The NDL is used during terminal descent; this is the phase of EDL in which terrain-relative decisions and final preparations for landing are made. During terminal descent, lander maneuvers include vehicle reorientation to facilitate surface relative sensing and using propulsion to divert away from hazards. During EDL, precise knowledge of the spacecraft state, as well as the properties of the landing area, are critically important.
The NDL directly measures radial velocity and line of sight distance, providing precise knowledge of the vehicle state estimates relative to the landing surface. The unprecedented velocity accuracy provided by the NDL is due to the continuous wave (CW) lidar waveform. As such, the only way to obtain distance measurements is to modulate the waveform. The Linear frequency modulation continuous wave (FMCW) waveform employed provides distance measurements without compromising the accuracy of the velocity measurements.
We propose an innovative integrated opto-electronic device hybridized into a new chip-scale waveform modulation system for Navigation Doppler Lidar. The innovation decreases sensor size, mass, power and cost while maintaining the operational performance needs of the GN&C system for precision navigation. Once developed, the complete integrated package of the proposed innovation will provide higher fidelity waveforms, added robustness during operational environments, in miniaturized package.
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 functional options in order to cover a wider range of vehicles and trajectories. The compactness also opens possibilities for applications in rendezvous and docking, or small lunar hoppers.
Miniaturization and increased efficiency also reduces cost and an increases reliability. 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. This work paves the way toward a faster transition to highly efficient and inexpensive Lidar sensors.