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The peculiar illumination and insolation conditions at the poles of the Moon lead to the formation of Permanently Shadowed Regions (PSR) that act as cold traps for volatiles and are important for In Situ Resource Utilization (ISRU). However, since these regions lie in shadows of surrounding topographic highs, the ability of optical remote sensing in imaging these regions for photo reconnaissance is limited and using other modes of remote sensing becomes imperative. In this work, reflectance from optical data, backscatter from active microwave data and temperature from thermal data from the surfaces of three craters – de Gerlache, Haworth and Shoemaker – on the South Pole of the Moon, in close proximity to the Artemis III candidate landing sites, has been studied. Images from Clementine UVVIS, LRO WAC and LRO NAC have been compared with fully polarimetric data from the L-bands sensor of Chandrayaan-2 DFSAR. Further, the temperatures at the surface of the craters have been studied using data from LRO DIVINER. Since large parts of the craters under study lie in permanent shadows, Clementine UVVIS and LRO WAC could image only some parts of the rims. LRO NAC, with its longer exposure times, could image some parts within the crater however the walls of the crater and the floor near the walls remained in shadow. DFSAR was found to be useful in viewing the permanently shadowed regions of the craters. Overall, the backscatter in HH and VV (co-pol) channels was higher than the backscatter in HV and VH (cross-pol) channels. The elevated rims of the craters were clearly visible in co-pol channels and the rough texture of the ejecta of the craters had a distinct high backscatter in cross-pol channels. This fully polarimetric data can be used to map the interiors of the craters where optical data has low albedo. Analysis of the thermal data revealed that within the craters, in the regions that were in perpetual shadows, the maximum summer temperatures were less than 150 K making these regions cold traps for volatiles and possible locations of surface water–ice. The parts of craters lying in the shadows of surrounding higher features had lower maximum temperatures in summer and the parts facing them had higher maximum temperatures due to reflected insolation. Seleno Referenced Image (SRI) product from Chandrayaan-2 DFSAR was found to be a viable alternative to optical data for viewing the PSRs and for their geologic mapping. [ABSTRACT FROM AUTHOR]

Imaging spectrometry is a powerful tool among remote sensing techniques to analyze the chemical compositions and physical properties of the lunar regolith. Recalibration of the classical method byLucey and co-workers with Moon Mineralogy Mapper (M3) data provides an opportunity to understand the FeO, TiO 2, and optical maturity distributions over the lunar nearside on a global scale. We estimated the chemical compositionsand optical maturity from the M3 spectral reflectance around the 1 µm region. The standard chemical compositions of the lunar landing sites were estimated based on origin optimization and data fitting. We obtained an optimized origin of (0.08, 1.18) for FeO and (0.07, 0.71) for TiO 2. The Spectrophotometric evaluations of Catharina and Cyrillus craters, located in the lunar nearside are categorized under the matured category. The estimation results reveal that the FeO wt % of the Catharina crater varies from 0.0002 to 19.62, and that of the Cyrillus crater varies from 0.0001 to 12.32. TiO 2 wt% of Catharina crater varies from 0.01 to 86.12, while Cyrillus Crater varies from 0.01 to 4.34. The optical maturity (OMAT) of the Catharina crater varies from 0.0001 to 0.19 to that of the Cyrillus Crater Varies from 0.01 to 0.17. The overall summary of the results points out that lunar regolith is a fabulous repository of FeO and TiO 2 and quantitatively this metal abundance may be more than the anticipated values. [ABSTRACT FROM AUTHOR]

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 (section " 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 section " 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 " section 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. [ABSTRACT FROM AUTHOR]

