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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Satellite Missions for Earth and Planetary Exploration".

Deadline for manuscript submissions: 20 June 2024 | Viewed by 27562

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Special Issue Editors

Dr. Jianqing Feng

E-Mail Website
Guest Editor

Planetary Science Institute, Tucson, AZ, USA
Interests: lunar regolith properties and shallow structure

Prof. Dr. Jianzhong Liu

E-Mail Website
Guest Editor

Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Interests: lunar and deep space exploration

Special Issue Information

Dear Colleagues,

The Moon has captivated humans since we first set eyes on it as the most prominent object in the night sky. The mysteries of the origin and evolution of the Moon continue to attract the interest and excitement of scientists and engineers worldwide. Since the first spacecraft, Luna 2, reached the lunar surface in 1959, humans have conducted more than 100 lunar exploration missions, culminating when Apollo astronauts stepped on the Moon in 1969–1972. In the 21^st century, more probes with new detection technology have been deployed, including SMART-1; SELENE; Chandrayaan-1 and Chandrayaan-2; LCROSS; LRO; GRAIL; LADEE; and CE-1, CE-2, CE-3, CE-4, and CE-5, providing new insight into lunar science. In these missions, remote sensing is the most critical detection method, such as optical image, multiple-wavelength spectroscopy, passive and active microwave, gamma-ray, X-ray, neutron, etc. In the upcoming decades, lunar exploration will usher in new development. Represented by the Artemis program proposed by NASA of the United States, plans for crewed flights followed by moonbases were declared by the US, Russia, ESA, China, Japan, and India.

For this Special issue, “Future of Lunar Exploration”, we are inviting contributions on new findings in the field of lunar science, covering methods and applications, as well as overview papers. The topics include but are not limited to analysis of data from current or past explore missions, instrument concepts for planned or future missions, modeling of the remote sensing observations of the lunar surface or interior, laboratory analysis of returned samples, and Earth-based observation of the Moon.

Dr. Jianqing Feng
Prof. Dr. Jianzhong Liu
Guest Editors

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Keywords

lunar exploration
lunar geology
satellite remote sensing
data processing and interpretation
numerical modeling
sample analysis
earth-based observation

Published Papers (9 papers)

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Research

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23 pages, 33239 KiB

Open AccessArticle

Lunar Surface Resource Exploration: Tracing Lithium, 7 Li and Black Ice Using Spectral Libraries and Apollo Mission Samples

by Susana del Carmen Fernández, Fernando Alberquilla, Julia María Fernández, Enrique Díez, Javier Rodríguez, Rubén Muñiz, Javier F. Calleja, Francisco Javier de Cos and Jesús Martínez-Frías

Remote Sens. 2024, 16(7), 1306; https://doi.org/10.3390/rs16071306 - 08 Apr 2024

Viewed by 438

Abstract

This is an exercise to explore the concentration of lithium, lithium-7 isotope and the possible presence of black dirty ice on the lunar surface using spectral data obtained from the Clementine mission. The main interest in tracing the lithium and presence of dark ice on the lunar surface is closely related to future human settlement missions on the moon. We investigate the distribution of lithium and 7 Li isotope on the lunar surface by employing spectral data from the Clementine images. We utilized visible (VIS–NIR) imagery at wavelengths of 450, 750, 900, 950 and 1000 nm, along with near-infrared (NIR–SWIR) at 1100, 1250, 1500, 2000, 2600 and 2780 nm, encompassing 11 bands in total. This dataset offers a comprehensive coverage of about 80% of the lunar surface, with resolutions ranging from 100 to 500 m, spanning latitudes from 80°S to 80°N. In order to extract quantitative abundance of lithium, ground-truth sites were used to calibrate the Clementine images. Samples (specifically, 12045, 15058, 15475, 15555, 62255, 70035, 74220 and 75075) returned from Apollo missions 12, 15, 16 and 17 have been correlated to the Clementine VIS–NIR bands and five spectral ratios. The five spectral ratios calculated synthesize the main spectral features of sample spectra that were grouped by their lithium and 7 Li content using Principal Component Analysis. The ratios spectrally characterize substrates of anorthosite, silica-rich basalts, olivine-rich basalts, high-Ti mare basalts and Orange and Glasses soils. Our findings reveal a strong linear correlation between the spectral parameters and the lithium content in the eight Apollo samples. With the values of the 11 Clementine bands and the 5 spectral ratios, we performed linear regression models to estimate the concentration of lithium and 7 Li. Also, we calculated Digital Terrain Models (Altitude, Slope, Aspect, DirectInsolation and WindExposition) from LOLA-DTM to discover relations between relief and spatial distribution of the extended models of lithium and 7 Li. The analysis was conducted in a mask polygon around the Apollo 15 landing site. This analysis seeks to uncover potential 7 Li enrichment through spallation processes, influenced by varying exposure to solar wind. To explore the possibility of finding ice mixed with regolith (often referred to as `black ice’), we extended results to the entire Clementine coverage spectral indices, calculated with a library (350–2500 nm) of ice samples contaminated with various concentrations of volcanic particles. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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18 pages, 17303 KiB

