‐day period. This paper reports on our approach and the final field trials that took place in the Atacama Desert, Chile. Long‐range navigation and the associated remote rover field trials are a new departure for ESA, and this activity therefore represents a novel initiative in this area. The primary focus was to determine if current computer vision and artificial intelligence based software could enable such a capability on Mars, given the current limit of around 200 m per Martian day. The paper does not seek to introduce new theoretical techniques or compare various approaches, but it offers a unique perspective on their behavior in a highly representative environment. The final system autonomously navigated 5.05 km in highly representative terrain during one day. This work is part of a wider effort to achieve a step change in autonomous capability for future Mars/lunar exploration rover platforms.     

LUNARES: lunar crater exploration with heterogeneous multi robot systems

The LUNARES (Lunar Crater Exploration Scenario) project emulates the retrieval of a scientific sample from within a permanently shadowed lunar crater by means of a heterogeneous robotic system. For the accomplished earth demonstration scenario, the Shakelton crater at the lunar south pole is taken as reference. In the areas of permanent darkness within this crater, samples of scientific interest are expected. For accomplishment of such kind of mission, an approach of a heterogeneous robotic team consisting of a wheeled rover, a legged scout as well as a robotic arm mounted on the landing unit was chosen. All robots act as a team to reach the mission goal. To prove the feasibility of the chosen approach, an artificial lunar crater environment has been established to test and demonstrate the capabilities of the robotic systems. Figure 1 depicts the systems in the artificial crater environment. For LUNARES, preexisting robots were used and modified were needed in order to integrate all subsystems into a common system control. A ground control station has been developed considering conditions of a real mission, requiring information of autonomous task execution and remote controlled operations to be displayed for human operators. The project successfully finished at the end of 2009. This paper reviews the achievements and lessons learned during the project.