MarsSI (Acronym for Mars System of Information, https://emars.univ-lyon1.fr/MarsSI/) is a web Geographic Information System application which helps managing and processing martian orbital data. The ...MarsSI facility is part of the web portal called PSUP (Planetary SUrface Portal) developed by the Observatories of Paris Sud (OSUPS) and Lyon (OSUL) to provide users with efficient and easy access to data products dedicated to the martian surface. The portal proposes 1) the management and processing of data thanks to MarsSI and 2) the visualization and merging of high level (imagery, spectral, and topographic) products and catalogs via a web-based user interface (MarsVisu). The portal PSUP as well as the facility MarsVisu is detailed in a companion paper (Poulet et al., 2018). The purpose of this paper is to describe the facility MarsSI. From this application, users are able to easily and rapidly select observations, process raw data via automatic pipelines, and get back final products which can be visualized under Geographic Information Systems. Moreover, MarsSI also contains an automatic stereo-restitution pipeline in order to produce Digital Terrain Models (DTM) on demand from HiRISE (High Resolution Imaging Science Experiment) or CTX (Context Camera) pair-images. This application is funded by the European Union's Seventh Framework Programme (FP7/2007–2013) (ERC project eMars, No. 280168) and has been developed in the scope of Mars, but the design is applicable to any other planetary body of the solar system.
•MarsSI is a web application managing and processing Martian orbital data on demand.•MarsSI proposes on demand automatic stereo-restitution from HiRISE or CTX pair-images.•While developed in the scope of Mars, the design is applicable to any other planetary body of the solar system.
•Detections of smectites, chlorites, carbonates and possible serpentine.•Alteration evidence of the first 7km of the crust between the Hellas and Isidis basins.•Evidence of carbonation of the martian ...crust.
Recent investigations of alteration of martian crustal outcrops suggest putative crustal hydrothermal systems, which are favorable environments for the emergence of life. In this study, we perform an analysis of the CRISM targeted observations covering crustal outcrops in the region between the Hellas and Isidis basins with the goal of investigating the alteration phases. Over the wide studied region, we detect the presence of possible serpentines, chlorites, smectites and carbonates. These detections occur within ejecta blankets, crater walls and central uplifts of impact craters. We investigate the relation between the observed associations of minerals and the ages of the impact craters assessed by crater count. No clear relation is observed. We also investigate the relationship between the group of detected mineral and the pre-impact depth of the studied outcrops assessed from the size of the impact craters. This method allows us to reconstruct the pre-impact cross-section. We suggest that alteration of the first 7km of the crust between the Hellas and Isidis basins may have undergone alteration processes.
Mediterranean forests represent critical areas that are increasingly affected by the frequency of droughts and fires, anthropic activities and land use changes. Optical remote sensing data give ...access to several essential biodiversity variables, such as species traits (related to vegetation biophysical and biochemical composition), which can help to better understand the structure and functioning of these forests. However, their reliability highly depends on the scale of observation and the spectral configuration of the sensor. Thus, the objective of the SENTHYMED/MEDOAK experiment is to provide datasets from leaf to canopy scale in synchronization with remote sensing acquisitions obtained from multi-platform sensors having different spectral characteristics and spatial resolutions. Seven monthly data collections were performed between April and October 2021 (with a complementary one in June 2023) over two forests in the north of Montpellier, France, comprised of two oak endemic species with different phenological dynamics (evergreen: Quercus ilex and deciduous: Quercus pubescens) and a variability of canopy cover fractions (from dense to open canopy). These collections were coincident with satellite multispectral Sentinel-2 data and one with airborne hyperspectral AVIRIS-Next Generation data. In addition, satellite hyperspectral PRISMA and DESIS were also available for some dates. All these airborne and satellite data are provided from free online download websites. Eight datasets are presented in this paper from thirteen studied forest plots: (1) overstory and understory inventory, (2) 687 canopy plant area index from Li-COR plant canopy analyzers, (3) 1475 in situ spectral reflectances (oak canopy, trunk, grass, limestone, etc.) from ASD spectroradiometers, (4) 92 soil moistures and temperatures from IMKO and Campbell probes, (5) 747 leaf-clip optical data from SPAD and DUALEX sensors, (6) 2594 in-lab leaf directional-hemispherical reflectances and transmittances from ASD spectroradiometer coupled with an integrating sphere, (7) 747 in-lab measured leaf water and dry matter content, and additional leaf traits by inversion of the PROSPECT model and (8) UAV-borne LiDAR 3-D point clouds. These datasets can be useful for multi-scale and multi-temporal calibration/validation of high level satellite vegetation products such as species traits, for current and future imaging spectroscopic missions, and by fusing or comparing both multispectral and hyperspectral data. Other targeted applications can be forest 3-D modelling, biodiversity assessment, fire risk prevention and globally vegetation monitoring.
