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.