Path shaping guidance for terminal lunar descent

Lunar descent guidance methods are investigated which provide soft landing in regions of undulating terrain. Path shaping guidance is developed to provide a family of descent paths which converge to a soft-landing, but avoid obstructions created by neighbouring terrain. A phase of terrain slope nulling is also considered to aid in the selection of a suitable landing location. These methods may be patched to a conventional gravity turn trajectory for the main braking phase of the descent. Since the guidance commands are provided in closed, analytic form the demands on the on-board flight computer are limited, freeing its capacity for more computationally intensive tasks. In principle, the methods also increase on-board autonomy, allowing more flexible mission operations.