Review on retrieval of lunar regolith thickness by active and passive microwave measurements

It is one of the imPortant methods to retrieve lunar regolith thickness using active and passive microwave techniques. The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulation in the regolith media. The lunar regolith model is first introduced, and the features of the involved physical parameters are indicated thereafter, such as dielectric constants, surface roughness, particle size and thermal grads of the lunar regolith. The time delay and the migration of the radar echoes from the different interfaces is the key problem for active microwave measurement. And the simulation of the microwave radiative transfer in the regolith media is the important technique for the passive microwave measurement. The important parameters and the physical mechanism for the two measurements are also presented.     

Influence of temperature and frequency on microwave dielectric properties of lunar regolith simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.     

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2010～2017年激光测月研究进展

简要介绍近几年激光测月(lunar laser ranging, LLR)的研究进展,包括设施建设、月球轨道、多源数据联合探测月球等。激光测月技术使我们能够全方位地了解地月系统,并且其用途广泛;下一代单棱镜反射器会将激光测月的精度提高1～2个量级;云南天文台站实现了中国激光测月零的突破,新台站的加入将帮助我们得到更准确的月球轨道;探测月球技术手段的增加、多种数据联合分析将使我们更加全面地认识月球。     

月球大地测量学的进展

介绍了月球大地测量(Selenodesy)的定义和方法。月球大地测量的一个特点是它的观测数据绝大部分都要依靠航天探测器或环月、绕月卫星来获取。月球大地测量的内容可以考虑3个方面：一是在月球上给出一个有确定定义的坐标参考系。并在其中布测一个控制网；二是确定这一月球参考系的大地测量几何和物理常数；三是求定月球的外部重力场。     

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JPL行星历表的发展及比较

基于DE405、DE421、DE430、DE440星历,计算各大行星在地球质心及太阳系质心惯性系中的位置,比较其他星历相对于DE440星历的行星位置精度。分析讨论各历表下月球的地心位置和速度精度,以及历表对于月球探测器的位置和速度从月心惯性系转为月固系的影响,并给出使用建议。结果表明,各大行星由于受观测数据等因素影响,位置精度差异较大,跨度从m级到10⁶ m量级。对于行星的位置精度,DE421和DE430相对于DE405有1~2个量级的提高,DE430相对于DE421提高50%。DE405历表的月球地心位置、速度精度分别为7 m和0.02 mm/s,DE421历表分别为1.5 m和0.004 mm/s,DE430历表分别为1.3 m和0.003 5 mm/s。对于星历用于月球探测器从月惯系转为月固系产生的坐标和速度误差,DE405分别为30 m和3 cm/s,DE421分别为1.3 m和1.2 mm/s,DE430分别为1 m和0.9 mm/s。历表对于月球坐标系转换的影响为m级。对于月球探测器导航及相关任务,推荐使用DE430或DE440行星历表。     

Regolith thickness modeling using a GIS approach for landslide distribution analysis,NW Himalayas

Regolith thickness is considered as a contributing factor for the occurrence of landslides. Although, mostly it is ignored because of complex nature and as it requires more time and resources for investigation. This study aimed to appraise the role of regolith thickness on landslide distribution in the Muzaffarabad and surrounding areas, NW Himalayas. For this purpose regolith thickness samples were evenly collected from all the lithological units at representative sites within different slope and elevation classes in the field. Topographic attributes (slope, aspect, drainage, Topographic Wetness Index, elevation and curvature) were derived from the Digital Elevation Model (DEM) (12.5 m resolution). ArcGIS Model Builder was used to develop the regolith thickness model. Stepwise regression technique was used to explore the spatial variation of regolith thickness using topographic attributes and lithological units. The derived model explains about 88% regolith thickness variation. The model was validated and shows good agreement (70%) between observed and predicted values. Subsequently, the derived regolith model was used to understand the relationship between regolith thickness and landslide distribution. The analysis shows that most of the landslides were located within 1–5 m regolith thickness. However, landslide concentration is highest within 5–10 m regolith thickness, which shows that regolith thickness played a significant role for the occurrence of landslide in the studied area.     

Advances in Research on Soil Moisture by Microwave Remote Sensing in China

Soil moisture is an important factor in global hydrologic circulation and plays a significant role in the research of hydrology, climatology, and agriculture. Microwave remote sensing is less limited by climate and time, and can measure in large scale. With these characteristics, this technique becomes an effective tool to measure soil moisture. Since the 1980s, Chinese researchers have investigated the soil moisture using microwave instruments. The active re- mote sensors are characteristic of high spatial resolution, thus with launch of a series of satellites, active microwave remote sensing of soil moisture will be emphasized. The passive microwave remote sensing of soil moisture has a long research history, and its retrieval algorithms were developed well, so it is an important tool to retrieve large scale moisture information from satellite data in the future.     

