Lidar systems for precision navigation and safe landing on planetary bodies

The ability of lidar technology to provide three-dimensional elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of robotic and manned vehicles with a high degree of precision. Currently, NASAis developing novel lidar sensors aimed at the needs of future planetary landing missions.These lidar sensors are a 3-Dimensional Imaging Flash Lidar, a Doppler Lidar, and a Laser Altimeter. The Flash Lidar is capable of generating elevation maps of theterrain toindicate hazardous features such as rocks, craters, and steep slopes. The elevation maps, which arecollected during the approach phase of a landing vehicle from about 1 km above the ground, can be used to determine the most suitable safe landing site. The Doppler Lidar provides highly accurate ground relative velocity and distance data thusenablingprecision navigation to the landing site. Our Doppler lidar utilizes three laser beams that are pointed indifferent directions to measure line-of-sight velocities and ranges to the ground from altitudes of over 2 km.Starting at altitudes of about 20km and throughout the landing trajectory,the Laser Altimeter can provide very accurate ground relative altitude measurements that are used to improve the vehicle position knowledge obtained from the vehicle'snavigation system. Betweenaltitudesof approximately 15 km and 10 km, either the Laser Altimeter or the Flash Lidar can be used to generate contour maps of the terrain, identifying known surface features such as craters to perform Terrain relative Navigation thus further reducing the vehicle's relative position error. This paper describes the operational capabilities of each lidar sensorand provides a status of their development.