Lunar Terrain Vehicle (LTV) Remote Teleoperation Studies Under Four Lunar Communication Latencies

Remotely operating a lunar rover from Earth while subject to an Earth-Moon time delay of multiple seconds could result in a dangerous state where the vehicle is either damaged or lost. Providing the right capabilities to the remote operator to manage inherent communication latencies will be important for remote driving to be successful. NASA conducted two studies to investigate the average speed and number of kilometers per day that an operator on Earth could teleoperate a notional Artemis unpressurized rover with minimal remote operator capabilities under 0, 4, 6 and 8-second communication delay. The primary goal of these studies was to understand if an Artemis Lunar Terrain Vehicle (L TV) could cover 6 kilometers (km) in 24 hours when operated remotely. During the April 2023 evaluation, operators used an in-house simulation of the lunar surface South Pole to teleoperate a NASA government reference LTV. Operators viewed the surrounding terrain via a single, rover mast-mounted, high-resolution camera with pan/tilt/zoom capabilities; continuous communication was provided throughout all testing. Additions in the August 2023 evaluation provided remote operators with an operator-selected rate limiter to enable finer sensitivity in the hand controller and a predictive circle function to better assist operators with predicting the path the vehicle could take. All operators were able to successfully navigate and drive through six different types of terrain and five planned traverse scenarios using natural lighting under all communication delays. Results for average speeds for each communication delay was computed then used to derive the total time needed to cover 6, 8, and 20 km. Generally, remote operators drove slower when subjected to a communication latency. Subjective workload assessments revealed that while operating in a latency the overall workload significantly increased with mental demand, frustration, and performance being the primary contributing factors. Driving strategies in the 0-s delay did not vary significantly among operators; however, in the 4-s delay condition, three different driving strategies were identified. Differences in the 6-s and 8-s latency conditions indicated the operators use of the cruise control to maintain speed was more apparent. Operators started to define more specific parameters in driving strategies for general operations. This consisted of setting the vehicle into a low-speed cruise mode of approximately 1-1.5 kilometers per hour (kph). Operators noticed driving performance of the vehicle seemed to be much harder at slower speeds 0.4-0.8 kph; however, the vehicle was more responsive at speeds of 2.9-3.6 kph. Regardless of communication delay, operators used both the horizontal translation rails and the vehicle fenders as guides to predict a path for the vehicle through heavily concentrated terrain features. Additionally, operators took advantage of the predictive circle indicator on the navigation display and over 95% of the operator's navigation used the mast camera 180-degree panning function for ground truthing in terms of boulders and craters. These studies provided a “first-look” answer to a potential system requirement; however, considerable general knowledge was gained to begin to understand what it will take to make a successful lunar rover teleoperation mission.