As of 24th September Thursday 2020, The CNSA –China National Space Administration Belt and Road Initiative Lunar Mission on the One Hundred Kilometer diameter Von Karman Crater Chang’e 4 lander and the “Yutu 2” lunar rover the Chang’e-4 lander and the “Yutu-2” lunar rover… Chang’e 4 lander and “Yutu 2” lunar rover awakened autonomously and entered the 22nd day of work] Today, the Chang’e 4 lander and “Yutu 2” lunar rover, which have been working on the back of the moon for 630 days….. In following.. The Chang’e-4 lander and the “Yutu-2” lunar rover will finish the 22nd month day work at 7:30 on September 24 and 23:18 on the 23rd, and complete the moon night mode setting according to ground instructions, and enter moon night sleep. Up to now, Chang’e-4 has spent 630 Earth days on the back of the moon and travelled 547.17 meters cumulatively.
Based on the 21st month day panoramic camera stitched images, DOM images and other data, the “Yutu 2” lunar rover mainly travels during the 22nd month day, successively in the impact crater and reflection about 1.3km northwest of the landing site Areas with higher rates were detected.
Researchers have made use of data such as panoramic camera ring-shot detection, infrared imaging spectrometer calibration detection, and simultaneous detection of lunar radar during driving, and obtained a number of scientific results, which were recently published in the International Journal of Nature Astronomy.
The scientific team conducted in-depth research on the radar detection data and obtained important discoveries about the lunar soil and shallow structures in the landing zone. Based on the characteristics of low-frequency radar signals, as shown in Figure 1, the shallow structure of the landing area is divided into three basic units, from top to bottom there are strong reflection units (unit 1), weak reflection units (unit 2), and medium reflection units. Unit (Unit 3). Combining basic constraints such as regional geology and the spatial distribution of large-scale impact craters, the results of the geological interpretation are as follows: Unit 1 (total thickness of about 130m) is the accumulation of sputtering materials near multiple impact craters (including Finsen, Alder, and von Carmen). Impact craters such as L and L’) and the basalt breccia layer at the bottom; unit 2 (total thickness about 110 m) is a basalt layer with multiple eruptions; unit 3 (thickness not less than 200 m) is Leibniz in the north of the landing zone Spatter from impact craters. The high-frequency radar signal further gives the fine structure of the upper part of the unit 1, as shown in Figure 2, which is characterized by the presence of a 12m thick lunar soil layer on the top, which basically does not contain large rocks, and the bottom is a strip of 22m thick Sputters, they are all projectiles from the Finsen impact crater, with a total thickness of 34m.
Fig.1 The detection profile and interpretation result of the low-frequency channel of the lunar radarFig.1 The detection profile and interpretation result of the low-frequency channel of the lunar radar
The lunar radar carried by the “Yutu-2” lunar rover can obtain the geological section below the driving path and reveal the layered structure of the underground. Because the lunar radar is directly based on the lunar surface for detection, the reflected signal detected by it has large energy and clear characteristics, and the effect is far better than that of spaceborne radars more than 100km away from the lunar surface. Moreover, due to the use of a frequency much higher than 5MHz of the spaceborne radar, its resolution advantage is also very obvious. The main frequencies of the two channels of the lunar radar are 60MHz and 500MHz, the spatial resolution is 10m and 0.3m, and the detection depth is about 50m and 500m. The high-frequency channel is used to detect the high-resolution structure of the shallow lunar soil and its underlying sputter, and the low-frequency channel is used to detect the layered structure of the deep sputter and basalt.
Figure 2 The detection profile and interpretation result of the high-frequency channel of the lunar radar
The shallow structural profile obtained by the lunar radar shows that the lunar material detected by “Yutu 2” comes from the Finsen impact crater, not from the filling basalt of the von Karman impact crater itself; at the same time, the radar profile also reveals the landing area has experienced multiple impacts, sputtering accumulation and multiple basalt magma eruptions filling. These new discoveries are of great significance for understanding the evolution of the Moon’s South Pole-Aiken Basin, and have an important guiding role for the subsequent exploration and study of the composition and structure of the Moon’s internal material.
科学团队对雷达探测数据开展了深入研究，获得了着陆区月壤和浅层结构的重要发现。基于低频雷达信号特征，如图1所示，将着陆区的浅层结构划分为三大基本单元，由上往下依次为强反射单元（单元1）、弱反射单元（单元2）和中等反射单元（单元3）。结合区域地质和大型撞击坑的空间分布等基本约束，地质解译结果如下：单元1（总厚度约130m）为临近多个撞击坑的溅射物堆积（包括芬森、阿尔德、冯·卡门L和L’等撞击坑）和底部的玄武岩角砾层；单元2（总厚度约110 m）为多次喷发的玄武岩层；单元3（厚度不小于200 m）为着陆区北部莱布尼兹撞击坑的溅射物。高频雷达信号进一步给出单元1上部的精细结构，如图2所示，其特征为顶部存在厚达12m的月壤层，基本不含大石块，其下为厚达22m的条带状溅射物，它们均是来自芬森撞击坑的抛射物，总厚度达34m。
图1 测月雷达低频通道的探测剖面及解译结果图1 测月雷达低频通道的探测剖面及解译结果
图2 测月雷达高频通道的探测剖面及解译结果图2 测月雷达高频通道的探测剖面及解译结果
Images and Visuals are from Weibo…