  This work establishes COMPRA, a compact and reactive autonomy framework for
fast deployment of Micro Aerial Vehicles (MAVs) in subterranean
Search-and-Rescue (SAR) missions. A COMPRA-enabled MAV is able to autonomously
explore previously unknown areas while specific mission criteria are considered
e.g. an object of interest is identified and localized, the remaining useful
battery life, the overall desired exploration mission duration. The proposed
architecture follows a low-complexity algorithmic design to facilitate fully
on-board computations, including nonlinear control, state-estimation,
navigation, exploration behavior and object localization capabilities. The
framework is mainly structured around a reactive local avoidance planner, based
on enhanced Potential Field concepts and using instantaneous 3D pointclouds, as
well as a computationally efficient heading regulation technique, based on
depth images from an instantaneous camera stream. Those techniques decouple the
collision-free path generation from the dependency of a global map and are
capable of handling imprecise localization occasions. Field experimental
verification of the overall architecture is performed in relevant unknown
Global Positioning System (GPS)-denied environments.
