Potential of Sentinel-2 satellite images to monitor vine fields grown at a territorial scale

Aim: The aim of this short note is to provide first insights into the ability of Sentinel-2 images to monitor vine growth across a whole season. It focuses on verifying the practical temporal resolution that can be reached with Sentinel-2 images, the main stages of Mediterranean vineyard development as well as potential relevant agronomic information that can be seen on the temporal vegetation curves arising from Sentinel-2 images. Methods and results: The study was carried out in 2017 in a production vineyard located in southern France, 2 km from the Mediterranean seashore. Sentinel-2 images acquired during the whole vine growing cycle were considered, i.e. between the 3rd of March 2017 and the 10th of October 2017. The images were used to compute the classical normalized difference vegetation index (NDVI). Time series of NDVI values were analyzed on four blocks chosen for exhibiting different features, e.g. age, missing plants, weeding practices. The practical time lag between two usable images was closer to 16 days than to the 10 theoretical days (with only one satellite available at the date of the experiment), i.e. near 60% of the theoretical one. Results show that it might be possible to identify i) the main steps of vine development (e.g. budburst, growth, trimming, growth stop and senescence), ii) weed management and inter-row management practices, and iii) possible reasons for significant inter-block differences in vegetative expression (e.g. young vines that have recently been planted, low-productive blocks affected by many missing vines). Conclusions: Although this experiment was conducted at a time when Sentinel-2b was not fully operational, results showed that a sufficient number of usable images was available to monitor vine development. The availability of two Sentinel satellites (2a and 2b) in upcoming seasons should increase the number of usable images and the temporal resolution of the time series. This study also showed the limitations of the Sentinel-2 images’ resolution to provide within-block information in the case of small blocks or blocks with complex borders or both. Significance and impact of the study: This technical note demonstrated the potential of Sentinel-2 images to characterize vineyard blocks’ vigor and to monitor winegrowers’ practices at a territorial (regional) scale. The impact of management operations such as weeding and trimming, along with their incidence on canopy size, were observed on the NDVI time series. Some relevant parameters (slope, maximum values) may be derived from the NDVI time series, providing new insights into the monitoring of vineyards at a large scale. These results provided areas for further investigation, especially regarding the development of new indicators to characterize block-climate relationships

Linking cause and effect: Nanoscale vibrational spectroscopy of space weathering from asteroid Ryugu

Airless bodies are subjected to space-weathering effects that modify the first few microns of their surface. Therefore, understanding their impact on the optical properties of asteroids is key to the interpretation of their color variability and infrared reflectance observations. The recent Hayabusa2 sample return mission to asteroid Ryugu offers the first opportunity to study these effects, in the case of the most abundant spectral type among the main-asteroid belt, C-type objects. This study employs vibrational electron energy-loss spectroscopy in the transmission electron microscope to achieve the spatial resolution required to measure the distinct mid-infrared spectral signature of Ryugu's space-weathered surface. The comparison with the spectrum of the pristine underlying matrix reveals the loss of structural -OH and C-rich components in the space-weathered layers, providing direct experimental evidence that exposure to the space environment tends to mask the optical signatures of phyllosilicates and carbonaceous matter. Our findings should contribute to rectifying potential underestimations of water and carbon content of C-type asteroids when studied through remote sensing with new-generation telescopes.The Hayabusa2 project has been developed and led by JAXA in collaboration with Deutsches Zentrum für Luft- und Raumfahrt (DLR) and Centre national d'études spatiales (CNES), and supported by NASA and Australian Space Agency (ASA). We thank all the members of the Hayabusa2 project for their technical and scientific contributions. This work was carried out on the electron microscopy facility of the Advanced Characterization Platform of the Chevreul Institute, University of Lille—CNRS. This project has been funded by ISITE ULNE and the "Métropole Européenne de Lille" through the "TEM-Aster project," the LARCAS ANR (Reference No. SAN-22199). It has also been funded by in part by the National Agency for Research (ANR) under the program of future investment TEMPOS-CHROMATEM (Reference No. ANR-10-EQPX-50). Micro-infrared spectroscopy was performed at the Institut de Planétologie et d'Astrophysique de Grenoble (IPAG). European Union's Horizon 2020 research and innovation program under grant Agreements No. 823717 (ESTEEM3). The Chevreul Institute is thanked for its help in the development of this work through the CHEMACT project supported by the "Ministère de l'Enseignement Supérieur de la Recherche et de l'Innovation," the region "Hauts-de-France" and the "Métropole Européenne de Lille." JSPS KAKENHI grant numbers related to this study are 19H00725, 19K0094, and 21H05424. This research was supported by the H2020 European Research Council (ERC) (SOLARYS ERC-CoG2017-771691). We acknowledge the funding by the Spanish University Ministry and Next Generation EU through a Margarita Salas fellowship.Peer reviewe

