  This work contributes a marsupial robotic system-of-systems involving a
legged and an aerial robot capable of collaborative mapping and exploration
path planning that exploits the heterogeneous properties of the two systems and
the ability to selectively deploy the aerial system from the ground robot.
Exploiting the dexterous locomotion capabilities and long endurance of
quadruped robots, the marsupial combination can explore within large-scale and
confined environments involving rough terrain. However, as certain types of
terrain or vertical geometries can render any ground system unable to continue
its exploration, the marsupial system can - when needed - deploy the flying
robot which, by exploiting its 3D navigation capabilities, can undertake a
focused exploration task within its endurance limitations. Focusing on
autonomy, the two systems can co-localize and map together by sharing
LiDAR-based maps and plan exploration paths individually, while a tailored
graph search onboard the legged robot allows it to identify where and when the
ferried aerial platform should be deployed. The system is verified within
multiple experimental studies demonstrating the expanded exploration
capabilities of the marsupial system-of-systems and facilitating the
exploration of otherwise individually unreachable areas.
