Visible And Infrared Research Articles

REAL-TIME IMPLEMENTATION OF LWT BASED NOVEL IR AND VI FUSION ALGORITHM USING RASPBERRY PI PLATFORM

One of the most important and active areas of image processing research is visible and thermallight image fusion. Moreover, real-time visible and thermal-light image fusion has been utilized in multiple kinds of applications such as surveillance devices, military applications, medical diagnosis, remote sensing, etc. Hence, this paper suggests a real-time application of visible and infrared (V-I) image fusion using lift wavelet transform (LWT) and implemented on the Raspberry Pi. The proposed morphological operations-based unsharp masking enhancement technique overcomes the low contrast issue of the fused image. Next, the LWT provides the good feature (smooth and detail) layers of visible image (VI) and infrared image (IRI) when compared to other transformations. Due to this, we have overcome the problem of spatial distortions in the fused image. Moreover, the proposed novel fusion techniques such as, mean-weighted fusion rule based on filters and max-weighted fusion rule based on filters generate the fused image with improved texture information and overcome the problem of edge information loss. The real-time application of the V-I image fusion is implemented through the portable hardware device Raspberry Pi. Finally, the experimental results show that the suggested framework has produced a fused image with improved visual quality, rich edge information, high contrast, low spatial distortions, and more texture information, when compared to the results of existing methodologies.

Estimating Early Summer Snow Depth on Sea Ice Using a Radiative Transfer Model and Optical Satellite Data

Sea ice regulates the overall energy exchange and radiation budget of the Arctic region, and understanding this relationship requires an accurate determination of snow depth. However, methods for deriving snow depth have a large error through the annual winter and early spring periods due to the potential complexity of surface melting during early summer. In this study, we explore the potential of retrieving snow depth during the early summer using optical satellite imagery of the sea-ice cover. Measurements using VIS/IR (visible and infrared) usually feature much higher spatial resolution than L-band satellite data and can provide additional surface melting and leads information; in addition, considering the snow grain size–snow surface temperature interaction, there is co-variability between the observed sea-ice surface broadband albedo using an optical satellite sensor, the sea-ice surface temperature, and the retrieval target of snow depth on the spatial scale of optical imagery samples. We applied a surface classification procedure to optical satellite imagery and introduce an approach to derive snow depth from optical satellite imagery and ice surface temperature data using two solar radiation transfer models: the Delta-Eddington solar radiation model, which is the shortwave radiative scheme of the Los Alamos sea-ice model, and a simplified snow albedo scheme, which is tuned to the observational data of buoys. The snow depth was inversed from the model simulation results using a lookup-table-based method. For comparison with the observational data, using the Delta-Eddington solar radiation model, about 55% of the differences are below 5 cm, and thicker snowpack has a larger bias; using the simplified snow albedo scheme, a mean difference of 4.1 cm between retrieval and measurements was found, with 93% of the differences being smaller than 5 cm. This approach can be applied to optical satellite imagery acquired under clear-sky conditions and can serve as an addition to overcome the limitations of existing methods.

Ultrahigh-efficient material informatics inverse design of thermal metamaterials for visible-infrared-compatible camouflage

Multispectral camouflage technologies, especially in the most frequently-used visible and infrared (VIS-IR) bands, are in increasing demand for the ever-growing multispectral detection technologies. Nevertheless, the efficient design of proper materials and structures for VIS-IR camouflage is still challenging because of the stringent requirement for selective spectra in a large VIS-IR wavelength range and the increasing demand for flexible color and infrared signal adaptivity. Here, a material-informatics-based inverse design framework is proposed to efficiently design multilayer germanium (Ge) and zinc sulfide (ZnS) metamaterials by evaluating only ~1% of the total candidates. The designed metamaterials exhibit excellent color matching and infrared camouflage performance from different observation angles and temperatures through both simulations and infrared experiments. The present material informatics inverse design framework is highly efficient and can be applied to other multi-objective optimization problems beyond multispectral camouflage.

