First-Principle Simulation of Spaceborne Micropulse Photon-Counting Lidar Performance on Complex Surfaces

To advance the science of lidar sensing of complex surfaces as well as in support of the upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission, this paper establishes a framework that simulates the performance of a spaceborne micropulse photon-counting detector system on a complex surface. A first-principle 3-D Monte Carlo approach is used to investigate returning photon distributions. The photomultiplier tube (PMT) detector simulation takes into account detector dead time and multiple pixels based on the latest ICESat-2 design, as well as photon detection efficiency for probabilistic modeling. To explore system behavior, Fourier synthesis is introduced to create a synthetic surface based on parameters derived from a real data set. A radiometric model using bidirectional reflection distribution functions is also applied in the synthetic scene. Such an approach allows the study of surface elevation retrieval accuracy for landscapes which have different shapes as well as reflectivities. As a case study, returning photon detection on an example snow surface is explored. Based on the simulation results for lidar sensing on synthetic complex surfaces with an elevation range of 10 m across the scene, the spaceborne photon-counting lidar system considered here is seen to have a derived elevation bias of up to 2 cm and a error standard deviation of 10 cm. Further study on multiple-pixel PMT performance for complex surfaces demonstrates that a less rough surface will result in higher accuracy and a surface with a smaller diffuse albedo will result in smaller bias.