真实和有效叶面积指数及聚集指数的尺度效应

尺度效应是地球科学和定量遥感中的重要研究课题,目前的许多研究大多集中在估算尺度效应带来的误差,而对一些关键的植被结构参数是否存在尺度效应及其尺度转换方法尚存在诸多不同见解.本文针对真实和有效叶面积指数(LeafAr-ea Index,LAI和Effective LAI,LAIe)以及聚集指数(Clumping Inde...     

Retrieval of Land-surface Temperature from AMSR2 Data Using a Deep Dynamic Learning Neural Network

It is more difficult to retrieve land surface temperature(LST) from passive microwave remote sensing data than from thermal remote sensing data, because the emissivities in the passive microwave band can change more easily than those in the thermal infrared band. Thus, it is very difficult to build a stable relationship. Passive microwave band emissivities are greatly influenced by the soil moisture, which varies with time. This makes it difficult to develop a general physical algorithm. This paper proposes a method to utilize multiple-satellite, sensors and resolution coupled with a deep dynamic learning neural network to retrieve the land surface temperature from images acquired by the Advanced Microwave Scanning Radiometer 2(AMSR2), a sensor that is similar to the Advanced Microwave Scanning Radiometer Earth Observing System(AMSR-E). The AMSR-E and MODIS sensors are located aboard the Aqua satellite. The MODIS LST product is used as the ground truth data to overcome the difficulties in obtaining large scale land surface temperature data. The mean and standard deviation of the retrieval error are approximately 1.4° and 1.9° when five frequencies(ten channels, 10.7, 18.7, 23.8, 36.5, 89 V/H GHz) are used. This method can effectively eliminate the influences of the soil moisture, roughness, atmosphere and various other factors. An analysis of the application of this method to the retrieval of land surface temperature from AMSR2 data indicates that the method is feasible. The accuracy is approximately 1.8° through a comparison between the retrieval results with ground measurement data from meteorological stations.     

土壤水分微波反演方法进展和发展趋势

土壤水分是连接地表水循环和能量循环的关键参量,精确获取该参量对于理解气候变化、地表水文过程、地气间能量交换机理等具有重要意义。微波遥感由于其较为合适的探测深度和坚实的理论基础在观测地表浅层土壤水分上具有很大优势,结合反演方法可以获取空间连续的土壤水分含量,有助于更加客观认知土壤水分的时空演变机理。随着微波遥感数据的不断丰富,多种微波遥感土壤水分反演方法相继涌现,为了更好地了解其发展和趋势,本文总结了当前土壤水分微波反演常用的卫星遥感数据并分析其发展趋势,后从主动微波反演、被动微波反演和多源协同反演3个方面梳理了各类土壤水分微波反演方法的原理、发展和优缺点,最终总结出目前微波遥感土壤水分反演方法的发展趋势：即土壤水分微波反演方法的时空普适性逐渐增强、面向高时空分辨率的土壤水分微波协同反演方法快速发展以及土壤水分微波反演方法的智能化水平不断提高。     

月球正面撞击坑的空间分布特征分析

通过IAU最新公布的撞击坑名录、“嫦娥一号”影像与DEM数据,本文使用数理统计和空间分析的方法研究了月球正面撞击坑分布的空间不均衡性.主要体现在:(1)月球正面直径较大的撞击坑主要分布在月陆区域,且集中趋势明显,而月海区域直径较大的撞击坑分布较少,周围有大量直径较小的撞击坑;(2)直径较大的撞击坑在月表具有一定随机性,...     

联合VLBI和天文导航的月球车定位结果分析

推导了联合甚长基线干涉测量（VLBI）和天文导航的月球车定位计算公式,并利用嫦娥三号（CE-3）实测数据分别解算VLBI单独定位和联合天文导航定位的月球车定位结果。结果表明,联合定位相对于单独VLBI定位,提高了天文导航的定位精度,改善了月球车的定位精度;同时,联合VLBI和天文导航定位也保障了月球车定位的可靠性与稳定性。     

Brightness Temperature Model of Sea Foam Layer at L-band

Permittivity of a sea foam layer is very important in investigating ocean brightness temperature model. At microwave frequency, the Rayleigh method is developed to estimate the effective permittivity of the sea foam layer. To simplify the tedious calculation of sea foam effective permittivity at L band(1.4 GHz), Pade’ approximation is adopted to fit the sea foam effective permittivity computed by the Rayleigh method. With this fitting formula, a new brightness temperature model of sea foam layer defined by certain geophysical parameters, such as air volume fraction(AVF), sea surface temperature(SST), sea surface salinity(SSS) and thickness of foam layer d, is given. Furthermore, the sensitivities of the brightness temperature model to SST, SSS, d and AVF of a sea foam layer at L band are discussed. The sensitivities are ranked from most to least in the order:(1) d;(2) AVF;(3) SSS;(4) SST. This result indicates that the measurement errors of d and AVF have significant impacts on the retrievals of SSS and SST. With the experimental brightness temperature data, the SSS and AFV are retrieved by cost function.     