An airborne hyperspectral survey of the Oman ophiolite (Sumail Massif) has been conducted using the HyMap airborne imaging spectrometer with associated field measurements (GER 3700). An ASD ...FieldSpec3 spectrometer was also used in order to constrain the spectral signatures of the principal lithologies cropping out in the surveyed area. Our objective was to identify and map the various igneous lithologies by a direct comparison at high spectral resolution between field and airborne spectra despite strong variations in outcropping conditions such as (1) lighting, (2) surface roughness geometry, (3) blocks coated with red/brown patina and exfoliation products, or (4) deep hydrothermal weathering. On the basis of spectral signatures, we are able to distinguish three end‐members of olivine‐orthopyroxene bearing assemblages in the mantle sequence: (1) harzburgites, (2) dunites, and (3) a harzburgite with interstitial carbonate. Because plagioclase is spectrally featureless in the wavelength range studied it cannot be detected. In the crustal sequence, we therefore identified four end‐members with variable abundance of clinopyroxene: (1) massive gabbros, (2) amphibolized (upper) gabbros associated with intrusive dykes, (3) wehrlite with high serpentine content, and (4) gabbronorite (a lithology not previously recognized in the studied area). With the exception of wehrlite, spectra of olivine‐rich end‐members display characteristic Mg‐OH narrow absorption features caused by their high serpentine content. We take advantage of this observation to split the data into two subsets, corresponding to the mantle and crustal sequences, respectively. Pixels of an image often correspond to heterogeneous areas in the field and a direct comparison between airborne and in situ spectra is not straightforward. However, comparing spectra of pixels associated with the most homogeneous areas in the field with the spectra acquired in situ at the same location, we found a systematic change both in mean intensity and overall spectral shape. Dividing each spectrum by its low‐pass trend removes the effects caused by surface light scattering associated with each scale of analysis and results in an exceptional match between field and airborne spectra. However, the albedo information is lost and as a consequence, rock types only characterized by albedo change cannot be discriminated. A spectrum of a mixture of powdered minerals is usually seen as a linear combination of mineral spectra proportional to their abundance. However, this is no longer the case when minerals occur in complex arrangements in rock types. We thus develop a synthetic spectral library of all possible combinations of rock types covering the surface area of a pixel and use a simple distance calculation to identify the best match between each pixel and modeled spectra. This procedure allows the determination of the fractional cover of each rock type in a given pixel and to establish maps for each spectral end‐member. The final product is a geological map, derived from the combination of end‐member fractional cover maps, and is broadly consistent with the existing geological maps. Beyond this general agreement which demonstrates the potential of this new approach for geological mapping, imaging spectrometry allows (1) to map in detail the outline of the Moho north of Maqsad and (2) to identify a new crustal sequence enriched in silica south of Muqzah, revealing the presence of orthopyroxene, the nature and distribution of which are of relevance to the petrological and tectonic understanding of the Oman ophiolite evolution.
