As of 20th January 2021 Wednesday, The CNSA –China National Space Administration – CLEP- China Luna Exploration Program Belt and Road Initiative Lunar Mission……Chang’e-4 successfully awakened and entered the 26th day of the work period….Chang’e 4 enters the 26th moon night] The Chang’e 4 lander and the “Yutu 2” lunar rover completed the 26th day of the month at 21:10 and 14:06 on January 20, and were set up according to ground instructions. Enter the moonlit night dormancy. Up to now, the Chang’e 4 lander and the “Yutu 2” lunar rover have worked on the moon for 749 earth days, with a cumulative mileage of 628.47 meters.
The Chang’e 4 lander and the “Yutu 2” lunar rover completed the 26th day of the month at 21:10 and 14:06 on January 20, completed the set-up according to ground instructions, and entered moon-night sleep. Up to now, the Chang’e 4 lander and the “Yutu 2” lunar rover have worked on the moon for 749 earth days, with a cumulative mileage of 628.47 meters.
Based on the first-hand data obtained by the Chang’e-4 mission, the scientific research team continues to achieve scientific results. The team of researcher Wu Yunzhao from the Purple Mountain Observatory of the Chinese Academy of Sciences took a different approach and used the visible near-infrared spectrometer (VNIS) to study the thermal radiation characteristics, obtained the thermal radiation characteristics of the moon on the micro-scale, and performed thermal correction of the spectrum, and related results were published….. In Geophysical Research Letters…
Researcher Wu Yunzhao first discovered the existence of thermal radiation in the spectral data of Chang’e-3 (Wu and Hapke, 2018). The first-month diurnal spectrum data of Chang’e-4 confirmed the discovery, and the tenth day fixed-point measurement provided more observational support. Figure 1 shows that after 2 μm, the spectral uplift gradually strengthens as the sun rises, and gradually decreases as the sun sinks. On the one hand, this discovery helps to interpret spectral data correctly, and on the other hand, it expands the application of spectrometers, not only for studying minerals, but also for studying the thermal radiation of the moon. This study shows that even in the 2 μm and mid-latitude mineral inversion studies, thermal correction is required….
Even in the pure thermal radiation region, the solution of temperature and emissivity is an under-determined equation, while the mid-infrared has both reflection and thermal emission, and temperature solution is more complicated. The study found that, in addition to the material composition, the heat radiation characteristics are significantly affected by the micro-scale roughness (Figure 2). In addition to the phase angle, the influence of the relative azimuth angle between the observation and the incident is very obvious (Figure 3). The two-way roughness slope of the micro-scale topography of the Chang’e-4 lunar soil is 22°-24°.
In the past, the research on the temperature characteristics of the lunar surface was mainly based on macro-satellite remote sensing data, and the wavelength was in the thermal infrared band. This research carried out for the first time the micro-scale and short-wave thermal radiation characteristics of lunar soil, which is of great significance for mid-infrared research. The spectrum used in this study has the superposition of solar reflection and the moon’s own thermal radiation. There are great difficulties in spectral analysis and application, and it is a spectral region that has relatively little research. The mid-infrared spectrum is very useful. Water, OH, organic matter, and minerals have discriminative spectral characteristics in the mid-infrared, and they are the key spectrum for detecting extraterrestrial life substances…
Scientific achievements come from: Researcher Wu Yunzhao’s team at Purple Mountain Observatory, Chinese Academy of Sciences
嫦娥四号进入第26月夜，研究成果揭示月球微尺度热辐射特性
嫦娥四号着陆器和“玉兔二号”月球车分别于1月20日21时10分和14时06分完成第26月昼工作，按地面指令完成设置，进入月夜休眠。截至目前，嫦娥四号着陆器和“玉兔二号”月球车已在月面工作749个地球日，累计行驶里程628.47米。
科研团队根据嫦娥四号任务获取的第一手数据，持续取得科学成果。中国科学院紫金山天文台吴昀昭研究员团队另辟蹊径，将可见光近红外光谱仪（VNIS）用于热辐射特性研究，获得了月球在微尺度上的热辐射特性，并对光谱进行了热校正，相关成果发表在Geophysical Research Letters。
吴昀昭研究员首次在嫦娥三号光谱数据发现有热辐射存在（Wu and Hapke, 2018）。嫦娥四号第一月昼光谱数据证实了该发现，第十月昼定点测量给出了更多的观测支持。图1可见，2μm后光谱抬升随着太阳升高而逐渐加强，随着太阳下沉而逐渐降低。该发现一方面有助于正确解译光谱数据，另一方面拓展了光谱仪应用，不仅可用于研究矿物，还可用于研究月球的热辐射。该研究表明即便在2 μm且中纬度地区的矿物反演研究也需要进行热校正。
即便纯热辐射区，温度与发射率的求解也是欠定方程，而中红外既存在反射又存在热发射，温度求解更为复杂。研究发现，除了物质成分外，热辐射特性受微尺度粗糙度显著影响（图2）。除了相角，观测与入射相对方位角的影响非常明显（图3）。获得了嫦娥四号月壤微尺度地形双向粗糙度斜率为22° – 24°。
过去对月表温度特性的研究主要是宏观卫星遥感数据，波长上是热红外波段。本研究首次开展了微观尺度和短波方面的月壤热辐射特性研究，对于中红外研究具有重要意义。本次研究所用谱段存在太阳反射与月球自身热辐射叠加，光谱解析及应用存在较大困难，是研究相对较少的光谱区。而中红外谱段非常有用，水、OH、有机质、矿物在中红外有判断性光谱特征，是探测地外生命物质的关键谱段。
科学成果来自：中国科学院紫金山天文台吴昀昭研究员团队
Images and visuals are from Weibo CNSA –China National Space Administration –CLEP- China Luna Exploration Program..
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