Softs of Fildes Peninsula, King George Island, the maritime Antarctic: Part I. Formation processes and pedogenetic particularities

Based on the data obtained from tens of the investigated soil profiles scattered over the Fildes Peninsula, King George Island, the maritime Antarctic, the soil-forming processes were discussed. It was concluded that on the weathering crusts resulted from various physical courses, the strong freeze-thaw action within regolith, significant organic matter accumulation, evident leaching and illuviation, as well as initial argillification dominated the formation and development of the soils on the Fildes Peninsula. Furthermore, this study indicated that the juvenility of genesis, poor profile-expression, variation in column thickness, etc. characterized the pedogenetic features of the soils of the Fildes Peninsula.     

Soil-vegetation-atmosphere radiative transfer model in microwave region

The radiative transfer is one of the significant theories that describe the processes of scattering, emission, and absorption of electromagnetic radiant intensity through scattering medium. It is the basis of the study on the quantitative remote sensing. In this paper, the radiative characteristics of soil, vegetation, and atmosphere were described respectively. The numerical solution of radiative transfer was accomplished by Successive Orders of Scattering （SOS）. A radiative transfer model for simulating microwave brightness temperature over land surfaces was constructed, designed, and implemented. Analyzing the database generated from soil-vegetation-atmosphere radiative transfer model under Advanced Microwave Scanning Radiometer-Earth Observing System （AMSR-E） configuration showed that the atmospheric effects on microwave brightness temperature should not be neglected, particularly for higher frequency, and can be parameterized. At the same time, the relationship between the emissivities of the different channels was developed. The study results will promote the development of algorithm to retrieve geophysical parameters from microwave remotely sensed data.     

基于DEM纹理特征的月貌自动识别方法探究

月海和月陆是两种最主要的月貌单元,对于月海及月陆快速准确地识别是进行各项月球研究的重要基础。目前,月海和月陆的识别大多采用DEM结合其派生地形因子建立指标体系的方法。这种方法虽然可在宏观尺度对月海和月陆进行识别和提取,但仍存在2个问题：（1）可扩展性差,不同地区难以共用同一套地形因子构建指标体系;（2）指标体系中各因子权重设置具有较大的主观性。针对以上问题,本文以“嫦娥一号”探测器获取的全月球DEM数据,从月表地形纹理特征的角度出发,提出一种以月表DEM数据识别月海、月陆的自动快速的方法。首先,利用灰度共生矩阵模型,以DEM数据为基础,实现对典型月海、月陆地形纹理特征的量化,然后,对量化指标的筛选,构建能有效区分两类月表形貌单元的特征向量。在此基础上,选用离差平方和作为识别器,最终实现对月海和月陆的自动识别。本文识别方法的整体识别率达到85.7%;综上可知,该方法既能克服原有方法中因子权重设置的主观性,又具有较好的通用性。     

Petrography and mineralogy of new lunar meteorite MIL090036

MIL090036 is a previously unknown meteorite （a feldspathic lunar breccia） that was discovered in Antarctica. The detailed petrography and mineralogy of this meteorite forms the subject of this paper. It has a typical clastic texture that consists of various types of rock debris （e.g. anorthosite, gabbroic anorthosite, gabbro, regolith breccia, troctolite, microporphyritic crystalline impact melt and compound clasts）, mineral crystal fragments （e.g. pyroxenes, plagioclase, olivine and ilmenite） and feldspathic glass clasts. The ifne-grained recrystallized minerals and mineral clasts are cemented together in a glassy groundmass. The anorthite content of plagioclase in the gabbro （An81-83） and anorthosite （An88-93） both have relatively low calcium content compared to those from other breccias （An90-98）. The pyroxene composition （Fs12-35 Wo3-44 En22-79） in the rock debris, crystal mineral clasts and anorthositic glass clasts are relatively iron-deifcient compared to those from gabbro debris with melt glass （Fs37-65 Wo10-29 En21-49） and groundmass （Fs18-69 Wo3-45 En14-50）. In contrast, the pyroxene grains in the gabbroic anorthosite display a narrow compositional range （Fs24-27 Wo7-14 En59-69）. Olivine grains in mineral fragments and the groundmass have a wider compositional range （Fo57-79） than those in the rock debris （Fo67-77）. The Fe/Mn ratio in olivine is in the range of 47 to 83 （average 76） and 76 to 112 （average 73） in pyroxenes, and hence classify within the lunar ifeld. The characteristics of texture, mineral assemblage and compositions suggest that MIL090036 possibly originated from a region beyond that of the Apollo and Luna samples. Further study of MIL090036 is therefore likely to lead to a better understanding of the geological processes on the Moon and the chemical composition of the lunar crust.