Titan is one of the primary scientific objectives of the NASA–ESA–ASI Cassini–Huygens mission. Scattering by haze particles in Titan's atmosphere and numerous methane absorptions dramatically veil ...Titan's surface in the visible range, though it can be studied more easily in some narrow infrared windows. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft successfully imaged its surface in the atmospheric windows, taking hyperspectral images in the range 0.4–5.2
μm. On 26 October (TA flyby) and 13 December 2004 (TB flyby), the Cassini–Huygens mission flew over Titan at an altitude lower than 1200
km at closest approach. We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4
km/pixel. The pure atmospheric backscattering component is corrected by using both an empirical method and a first-order theoretical model. Both approaches provide consistent results. After the removal of scattering, ratio images reveal subtle surface heterogeneities. A particularly contrasted structure appears in ratio images involving the 1.59 and 2.03
μm images north of the Huygens landing site. Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150
km diameter impact crater with a central peak.
Three‐dimensional spectroscopy has the advantage of providing (quasi‐) simultaneously both spatial and spectral information. Coupled to adaptive optics, it conjugates spectroscopic power with high ...angular resolution. GriF offers these capabilities in the near‐infrared. As a new observing mode of KIR, the camera behind PUEO, the Canada‐France‐Hawaii Telescope adaptive optics bonnette, it provides images at the diffraction limit of the telescope in theKband. Spectroscopy at a resolution of 2000 is provided by a Fabry‐Pérot interferometer coupled with a grism, cooled to limit the background. This setup offers a large multiplex gain by observing simultaneously up to five monochromatic images. This article first describes the instrument and the calibration procedures. Next, we demonstrate GriF performances from its first observations, obtained on the Orion molecular cloud OMC‐1.
•The JMAK model is able to predict the magnetic ageing of electrical steels.•Coupling JMAK model and Arrhenius law allow to predict temperature-dependent ageing.•Magnetic ageing has a direct impact ...on iron losses and normal magnetization curve.
This paper deals with the temperature-dependent modelling of iron losses in the context of magnetic ageing of electricals steel used in high power electrical machines. First, two electrical steel sheet grades were heat treated at three temperatures in order to study the ageing effect evolution as a function of temperature. Results show a significant increase in iron losses for both steel grades. Then, considering the link between the macroscopic magnetic properties evolution (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. By coupling this model with the Arrhenius’ law, a model is developed to be able to predict the ageing for several temperature levels.
•Interest of outliers to get deeper insights into the data.•Unsupervised outlier detection methods do not label defective observations.•A labelling approach is proposed to help describe unlabeled ...yield outliers.
Suspicious observations, or the so-called outliers, are always present, to a greater or lesser extent, in agronomical and environmental datasets. Within field yield datasets are no exception. While most filtering approaches use expert thresholds and dedicated filters to remove these defective observations, more general and unsupervised methods will be required to process a growing number of yield maps. However, by using these last approaches, outliers would be solely identified and would remain unlabeled. This study proposes a methodology to provide a label to these defective observations so that users can better characterize the harvest process, e.g. functioning of the machine, driving of the operator, and provide guidelines for future improvements of equipment and operations processes. Here, it is assumed that outliers have already been detected by a non-parametric and unsupervised published approach. Clusters of outliers are first identified in the data to gather outliers with similar yield outlying characteristics. Once detected, these clusters are given a first-order label which describes the general yield outlying characteristics of the observations that belong to these clusters. Then, within each cluster, each outlier is given a second-order label to provide more information on the origin of the defective observation. Yield simulated datasets with known characteristics and labelled outliers were used to test the methodology. The proposed approach was then applied on real yield datasets with unlabeled outliers. This study shows that it might be conceivable to label outliers detected with an unsupervised approach but that some labels are more accurate than others, especially those related to an unknown cutting width of the harvester or to narrow finishes within the fields. Outlying observations behaved similarly between simulated and real datasets which made it possible to infer more precisely the label of defective observations. By labelling outlying observations, it was possible to provide an appropriate correction to one of the real yield dataset and to restore almost 15% of the outlying observations instead of removing them. This study is a first attempt to provide a label to yield outliers detected from an unsupervised manner.
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