Dielectric Properties of Plasma-Sprayed Fully Natural Garnets

Various kinds of natural garnets belonging to the almandine type (3FeO·Al2O3·3SiO2) were sprayed by plasma spray technique to build coatings on metallic substrates. The experimental garnet powders came from different mines in the Czech Republic and Mongolia. After coating and cooling the substrates were removed. In this way, self-supporting plates were obtained and further studied with microscopy, X-ray diffraction, and dielectric spectroscopy. Mechanical properties were in our focus as well. Microhardness was measured on cross sections dedicated to microstructure observation. Wear resistance in wet conditions was tested in a slurry. Reflectance was measured applying visible and infrared (VIS-NIR) radiation. Dielectric properties of coatings were studied at low voltage capacitance, loss tangent and also under direct current (DC) resistance. The results show that garnet minerals are interesting candidates for various optical and electronic applications; they have similar dielectric behavior as, for example, aluminum oxide or similar high-purity synthetic oxides, and, simultaneously, they have extraordinarily low reflectance in VIS-NIR radiation. The differences between natural powders and resulting coatings are discussed in connection with their chemical and phase compositions.

Homogeneity assessment of the SuperCam calibration targets onboard rover perseverance

The SuperCam instrument, onboard the Perseverance rover (Mars 2020 mission) is designed to perform remote analysis on the Martian surface employing several spectroscopic techniques such as Laser Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman (TRR), Time-Resolved Fluorescence (TRF) and Visible and Infrared (VISIR) reflectance. In addition, SuperCam also acquires high-resolution images using a color remote micro-imager (RMI) as well as sounds with its microphone. SuperCam has three main subsystems, the Mast Unit (MU) where the laser for chemical analysis and collection optics are housed, the Body Unit (BU) where the different spectrometers are located inside the rover, and the SuperCam Calibration Target (SCCT) located on the rover's deck to facilitate calibration tests at similar ambient conditions as the analyzed samples. To perform adequate calibrations on Mars, the 22 mineral samples included in the complex SCCT assembly must have a very homogeneous distribution of major and minor elements. The analysis and verification of such homogeneity for the 5–6 replicates of the samples included in the SCCT has been the aim of this work. To verify the physic-chemical homogeneity of the calibration targets, micro Energy Dispersive X-ray Fluorescence (EDXRF) imaging was first used on the whole surface of the targets, then the relative abundances of the detected elements were computed on 20 randomly distributed areas of 100 × 100 μm. For those targets showing a positive Raman response, micro-Raman spectroscopy imaging was performed on the whole surface of the targets at a resolution of 100 × 100 μm. The %RSD values (percent of relative standard deviation of mean values) for the major elements measured with EDXRF were compared with similar values obtained by two independent LIBS set-ups at spot sizes of 300 μm in diameter. The statistical analysis showed which elements were homogeneously distributed in the 22 mineral targets of the SCCT, providing their uncertainty values for further calibration. Moreover, nine of the 22 targets showed a good Raman response and their mineral distributions were also studied. Those targets can be also used for calibration purposes of the Raman part of SuperCam using the wavenumbers of their main Raman bands proposed in this work.

SuperCam calibration targets on board the perseverance rover: Fabrication and quantitative characterization

The Perseverance rover is exploring Jezero crater on Mars since February 2021. SuperCam instrument is part of the scientific payload, combining five different techniques in order to characterize the targets to sample: LIBS (Laser-Induced Breakdown Spectroscopy), Raman and Visible and Infrared (VISIR) spectroscopies, Sound Recording and a colored Imager. Thirty-six calibration targets have been developed for this instrument. Twenty-three of these calibration targets are dedicated to the LIBS technique, corresponding to rocks and/or minerals. Raman and VISIR spectroscopy have their own calibration targets but may also use the LIBS mineral targets as reference on Mars to test mineral detections. The choice and the fabrication of these calibration targets have been made in order to fulfill the science intents of the mission, as well as the technical and science intents of each of the SuperCam technique. These calibration targets have been spectrally characterized and they have shown to be chemically homogeneous at the SuperCam LIBS scale. Their elementary compositions are given, using two different quantitative methods. The composition of the calibration targets will be used as reference for future assessment of the quantitative capability of the SuperCam LIBS technique.

