The invention relates to a method and device for determining the chlorophyll content ratio and a ... more The invention relates to a method and device for determining the chlorophyll content ratio and a non-fluorescent chromophore compound in the fluorescence band of the chlorophyll of a plant tissue, without the determination of said contents. The method comprises: - an emission of two fluorescence excitation radiation of chlorophyll, one of the excitation radiation being absorbed by the chromophoric compound and the other not, - a measurement of the induced fluorescence radiation, fluorescence radiation induced by the excitation radiation absorbed by the chromophore compound being measured outside the chlorophyll absorption spectrum and the fluorescence radiation induced by the excitation radiation not absorbed by the chromophore compound being measured in the spectrum absorption of chlorophyll, - the ratio of the contents is determined by the ratio of the fluorescence radiation mesures.L'invention can be implemented for measuring an indicator, called NBI (nitrogen Balance Index),...
Current techniques for large scale remote sensing of fluorescence aim at quantifying the sun-indu... more Current techniques for large scale remote sensing of fluorescence aim at quantifying the sun-induced fluorescence (SIF) in absorption features present in the incoming radiation. However, these techniques allow measurement of the emitted fluorescence flux but do not provide a direct assessment of the fluorescence yield, which is the true variable linked to the physiological status of the plant. To overcome these limitations, the authors initiated, with the support from CNES and ANR, the CALSIF project whose main purpose is to build an airborne instrument for simultaneous measurement of laser induced fluorescence (LIF) and SIF. By combining fluorescence yield and radiance measurements over different vegetation types, a partitioning of structure and physiological effects on fluorescence can be derived. Additionally, by analyzing the lidar waveform, the vertical structure of the canopy will also be resolved. In parallel, a new fluorescence canopy model is developed. The new model will s...
Sun-induced chlorophyll fluorescence (SIF) is a promising new tool for remotely estimating photos... more Sun-induced chlorophyll fluorescence (SIF) is a promising new tool for remotely estimating photosynthesis. However, the degree to which incoming sunlight and the structure of the canopy rather than leaf physiology contribute to SIF variations is still not well characterized. Here we demonstrate that the canopy structure-related near-infrared reflectance of vegetation multiplied by incoming sunlight (NIRvP) is a robust proxy of far-red SIF across a wide range of spatial and temporal scales. Our findings indicate that contributions from leaf physiology to SIF variability are small compared to its structure and radiation components. NIRvP captured spatio-temporal patterns of photosynthesis better than SIF, which seems to be mostly due to the retrieval noise of SIF. Our results highlight the promise of using widely available NIRvP data for vegetation monitoring and also indicate the potential of using SIF and NIRvP in combination to extract physiological information from SIF.
(54%) were imaged following NAC. Mastectomy was performed on 17 (49%) tumours and breast conserva... more (54%) were imaged following NAC. Mastectomy was performed on 17 (49%) tumours and breast conservation (BC) on 18 (51%). Median tumour size on final pathology was 28 mm (7-60mm). 18 (51%) tumours had positive axillary nodes on imaging. pCR was achieved in 22 (63%) tumours; 12 (79%) within the mastectomy and 10 (56%) within the BC group. Higher pCR rates were seen in ER negative 9/13 (69%) compared to ER positive 13/ 22 (59%) tumours. Conclusion: Our pCR rates were comparable to the Neosphere trial results. We recommend Pertuzumab-based NAC for HER2 positive patients as this is associated with higher pCR rates and would make breast conservation surgery more amenable.
Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing pr... more Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing proxies. Solarinduced chlorophyll fluorescence (SIF) has been shown to be a good indicator of photosynthetic activity across various spatial scales. However, a global and spatially challenging estimate of terrestrial gross primary production (GPP) based on satellite SIF remains unresolved due to the confounding effects of species-specific physical and physiological traits and external factors, such as canopy structure or photosynthetic pathway (C 3 or C 4). Here we analyze an ensemble of far-red SIF data from OCO-2 satellite and ground observations at multiple sites, using the spectral invariant theory to reduce the effects of canopy structure and to retrieve a structurecorrected total canopy SIF emission (SIF total). We find that the relationships between observed canopy-leaving SIF and ecosystem GPP vary significantly among biomes. In contrast, the relationships between SIF total and GPP converge around two unique models, one for C 3 and one for C 4 plants. We show that the two single empirical models can be used to globally scale satellite SIF observations to terrestrial GPP. We obtain an independent estimate of global terrestrial GPP of 129.56 ± 6.54 PgC/year for the 2015-2017 period, which is consistent with the state-of-the-art data-and process-oriented models. The new GPP product shows improved sensitivity to previously undetected 'hotspots' of productivity, being able to resolve the double-peak in GPP due to rotational cropping systems. We suggest that the direct scheme to estimate GPP presented here, which is based on satellite SIF, may open up new possibilities to resolve the dynamics of global terrestrial GPP across space and time.
