purposes. The tier-scalable reconnaissance paradigm is also highly automated. Spaceborne orbiters command and control the airborne vehicles autonomously, and the airborne vehicles in turn command and control the ground-tier reconnaissance vehicles. This allows orbiters, airships, and rovers to act in a unified, controlled manner. A mission that uses this paradigm is also considered more survivable. Since the airborne and ground-tier vehicles can be quite inexpensive, even expendable, many such vehicles can be used collectively to explore numerous science targets with complementary suites of instruments. Even if one or more vehicles should fail, others are present to take up the slack and continue the mission. Scenarios Tier-scalable reconnaissance missions allow access to targets of great interest on planetary bodies, something which is not currently feasible with conventional single-rover or single-orbiter mission designs. Tier-scalable reconnaissance missions also enable spanning larger surface areas than previously possible – mimicking the way geologists explore regions on Earth – and therefore allow for greater data return. Consider how the tier-scalable paradigm adapts to various environmental scenarios: Environments with atmospheres and with non-extreme surface temperatures (Earth, Mars): Tier 1: Spaceborne orbiters, which guide deployment and control of Tier 2: Airborne balloons or blimps, which in turn deploy and control Tier 3: Surface-based buoys, and sensors, which in turn deploy and control Tier 4: Submersibles and sensors. Environments with atmospheres and with extreme surface temperatures (Venus, Titan): Tier 1: Spaceborne orbiters, which guide deployment and control of Tier 2: Airborne balloons or blimps, which, if conditions permit, deploy and control Tier 3: Ground sensor webs, rovers, or submersibles. Environments without atmospheres and with extreme surface conditions (Mercury, Moon, Europa):''' Tier 1: Spaceborne orbiters, which guide deployment of and communicate with Tier 2: Ground-based rovers and sensor webs. Commanding and operation Using traditional means, simultaneous commanding of even a few reconnaissance vehicles becomes exceedingly complex, and so the logistical and computational demands of the tier-scalable paradigm scale quickly beyond the computers able to fit on such vehicles. This problem is overcome by using a round-robin concurrent commanding scheme''. In this scheme, the vehicles are not commanded simultaneously; instead, each is commanded in turn, one by one. Moreover, each vehicle is given a small command set to execute. In this way, one vehicle is being commanded while the others are executing their issued commands. Depending on how close the vehicles are to each other and how accurately they execute their