URBAN RECONNAISSANCE AND search-and-rescue missions are ideal candidates for multi-robot teams due to the potential hazard the missions pose to humans and the inherent parallelism that can be exploited by teams of cooperating robots. However, these domains also involve challenging problems due to having to work in complex, stochastic, and partially observable environments. In particular, non-uniform and cluttered terrain in unknown environments is a challenge for both state-estimation and control, resulting in complicated planning and perception problems. Limited and unreliable communications 62 COMMUNICATIONS OF THE ACM MARCH 2013 VOL. 56 ! NO. 3 key insights Human operators can help a robot team be more efficient and recover from errors. A good state estimate, in the form of a map, is the most critical piece of information for a team of robots-and the most difficult to obtain. Grand Challenge competitions like MAGiC highlight challenging open problems and provide a venue for evaluating new approaches.