A coherent Doppler lidar has been developed by NASA for providing vector velocity and altitude data to landing vehicles. Future robotic and manned missions to planetary bodies demand precise ground-relative velocity and altitude data to execute complex descent maneuvers for safe, soft and pinpoint 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. The capabilities of NDL were recently demonstrated on the first commercial lunar landing mission. This paper describes the development of NDL for spaceflights, explains its operation onboard landing vehicles, and highlights the results of its recent lunar landing mission.
Amzajerdian et al. (Thu,) studied this question.