A New Data Fusion Neural Network Scheme for Rainfall Retrieval Using Passive Microwave and Visible/Infrared Satellite Data

A new data fusion technique based on Artificial Neural Networks (ANN) for the design of a rainfall retrieval algorithm is presented. The use of both VIS/IR (VISible and InfraRed) data from GEO (Geostationary Earth Orbit) satellite and of passive microwave data from LEO (Low Earth Orbit) satellite can take advantage of both types of sensors reducing their limitations. The technique can reconstruct the surface rain field with the MSG-SEVIRI (Meteosat Second Generation–Spinning Enhanced Visible Infrared Imager) spatial and temporal resolution, which means 3 km at the sub satellite point and 5 km at mid-latitudes, every 15 min, respectively. Rainfall estimations are also compared with H-SAF (Hydrology Satellite Application Facility) PR-OBS3A operational product showing better performance both on the identification of rainy areas and on the retrieval of the amount of precipitation. In particular, in the considered test cases, results report an improvement in average of 83% in terms of probability of rainy areas detection, of 45% in terms of false alarm rate, and of 47% in terms of root mean square error in the retrieval of the amount of precipitation.

Visible and near-infrared hyperspectral imaging techniques allow the reliable quantification of prognostic markers in lymphomas: A pilot study using the Ki67 proliferation index as an example

In this study, we examined the suitability of visible and infrared (Vis-NIR) hyperspectral imaging (HSI) for the quantification of prognostic markers in non-Hodgkin lymphoma on the example of the Ki67 proliferation index. Ki67 quantification was done on six follicular lymphomas (FLs) and 12 diffuse large B-cell lymphomas (DLBCLs) by applying classic immunohistochemistry. The Ki67 index was comparatively assessed visually, using HSI-based quantification and a digital imaging analysis (DIA) platform. There was no significant difference between visual assessment (VA), DIA, and HSI in FLs. For DLBCLs, VA resulted in significantly higher Ki67 values than HSI (p = 0.023) and DIA (p = 0.006). No such difference was seen comparing analysis by HSI and DIA (p = 0.724). Cohen's κ revealed a "substantial correlation" of Ki67 values for HSI and DIA in FLs and DLBCLs (κ = 0.667 and 0.657). Here we provide the first evidence that, comparably to traditional DIA, HSI can be used reliably to quantify protein expression, as exemplified by the Ki67 proliferation index. By covering the near-infrared spectrum, HSI might offer additional information on the biochemical composition of pathological specimens, although our study could not show that HSI is clearly superior to conventional DIA. However, the analysis of multiplex immunohistochemistry might benefit from such an approach, especially if overlapping immunohistochemical reactions were possible. Further studies are needed to explore the impact of this method on the analysis and quantification of multiple marker expression in pathological specimens.

New Insights of Geomorphologic and Lithologic Features on Wudalianchi Volcanoes in the Northeastern China from the ASTER Multispectral Data

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging system onboard NASA’s (National Aeronautics and Space Administration’s) Terra satellite is capable of measuring multispectral reflectance of the earth’s surface targets in visible and infrared (VNIR) to shortwave infrared (SWIR) (until 2006) as well as multispectral thermal infrared (TIR) regions. ASTER VNIR stereo imaging technique can provide high-resolution digital elevation models (DEMs) data. The DEMs data, three-dimensional (3D) perspective, and ratio images produced from the ASTER multispectral data are employed to analyze the geomorphologic and lithologic features of Wudalianchi volcanoes in the northeastern China. Our results indicate that the 14 major conical volcanic craters of Wudalianchi volcanoes are arranged as three sub-parallel zones, extending in a NE (Northeast) direction, which is similar to the direction of regional fault system based on the ASTER DEMs data. Among the 14 volcanic craters in Wudalianchi, the Laoheishan, and Huoshaoshan lavas flows, after the historic eruptions, pouring down from the crater, partially blocked the Baihe River, which forms the Five Large Connected Pools, known as the Wudalianchi Lake. Lithologic mapping shows that ASTER multispectral ratio imagery, particularly, the Lava Flow Index (LFI) (LFI = B10/B12) imagery, can clearly distinguish different lava flow units, and at least four stages of volcanic eruptions are revealed in the Wudalianchi Quaternary volcano cluster. Thus, ASTER multispectral TIR data can be used to determine relative dating of Quaternary volcanoes in the semi-arid region. Moreover, ASTER 3D perspective image can present an excellent view for tracking the flow directions of different lavas of Wudalianchi Holocene volcanoes.

