Thermal Emission Features Research Articles

Microwave Thermal Emission Features of Mare Tranquillitatis Revealed by CE-2 CELMS Data

Microwave Thermal Emission Features of Mare Tranquillitatis Revealed by CE-2 CELMS Data

Analyzing the microwave thermal emission features of lunar regolith in Chang’E landing sites and its geologic significance

嫦娥三、四和五号的原位月壤探测为基于嫦娥一、二号卫星微波辐射计数据的月球科学研究提供了重要参考。论文基于嫦娥二号卫星微波辐射计数据，生成了着陆区亮温图；为了消除亮温随纬度变化的影响，突出亮温与月壤成分之间的关系，定义和制作了规则亮温图和亮温差图；基于Kaguya MI数据，制作了研究区氧化亚铁、氧化钛、单斜辉石和橄榄石含量图；结合原位月壤探测成果，系统分析了嫦娥三、四和五号着陆区月壤的微波热辐射特性。主要研究发现包括以下三点：（1）嫦娥五号着陆区具有稳定的亮温表现，表明该地区月壤成分随深度的变化不明显，可以作为微波热辐射异常研究的重要参考；（2）嫦娥三号着陆区微波数据探测范围内月壤存在分层结构，以低频数据为代表的深层、以高频数据探测为代表的浅层和以可见光成果为代表的表层，成分变化很大；（3）在嫦娥四号着陆区发现并提出了微波冷异常的存在，并初步分析了微波冷异常的成因机制。论文研究发现微波辐射计数据可用于月海玄武岩的识别，可以为深化未来的月海岩浆演化研究提供重要的科学参考。

New Insights into Surface Deposits in the Balmer-Kapteyn Cryptomare Region Provided by Chang’E-2 Microwave Radiometer Data

Lunar cryptomare records both early-stage mare volcanisms and large-scale impact cratering, which can provide important information about the thermal evolution of the Moon. We built a mixing dielectric constant model to represent the cryptomare deposits mixed by highland debris and mare deposits, and the proper radiative transfer simulation was constructed to evaluate the thermal emission features of surface deposits in the cryptomare region. The microwave radiometer (MRM) data in the Balmer-Kapteyn region were extracted, and the linear interpolation method was used to generate brightness temperature (TB) maps at noon and at night. To enhance the correlation between cryptomare deposits and TB performances, normalized TB (nTB) and TB difference (dTB) maps were also generated. Combined with the datasets, including Lunar Reconnaissance Orbiter Wide Angle Camera, Lunar Orbiter Laser Altimeter, and Diviner and Clementine UV–VIS, the main findings are as follows: (1) The mare-like cryptomare deposits were discovered and identified according to the nTB and dTB performances. Combined with the surface compositions, at least two kinds of buried mare deposits were identified in the B-K region, which erupted during different episodes. (2) A construct-like volcanic feature was suggested by the nTB and dTB performances. (3) The results of our analysis indicated the presence of materials with low dTB anomalies in the northern and southwestern parts of the cryptomare region and in the mare unit within the Vendelinus crater, which illustrates the heterogeneity of the lunar crust in the vertical direction.

Potential Applications of CE-2 Microwave Radiometer Data in Understanding Basaltic Volcanism in Heavily Ejecta-Contaminated Mare Frigoris

