The characterization of the lunar surface and subsurface through the utilization of synthetic aperture radar data has assumed a pivotal role in the domain of lunar exploration science. This investigation concentrated on the polarimetric analysis aimed at identifying water ice within a specific crater, designated Erlanger, located at the lunar north pole, which is fundamentally a region that is perpetually shaded from solar illumination. The area that is perpetually shaded on the moon is defined as that region that is never exposed to sunlight due to the moon's slightly tilted rotational axis. These permanently shaded regions serve as cold traps for water molecules. To ascertain the presence of water ice within the designated study area, we conducted an analysis of two datasets from the Chandrayaan mission: Mini-SAR data from Chandrayaan-1 and Dual-Frequency Synthetic Aperture Radar (DFSAR) data from Chandrayaan-2. The polarimetric analysis of the Erlanger Crater, located in a permanently shadowed region of the lunar north pole, utilizes data from the Dual-Frequency Synthetic Aperture Radar (DFSAR) and the Mini-SAR. This study focuses exclusively on the L-band DFSAR data due to the unavailability of S-band data for the Erlanger Crater. The crater, identified by the PSR ID NP_869610_0287570, is of particular interest for its potential water ice deposits. The analysis employs three decomposition models-m-delta, m-chi, and m-alpha-derived from the Mini-SAR data, along with the H-A-Alpha model known as an Eigenvector and Eigenvalue model, applied to the DFSAR data. The H-A-Alpha helps in assessing the entropy and anisotropy of the lunar surface. The results reveal a correlation between the hybrid polarimetric models (m-delta, m-chi, and m-alpha) and fully polarimetric parameters (entropy, anisotropy, and alpha), suggesting that volume scattering predominates inside the crater walls, while surface and double bounce scattering are more prevalent in the right side of the crater wall and surrounding areas. Additionally, the analysis of the circular polarization ratio (CPR) from both datasets suggests the presence of water ice within and around the crater, as values greater than 1 were observed. This finding aligns with other studies indicating that the high CPR values are indicative of ice deposits in the lunar polar regions. The polarimetric analysis of the Erlanger Crater contributes to the understanding of lunar polar regions and highlights the potential for future exploration and resource utilization on the Moon.

Studies of the lunar surface from Synthetic Aperture Radar (SAR) data have played a prominent role in the exploration of the lunar surface in recent times. This study uses data from SAR sensors from three Moon missions: Chandrayaan-1 Mini-SAR, Lunar Recon-naissance Orbiter (LRO) Mini-RF and Chandrayaan-2 Dual Frequency Synthetic Aperture Radar (DFSAR). DFSAR sensor is the first of its kind to operate at L-band and S-band in fully and hybrid polarimetric modes. Due to the availability of only L-band data out of the two bands (L-and S-band) for the study site, this study only used DFSAR's L-band data. The dielectric characterization and polarimetric analysis of the lunar north polar crater Hermite-A was performed in this study using Chandrayaan-1 Mini-SAR, LRO Mini-RF and Chandrayaan-2 DFSAR data. Hermite-A lies in the Permanently Shadowed Region (PSR) of the lunar north pole and whose PSR ID is NP_879520_3076780. Because of its location within the PSR of the lunar north pole, the Hermite-A makes an ideal candidate for a probable location of water-ice deposits. This work utilizes S-band hybrid polarimetric data of Mini-SAR and Mini-RF and L -band fully polarimetric data of DFSAR for the lunar north polar crater Hermite-A. This study characterizes the scattering mechanisms from three decomposition techniques of Hybrid Polarimetry namely m-delta, m-chi, and m-alpha decompositions, and for fully polari-metric data Barnes decomposition technique was applied which is based on wave dichotomy. Eigenvector and Eigenvalue-based decom-position model (H-A-Alpha decomposition) was also applied to characterize the scattering behavior of the crater. This study utilizes the hybrid-pol and fully polarimetric data-based Integral Equation Model (IEM) to retrieve the values of dielectric constant for Hermite-A crater. The dielectric constant values for the Hermite-A crater from Chandrayaan-1 Mini-SAR and LRO Mini-RF are similar, which goes further in establishing the presence of water-ice in the region. The values of the dielectric constant for Chandrayaan-2 in some regions of the crater especially on the left side of the crater is also around 3 but overall the range is relatively higher than the com-pact/hybrid polarimetric data. The dielectric characterization and polarimetric analysis of the Hermite-A indicatively illustrate that the crater may have surface ice clusters in its walls and on some areas of the crater floor, which can be explored in the future from the synergistic use of remote sensing data and in-situ experiments to confirm the presence of the surface ice clusters.(c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Mineralogy of the Lunar surface provides important clues for understanding the composition and evolution of the primordial crust in the Earthe-Moon system. The primary rock forming minerals on the Moon such as pyroxene, olivine and plagioclase are potential tools to evaluate the Lunar Magma Ocean (LMO) hypothesis. Here we use the data from Moon Mineralogy Mapper (M-3) onboard the Chandrayaan-1 project of India, which provides Visible/Near Infra Red (NIR) spectral data (hyperspectral data) of the Lunar surface to gain insights on the surface mineralogy. Band shaping and spectral profiling methods are used for identifying minerals in five sites: the Moscoviense basin, Orientale basin, Apollo basin, Wegener crater-highland, and Hertzsprung basin. The common presence of plagioclase in these sites is in conformity with the anorthositic composition of the Lunar crust. Pyroxenes, olivine and Fe-Mg-spinel from the sample sites indicate the presence of gabbroic and basaltic components. The compositional difference in pyroxenes suggests magmatic differentiation on the Lunar surface. Olivine contains OH/H2O band, indicating hydrous phase in the primordial magmas. (C) 2016, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.