CHARACTERIZING KI67 ANTIBODY STAINING FOR NON-HODGKIN'S LYMPHOMA USING VISIBLE AND NEAR-INFRARED HYPERSPECTRAL IMAGING TECHNIQUES

Objective To assess the model of quantitation of the Ki67 index by employing visible and infrared (Vis-NIR) hyperspectral imaging (HSI) in Non-Hodgkin Lymphomas (NHL) as time and cost-efficient tissue-sparing alternative to standard diagnostic procedures. Material and Methods Ki67 quantitation was done on 19 formalin-fixed paraffin embedded specimens (6 follicular lymphomas (FL); 12 diffuse large B-cell lymphomas (DLBCL) and one Burkitt-lymphoma (BL) by applying classical immunohistochemistry using an automated platform. Subsequent visual quantification of the Ki67 index was comparatively assessed visually and to HSI-based Ki67 index quantification. Results HSI was successfully implemented for analyzing histopathological slides using the IMEC SNAPSCAN camera. There was no significant difference between visual assessment (VA) and HSI (p = 0.257) in FL, while in DLBCL VA resulted in significantly higher Ki67 values than HSI (p = 0.006). Cohens Kappa showed a fair correlation for both FL and DLBCL (Kappa: 0.333 and 0.316, respectively). The case of BL added as a”super-positive” control was consistently measured by both techniques. Conclusion HSI can be used to quantify marker expression using the Ki67 index model. HSI offers additional information on the biochemical composition of tissues, while preserving limited samples. HSI is easy to install enabling optimization of workflows by restricting analysis times at low costs. Future application by automated imaging analyses systems may allow quantitative measurement of more significant areas of tissue samples, diminishing selection bias in commonl visual pathology and improving information on the tissue heterogeneity of a given marker. In summary, HSI is a cost-effective and quick alternative imaging platform when compared to other digital image analysis systems that are significantly more costly and time-consuming.

The mineralogy of Ceres’ Nawish quadrangle

Quadrangle Ac-H-08 Nawish is located in the equatorial region of Ceres (Lat 22°S-22°N, Lon 144°E- 216°E), and it has variable mineralogy and geology. Here, we report on the mineralogy using spectra from the Visible and InfraRed (VIR) mapping spectrometer onboard the NASA Dawn mission. This quadrangle has two generally different regions: the cratered highlands of the central and eastern sector, and the eastern lowlands. We find this dichotomy is also associated with differences in the NH4-phyllosilicates distribution. The highlands, in the eastern part of the quadrangle, appear depleted in NH4-phyllosilicates, conversely to the lowlands, in the north-western side. The Mg-phyllosilicates distribution is quite homogeneous across Nawish quadrangle, except for few areas. The 2.7 µm band depth is lower in the south-eastern part, e.g. in the Azacca ejecta and Consus crater ejecta, and the band depth is greatest for the Nawish crater ejecta, and indicates the highest content of Mg-phyllosilicates of the entire quadrangle. Our analysis finds an interesting relationship between geology, mineralogy, topography, and the age in this quadrangle. The cratered terrains in the highlands, poor in NH4 phyllosilicates, are older (̴2 Ga). Conversely, the smooth terrain, such as with Vindimia Planitia, is richer in ammonia-bearing phyllosilicates and is younger (̴1 Ga). At the local scale, Ac-H-8 Nawish, displays several interesting mineralogical features, such as at Nawish crater, Consus crater, Dantu and Azzacca ejecta, which exhibit localized Na-carbonates deposits. This material is superimposed on the cratered terrains and smooth terrains and shows the typical depletion of phyllosilicates, already observed on Ceres in the presence of Na-carbonates.

Ambient and cold‐temperature infrared spectra and XRD patterns of ammoniated phyllosilicates and carbonaceous chondrite meteorites relevant to Ceres and other solar system bodies

