  With autonomous aerial vehicles enacting safety-critical missions, such as
the Mars Science Laboratory Curiosity rover's landing on Mars, the tasks of
automatically identifying and reasoning about potentially hazardous landing
sites is paramount. This paper presents a coupled perception-planning solution
which addresses the hazard detection, optimal landing trajectory generation,
and contingency planning challenges encountered when landing in uncertain
environments. Specifically, we develop and combine two novel algorithms,
Hazard-Aware Landing Site Selection (HALSS) and Adaptive Deferred-Decision
Trajectory Optimization (Adaptive-DDTO), to address the perception and planning
challenges, respectively. The HALSS framework processes point cloud information
to identify feasible safe landing zones, while Adaptive-DDTO is a multi-target
contingency planner that adaptively replans as new perception information is
received. We demonstrate the efficacy of our approach using a simulated Martian
environment and show that our coupled perception-planning method achieves
greater landing success whilst being more fuel efficient compared to a
nonadaptive DDTO approach.
