A Single-Photon Transit Lidar for Altitude and Terrain Navigation

Terrain-referenced navigation needs an altimeter that works at low light, long range and high precision, returning ranges that can be matched against a stored elevation model. This paper designs a single-photon lidar for that role and computes its ranging precision from detector timing jitter and photon counting statistics. With system jitter of 80 ps and 400 detected photons accumulated per range estimate, the computed precision is 0.60 mm. Each 10 microjoule pulse at 1550 nm carries 7.80e+13 photons, so useful returns are available even when the received fraction is extremely small. The transit-law element of the design is its scan timing pattern, which schedules dwells so that successive footprints sample the terrain at geometrically regular intervals for map matching. Performance is computed, not measured.