Liam Pedersen

Mission planning and target tracking for autonomous instrument placement

Future planetary rover missions, such as the upcoming Mars Science Laboratory, will require rovers to autonomously navigate to science targets specified from up to 10 meters away, and to place instruments against these targets with up to 1 centimeter precision. The current state of the art, demonstrated by the Mars Exploration Rover (MER) mission, typically requires three sols (Martian days) for approach and placement, with several communication cycles between the rovers and ground operations. The capability for goal level commanding of a rover to visit multiple science targets in a single sol represents a tenfold increase in productivity, and decreases daily operations costs. Such a capability requires a high degree of robotic autonomy: visual target tracking and navigation for the rover to approach the targets, mission planning for determining the most beneficial course of action given a large set of desired goals in the face of uncertainty, and robust execution for coping with variations in time and power consumption, as well as the possibility of failures in tracking or navigation due to occlusion or unexpected obstacles. We have developed a system that provides these features. The system uses a vision-based target tracker that recovers the 6-DOF transformations between the rover and the tracked targets as the rover moves, and an off-board planner that creates plans that are carried out on an on-board robust executive. The tracker comprises a feature based approach that tracks a set of interest points in 3D using stereo, with a shape based approach that registers dense 3D meshes. The off-board planner, in addition to generating a primary activity sequence, creates a large set of contingent, or alternate plans to deal with anticipated failures in tracking and the uncertainty in resource consumption. This paper describes our tracking and planning systems, including the results of experiments carried out using the K9 rover. These systems are part of a larger effort, which includes tools for target specification in 3D, ground-based simulation and plan verification, round-trip data tracking, rover software and hardware, and scientific visualization. The complete system has been shown to provide the capability of multiple instrument placements on rocks within a 10 meter radius, all within a single command cycle.

Autonomy in Space Exploration: Current Capabilities and Future Challenges

Deep space exploration requires vehicles with appropriate autonomous capabilities. In order to accomplish their missions, spacecraft need to respond to potential hazards while seeking to expand human knowledge of deep space. This paper provides an overview of the role of autonomy for space exploration. First, we explore the range of autonomous behavior that is useful in space exploration. Second, three core requirements are defined for autonomous space systems. Fourth, we identify the decision-making capabilities that will ensure the effectiveness and safety of autonomous systems. Fifth, we describe architectures for integrating capabilities into an autonomous system. Finally, we discuss the challenges that are faced currently in developing and deploying autonomy technologies for space.

Terrain model registration for single cycle instrument placement

This paper presents an efficient and robust method for registration of terrain models created using stereovision on a planetary rover. Our approach projects two surface models into a virtual depth map, rendering the models, as they would be seen from a single range sensor. Correspondence is established based on which points project to the same location in the virtual range sensor. A robust norm of the deviations in observed depth is used as the objective function, and the algorithm searches for the rigid transformation, which minimizes the norm. An initial coarse search is done using rover pose information from odometry and orientation sensing. A fine search is done using Levenberg-Marquardt. Our method enables a planetary rover to keep track of designated science targets as it moves, and to hand off targets from one set of stereo cameras to another. These capabilities are essential for the rover to autonomously approach a science target and place an instrument in contact in a single command cycle.

Combined feature based and shape based visual tracker for robot navigation

We have developed a combined feature based and shape based visual tracking system designed to enable a planetary rover to visually track and servo to specific points chosen by a user with centimeter precision. The feature based tracker uses invariant feature detection and matching across a stereo pair, as well as matching pairs before and after robot movement in order to compute an incremental 6-DOF motion at each tracker update. This tracking method is subject to drift over time, which can be compensated by the shape based method. The shape based tracking method consists of 3D model registration, which recovers 6-DOF motion given sufficient shape and proper initialization. By integrating complementary algorithms, the combined tracker leverages the efficiency and robustness of feature based methods with the precision and accuracy of model registration. In this paper, we present the algorithms and their integration into a combined visual tracking system.