Linking Cause and Effect: Nanoscale Vibrational Spectroscopy of Space Weathering from Asteroid Ryugu

Airless bodies are subjected to space-weathering effects that modify the first few microns of their surface. Therefore, understanding their impact on the optical properties of asteroids is key to the interpretation of their color variability and infrared reflectance observations. The recent Hayabusa2 sample return mission to asteroid Ryugu offers the first opportunity to study these effects, in the case of the most abundant spectral type among the main-asteroid belt, C-type objects. This study employs vibrational electron energy-loss spectroscopy in the transmission electron microscope to achieve the spatial resolution required to measure the distinct mid-infrared spectral signature of Ryugu's space-weathered surface. The comparison with the spectrum of the pristine underlying matrix reveals the loss of structural -OH and C-rich components in the space-weathered layers, providing direct experimental evidence that exposure to the space environment tends to mask the optical signatures of phyllosilicates and carbonaceous matter. Our findings should contribute to rectifying potential underestimations of water and carbon content of C-type asteroids when studied through remote sensing with new-generation telescopes

Influx of nitrogen-rich material from the outer Solar System indicated by iron nitride in Ryugu samples

Large amounts of nitrogen compounds, such as ammonium salts, may be stored in icy bodies and comets, but the transport of these nitrogen-bearing solids into the near-Earth region is not well understood. Here, we report the discovery of iron nitride on magnetite grains from the surface of the near-Earth C-type carbonaceous asteroid Ryugu, suggesting inorganic nitrogen fixation. Micrometeoroid impacts and solar wind irradiation may have caused the selective loss of volatile species from major iron-bearing minerals to form the metallic iron. Iron nitride is a product of nitridation of the iron metal by impacts of micrometeoroids that have higher nitrogen contents than the CI chondrites. The impactors are probably primitive materials with origins in the nitrogen-rich reservoirs in the outer Solar System. Our observation implies that the amount of nitrogen available for planetary formation and prebiotic reactions in the inner Solar System is greater than previously recognized

Four‐dimensional‐STEM analysis of the phyllosilicate‐rich matrix of Ryugu samples

Ryugu asteroid grains brought back to the Earth by the Hayabusa2 space mission are pristine samples containing hydrated minerals and organic compounds. Here, we investigate the mineralogy of their phyllosilicate-rich matrix with four-dimensional scanning transmission electron microscopy (4D-STEM). We have identified and mapped the mineral phases at the nanometer scale (serpentine, smectite, pyrrhotite), observed the presence of Ni-bearing pyrrhotite, and identified the serpentine polymorph as lizardite, in agreement with the reported aqueous alteration history of Ryugu. Furthermore, we have mapped the d-spacings of smectite and observed a broad distribution of values, ranging from 1 to 2 nm, with an average d-spacing of 1.24 nm, indicating significant heterogeneity within the sample. Such d-spacing variability could be the result of either the presence of organic matter trapped in the interlayers or the influence of various geochemical conditions at the submicrometer scale, suggestive of a range of organic compounds and/or changes in smectite crystal chemistry

A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss

How to measure and report within-field variability: a review of common indicators and their sensitivity