Open AccessArticle

Constraints on the Fault Dip Angles of Lunar Graben and Their Significance for Lunar Thermal Evolution

by Kai Zhu, Jianzhong Liu, Gregory Michael, Danhong Lei and Xuejin Zeng

Remote Sens. 2024, 16(1), 107; https://doi.org/10.3390/rs16010107 - 26 Dec 2023

Viewed by 618

Abstract

Lunar grabens are the largest tensional linear structures on the Moon. In this paper, 17 grabens were selected to investigate the dips and displacement–length ratios (γ) of graben-bounding faults. Several topographic profiles were generated from selected grabens to measure their rim elevation, width and depth through SLDEM2015 (+LOLA) data. The differences in rim elevation (∆h) and width (∆W) between two topographic profiles on each graben were calculated, yielding 146 sets of data. We plotted ∆h vs. ∆W for each and calculated the dip angle (α) of graben-bounding faults. A dip of 39.9° was obtained using the standard linear regression method. In order to improve accuracy, large error data were removed based on error analysis. The results, 49.4° and 52.5°, were derived by the standard linear regression and average methods, respectively. Based on the depth and length of grabens, the γ value of the graben-bounding normal fault is also studied in this paper. The γ value is 3.6 × 10⁻³ for lunar normal faults according to the study of grabens and the Rupes Recta normal fault. After obtaining the values of α and γ, the increase in lunar radius indicated by the formation of grabens was estimated. We suggest that the lunar radius has increased by approximately 130 m after the formation of grabens. This study could aid in the understanding of normal fault growth and provide important constraints on the thermal evolution of the Moon. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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16 pages, 8359 KiB

Open AccessArticle

Inversion of the Lunar Subsurface Rock Abundance Using CE-2 Microwave Brightness Temperature Data

by Wei Yang, Guoping Hu, Fan Yang and Wenchao Zheng

Remote Sens. 2023, 15(20), 4895; https://doi.org/10.3390/rs15204895 - 10 Oct 2023

Viewed by 913

Abstract

The rock strongly affects the surface and subsurface temperature due to its different thermophysical properties compared to the lunar regolith. The brightness temperature (TB) data observed by Chang’E-1 (CE-1) and Chang’E-2 (CE-2) microwave radiometers (MRM) give us a chance to retrieve the lunar [...] Read more.

