Sun and Earth Access Trades for Lunar South Pole Landing Site Selection

摘要

One of the leading candidate sites for future lunar exploration is Shackleton Crater, a 20-km-diameter, 4-km-deep depression offset 10 km from the south pole of the Moon. The perpetual darkness that exists at the floor of the crater, which makes it scientifically interesting and a potential supply of resources, is coupled with near-continuous sunlight atop the rim and some of the surrounding area. In order to leverage favorable Sun and Earth access conditions in the region, engineers designing future missions must be able to quantify these access conditions and effectively use this data to select an ideal landing or outpost site. This paper details work completed to develop this capability within Team X at the NASA Jet Propulsion Laboratory using a Satellite Tool Kit (STK) model coupled with a MATLAB site selection tool employing multi-attribute decision-making (MADM) techniques. Three scenarios are analyzed in terms of the fraction of the year for which Sun and Earth access exists, the maximum durations for which access is nonexistent, and access consistency. These multiple metrics are combined into an aggregate suitability score based on user weights and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and optimal sites are identified. In addition, weighting-independent Pareto-optimal points are identified and are shown to be clustered in four geographic regions. The most promising points have access to the Sun 89-93% of the year and to the Earth about 58% of the year. It is shown that access results are highly sensitive to a spacecraft's effective solar array or antenna altitude above the surface. Recommendations of future sites to consider are provided, and avenues for future expansion of this analysis and its tools are identified.