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Development of a fiber-based Doppler LiDAR sensor for autonomous vehicles (Conference Presentation)

This paper describes a coherent Doppler lidar developed by NASA to address a need for a high-performance, compact, and cost-effective velocity and altitude sensor onboard its landing vehicles. Future robotic and manned missions to solar system bodies require precise ground-relative velocity vector and altitude data to execute complex descent maneuvers and soft landing at a pre-designated site. This lidar sensor, referred to as Navigation Doppler Lidar (NDL), transmits three laser beams at different pointing angles toward the ground and measures range and velocity along each beam using a frequency modulated continuous wave (FMCW) technique. The three line-of-sight measurements are then combined in order to determine the three components of the vehicle velocity vector and its altitude relative to the ground with about 2 cm/sec and 2 meters precision, respectively, dominated by the vehicle motion. The NDL can also benefit terrestrial aerial vehicles that cannot rely on GPS for position and velocity data. The NDL offers a viable option for enabling aircraft operation in areas where the GPS signal can be blocked or jammed by intentional or unintentional interference. A modified version of the NDL incorporating a beam steering device can produce 3-dimensional range and Doppler images that are critical for safe andefficient operation of autonomous ground vehicles. This paper describes the design of the NDL and its capabilities as demonstrated through extensive ground tests and flight tests onboard helicopters and autonomous rocket-powered vehicles. Then, the utilization of the NDL technologies for terrestrial vehicles will be discussed.