β

of the mixture has been employed to estimate the physical temperature profile of the mixed layer (rock and regolith). Parameter

β

and the physical temperature profile of the mixed layer are constrained by the Diviner Channel 7 observations. Then, the subsurface RA on the 16 large (Diameter > 20 km) Copernican-age craters of the Moon is extracted from the average nighttime TB of the CE-2 37 GHz channel based on our previous rocky TB model. Two conclusions can be derived from the results: (1) the subsurface RA values are usually greater than the surface RA values retrieved from Diviner observations of the studied craters; (2) the spatial distribution of subsurface RA extracted from CE-2 MRM data is not necessarily consistent with the surface RA detected by Diviner data. For example, there are similar RA spatial distributions on both the surface and subsurface in Giordano Bruno, Necho, and Aristarchus craters. However, the distribution of subsurface RA is obviously different from that of surface RA for Copernicus, Ohm, Sharonov, and Tycho craters. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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20 pages, 11983 KiB

Open AccessArticle

Slip Estimation Using Variation Data of Strain of the Chassis of Lunar Rovers Traveling on Loose Soil

by Kojiro Iizuka and Kohei Inaba

Remote Sens. 2023, 15(17), 4270; https://doi.org/10.3390/rs15174270 - 30 Aug 2023

Viewed by 17925

Abstract

The surface of the Moon and planets have been covered with loose soil called regolith, and there is a risk that the rovers may stack, so it is necessary for them to recognize the traveling state such as its posture, slip behavior, and sinkage. There are several methods for recognizing the traveling state such as a system using cameras and Lidar, and they are used in real exploration missions like Mars Exploration Rovers of NASA/JPL. When a rover travels and travels across loose soil with steep slopes like a side wall of a crater on the lunar surface, the rover has side slipping. It means that its behavior makes the rover slip down to the valley direction. Even if this detection uses sensors like a camera and Lidar or other controlling systems like SLAM (Simultaneous Localization and Mapping), it would be too difficult for the rover to avoid slipping down to valley direction, because it is not able to detect the traction or resistance given from ground by individual wheel of the rover, as the traction of individual wheel of the rover is not clear. This means that the movement of the rover appeared by integrating the traction of all wheels mounted on the rover. Even if the localization by sensors is carried out, the location would be the location after slipping down. This is because when traveling on unstable ground, the driving force of each individual wheel cannot be accurately predicted, and the sum of the driving force of all wheels is the motion of the rover, which is detected after the position changes. Therefore, if the rover obtains information on the traction of each wheel, its maneuver to change its posture would work sooner and it would be able to travel more efficiently than in a state without that information. Because the onboard computer of rovers can identify their location and state from the information of the traction of each wheel, they can decide the next work carefully and in detail. From these tasks, we focused on the intrinsic sensation of a biological function like a human body and aimed to develop a system that recognizes the traveling state (slip condition) from the shape deformation of the chassis. In this study, we experimentally verified the relationship between the change in strain, which is the amount of deformation acting on the chassis, and the traveling state while the wheel is traveling. From the experimental results, we confirmed that the strain in the chassis was displaced dynamically and that the strain changed oscillatory while the wheel was traveling. In addition, based on the function of muscle spindles as mechanoreceptors, we discussed two methods of analyzing strain change: nuclear chain fiber analysis and nuclear bag fiber analysis. These analyses mean that the raw data of the strain are updated to detect the characteristic strain elements of a chassis while the wheel is traveling through loose soil. Eventually, the slipping state could be estimated by updating the data of a lot of strain raw data, and it was confirmed that the traveling state could be detected. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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36 pages, 11148 KiB

Open AccessArticle

A Measurement Method for Cislunar Spacecraft Based on Connected Element Interferometry and BeiDou-3 Interplanetary Link in Future Lunar Exploration

by Zefu Gao, Wenge Yang, Hongbin Ma, Fei Teng, Chao Li, Xuejian Li, Yuxin Wang and Yiwen Jiao

Remote Sens. 2023, 15(15), 3744; https://doi.org/10.3390/rs15153744 - 27 Jul 2023