Mare Frigoris is the fifth largest and almost northernmost mare located on the near side of the Moon. Mare Frigoris has an elongated shape, with a length of approximately 1500 km and a width of approximately 200 km, which makes it susceptible to becoming contaminated by the impact ejecta from the nearby highlands. Comparatively speaking, microwave radiometer (MRM) data have good penetration capabilities. Therefore, the MRM data from Chang’e-2 satellite were employed to study the volumetric thermal emission features of basaltic deposits in Mare Frigoris. Combining the MRM data with the basaltic units with FeO and TiO2 abundances identified using the small crater rim and ejecta probing (SCREP) methodology and with the gravity from Gravity Recovery and Interior Laboratory (GRAIL), the four potential conclusions that were obtained are as follows: (1) The MRM data are strongly related to the (FeO + TiO2) abundance of pristine basalts and are less influenced by ejecta contamination; (2) in every quadrant of Mare Frigoris, the (FeO + TiO2) abundance of the basalt decreases with an increase in age; (3) at least in Mare Frigoris, the main influencing factor regarding the brightness temperature remains the (FeO + TiO2) abundance of surface deposits; (4) a warm microwave anomaly was revealed in the western-central and eastern-central areas of Mare Frigoris which has a strong relationship with the positive Bouguer gravity anomaly derived from GRAIL data in terms of spatial distribution. The results are significant in the context of improving our understanding the basaltic igneous rock and thermal evolution of the Moon using MRM data.

Mare Deposits Identification and Feature Analysis in Mare Australe Based on CE‐2 CELMS Data

AbstractThe microwave signal has the penetration capability, which provides a potential chance to improve understanding of the mare deposits and the formation process of Mare Australe, a complex, extensive, and poorly understood region on the Moon. In this paper, the Chang'E‐2 microwave radiometer (CELMS) data were selected and processed to evaluate the microwave thermal emission features of the mare deposits in Mare Australe. After comparison, the dTB map at 3.0 GHz is employed. The results are as follows. (a) The possible cryptomare is much more extensive in Australe region than that identified with optical data. (b) The basaltic volcanism is re‐understood as three major episodes. (c) The high dTB anomaly is interpreted as the location of the vent areas in the mare patches. (d) The K‐means algorithm was first used to process the CELMS data, and the identified linear and ring structures indicate some important information about the formation processes of Mare Australe. These special findings will be of fundamental significance to better understand the basaltic volcanism and the evolution of the lunar surface.

Reevaluating Mare Moscoviense And Its Vicinity Using Chang’e-2 Microwave Sounder Data

Mare Moscoviense (148°E, 27°N) is one of the few large maria on the lunar farside, with the thinnest crust and a positive gravity anomaly. In this paper, the Chang’E-2 Microwave Sounder (CELMS) data was employed to study the microwave thermal emission features of mare basalts in Moscoviense Basin. The time angle and linear interpolation method are used to generate the brightness temperature (TB) maps at noon and night, as well as the TB difference (dTB) map. The obtained important results are as follows. (1) A new geologic map is generated with the TB and dTB maps using the maximum likelihood method, which gives a new expression about the basaltic units in Mare Moscoviense compared to the optical results; (2) the substrate temperature of Moscoviense Basin is likely warmer than what we know; (3) unit Ihtm (a Late (?) Imbrian, mid- to high-Ti, high-Fe basalt) is re-understood as two independent volcanic features with their own fissures; (4) the dTB maps firstly indicate that the depth lunar regolith is homogeneous in the highlands surrounding Mare Moscoviense, at least in the microwave domain, and secondly that there exists a special material bringing about the low dTB anomaly in the shallow layer of the east highlands. The results will be of great significance to better understand the basaltic volcanism of the Moon.

MTE Features of Apollo Basin and Its Significance in Understanding the SPA Basin

Apollo basin is located within the large South Pole–Aitken (SPA) basin. The study on Apollo basin will provide interesting information about the basic geologic issues about the lunar farside. In this paper, the normalized brightness $(T_{B})$ temperature $(nT_{B})$ maps and the $T_{B}$ difference $(dT_{B})$ maps are generated with the Chang'E-2 microwave sounder data to study the microwave thermal emission features of Apollo basin. The results are as follows. First, the mare volcanism in Apollo basin is re-understood according to the $nT_{B}$ performances at noon, and they should be originated from the southern part of the Apollo basin and strongly altered by the later impact ejecta. Second, the $nT_{B}$ maps indicate that there exists a special material from Dryden crater to Chaffee crater, whose thickness is more than 31 cm but less than 76.9 cm. Third, the similar $dT_{B}$ performances at 3.0 GHz indicate the homogeneous regolith thermophysical parameters of Apollo basin in the lateral direction. Fourth, the $dT_{B}$ maps and the discovered cold $T_{B}$ anomaly indicate the homogeneity of the SPA basin at least in the microwave thermophysical parameters. Our study also shows that the scientific study about the lunar surface is not sufficient only by visible data.

