  This paper develops a communication-efficient distributed mapping approach
for rapid exploration of a cave by a multi-robot team. Subsurface planetary
exploration is an unsolved problem challenged by communication, power, and
compute constraints. Prior works have addressed the problems of rapid
exploration and leveraging multiple systems to increase exploration rate;
however, communication considerations have been left largely unaddressed. This
paper bridges this gap in the state of the art by developing distributed
perceptual modeling that enables high-fidelity mapping while remaining amenable
to low-bandwidth communication channels. The approach yields significant gains
in exploration rate for multi-robot teams as compared to state-of-the-art
approaches. The work is evaluated through simulation studies and hardware
experiments in a wild cave in West Virginia.