International audienceIn agricultural fields, observations near in space share more similarities than observations far apart. This phenomenon of closely related points, the so-called spatial autocorrelation or in that case, the within-field spatial variability, is well-recognized and needs to be characterized to consider site-specific management. Quantifying spatial dependency is fundamental for understanding the underlying factors affecting field productivity. An examination of multiple scientific papers was carried out to assess why and how practitioners were evaluating the spatial variability across their fields. An analysis of the existing descriptors of within-field variability was performed to identify the most relevant indicators to use based on (i) the case studies that practitioners employed, (ii) the different nature of data to which users were confronted, and (iii) the complexity and ease of access to information in support of these available approaches. Finally, this paper provides users with a comprehensive decision tree that should help them select an appropriate index of spatial variability for their work. Results also highlight the needs for further investigation, especially regarding the implementation of more general and standardized approaches that will enable cross-study comparison

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A simple index to determine if within-field spatial production variation exhibits potential management effects: application in vineyards using yield monitor data

International audienceAs agricultural data and information becomes more abundant, diagnostics are needed to quickly and efficiently interrogate these data. Indices exist to identify sensor data with structured spatial variation, conducive to site-specific management. However, these indices do not indicate if this spatial variation is driven by managerial or environmental effects. A new index is proposed to identify perennial (or ordered row) fields that are likely or highly likely to have management effects within the spatial pattern of sensor data. This is determined by investigating differences in anisotropic (directional) variograms parallel and perpendicular to the direction of management (row orientation). Small differences are indicative of isotropic (environmental-driven) variation. Large differences indicate row and management effects. The index is derived, run on a database of 1080 simulated fields and applied to yield data from 124 vineyard blocks to assess index performance and response to different levels of variation. Simulations showed that the index is non-responsive to the magnitude of variation but responds strongly to anisotropy in the data. The stochastic variance in the data was observed to have an effect on index response and may be problematic when applied to noisy data sets. The index scores for the simulated and real-world data showed a similar pattern of response and the index was able to identify vineyard blocks where differential row management had generated differing yield responses. The index scores are continuous and some general guidelines for use of the index are proposed

Potential of Sentinel-2 satellite images to monitor vine fields grown at a territorial scale

Aim: The aim of this short note is to provide first insights into the ability of Sentinel-2 images to monitor vine growth across a whole season. It focuses on verifying the practical temporal resolution that can be reached with Sentinel-2 images, the main stages of Mediterranean vineyard development as well as potential relevant agronomic information that can be seen on the temporal vegetation curves arising from Sentinel-2 images. Methods and results: The study was carried out in 2017 in a production vineyard located in southern France, 2 km from the Mediterranean seashore. Sentinel-2 images acquired during the whole vine growing cycle were considered, i.e. between the 3(rd) of March 2017 and the 10(th) of October 2017. The images were used to compute the classical normalized difference vegetation index (NDVI). Time series of NDVI values were analyzed on four blocks chosen for exhibiting different features, e.g. age, missing plants, weeding practices. The practical time lag between two usable images was closer to 16 days than to the 10 theoretical days (with only one satellite available at the date of the experiment), i.e. near 60% of the theoretical one. Results show that it might be possible to identify i) the main steps of vine development (e.g. budburst, growth, trimming, growth stop and senescence), ii) weed management and inter-row management practices, and iii) possible reasons for significant inter-block differences in vegetative expression (e.g. young vines that have recently been planted, low-productive blocks affected by many missing vines). Conclusions: Although this experiment was conducted at a time when Sentinel-2b was not fully operational, results showed that a sufficient number of usable images was available to monitor vine development. The availability of two Sentinel satellites (2a and 2b) in upcoming seasons should increase the number of usable images and the temporal resolution of the time series. This study also showed the limitations of the Sentinel-2 images' resolution to provide within-block information in the case of small blocks or blocks with complex borders or both. Significance and impact of the study: This technical note demonstrated the potential of Sentinel-2 images to characterize vineyard blocks' vigor and to monitor winegrowers' practices at a territorial (regional) scale. The impact of management operations such as weeding and trimming, along with their incidence on canopy size, were observed on the NDVI time series. Some relevant parameters (slope, maximum values) may be derived from the NDVI time series, providing new insights into the monitoring of vineyards at a large scale. These results provided areas for further investigation, especially regarding the development of new indicators to characterize block-climate relationships