Lunar Brightness Temperature Map and TB Distribution Model

The microwave radiometer (MRM) on-board the Chinese Chang’e-2 (CE-2) lunar probe measures the lunar brightness temperature (also referred to as TB) data that are large-scale scientific data. In order to construct lunar TB map, the optimized hierarchical MK splines method is proposed, which uses a hierarchy of coarse-to-fine control lattices to generate a fine control lattice. The computation of the TB construction function is limited to the small number of control points in the merged control lattice, and then the desired high-resolution TB maps are constructed. At the same time, some basis relations between the lunar TB and frequencies are also analyzed based on the constructed TB maps. It can be found that the high-frequency TB map shows lunar topographic features with close similarity. Furthermore, to express the TB distribution features quantitatively, the lunar TB distribution models, including the global TB model of the Moon, the TB model of the lunar far side, and the TB model of the lunar near side, are established based on the constructed TB maps, and the obtained TB distribution models are log-normal distributions. The establishment of the lunar TB distribution model is important to reasonably select the color layer and intensity of color for the lunar TB maps, and is helpful for studying the lunar TB distribution law. In addition, the topographic data measured by the lunar orbiter laser altimeter are selected to discuss the influence of elevation on the lunar TB, and the CE-2 TB data combined with the FeO and TiO2 abundances are used to study the microwave thermal emission features of the lunar regolith. The research results have important implications for studying the thermal radiation of the Moon.

Microwave Thermal Emission Features of Mare Orientale Revealed by CELMS Data

Mare Orientale is the youngest and best-preserved multiring impact basin, whose microwave thermal emission (MTE) research has great significance for studying the internal thermal features and thermal structures of the lunar surface. In this paper, the microwave sounder (Chang'E Lunar Microwave Sounder, CELMS) data from Chang'E-2 satellite were used to study the MTE features of the Mare Orientale. The results indicate that the MTE features of the lunar regolith are much different between those in the superficial layer and in the substrate layer. Also, substrate temperature in the Orientale Basin is likely much higher than what we know. In addition, a new perspective is given to the Hevelius Formation, which is divided into the northeastern, northwestern, and southern parts, and has several potential linear structures. The results are of substantial geologic importance to study the thermal evolution of the Moon.

Numerical simulation on the thermal radiative properties of a 2D SiO2/W/SiO2/W layered grating for thermophotovoltaic applications

Tailoring the spectrum of thermal emission from the emitter is important for improving the performance of a thermophotovoltaic (TPV) system. In this work, a two-dimensional (2D) layered grating structure made of SiO2 and tungsten (W), which can realize wavelength-selective control of thermal emission, was proposed for a potential emitter in TPV applications. Numerical simulations of the spectral emissivity of the structure from the ultraviolet (UV) to the mid-infrared region reveals that the spectral-normal emissivity of the structure is enhanced to above 0.95 in the wavelength region from 0.55μm to 1.9μm for both TE and TM waves, but drops sharply at wavelength larger than 2μm. Physical mechanisms responsible for the wavelength-selective emissivity were elucidated as due to resonance of magnetic polaritons (MPs) in the SiO2 spacer and in the grooves of the tungsten grating, Wood׳s anomaly (WA), excitation of surface plasmon polaritons (SPPs) and wave interference. Furthermore, the structure was found to exhibit quasi-diffuse and polarization-insensitive features of thermal emission, suggesting that the proposed structure can serve as the emitter in the design of high performance TPV systems.