The High Energy X-ray spectrometer (HEX) on Chandrayaan-1 was designed to study the photon emission in the range of 30-270 keV from naturally occurring radioactive decay of U-238 and Th-232 series nuclides from the lunar surface. The primary objective of HEX was to study the transport of volatiles on the lunar surface using radon as a tracer and mapping the 46.5 keV line from Pb-210, a decay product of Rn-222. HEX was tested for two days during the commissioning phase of Chandrayaan-1 and performance of all sub systems was found to be as expected. HEX started collecting science data during the first non-prime imaging season (February-April, 2009) of Chandrayaan-1. Certain anomalies persisted in this data set and the early curtailment of Chandrayaan-1 mission in August, 2009, did not allow any further operation of HEX. Despite these issues, HEX provided the first data set for 30-270 keV continuum emission, averaged over a significant portion of the lunar surface, including the polar region. (C) 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.

High Circular Polarization Ratio (CPR) was thought to be a robust diagnostic of water-ice on the lunar surface. Recent researches have reported such findings on walls, floors, and proximal ejecta of impact craters, as well as on sunlit zones. These signatures could not be explained with water-ice as the probable cause. In an attempt to explain such sightings, this paper portrays the character of radar waves backscattered from the lunar surface. This characterization is performed with the aid of daughter products derived from the Stokes vector.

Chandrayaan-1, the first Indian planetary exploration mission, will carry out high resolution remote sensing studies of the moon to further our understanding about its origin and evolution. Hyper-spectral imaging in the UV-VIS-NIR region using three imaging spectrometers, along with a low energy X-ray spectrometer will provide mineralogical and chemical composition of the lunar surface at high spatial resolution. A terrain mapping camera will provide high resolution three-dimensional images of the lunar surface and will be complemented by a laser ranging instrument that will provide lunar altimetry. Three payloads - a high energy X-gamma ray spectrometer, a sub-keV atom reflecting analyser, and miniature imaging radar - will be used for the first time for remote sensing exploration of a planetary body. They will investigate transport of volatiles on the lunar surface, presence of localized lunar mini-magnetosphere and possible presence of water ice in the permanently shadowed lunar polar region respectively. A radiation dose monitor will provide information on energetic particle flux en route to the moon and in lunar orbit. An impact probe carrying an imaging system, a radar altimeter and a mass spectrometer will be released from the spacecraft to land at a predestinated lunar site. The design of the one tonne-class spacecraft is primarily adapted from flight proven Indian Remote Sensing satellite bus with several modifications that are specific to the lunar mission. The spacecraft was launched by using a variant of the indigenous Polar Satellite Launch Vehicle (PSLV-XL) and placed in a 100 km circular polar orbit around the moon with a planned mission life of two years. An Indian Deep Space Network and an Indian Space Science Data Center have been established as a part of Chandrayaan-1 mission and will cater to the need of future Indian space science and planetary missions.

Chandrayaan-1, India's first planetary exploration mission to Moon carries a suite of payloads including a High Energy X-ray spectrometer (HEX) designed to study low-energy (30-270 keV) natural gamma rays emitted from the lunar surface due to decay of uranium and thorium. The primary science objective of HEX is to study transport of volatiles on the lunar surface through the detection of the 46.5 keV line from Pb-210 decay, which is a decay product of volatile Rn-222, both belonging to the U-238 decay series. HEX is designed to have a spatial resolution of similar to 33 km at energies below 120 keV. The low signal strength of these emissions requires a large area detector with high sensitivity and energy resolution, and a new generation Cd-Zn-Te (CZT) solid state array detector is used in this experiment. Long time integration will be required to detect the emission because of the significant lunar continuum background and weak signal strength. The various sub-systems of the HEX flight payload and test results from ground calibration are described in this article. HEX will be the first experiment aimed at detecting low energy (<300 keV) gamma ray emission from a planetary surface.

The Chandrayaan-1 mission to the Moon scheduled for launch in late 2007 will include a high energy X-ray spectrometer (HEX) for detection of naturally occurring emissions from the lunar surface due to radioactive decay of the U-238 and Th-232 series nuclides in the energy region 20-250 keV. The primary science objective is to study the transport of volatiles on the lunar surface by detection of the 46.5 keV line from radioactive Pb-210, a decay product of the gaseous Rn-222, both of which are members of the U-238 decay series. Mapping of U and Th concentration over the lunar surface, particularly in the polar and U-Th rich regions will also be attempted through detection of prominent lines from the U and Th decay series in the above energy range. The low signal strengths of these emissions require a detector with high sensitivity and good energy resolution. Pixelated Cadmium-Zinc-Telluride (CZT) array detectors having these characteristics will be used in this experiment. Here we describe the science considerations that led to this experiment, anticipated flux and background (lunar continuum), the choice of detectors, the proposed payload configuration and plans for its realization.