Integrated Guidance and Control for Lunar Landing using a Stabilized Seeker

The selected landing site should be at a low slope with respect to the planetary equipotential surface, free of hazards, and also be located such that it satisfies mission objectives. The Apollo Lunar missions allowed the lander pilot to steer towards a manually selected landing site by manipulating a control stick until the designated landing site (DLS) appeared in a window fixed reticle [1], but the actual trajectory flown to reach that point in a manner consistent with a soft landing was automated by the guidance and control system. The Chinese Chang'e 3 mission [2] used coarse hazard detection from greyscale images during the powered descent, and once the lander reached an altitude of 100 m, hovered while a hazard free landing site was selected, after which the lander diverted horizontally until directly above the selected landing site, and then continued straight down to the surface. Finally, the Morpheus project [3] demonstrated integration of flash LIDAR based hazard detection with guidance and control on Earth using a hazard field with a mix of terrain hazards and safe landing sites. During the powered descent the landing site detection system will likely change the DLS as distance to surface decreases and resolution increases. Consequently, a suitable guidance and control system should be capable of multiple divert maneuvers during the powered descent phase.