The special features of the formation of molecular ions on the surface of tantalum

Thermal emission of singly charged positive molecular ions, mass 254, from the surface of a tantalum band was studied. Thermal emission appeared if, first, oxygen acted on a tantalum band at a temperature higher than 600°C, and then the band was held at room temperature. At the time of holding t longer than a minute, thermal emission linearly depended on \( \sqrt t \). The special features of thermal emission were explained by the presence of a critical temperature of tantalum close to 400°C, at which all the molecular ions were emitted from the surface. A new model of their formation was suggested.

Filling the disk hollow following binary black hole merger: The transient accretion afterglow

Tidal torques from a binary black hole empty out the central regions in any circumbinary gaseous accretion disk. The balance between tidal torques and viscosity maintain the inner edge of the disk at a radius $r\ensuremath{\sim}1.5a--2a$, where $a$ is the binary semimajor axis. Eventually, the inspiraling binary decouples from the disk and merges, leaving behind a central hollow (``donut hole'') in the disk orbiting the remnant black hole. We present a simple, time-dependent, Newtonian calculation that follows the secular (viscous) evolution of the disk as it fills up the hollow down to the black hole innermost stable circular orbit and then relaxes to stationary equilibrium. We use our model to calculate the electromagnetic radiation (``afterglow'') spectrum emitted during this transient accretion epoch. Observing the temporal increase in the total electromagnetic flux and the hardening of the spectrum as the donut hole fills may help confirm a binary black hole merger detected by a gravitational wave interferometer. We show how the very existence of the initial hollow can lead to super-Eddington accretion during this secular phase if the rate is not very far below Eddington prior to decoupling. Our model, though highly idealized, may be useful in establishing some of the key parameters, thermal emission features and scalings that characterize this transient. It can serve as a guide in the design and calibration of future radiation-magnetohydrodynamic simulations in general relativity.

Chandradiscovery of extended non-thermal emission in 3C 207 and the spectrum of the relativistic electrons

We report on the Chandra discovery of large scale non–thermal emission features in the double lobed SSRL quasar 3C 207 (). These are: a diffuse emission well correlated with the western radio lobe, a bright one sided jet whose structure coincides with that of the eastern radio jet and an X-ray source at the tip of the jet coincident with the hot spot of the eastern lobe. The diffuse X-ray structure is best interpreted as inverse Compton (IC) scattering of the IR photons from the nuclear source and provides direct observational support to an earlier conjecture (Brunetti et al. [CITE]) that the spectrum of the relativistic electrons in the lobes of radio galaxies extends to much lower energies than those involved in the synchrotron radio emission. The X-ray luminous and spatially resolved knot along the jet is of particular interest: by combining VLA and Chandra data we show that a SSC model is ruled out, while the X-ray spectrum and flux can be accounted for by the IC scattering of the CMB photons (EIC) under the assumptions of a relatively strong boosting and of an energy distribution of the relativistic electrons as that expected from shock acceleration mechanisms. The X-ray properties of the hot spot are consistent with a SSC model. In all cases we find that the inferred magnetic field strength are lower, but close to the equipartition values. The constraints on the energy distribution of the relativistic electrons, imposed by the X-ray spectra of the observed features, are discussed. To this aim we derive in the Appendices precise semi–analytic formulae for the emissivities due to the SSC and EIC processes.

Materials for solar energy conversion: An overview

We introduce the radiative properties of our natural surroundings and demonstrate how the characteristic features of thermal emission, solar irradiation, atmospheric absorption, and sensitivity of the human eye and of plant photosynthesis lead naturally to a set of solar energy materials with well-defined wavelength- and angular-dependent absorptance, emittance, reflectance, and transmittance. Specific discussions are given of antireflection through microstructuring and of overheating protection through thermotropism. The paper ends with a look in the crystal ball at some possible solar materials research in the future.