This review article provides an overview of various aspects of lunar exploration, including missions to the Moon, collection and analysis of lunar sample data in laboratories, and the processing and analysis of remote sensing data, particularly using radar techniques. Both remote sensing and in-situ methods are critical for advancing our understanding of the lunar surface and its properties. This review article focuses on the identification and quantification of water-ice deposits located in areas such as Permanently shadowed areas (PSRs) and the lunar poles ( Lunar Poles and PSRs: A Special Environment). These volatile resources have the potential to serve as valuable sources of fuel for future missions, making it crucial for the lunar community to determine their abundance and distribution. After thoroughly examining lunar samples using high-precision laboratory techniques, many preconceptions were dispelled which is highlighted in the Laboratory Investigation of Lunar samples. But as in-situ observations are difficult to acquire, especially terrestrial bodies samples, remote sensing techniques allow the global understanding of the surface. The article specifically highlights the importance of understanding the electrical characteristics of the lunar surface and how radar inversion can provide valuable information in this regard. The Conclusion of this review article serves as a key takeaway for readers, underscoring the critical role that both in-situ and remote sensing techniques play in advancing our understanding of the Moon. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.
The mapping of available water-ice is a crucial step in the lunar exploration missions. Ground penetrating radars have the potential to map the subsurface structure and the existence of water-ice in terms of the electromagnetic properties, specifically, the permittivity. Slight differences in permittivity can be significantly important when applied in a dry environment, such as on the Moon and Mars. The capability of detecting a small fraction of putative water-ice depends on the permittivity changes in terms of its dependent parameters, such as the frequency, the temperature, the porosity, and the chemical composition. Our work aims at mitigating false detection or overlooking of water-ce by considering their conditions that previous researches did not cover. We measured the permittivity of different lunar regolith relevant analogue samples with a fixed 40 % porosity in the ultra-high-frequency-super-high-frequency band. We used the coaxial probe method to measure anorthosite, basalt, dunite and ilmenite at 20 C-?, -20 C-? and -60 C-?, and we find that, at -60 C-?, the permittivity decreases about 6-18 % compared with the values at 20 C-?. Within this temperature range, the permittivity is quite similar to the permittivity of water-ice. We find that the conventional calculation would overestimate the permittivity in the low temperature areas, such as the permanently shadowed regions. We also find that each component in the lunar regolith has different temperature-dependent permittivity, which might be important for radar data analysis to detect lunar polar water-ice. Our results also suggest that it should be possible to estimate the water-ice content from radar measurements at different temperatures given an appropriate method.
Solar wind precipitation on atmosphere-less bodies like the Moon generates backscattered and sputtered energetic neutral atoms (ENAs) from the surface. Since ENAs does not sense electromagnetic fields, ENAs can be assumed to retain the initial velocity if gravity effect can be ignored. This makes remote sensing of surface properties and near-surface plasma conditions possible from a spacecraft orbit. Lunar Neutrals Telescope (LNT) is an ENA instrument on the first Turkish Lunar Mission. LNT is tailored to answer several fundamental scientific questions. Three scientific objectives are set: (1) To search for volatile-rich areas on the surface including permanently shadowed regions, (2) to investigate the structure of mini- magnetosphere created by lunar magnetic anomalies and its response to the solar wind, and (3) to investigate the formation and maintenance processes of the lunar exosphere. We will present LNT scientific objectives as well as a brief description of the instrument.
A renaissance is being observed currently in investigations of the Moon. The Luna-25 and Luna-27 missions are being prepared in Russia. At the same time, in connection with the future lunar missions, theory investigations of dust and dusty plasmas at the Moon are being carried out by scientists of the Space Research Institute of the Russian Academy of Sciences. Here, the corresponding results are reviewed briefly. We present the main theory results of these investigations concerning the lunar dusty plasmas. We show, in particular, the absence of the dead zone near a lunar latitude of 80 where, as was assumed earlier, dust particles cannot rise over the surface of the Moon. This indicates that there are no significant constraints on the Moon landing sites for future lunar missions that will study dust in the surface layer of the Moon. We demonstrate that the electrostatically ejected dust population can exist in the near-surface layer over the Moon while the dust appearing in the lunar exosphere owing to impacts of meteoroids present everywhere. The calculated values of number densities at high altitudes of the particles formed as a result of the impacts of meteoroids with the lunar surface are in accordance (up to an order of magnitude) with the data obtained by the recent NASA mission LADEE. Finally, we formulate new problems concerning the dusty plasma over the lunar surface.
The Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is designed to characterize the exospheric dust environment using an on-board suite of specialized sensors. The objective of this paper is to present results from scattering experiments using an aqueous suspension of lunar simulants that contains a population of dust grains ranging in size from similar to 0.1 pm to 10 pm. The intensity of scattered light is measured with a commercial version of the ultraviolet-visible spectrometer (UVS) used in the LADEE mission. We show that our data is consistent with the fact that micron-sized particles tend to form agglomerates rather than remaining isolated entities and that certain characteristics of the target particles can be predicted from intensity measurements alone. These results can be used directly to assess general features of the lunar exosphere. Further analysis of particle properties from such remote sensing data will require more refined measurements such as polarization features or other components of the Stokes vector. Published by Elsevier Ltd.
This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing of the lunar surface via detection of neutral atoms in the. energy range from 10 eV to 3 keV from a 100 kin polar orbit. In this report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The SARA. instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica of SARA is planned to fly to Mercury onboard the BepiColombo mission.