AbstractMg‐phyllosilicate‐bearing, dark surface materials on the dwarf planet Ceres have NH4‐bearing materials, indicated by a distinctive 3.06 μm absorption feature. To constrain the identity of the Ceres NH4‐carrier phase(s), we ammoniated ground particulates of candidate materials to compare their spectral properties to infrared data acquired by Dawn's Visible and Infrared (VIR) imaging spectrometer. We treated Mg‐, Fe‐, and Al‐smectite clay minerals; Mg‐serpentines; Mg‐chlorite; and a suite of carbonaceous meteorites with NH4‐acetate to exchange ammonium. Serpentines and chlorites showed no evidence for ammoniation, as expected due to their lack of exchangeable interlayer sites. Most smectites showed evidence for ammoniation by incorporation of NH4+ into their interlayers, resulting in the appearance of absorptions from 3.02 to 3.08 μm. Meteorite samples tested had weak absorptions between 3.0 and 3.1 μm but showed little clear evidence for enhancement upon ammoniation, likely due to the high proportion of serpentine and other minerals relative to expandable smectite phases or to NH4+ complexing with organics or other constituents. The wavelength position of the smectite NH4 absorption showed no variation between IR spectra acquired under dry‐air purge at 25 °C and under vacuum at 25 °C to −180 °C. Collectively, data from the smectite samples show that the precise center wavelength of the characteristic ~3.05 μm v3 absorption in NH4 is variable and is likely related to the degree of hydrogen bonding of NH4‐H2O complexes. Comparison with Dawn VIR spectra indicates that the hypothesis of Mg‐saponite as the ammonium carrier phase is the simplest explanation for observed data, and that Ceres dark materials may be like Cold Bokkeveld or Tagish Lake but with proportionally more Mg‐smectite.

Artifacts reduction in VIR/Dawn data

Remote sensing images are generally affected by different types of noise that degrade the quality of the spectral data (i.e., stripes and spikes). Hyperspectral images returned by a Visible and InfraRed (VIR) spectrometer onboard the NASA Dawn mission exhibit residual systematic artifacts. VIR is an imaging spectrometer coupling high spectral and spatial resolutions in the visible and infrared spectral domain (0.25-5.0 μm). VIR data present one type of noise that may mask or distort real features (i.e., spikes and stripes), which may lead to misinterpretation of the surface composition. This paper presents a technique for the minimization of artifacts in VIR data that include a new instrument response function combining ground and in-flight radiometric measurements, correction of spectral spikes, odd-even band effects, systematic vertical stripes, high-frequency noise, and comparison with ground telescopic spectra of Vesta and Ceres. We developed a correction of artifacts in a two steps process: creation of the artifacts matrix and application of the same matrix to the VIR dataset. In the approach presented here, a polynomial function is used to fit the high frequency variations. After applying these corrections, the resulting spectra show improvements of the quality of the data. The new calibrated data enhance the significance of results from the spectral analysis of Vesta and Ceres.

Temperature-dependent VNIR spectroscopy of hydrated Mg-sulfates

We investigate two poly-hydrated magnesium sulfates, hexahydrite (MgSO4 · 6H2O) and epsomite (MgSO4 · 7H2O), in the visible and infrared (VNIR) spectral range 0.5/4.0µm, as particulate for three different grain size ranges: 20–50µm, 75–100µm and 125–150µm. All samples were measured in the 93–298K temperature range. The spectra of these hydrated salts are characterized by strong OH absorption bands in the 1.0–1.5µm region, and by H2O absorption bands near 2 and 3µm. Other weak features show up at low temperatures near 1.75µm (in both hexahydrite and epsomite) and 2.2µm (only in hexahydrite). The spectral behavior of the absorption bands of these two minerals has been analyzed as a function of both grain size and temperature, deriving trends related to specific spectral parameters such as band center, band depth, band area, and band width. Hydrated minerals, in particular mono- and poly-hydrated sulfates, are present in planetary objects such as Mars and the icy Galilean satellites. Safe detection of these minerals shall rely on detailed laboratory investigation of these materials in different environmental conditions. Hence an accurate spectral analysis of such minerals as a function of temperature is key to better understand and constrain future observations.

Lithologic variation within bright material on Vesta revealed by linear spectral unmixing

Vesta’s surface is mostly composed of pyroxene-rich lithologies compatible with howardite, eucrite and diogenite (HED) meteorites (e.g., McCord et al. [1970] Science, 168, 1445–1447; Feierberg & Drake [1980] Science, 209, 805–807). Data provided by the Visible and Infrared (VIR) spectrometer, onboard the NASA Dawn spacecraft, revealed that all Vesta reflectance spectra show absorption bands at ∼0.9 and ∼1.9 µm, which are typical of iron-bearing pyroxenes (De Sanctis et al. [2012] Science, 336, 697–700). Other minerals may be present in spectrally significant concentrations; these include olivine and opaque phases like those found in carbonaceous chondrites. These additional components modify the dominant pyroxene absorptions. We apply linear spectral unmixing on bright material (BM) units of Vesta to identify HEDs and non-HED phases. We explore the limits of applicability of linear spectral unmixing, testing it on laboratory mixtures. We find that the linear method is applicable at the VIR pixel resolution and it is useful when the surface is composed of pyroxene-rich lithologies containing moderate quantities of carbonaceous chondrite, olivine, and plagioclase. We found three main groups of BM units: eucrite-rich, diogenite-rich, and olivine-rich. For the non-HED spectral endmember, we choose either olivine or a featureless component. Our work confirms that Vesta’s surface contains a high content of pyroxenes mixed with a lower concentration of other phases. In many cases, the non-HED endmember that gives the best fit is the featureless phase, which causes a reduction in the strength of both bands. The anticorrelation between albedo and featureless endmember indicates that this phase is associated with low-albedo, CC-like opaque material. Large amounts of olivine have been detected in Bellicia, Arruntia and BU14 BM units. Other sites present low olivine content (<30%) mostly with a high concentration of diogenite.

