Assumptions and Constraints
Astronauts are permitted to spend no more than 8 hours in their spacesuits (i.e., in EVA mode) during each day. ("Day" as used here refers to a 24-hour period as on Earth, not to the rotational period of the Moon.) They are also to sleep for 8 hours each day. The remaining 8 hours are spent in some combination of eating, exercising, record-keeping, evaluating collected samples, and other unspecified activities inside the pressurized cabin of either an SPR or the lander-habitat. With the exception of sleeping, these Intra-Vehicular Activities (IVAs) are not individually constrained or scheduled in this study.
Both the UPR and the SPR need to be recharged at the lander-habitat after every 72 hours of operation. Astronauts are required to rest in the lander-habitat for 2 days after each 3-day work period. Thus, the astronauts have a maximum allowance for EVA work of 8 days during the 14-day mission, assuming one day each for settling in after arrival on the lunar surface and for preparing to depart. (These restrictions may well be relaxed in future iterations.)
Four of the seven primary activities (collecting rocks, collecting regolith -- i.e., fine gravel and soil on the lunar surface, digging shallow trenches, and hammering a "drive tube" into the soil) are required to be conducted by the astronauts working outside in their spacesuits. The remaining three activities (drilling soil cores, drilling rock cores, and raking) are to be conducted by the robotic rovers after being set up by the astronauts. (As seen in the Allocating Tasks 1, HURON is capable of allowing all agents -- whether human or robot -- to compete for tasks. However, the decision-makers for whom this study was conducted preferred in this case to associate the tasks requiring the most time and the least amount of human judgment (e.g., drilling and raking) with the robots, and to allocate the remaining tasks to the astronauts.) As the robots operate, they are to be monitored by a team observing remotely from Earth. In the event that a robot encounters a problem (such as a drill getting stuck), the monitors are able to command the robot to employ a corrective action (such as stopping and reversing the drill).
Each of the science activities is assigned a relative value for the user/analyst to consider in determining which ones to omit if required by the time constraints. The value assigned to each task, total number of samples to be collected, average mass of each sample, and amount of time required to perform the experiments, as employed by our model, are given in Table I.
The two most time-consuming tasks, drilling soil cores and drilling rock cores, are to be conducted only at the first science-activity site at each of the 5 localities. As mentioned, deposition of the Lunar Environmental Monitoring Station is to be done only once. All other tasks are to be performed at all 7 sites in each locality. For purpose of this study, it is assumed that each of the five localities is equally important and therefore has equal weight in the analysis.
For safety reasons, in each of the two scenarios, the two teams (each of which consists of two astronauts and one rover) are required to stay within close range of each other at all times. In the UPR scenario, the two teams are required to be at the same science-activity site. In the SPR scenario, the teams are required to be at the same locality, but not necessarily at the same science-activity site. Since astronauts in the SPR scenario would have access to a pressurized cabin, it is thought that it would be permissible for the rescue team to take somewhat longer to arrive.
Rovers are assumed to travel at a speed of 10 km/hr. However, since maps of sufficient resolution to plan realistic routes around hazards and obstacles are not yet available, a 20% margin is added to each bee-line route.
