A small all-range LIDAR for topographic mapping from orbit and navigation guidance during descent and touchdown

We report on the design, measurement capabilities, and measured performance of a new Small All-range Lidar (SALI). The lidar transmitter uses a 1.55-μm Erbium-Doped Fiber-Amplifier (EDFA) laser modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver uses a 2x8-pixel HgCdTe avalanche photodiode (APD) array in linear single photon detection mode of operation. The receiver electronics calculate the target range by correlating the received signal with a patented 3-state RZPN kernel. A field programmable gate array (FPGA) processes the signal in real time up to a 120 Hz measurement rate for eight parallel receiver channels. The output power of the fiber laser, the detector gain, and the receiver integration time are all adjustable so that it can measure planetary surface at range from more than 100 kilometers down to a fraction of a meter without saturation. SALI is primarily designed for mapping planetary bodies from orbit but can also be used as a guidance sensor for sample collection or landing. The instrument uses all standard components from the fiber optic communications industry except for the detector and it can be built at a much lower cost compared to previous planetary lidars. SALI is also modular and can use different lasers and detectors at different wavelengths and different receiver telescope sizes to best fit the specific mission requirements. We have recently completed the instrument integration and performed function and performance testing. The measured performance is close to the prediction given in our earlier publications. We will soon conduct a vibration and thermal-vacuum tests to demonstrate its readiness for use in a space mission.