Visible and infrared image registration based on visual salient features

In order to improve the precision of visible and infrared (VIS/IR) image registration, an image registration method based on visual salient (VS) features is presented. First, a VS feature detector based on the modified visual attention model is presented to extract VS points. Because the iterative, within-feature competition method used in visual attention models is time consuming, an alternative fast visual salient (FVS) feature detector is proposed to make VS features more efficient. Then, a descriptor-rearranging (DR) strategy is adopted to describe feature points. This strategy combines information of both IR image and its negative image to overcome the contrast reverse problem between VIS and IR images, making it easier to find the corresponding points on VIS/IR images. Experiments show that both VS and FVS detectors have higher repeatability scores than scale invariant feature transform in the cases of blurring, brightness change, JPEG compression, noise, and viewpoint, except big scale change. The combination of VS detector and DR registration strategy can achieve precise image registration, but it is time-consuming. The combination of FVS detector and DR registration strategy can also reach a good registration of VIS/IR images but in a shorter time.

Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key features

This work is aimed at developing and interpreting infrared albedo, pyroxene and OH band depths, and pyroxene band center maps of Vesta’s Gegania and Lucaria quadrangles, obtained from data provided by the Visible and InfraRed (VIR) mapper spectrometer on board NASA’s Dawn spacecraft.The Gegania and Lucaria quadrangles span latitudes from 22°S to 22°N and longitudes from 0°E to 144°E. The mineralogical and spectral maps identify two large-scale units on this area of Vesta, which extend eastwards and westward of about 60°E, respectively. The two regions are not associated to large-scale geological units, which have a latitudinal distribution rather than longitudinal, but are defined by different contents of carbonaceous chondrites (CC): the eastern region, poor in CCs, is brighter and OH-depleted, whereas the western one, rich in CCs, is darker and OH-enriched.A detailed analysis of the small-scale units in these quadrangles is also performed. Almost all the units show the typical correspondence between high albedo, deep pyroxene bands, short band centers and absence of OH and vice versa. Only a few exceptions occur, such as the ejecta from the Aelia crater, where dark and bright materials are intimately mixed.The most characteristic features of these quadrangles are the equatorial troughs and the Lucaria tholus.The equatorial troughs consist of graben, i.e. a depression limited by two conjugate faults. The graben do not present their own spectral signatures, but spectral parameters similar to their surroundings, in agreement to their structural origin. This is observed also in graben outside the Gegania and Lucaria quadrangles. However, it is possible to observe other structural features, such as tectonic grooves, characterized by a changing composition and hence an albedo variation. This result is confirmed not only by mineralogical maps of Vesta, but also by analyzing the VIRTIS-Rosetta observations of Lutetia. The albedo change is instead a typical behavior of geomorphic grooves. Finally, ridges are characterized by a bluer color and, in some cases, shorter band centers than their surroundings, suggesting that they are composed of fresher materials.We also performed a comparative analysis between the three tholi of Vesta, i.e. Lucaria (which gives the name to its quadrangle), Aricia (in the Marcia quadrangle) and Brumalia (Numisia quadrangle). Whereas Brumalia tholus is a young magmatic intrusion, the absence of diogenites, the low albedo, and the orientation of Aricia and Lucaria tholi suggest that they are older features, which are covered by dark materials and therefore experienced a different geological history than Brumalia.

