Real time processing enables fast 3D imaging at single photon level

3D LIDAR imaging is a key enabling technology for automatic navigation of future spacecraft, including landing, rendezvous and docking and rover navigation. Landing is typically the most demanding task because of the range of operation, speed of movement, field of view (FOV) and the spatial resolution required. When these parameters are combined with limited mass and power budget, required for interplanetary operations, the technological challenge becomes significant and innovative solutions must be found. Single Photon Avalanche Photodiodes (SPADs) can reduce the laser power by orders of magnitude, array detector format can speed up the data acquisition while some limited scanning may extend the FOV without pressure on the mechanics. In the same time, SPADs have long dead times that complicate their use for rangefinding. Optimization and balance between the instrument subsystems are required. We discuss how the implementation of real-time control as an integral part of the LIDAR allows the use of SPAD array detectors in conditions of high dynamics. The result is a projected performance of more than 1 million 3D pixels/s at a distance of several kilometers within a small mass/power package. The work is related to ESA technology development for future planetary landing missions.