Autonomy in Space: Current Capabilities and Future Challenge

This article provides an overview of the nature and role of autonomy for space exploration, with a bias in focus towards describing the relevance of AI technologies. It explores the range of autonomous behavior that is relevant and useful in space exploration and illustrates the range of possible behaviors by presenting four case studies in space-exploration systems, each differing from the others in the degree of autonomy exemplified. Three core requirements are defined for autonomous space systems, and the architectures for integrating capabilities into an autonomous system are described. The article concludes with a discussion of the challenges that are faced currently in developing and deploying autonomy technologies for space.

Instrument deployment for Mars Rovers

Future Mars rovers, such as the planned 2009 MSL rover, require sufficient autonomy to robustly approach rock targets and place an instrument in contact with them. It took the 1997 Sojourner Mars rover between 3 and 5 communications cycles to accomplish this. This paper describes the NASA Ames approach to robustly accomplishing single cycle instrument deployment, using the K9 prototype Mars rover. An off-board 3D site model is used to select science targets for the rover. K9 navigates to targets using deduced reckoning, and autonomously assesses the target area to determine where to place an arm mounted microscopic camera. Onboard K9 is a resource cognizant conditional executive, which extends the complexity and duration of operations that a can be accomplished without intervention from mission control.

Performance Evaluation of Handoff for Instrument Placement

[Abstract] Single Cycle Instrument Placement (SCIP), the ability to autonomously approach rocks and place contact instruments within 1cm of selected features, has been identified as a high priority for increasing the efficiency and science return for planetary rover surface operations. Because of imprecise localization, it is necessary for a rover to visually keep track of targets, using images from onboard stereo cameras, as the rover navigates to them. “Handoff” is the problem of matching a tracked point in one camera to the corresponding point in another camera pair. Handoff facilitates visual tracking of a point using multiple camera pairs, allowing at any time the choice of camera pair with the best view of the portion of the scene that is of interest. A significant fraction of the tracking error budget is due to handoff. In this paper, we review several methods for solving what we refer to as the handoff problem and evaluate their performance in the context of integrated planetary rover test beds analogous to the MER Spirit and Opportunity vehicles.

Planetary LakeLander-A Robotic Sentinel to Monitor Remote Lakes

This field report describes the design and operations of the Planetary LakeLander PLL probe and its ground data systems. LakeLanders primary mission is to characterize the physical, chemical, and biological processes occurring in a high-altitude lake, and how they are being impacted by rapid deglaciation. LakeLanders secondary purpose is to test operation concepts for future exploration of Titans lakes. The LakeLander probe is a permanently anchored buoy that measures both surface meteorology and water quality parameters in the top 40i¾?m of the water column. The concept of operations calls for the probe to continue collecting and downlinking data through the Andean winter, when the lake is inaccessible; this drives the power system design and forces a strong focus on system reliability, analogous to a space mission. The PLL ground data system provides the central archive of downlinked data. They are structured around a unified data-sharing web site that includes tools for mapping, data visualization, documentation, and numerical analysis. The web site provides a hub for engaging the science team and enables interdisciplinary collaboration. This report concludes with lessons learned during field deployment and several months of remote operations on the lake. Among the conclusions: 1 the choice to use an off-the-shelf profiling system has proven wise; 2 effective maintenance of a long-lived remote system requires extensive measurement, logging, and display of as many system variables as possible; and 3 the visualization sandbox component of the data-sharing web site has made numerical analysis of probe data much easier and more accessible to the entire interdisciplinary science team.

Inspection with Robotic Microscopic Imaging

Future Mars rover missions will require more advanced onboard autonomy for increased scientific productivity and reduced mission operations cost. One such form of autonomy can be achieved by targeting precise science measurements to be made in a single command uplink cycle. In this paper we present an overview of our solution to the subproblems of navigating a rover into place for microscopic imaging, mapping an instrument target point selected by an operator using far away science camera images to close up hazard camera images, verifying the safety of placing a contact instrument on a sample or finding nearby safe points, and analyzing the data that comes back from the rover. The system developed includes portions used in the Multiple Target Single Cycle Instrument Placement demonstration at NASA Ames in October 2004, and portions of the MI Toolkit delivered to the Athena Microscopic Imager Instrument Team for the MER mission still operating on Mars today. Some of the component technologies are also under consideration for MSL mission infusion.