Viewed by 1386

Abstract

To meet the urgent need for high-precision tracking and reliable cataloging of non-cooperative targets in the Earth–Moon space, this paper proposes a GNSS Inter-Satellite Link and Connected Element Interferometry (CEI)-based measurement method for high-value cislunar space targets. Firstly, the general flow and basic scenario of the proposed method are given, followed by the mathematical model which, mainly includes four parts: (i) dynamical constraint equations for targets; (ii) GNSS-based interplanetary link for irradiation of targets; (iii) transmission loss equation of GNSS inter-satellite link signal in Earth–Moon space; (iv) CEI-based precision measurements of targets. On this basis, the full process link budget analysis is carried out, followed by the performance evaluation, which includes the reception performance of CEI receiving arrays and the measurement accuracy of targets. The feasibility of the proposed method is evaluated and verified in experiments, and it is illustrated that (i) for inter-satellite link visibility analysis, at least 20 satellites can simultaneously provide inter-satellite link signals to the Earth–Moon space targets, with a single GEO satellite up to

8.5

h continuously, while the chain access can be available at up to 73,000 km, with the angle ranging from

- 80^{\circ}

360^{\circ}

; (ii) the Max Duration of Chain Access for BD3-lunarprobe-CEI (from 24 March 2023 04:00:00.000 to 31 March 2023 10:00:00.000) is 50,998.804 s/day, with a Total Duration of 358,408.797 s in 7 days; (iii) for link budget and measurement accuracy analysis, even beyond the farthest Earth–Moon Lagrangian point, the

C / N_{0}

will be above

56.1

dBHZ, while even approaching the distances of

4.5 \times 1 0^{5} km

, the

σ_{D L L}

and

σ_{F L L}

will be below 5.345 m and

3.475 \times 10^{- 4}

m/s, respectively, and the final measurement error will remain at 62.5 m with the proposed method. The findings of this paper could play a key role in future increasingly serious space missions, such as Earth–Moon space situational awareness, and will have a broad application prospect, if put into actual testing and operations. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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17 pages, 8950 KiB

Open AccessArticle

Improvement of Lunar Surface Dating Accuracy Utilizing Crater Degradation Model: A Case Study of the Chang’e-5 Sampling Area

by Feiyue Zhao, Wei Zuo and Chunlai Li

Remote Sens. 2023, 15(9), 2463; https://doi.org/10.3390/rs15092463 - 08 May 2023

Viewed by 1115

Abstract

Taking the Chang’e-5 (CE-5) sampling area as an example, this study carried out an investigation on improving the crater size-frequency distribution (CSFD) dating accuracy of lunar surface geologic units based on the crater degradation model. We constructed a three-parted crater degradation model, which consists of the diffusion equation describing crater degradation and equations describing the original crater profile for small craters (D < 1 km) and larger craters (D ≥ 1 km). A method that can improve the accuracy of CSFD dating was also proposed in this study, which utilizes the newly constructed degradation model to simulate the degradation process of the craters to help determine the crater degradation process and screen out the craters suitable for CSFD analysis. This method shows a good performance in regional dating. The age determined for the CE-5 sampling area is 2.0 ± 0.2 Ga, very close to the 2.03 ± 0.004 Ga of isotopic dating result of the returned sample. We found that the degradation state of the craters simulated by our constructed degradation model is highly consistent with the real existing state of the craters in terms of their topographic, geomorphological, and compositional (e.g., FeO) features. It fully demonstrates that the degradation model proposed in this study is effective and reliable for describing and distinguishing the degradation state of craters over time due to the cumulative effects of small craters. The proposed method can effectively distinguish between diffusively degraded (which conform to the degradation model) and non-diffusively degraded (which do not conform to the degradation model) craters and improve the CSFD accuracy through the selection of the craters. This not only provides an effective solution to the problem of obtaining a more “exact” frequency distribution of craters, which has long plagued the practical application of the CSFD method in dating the lunar surface but also advances our understanding of the evolutionary history of the geologic units of the study area. The results of this work are important for the in-depth study of the formation and evolution of the moon, especially for lunar chronology. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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22 pages, 7862 KiB

