As the solar wind flows by the Moon, an antisunward-directed low-density wake forms as the plasma expands to fill in the trailing void in the plasma flow. Analytical modeling and modern plasma simulations suggest that plasma quasi-neutrality could possibly be broken close to the terminator obstruction as solar wind electrons expand into the wake ahead of the ions, leading to the formation of a standing (time-stationary) double layer. The objective of the Terminator Double Layer Explorer is to extend the fundamental understanding of the plasma expansion into the trailing near-vacuum wake region by (1) identifying any plasma expansion density anomalies at low altitudes near the terminator wake initiation region, (2) assessing the highly variable solar wind’s effect on the low-altitude wake region, and (3) determining if plasma neutrality is maintained or lost during passages through the low-altitude expansion region. The mission concept uses a propulsion-driven CubeSat with ion spectrometer and plasma wave system in elliptical orbit about the Moon with periselene near the terminator. Over the course of the mission, the periselene decreases, placing the CubeSat ever closer to the terminator wake initiation location and the possible nonneutral region.

太阳风由月亮，一个antisunward定向低密度唤醒形式的等离子体膨胀以填充在等离子体流尾随空隙流动。分析建模和现代等离子体模拟表明，等离子体准中性可以作为太阳风电子膨胀到离子的唤醒提前，导致直立（时间静止）双层的形成可能被接近终止子梗阻断裂。终结者双层的目标资源管理器是由（1）到等离子体膨胀的基本理解延伸到后端接近真空的尾流区域识别所述终止唤醒起始区附近低空任何等离子体膨胀密度异常，（2）评估高度可变的太阳风对低空尾流区域的效果，和（3）确定如果等离子体中立保持或通过低海拔膨胀区域传代期间丢失。任务概念使用与在对月球椭圆轨道与终止子附近periselene离子光谱仪和等离子体波系统的推进驱动的立方体卫星。在任务过程中，periselene下降，放置的CubeSat更接近终止之后开始的位置和可能的非中性区域。