Observation of plasma interaction with Lunar surface and near-surface environment: Science case for Lunar Neutrals Telescope on Turkish Lunar Mission AYAP-

Solar wind precipitation on atmosphere-less bodies like the Moon generates backscattered and sputtered energetic neutral atoms (ENAs) from the surface and near-surface environment. Since ENAs does not sense electromagnetic fields, ENAs can be assumed to retain the initial velocity if gravity effect can be ignored. This makes global remote sensing of surface properties and near-surface environment possible from an orbiting spacecraft. Lunar Neutrals Telescope (LNT) is an ENA instrument onboard the first Turkish Lunar Mission AYAP-1 [1], which is planned to be launched in 2026. The LNT is designed to measure energetic neutral atoms generated at the Moon surface from the orbiting spacecraft around the Moon and make a global map of plasma precipitation onto the Moon surface. There are three major scientific objectives for LNT observations: (A) To investigate the structure (shape) of mini-magnetosphere created by lunar magnetic anomalies and its response to the solar wind, (B) to search for volatile-rich areas on the Moon’s surface with the special focus on permanently shadowed regions, and (C) to investigate the formation and maintenance processes of the lunar exosphere. Figure 1. Cutaway view of LNT instrument The Design of the LNT, as shown in Figure 1, is based on the successful predecessor CENA/SARA sensor on Chandrayaan-1 [2] and is updated to achieve unprecedentedly high angular resolution (∼7° × 7°), which is approximately factor of 7 higher than the predecessor. Owing to its high angular resolution, the expected spatial resolution at the Lunar surface is ~12 km, which is small enough to resolve the fine structure of the mini-magnetosphere and properties of the permanently shadowed regions. The predicted performance of LNT is shown in the Table I. Energy and mass resolution of LNT also allows us to discriminate the process of plasma interaction with the surface (i.e. backscattered or sputtered) from which information of surface properties can be derived. We will present the predicted performance of LNT with the current status of development and discuss the expected sciences by LNT observations. Table I. Predicted performance of LNT References: [1] B. Yağlioğlu, et al. (2023), "The First Turkish Lunar Mission Part 1: Programmatic, Mission and System Aspects," 2023 10th International Conference on Recent Advances in Air and Space Technologies (RAST), Istanbul, Turkiye, 2023, pp. 1-6, doi: 10.1109/RAST57548.2023.10197907. [2] M. Wieser et al. (2010), First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms, Geophys. Res. Lett., 37, L05103, doi:10.1029/2009GL041721.