Open AccessArticle

New Lunar Crater Production Function Based on High-Resolution Images

by Jianan Liu, Zongyu Yue, Kaichang Di, Sheng Gou and Yangting Lin

Remote Sens. 2023, 15(9), 2421; https://doi.org/10.3390/rs15092421 - 05 May 2023

Viewed by 1508

Abstract

The lunar crater production function describes the general pattern of the size–frequency distribution of craters on the lunar surface, and it is the foundation of the surface dating method via crater counting. In addition, the lunar crater production function has been extended to other celestial bodies and used to analyze the meteorite flux of the inner solar system. The basic process of establishing the lunar crater production function is to map in an ideal way the primary craters in different geological units, and then to normalize all of the corresponding size–frequency distributions using a mathematical model. Currently, the most widely used lunar crater production functions have been established based on the images acquired in the last century. However, now they can be refined with newly obtained high-resolution images. In this research, we mapped all of the primary craters in 13 regions on the lunar surface with the images acquired using the narrow angle camera and wide angle camera onboard the Lunar Reconnaissance Orbiter, and then we fitted the lunar crater production function with a polynomial. The resultant new lunar crater production function is largely comparable with the previous results, and the difference is mainly at the large diameter end. We analyzed the uncertainty of model fitting as well as the difference in the crater measurements and demonstrated the reliability of the new production function. It is expected to refine the lunar surface dating models, which can provide more accurate information on the impact rate in related studies. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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13 pages, 10123 KiB

Open AccessCommunication

Hybrid Volcanic Episodes within the Orientale Basin, Moon

by Shreekumari Mukeshbhai Patel, Harish, Deep Patel, Paras M. Solanki and Mohamed Ramy El-Maarry

Remote Sens. 2023, 15(7), 1801; https://doi.org/10.3390/rs15071801 - 28 Mar 2023

Viewed by 1464

Abstract

Basalts from Mare Orientale are representative of lunar flood volcanism, which sheds light on the lunar farside’s thermal and volcanic past. We use Chandrayaan’s Moon Mineralogy Mapper data to examine the spectral and chemical makeup of the volcanic units located in the Orientale basin; the analysis specifically focuses on three formations: Mare Orientale, Lacus Veris, and Lacus Autumni. The main assemblage in these basaltic units consists of calcic augite and ferroaugite. Pyroxenes in the Orientale volcanic units have an average chemical composition of En_35.53 Fs_34.11 Wo_30.35. The trend in the composition of pigeonites and augites suggests that the magma was fractionated as it crystallized. The pyroxene quadrilateral plot’s distinct chemical trends indicate that the Orientale Basin underwent a number of volcanic eruptions from heterogeneous magma sources during the Imbrium to Eratosthenian period. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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Review

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24 pages, 24292 KiB

Open AccessReview

In-Situ Radar Observation of Shallow Lunar Regolith at the Chang’E-5 Landing Site: Research Progress and Perspectives

by Feiyang Fang, Chunyu Ding, Jianqing Feng, Yan Su, Ravi Sharma and Iraklis Giannakis

Remote Sens. 2023, 15(21), 5173; https://doi.org/10.3390/rs15215173 - 30 Oct 2023

Viewed by 1090

Abstract

China accomplished a historic milestone in 2020 when the mission Chang’e-5 (CE-5) to the Lunar’s surface was successfully launched. An extraordinary component of this mission is the “Lunar Regolith Penetrating Radar” (LRPR) housed within its lander, which currently stands as the most advanced payload in terms of vertical resolution among all penetrating radars employed in lunar exploration. This provides an unprecedented opportunity for high-precision research into the interior structure of the shallow lunar regolith. Previous studies have achieved fruitful research results based on the data from LRPR, updating our perception of the shallow-level regolith of the Moon. This paper provides an overview of the new advancements achieved by the LRPR in observing the basic structure of the shallow regolith of the Moon. It places special emphasis on the role played by the LRPR in revealing details about the shallow lunar regolith’s structure, its estimated dielectric properties, the provenance of the regolith materials from the landing area, and its interpretation of the geological stratification at the landing site. Lastly, it envisions the application and developmental trends of in situ radar technology in future lunar exploration. Full article

(This article belongs to the Special Issue Future of Lunar Exploration)

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