Hyper-hemispherical structure from motion for lunar cave exploration

The paper presents "HH-SfM" (Hyper-Hemispherical Structure from Motion) a global structure-from-motion algorithm developed for the ESA Daedalus mission to explore and map Moon caves using a robot with a hyper-hemispherical lens system. The goal is to reconstruct the robot’s trajectory and environment during its descent into a lava tube. The system’s rig consists of four cameras, allowing each cave point to be seen by at least three cameras. The algorithm optimizes the rig's position and triangulated points using a global bundle adjustment, incorporating odometry for scale correction. The resulting geometry enables photogrammetric reconstruction for geological analysis and exploration of Moon channels, with potential applications on Earth.