The Navigation Doppler Lidar (NDL) is used during the phase of Entry Descent and Landing (EDL) in which terrain-relative decisions and final preparations for landing are made. Lander maneuvers include vehicle reorientation to facilitate surface relative sensing, using propulsion to divert away from sensed hazards, or navigate to designated landing site. During EDL, precise knowledge of the spacecraft state, as well as the properties of the landing area, are critically important. An innovative NDL is proposed that significantly reduces power, mass, and volume, while improving system performance, meeting or exceeding requirements for precision GN&C. The proposed innovation fuses a high power capable electro-optic system-on-chip into the NDL fiber lidar network to create a unique lidar ideally suited for ranging and 3-axis velocimetry. Additionally, more options are available in terms of telescope mounting, redundancy, and sensor measurement availability during different stages of a landing trajectory.
The NDL is one of several sensors base-lined at NASA for lander GN&C subsystems, as it shows great promise to aide in navigation of the vehicle autonomously to lunar touchdown. The significant innovative advances proposed here reduce size, mass, and power, increase sensitivity, and offers more options that will cover a wider range of vehicles and trajectories. The compactness also opens possibilities for applications in rendezvous and docking, or small lunar hoppers.
The reduced size and increased efficiency of the proposed architecture will also offer a reduction in cost and an increase in reliability. For those reasons, commercial lunar landers will benefit from this development. On earth, the new architecture opens many possibilities and applications in autonomous navigation of air and land vehicles, for the consumer and for the military.