Monte Carlo simulations of SPAD arrays for spaceborne LiDAR applications

Spaceborne LiDARs have long been used to observe the Earth and are now attracting increasing interest for marine ecosystems monitoring because of oceans’ role in regulating the Earth’s radiative budget and climate. However, conventional photodetectors employed so far in spaceborne LiDARs, namely photomultiplier tubes and avalanche photodiodes, have shown limited capability in resolving oceanic backscatter profiles. Single-Photon Avalanche Diode (SPAD) arrays represent a promising alternative, as they combine single-photon sensitivity, picosecond level temporal resolution, and high dynamic range. To identify an optimal SPAD array architecture and address the associated design trade-offs, we developed a Monte Carlo model that reproduces SPAD array behavior at the single-pixel level, accounting for the stochastic nature of photon detection and the dominant noise mechanisms. The proposed tool enables accurate prediction of the array response under different incident photon flux conditions and provides quantitative guidelines for the design optimization of SPAD arrays for spaceborne LiDAR applications.