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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

Cited by 4 | Viewed by 3447

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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18 pages, 13639 KiB

Open AccessTechnical Note

Electromagnetic Signal Attenuation Characteristics in the Lunar Regolith Observed by the Lunar Regolith Penetrating Radar (LRPR) Onboard the Chang’E-5 Lander

by Chunyu Ding, Yan Su, Zhonghan Lei, Zongyu Zhang, Mi Song, Yuanzhou Liu, Ruigang Wang, Qingquan Li, Chunlai Li and Shaopeng Huang

Remote Sens. 2022, 14(20), 5189; https://doi.org/10.3390/rs14205189 - 17 Oct 2022

Cited by 12 | Viewed by 3686

Abstract

The Chinese Chang’E-5 probe landed in the Mons Rümker of Oceanus Procellarum on the near side of the Moon. The lunar regolith penetrating radar (LRPR) carried by the Chang’E-5 probe allows for the determination of in situ lunar regolith dielectric properties, which are probably related to the age and chemical composition of the regolith. In this paper, we analyze the Chang’E-5 LRPR data with the frequency shift method to estimate the loss tangent of the lunar regolith within a depth of ∼2.8 m. The loss tangent of the Chang’E-5 landing site is constrained to be 0.0148 ± 0.0016, which is substantially higher than that of the typical lunar regolith. The high loss tangent is found to be characteristic of the young basalt age (∼2.0 Ga) and high TiO

_{2}

+FeO content (28.21 ± 1.57%) of the Chang’E-5 landing site. Integrated analysis of results from Chang’E-3, Chang’E-4, and Chang’E-5 show that the younger is the geologic age of the mare unit, the greater is the loss tangent of the lunar regolith, and the weaker is the radar electromagnetic signal penetrating ability. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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13 pages, 4562 KiB

Open AccessTechnical Note

The Lunar Regolith Structure and Electromagnetic Properties of Chang’E-5 Landing Site

by Yuxi Li, Bin Zhou, Shaoxiang Shen, Wei Lu, Chuanjun Tang, Shidong Li, Yan Su, Shun Dai and Guangyou Fang

Remote Sens. 2022, 14(18), 4539; https://doi.org/10.3390/rs14184539 - 11 Sep 2022

Cited by 8 | Viewed by 4302

Abstract

On 1 December 2020, China’s Chang’E-5 (CE-5) probe successfully landed in the northeastern Oceanus Procellarum. This work mainly presents the results of Lunar Regolith Penetrating Radar (LRPR) equipped on the CE-5 Lander. The lunar regolith structure of the landing site from the surface to 3-m depth is unveiled by LRPR, which found that abundant rock fragments are distributed in uniform lunar regolith. The imaging result proved that the drilling and sampling process was prevented by big rocks at about 100 cm depth. On the basis of the response of lunar soil to electromagnetic (EM) wave, the EM properties of the landing site estimate that the relative dielectric constant and the loss tangent are 2.520 ± 0.186 and 0.0133 ± 0.0020, respectively. Full article

(This article belongs to the Special Issue Advances in Exploring the Moon, Mars, and Asteroids Using Spacecraft Remote Sensing and Other Toolkits)

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11 pages, 4528 KiB

Open AccessCommunication

Shallow Regolith Structure and Obstructions Detected by Lunar Regolith Penetrating Radar at Chang’E-5 Drilling Site

by Jianqing Feng, Matthew A. Siegler and Mackenzie N. White

Remote Sens. 2022, 14(14), 3378; https://doi.org/10.3390/rs14143378 - 13 Jul 2022

