navigation commands, an airborne deployment reassessment is done so that refined trajectories are computed for each vehicle. Thus, each vehicle can be commanded in turn without threat of collision. In the tier-scalable paradigm, ground-tier vehicles are commanded typically through the use of local airborne vehicles, such as blimps or balloons. The airborne vehicles contain onboard tracking and command systems for use with the ground-tier vehicles. With a wide field of view, the tracking and commanding systems on board the airborne vehicles determine optimal paths for the ground-tier vehicles, identifying both obstacles and interesting science targets. The ground-tier vehicles are then commanded to navigate through the operational area to the designated targets, while avoiding the identified obstacles. Therefore, this approach does not rely on the limited horizontal view of the ground-tier vehicles. Each ground-tier vehicle includes its own instrument suite to collect information, which is transmitted back to the airborne tier. The ground-tier vehicles may conduct measurements en route to their targets. If an interesting object is encountered along the way, a vehicle may request permission of the commanding tier to explore it. A ground-tier vehicle may also find itself in an area of geography through which it cannot pass. In this case, it would request an alternate trajectory to its target, or even a target reassignment. These resolutions are possible because the higher-level airborne commanding tier is able to reassess the deployment of the vehicles, refining the trajectories of each of the vehicles at each step. In this way, even if a vehicle should go off-course, such as from sliding on sandy soil, the commanding tier will recalculate a path to the target based on the vehicle's current position. Applications Robotic reconnaissance operations are called for in extreme environments such as space, as well as in potentially hazardous or inaccessible operational areas on Earth, such as those related to military or terrorist activities, or areas that have been exposed to biochemical agents, radiation, or natural disasters. Tier-scalable reconnaissance opens access to geologic sites not currently feasible to visit, such as canyons, mountain ranges, chaotic and rugged terrain, impact basins and craters, even volcanoes and liquid pools or lakes. In addition, other exotic locales of scientific interest exist on the planetary bodies of the Solar System that are particularly crucial in the search for extraterrestrial biological activity in general, and sample return missions in particular. Potential terrestrial applications include Homeland Security,