An overview of passive and active dust detection methods using satellite measurements

In this paper, the methods to detect dust based on passive and active measurements from satellites have been summarized. These include the visible and infrared (VIR) method, thermal infrared (TIR) method, microwave polarized index (MPI) method, active lidar-based method, and combined lidar and infrared measurement (CLIM) method. The VIR method can identify dust during daytime. Using measurements at wavelengths of 8.5, 11.0, and 12.0 µm, the TIR method can distinguish dust from other types of aerosols and cloud, and identify the occurrence of dust over bright surfaces and during night. Since neither the VIR nor the TIR method can penetrate ice clouds, they cannot detect dust beneath ice clouds. The MPI method, however, can identify about 85% of the dust beneath ice clouds. Meanwhile, the active lidar-based method, which uses the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data and five-dimensional probability distribution functions, can provide very high-resolution vertical profiles of dust aerosols. Nonetheless, as the signals from dense dust and thin clouds are similar in the CALIOP measurements, the lidar-based method may fail to distinguish between them, especially over dust source regions. To address this issue, the CLIM method was developed, which takes the advantages of both TIR measurements (to discriminate between ice cloud and dense dust layers) and lidar measurements (to detect thin dust and water cloud layers). The results obtained by using the new CLIM method show that the ratio of dust misclassification has been significantly reduced. Finally, a concept module for an integrated multi-satellites dust detection system was proposed to overcome some of the weaknesses inherent in the single-sensor dust detection.

Daytime precipitation identification scheme based on multiple cloud parameters retrieved from visible and infrared measurements

Visible and infrared (VIR) measurements and the retrieved cloud parameters are commonly used in precipitation identification algorithms, since the VIR observations from satellites, especially geostationary satellites, have high spatial and temporal resolutions. Combined measurements from visible/infrared scanner (VIRS) and precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite are analyzed, and three cloud parameters, i.e., cloud optical thickness (COT), effective radius (Re), and brightness temperature of VIRS channel 4 (BT4), are particularly considered to characterize the cloud status. By associating the information from VIRS-derived cloud parameters with those from precipitation detected by PR, we propose a new method for discriminating precipitation in daytime called Precipitation Identification Scheme from Cloud Parameters information (PISCP). It is essentially a lookup table (LUT) approach that is deduced from the optimal equitable threat score (ETS) statistics within 3-dimensional space of the chosen cloud parameters. South and East China is selected as a typical area representing land surface, and the East China Sea and Yellow Sea is selected as typical oceanic area to assess the performance of the new scheme. It is proved that PISCP performs well in discriminating precipitation over both land and oceanic areas. Especially, over ocean, precipitating clouds (PCs) and non-precipitating clouds (N-PCs) are well distinguished by PISCP, with the probability of detection (POD) near 0.80, the probability of false detection (POFD) about 0.07, and the ETS higher than 0.43. The overall spatial distribution of PCs fraction estimated by PISCP is consistent with that by PR, implying that the precipitation data produced by PISCP have great potentials in relevant applications where radar data are unavailable.

Thermal measurements of dark and bright surface features on Vesta as derived from Dawn/VIR

Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1–10km) is related to physical properties that can provide information about the origin of those materials. We use Dawn’s Visible and InfraRed (VIR) mapping spectrometer hyperspectral data to retrieve surface temperatures and emissivities, with high accuracy as long as temperatures are greater than 220K. Some of the dark and bright features were observed multiple times by VIR in the various mission phases at variable spatial resolution, illumination and observation angles, local solar time, and heliocentric distance. This work presents the first temperature maps and spectral emissivities of several kilometer-scale dark and bright material units on Vesta. Results retrieved from the infrared data acquired by VIR show that bright regions generally correspond to regions with lower temperature, while dark regions correspond to areas with higher temperature. During maximum daily insolation and in the range of heliocentric distances explored by Dawn, i.e. 2.23–2.54AU, the warmest dark unit found on Vesta rises to a temperature of 273K, while bright units observed under comparable conditions do not exceed 266K. Similarly, dark units appear to have higher emissivity on average compared to bright units. Dark-material units show a weak anticorrelation between temperature and albedo, whereas the relation is stronger for bright material units observed under the same conditions. Individual features may show either evanescent or distinct margins in the thermal images, as a consequence of the cohesion of the surface material. Finally, for the two categories of dark and bright materials, we were able to highlight the influence of heliocentric distance on surface temperatures, and estimate an average temperature rate change of 1% following a variation of 0.04AU in the solar distance.