Future planetary explorations will require surface traverses of unprecedented frequency, length, and duration. As a result, there is need for exploration support tools to maximize productivity, scientific return, and safety. The Massachusetts Institute of Technology is currently developing such a system, called the Surface Exploration Traverse Analysis and Navigation Tool (SEXTANT). The goal of this system is twofold: to allow for realistic simulations of traverses in order to assist with

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... re design, and to give astronauts an aid that will allow for more autonomy in traverse planning and re-planning. SEXTANT is a MATLAB-based tool that incorporates a lunar elevation model created from data from the Lunar Orbiter Laser Altimeter instrument aboard the Lunar Reconnaissance Orbiter spacecraft. To assist in traverse planning, SEXTANT determines the most efficient path across a planetary surface for astronauts or transportation rovers between user-specified Activity Points. The path efficiency is derived from any number of metrics: the traverse distance, traverse time, or the explorer's energy consumption. The generated path, display of traverse obstacles, and selection of Activity Points are visualized in a 3D mapping interface. After a traverse has been planned, SEXTANT is capable of computing the most efficient path back home, or "walkback", from any point along the traverse -an important capability for emergency operations. SEXTANT also has the ability to determine shadowed and sunlit areas along a lunar traverse. This data is used to compute the thermal load on suited astronauts and the solar power generation capacity of rovers over the entire traverse. These both relate directly to the explorer's consumables, which place strict constraints on the traverse. This paper concludes by presenting three example traverses, detailing how SEXTANT can be used to plan and modify paths for both explorer types. Nomenclature ! " = terrain slope ! " suit = absorptivity of the space suit ! A " = space suit surface area perpendicular to the sun 2 ! A SA = rover solar array area ! A suit = surface area of the space suit ! C = conductance of the space suit ! c p,suit = specific heat of the space suit ! c p,water = specific heat of water ! " suit = emissivity of the space suit ! " env = emissivity of an environmental component (the lunar surface or deep space) ! E = mechanical efficiency of astronaut locomotion ! E planet = scaling factor for mechanical efficiency of astronaut locomotion on the Moon and Mars ! F suit"env = view factor between the space suit and the environmental component (the lunar surface or deep space) ! g = planetary gravity ! " SA = rover solar array efficiency ! h = heat of sublimation of ice ! I = flux of solar radiation arriving at the lunar surface ! m = explorer mass ! ˙ m water = mass flow rate of water in the liquid cooling and ventilation garment ! m suit = mass of the space suit ! P e = energy of rover electronics' ! P SA = power from rover solar array ! " = Stefan-Boltzmann constant ! t = stage duration ! T atm = internal, atmospheric temperature of the space suit ! T env = temperature of an environmental component (the lunar surface or deep space) ! T LCVG = temperature of water in the liquid cooling and ventilation garment ! T sub = temperature of the water temperature in sublimator of the liquid cooling and ventilation garment ! T suit = external temperature of the space suit ! ˙ Q = generic heat flux ! ˙ Q b = astronaut basal metabolic rate ! ˙ Q env = total environmental heat flux ! ˙ Q ext = external heat flux conducted through space suit ! ˙ Q m = total astronaut energy consumption ! ˙ Q n = heat loss from the astronaut body to the space suit in astronaut locomotion ! ˙ Q s = heat storage of the astronaut body in astronaut locomotion ! ˙ Q suit" env = heat flux between the space suit and the environmental component (the lunar surface or deep space) ! ˙ Q sun = heat flux from direct sun radiation ! ˙ Q total = total space suit heat flux ! ˙ Q waste = space suit electronics waste heat ! v = explorer velocity ! V sun = percentage of the solar disk visible ! W level = explorer energy consumption over level terrain ! W slope = explorer energy consumption over non-level terrain ! ˙ W w = external mechanical work in astronaut locomation ! ˙ W wc = work done by the ground counterforce in astronaut locomotion ! ˙ W wr = work done by moving the body's limbs in astronaut locomotion