Identification and extraction of material in the urban scenario are always challenging due to the presence of different heterogeneous materials. Airborne hyperspectral sensors with the advantage of both high spectral and spatial resolution can be used in such areas for the identification and mapping of urban materials. Manual extraction of the endmembers in highly dense heterogeneous urban regions is a very difficult task to achieve, but with automated extraction techniques, it yields promising results. To counter the mixed pixels problem in heterogeneous urban areas automated endmember extraction techniques like Endmember Average RMS (EAR), Minimum Average Spectral Angle (MASA), and Count Based Endmember Selection (CoB) was used for pure endmember identification in the densely populated urban area of Kolkata region using AVIRIS NG imagery. Spectral Unmixing Multiple Endmember Spectral Mixture Analysis (MESMA), Linear Spectral Unmixing (LSU), and Mixture Tuned Matched Filtering (MTMF) was performed on AVIRIS NG data using the extracted endmembers of different urban materials. The rule-based classification was performed on abundance images obtained from MESMA, MTMF, and LSU techniques for comparative analysis. Classification using MESMA abundance images outperformed in mapping mixed urban environments with an overall accuracy (OA) of 88.6 % followed by the rule-based classified output of MTMF and LSU with OA of 75.27% and 72.45% respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel nonlinear guidance law for an autonomous unmanned aerial vehicle (UAV) that enables it to track any predefined path while taking into account wind effects. The approach involves treating the desired path as the trajectory of the virtual target, which the UAV tracks without relying on knowledge of the path's curvature. This makes the design applicable to paths with varying levels of complexity and smooth curvatures. Additionally, the proposed method draws inspiration from pursuit guidance, known for its simplicity and ease of implementation. Theoretical analysis ensures that the UAV will converge to the intended path within a fixed time, irrespective of its initial configuration relative to the path. Simulations demonstrate the effectiveness of the proposed method, showcasing the UAV's ability to accurately follow diverse curvilinear paths. [ABSTRACT FROM AUTHOR]

This paper proposes a polynomial-based three-dimensional (3D) impact angle-constrained guidance law considering the seeker's field-of-view (FOV) bound. The guidance laws are derived using nonlinear coupled dynamics of the interceptor-target engagement against stationary as well as constant velocity targets. Line-of-sight (LOS) orientations between the interceptor and the target in both pitch and yaw planes are shaped as two cubic polynomial functions of relative range. An explicit expression for the look angle of the interceptor is acquired in terms of the LOS polynomials. This expression facilitates the embodiment of the FOV constraint in the boundary conditions inflicted on the polynomials. A system of equations with the eight unknown coefficients is obtained by employing the appropriate launch and terminal conditions of the interceptor-target engagement. Reference LOS angle and lead angle profiles are generated using the calculated coefficients, complying to which the interceptor achieves a zero miss distance with desired impact angle and FOV constraints. A tracking controller is then designed using a nonlinear control technique that enables the interceptor to follow reference lead angle profiles in mutually orthogonal planes. Unlike the already existing guidance strategies for 3D impact angle and FOV-constrained target interception, the proposed nonlinear guidance strategy is designed without the use of linearization or decoupling. Moreover, no switching logic or multi-phase guidance structures are employed in the proposed guidance strategy, which eliminates possible jumps in the guidance command. The effectiveness of the proposed guidance law is validated using numerical simulations, along with a comparison study with the existing strategy. [ABSTRACT FROM AUTHOR]

The present study addresses a comparative evaluation of airborne AVIRIS-NG and spaceborne PRISMA hyperspectral datasets for mapping hydrothermally altered minerals in Jahazpur town (25°25′23.37″N; 75°06′23.17″E) of Bhilwara district in southeastern Rajasthan. This area is located in Aravalli Craton which host notable base metal mineralization namely Rampura-Agucha, Pur-Banera and Rajpura-Dariba. The hyperspectral datasets were classified using spectral angle mapper which identified talc, soapstone, and kaolinite clay minerals in the study area. The samples were collected from the identified areas. Their spectral signature was compared with AVIRIS-NG, PRISMA, and USGS mineral spectral library and showed greater similarity in spectral absorption features. Conventional geological techniques such as thin section studies and XRD diffraction pattern analysis were carried out to validate the presence of minerals in the study area. Comparative analysis shows AVIRIS-NG and PRISMA sensor capability to identify altered/weathered minerals. The PRISMA dataset did not identify small surface exposure of talc deposit at the Padampura location due to its low spatial resolution (30 m) and SNR values. In contrast, AVIRIS-NG imagery successfully maps this exposure in the classified mineral map. The types of alteration in the area show formation of talc mineral from dolomite and argillic alteration resulting in kaolinite and montmorillonite formation. Therefore, airborne AVIRIS-NG proves its efficiency in mapping of relatively small surface exposure of altered minerals compared with the spaceborne PRISMA hyperspectral dataset. [ABSTRACT FROM AUTHOR]