Cited by 15 | Viewed by 3037

Abstract

This work analyzes the observations from the Lunar Regolith Penetrating Radar (LRPR) onboard Chang’E-5 to reconstruct the subsurface structure of the regolith under the lander at the drilling site. This is the first stationary Ground-Penetrating Radar (GPR) array to operate on the Moon. Imaging results of pre-drilling and post-drilling measurements show that the thickness of local regolith is larger than 2 m. Within the LRPR’s detection range, we do not find any continuous layer. Instead, irregular, high-density zones are identified in the regolith. Two of these zones are on the drilling trajectory at ~30 cm and ~70 cm, consistent with the recorded drilling process. We speculate a rock fragment from the deeper, high-density zone obstructed the drill, which led to an early termination of the drilling. Based on our interpretation of subsurface structure, we modeled the LRPR echoes using a finite-difference time-domain method. The same imaging algorithm was also applied to the simulation data. The modeled data verify our inference of the regolith structure under the lander. Full article

(This article belongs to the Section Satellite Missions for Earth and Planetary Exploration)

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20 pages, 25407 KiB

Open AccessArticle

Pseudo-Spectral Time-Domain Method for Subsurface Imaging with the Lunar Regolith Penetrating Radar

by Yuxian Zhang, Naixing Feng, Guoda Xie, Lixia Yang and Zhixiang Huang

Remote Sens. 2022, 14(12), 2791; https://doi.org/10.3390/rs14122791 - 10 Jun 2022

Cited by 1 | Viewed by 2199

Abstract

Recently and successfully, the Chang’E-5 (CE-5) lander was launched on a mission to bring 1.731 kg of lunar soil back to Earth. To investigate various compositions of lunar regolith, we apply the Lunar Regolith Penetrating Radar (LRPR) as the same scientific payload installed on the CE-5 lander. Based on the high-accuracy imaging technique, we achieve subsurface imaging to process LRPR-measured data collected from the lunar-like exploration tests in our laboratory. In this paper, we propose the pseudo-spectral time-domain (PSTD) method as the underlying code to implement the reverse-time migration (RTM) method and restore the uncertain subsurface area. With the significant advantage of lower spatial sampling density, the PSTD-RTM method not only saves major computational resources, but also rapidly confirms the object prediction in the effective imaging area. To further analyze the LRPR measured data, we employ the spectrum window to remove high- and low-frequency noise, and thus improve imaging visibility to some extent. The imaging results in this paper can prove the reliability and efficiency of the PSTD-RTM method for subsurface discoveries in planetary exploration. Full article

(This article belongs to the Special Issue Microwave Remote Sensing for Quantitative Parameters Retrieval: Methods and Applications)

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12 pages, 6124 KiB

Open AccessEditor’s ChoiceArticle

Ultra-Wideband MIMO Array for Penetrating Lunar Regolith Structures on the Chang’e-5 Lander

by Wei Lu, Yuxi Li, Yicai Ji, Chuanjun Tang, Bin Zhou and Guangyou Fang

Electronics 2021, 10(1), 8; https://doi.org/10.3390/electronics10010008 - 23 Dec 2020

Cited by 7 | Viewed by 2918

Abstract

The Chang’e-5 lunar exploration mission of China is equipped with a Lunar Regolith Penetrating Radar (LRPR) for measuring the thickness and structures of the lunar regolith in the landing area. Since the LRPR is stationary, an ultra-wideband multiple-input multiple-output (MIMO) array is designed as a replacement for conventional mobile subsurface probing systems. The MIMO array, with 12 antenna elements and a switch matrix, operates in the frequency band from 1.0 to 4.75 GHz. In this work, the design and layout of the antenna elements were optimized with respect to the lander. To this end, the antenna elements were designed as miniaturized Vivaldi antennas with quarter elliptical slots (i.e., quarter elliptical slotted antenna, or QESA). QESAs are significantly small while being able to mitigate the impact of the lander on antenna electrical performances. QESAs also have a wide operating bandwidth, flat gain, and excellent time domain characteristics. In addition, a high-temperature resistant ultra-light radome with high transmissivity is designed to protect the external antenna array. After calibration, the MIMO array is used to detect targets embedded in volcanic ash. The detection depth reaches 2.5 m, and the detection effect is good. Full article

(This article belongs to the Section Microwave and Wireless Communications)

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