Near-Surface Lunar Plasma Characteristics Derived from Chandrayaan-3 RAMBHA-LP Measurements

Abstract

Abstract We present an independent analysis of near-surface lunar plasma parameters derived from the RAMBHA-LP payload aboard the Chandrayaan-3 lander during daytime operations from August 24 to September 3, 2023. Although Manju et al. (2025) already provided a detailed characterization using RAMBHA-LP measurements combined with ionospheric modeling, the present work re-examines the plasma conditions using a fully reproducible Python-based workflow applied to publicly available sweep data. Electron temperature and electron density are obtained from current–voltage characteristics, assuming orbital-motion-limited collection by a spherical probe. The plasma potential is determined from the peak in the current derivative, and fixed voltage intervals in the electron-retarding region are used for log–linear fits to estimate temperature and density. To ensure reliable parameter extraction, we apply a normalized root mean square error criterion in log-current space, rejecting sweeps with values above 0.20. The derived electron temperatures mostly range from 3000 to 13 000 K, with 2-h averages reaching about 10 000 to 13 000 K, while daytime electron densities typically fall between approximately 200 and 430 cm–3 and occasionally approach 600 cm–3. These results are broadly consistent with previous RAMBHA-LP findings. In addition, we evaluate how fit-window selection, error thresholds, and temporal averaging influence the retrieved values, showing that the overall time evolution of the plasma remains robust. The open-source workflow and validated time series offered here provide a reusable baseline for future studies of lunar surface charging and plasma–surface interactions relevant to exploration systems.