Constrained Visibility Guidance for Terrain Scanning Using 6-DOF Sequential Convex Programming

Recent advances in perceptive sensors and computer vision have motivated new formulations for powered descent guidance, wherein a vehicle must perform a pinpoint landing on a celestial body while simultaneously conducting close-range scans of the landing environment to detect and avoid potentially-unsafe hazards. Furthermore, mission plans may necessitate exploration and scouting of the environment to determine candidate landing sites in real time. In this paper, a novel six degree-of-freedom (6-DOF) optimal control formulation is presented to model visibility-based constraints such that line-of-sight to a circular ground-based region of interest is guaranteed, up to a specified discrete temporal resolution, with an accommodating theory of constrained conic intersections introduced to support this approach. This formulation, termed Constrained Visibility Guidance (CVG), further leverages and extends theory in sequential convex programming and state-triggered constraints to enable mission-practical constraint specification and transformation of a highly-nonconvex problem into one that can be iteratively solved with modern second-order cone program solvers. Ultimately, CVG is shown to be highly performant in terms of solve time and convergence properties, even under complex and highly-constrained problem design. Numerical simulation results are presented to validate these claims.