border control, battlefield surveillance and reconnaissance, telecommunications relay, and weather observations, as well as monitoring of military checkpoints, standoff detection, and delivery/removal of explosives such as landmine cleanup. Advantages and implications Some of the major advantages of tier-scalable reconnaissance architectures include: Overhead navigation, enabling deployment of simple, inexpensive, expendable ground vehicles; Efficient commanding of multiple ground vehicles; Mission safety, reliability, and survivability; Optimized target identification, path planning, and obstacle avoidance; and Real time reconnaissance, allowing identification and characterization of active events. Also, tier-scalable reconnaissance reduces driving requirements for ground vehicles, since they already are deployed in the vicinity of where they need to be. Therefore, driving is limited to “fine-tuning” the location of the ground-tier vehicles to perform local sampling, as opposed to “long-distance” driving towards the location where they need to be. Hence, inexpensive, expendable miniaturized vehicles with limited driving capabilities can be used. The ground-tier vehicles have limited onboard computing capabilities, since they off-load data analysis to a primary lander or higher tiers that have higher-grade computing equipment. Conceptually, a primary lander is a higher-grade computing engine that also acts as a communication relay, much like a planetary internet router between the tiers. Thus, the tier-scalable reconnaissance paradigm, by its inherent architecture, is an extended distributed computing topology unto itself. Developments Individual components of the tier-scalable reconnaissance paradigm are either under development or have already been tested and proven “in the field.” These include orbiters, balloons, blimps, airships, and ground-based vehicles such as rovers and landers as well as sensor webs. The biggest challenge, however, appears to be not so much the hardware but the “intelligent” software that would enable all the components of a tier scalable mission to be integrated and function autonomously. References Remote sensing