Remote sensing of far-red sun-induced chlorophyll fluorescence (SIF) has emerged as an important ... more Remote sensing of far-red sun-induced chlorophyll fluorescence (SIF) has emerged as an important tool for studying gross primary productivity (GPP) at the global scale. However, the relationship between SIF and GPP at the canopy scale lacks a clear mechanistic explanation. This is largely due to the poorly characterized role of the relative contributions from light absorption, leaf physiology and canopy scattering to the variability of the top-of-canopy, observed SIF signal. In particular, the effect of the canopy structure beyond light absorption is that only a fraction (fesc) of the SIF emitted from all leaves in the canopy can escape from the canopy due to the strong scattering of near-infrared radiation. We combined rice, wheat and corn canopy-level in-situ datasets to study how the physiological and structural components of SIF individually relate to GPP. At seasonal time scales, we found that the structural component of SIF, defined as the product of APAR and fesc, explained t...
The interest of the scientific community on the remote observation of sun‐induced chlorophyll flu... more The interest of the scientific community on the remote observation of sun‐induced chlorophyll fluorescence (SIF) has increased in the recent years. In this context, hyperspectral ground measurements play a crucial role in the calibration and validation of future satellite missions. For this reason, the European cooperation in science and technology (COST) Action ES1309 OPTIMISE has compiled three papers on instrument characterization, measurement setups and protocols, and retrieval methods (current paper). This study is divided in two sections; first, we evaluated the uncertainties in SIF retrieval methods (e.g., Fraunhofer line depth (FLD) approaches and spectral fitting method (SFM)) for a combination of off-the-shelf commercial spectrometers. Secondly, we evaluated how an erroneous implementation of the retrieval methods increases the uncertainty in the estimated SIF values. Results show that the SFM approach applied to high-resolution spectra provided the most reliable SIF retri...
Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used t... more Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with other vegetation information derived from spectral data) and low signal intensity, several environmental, physiological, and experimental aspects have to be considered during signal acquisition and are key for its reliable interpretation. The European Cooperation in Science and Technology (COST) Actio...
Vegetation transpiration (T) is the process of plant water loss through the stomata on the leaf s... more Vegetation transpiration (T) is the process of plant water loss through the stomata on the leaf surface and plays a key role in the energy and water balance of the land surface, especially with dense vegetation cover. To date, however, estimation of ecosystem-scale T is still rather uncertain mainly due to errors in modeling canopy resistance or conductance. Considering the intrinsic link between photosynthesis and chlorophyll fluorescence, the recent available remote sensing of solar-induced chlorophyll fluorescence (SIF) provides a valuable opportunity to estimate plants T at large scales. In this study, we demonstrate how remote sensing of SIF relates to canopy stomatal conductance and transpiration at diurnal and seasonal scales with continuous ground measurements of SIF at three flux sites in forest, cropland and grassland ecosystems. The results show that both ground and spaceborne SIF observations are good indicators of canopy conductance at both diurnal and seasonal scales (R 2 = 0.57 and 0.74 for forest, R 2 = 0.62 and 0.80 for cropland, R 2 = 0.52 and 0.63 for grassland, respectively). Then, empirical SIF-based canopy conductance models are employed to estimate hourly and daily transpiration. We evaluate our ecosystem T estimations against latent heat fluxes measured by eddy covariance systems with more satisfactory results for forest (R 2 = 0.57 and 0.71), and cropland (R 2 = 0.77 and 0.83) than for grassland (R 2 = 0.13 and 0.22) at hourly and daily time scales. Our results suggest the potential of remotelysensed SIF for estimating canopy conductance and plant transpiration, but a more mechanistic understanding is needed for their link. Penman-Monteith model or empirical relations driven by RS-derived indices are widely used to estimate ET (
L'arrivée de nouvelles données satellitaires en accès libre (notamment du programme européen Sent... more L'arrivée de nouvelles données satellitaires en accès libre (notamment du programme européen Sentinel de Copernicus) fait avancer la caractérisation de l'occupation des sols et des cycles de l'eau et du carbone. La résolution spatiale décamétrique de ces données, disponibles à une fréquence élevée, permet de produire des variables biogéophysiques à l'échelle des parcelles agricoles. Des applications en agrométéorologie sont possibles, mais également pour la validation et l'amélioration des modèles des surfaces terrestres utilisés en météorologie et en climat. Deux nouvelles missions de l'Agence spatiale européenne, Biomass et Flex, dont les lancements sont programmés respectivement pour 2021 et 2022, vont apporter des connaissances nouvelles sur la photosynthèse et le stockage de carbone par les forêts.
IEEE Transactions on Geoscience and Remote Sensing, 2017
In November 2015, the FLuorescence EXplorer (FLEX) was selected as the eighth Earth Explorer miss... more In November 2015, the FLuorescence EXplorer (FLEX) was selected as the eighth Earth Explorer mission of the European Space Agency. The tandem mission concept will provide measurements at a spectral and spatial resolution enabling the retrieval and interpretation of the full chlorophyll fluorescence spectrum emitted by the terrestrial vegetation. This paper provides a mission concept overview of the scientific goals, the key objectives related to fluorescence, and the requirements guaranteeing the fitness for purpose of the resulting scientific data set. We present the mission design at the time of selection, i.e., at the end of project phase Phase A/B1, as developed by two independent industrial consortia. The mission concepts both rely on a single payload Fluorescence Imaging Spectrometer, covering the spectral range from 500 to 780 nm. In the oxygen absorption bands, its spectral resolution will be 0.3 nm with a spectral sampling interval of 0.1 nm. The swath width of the spectrometer is 150 km and the spatial resolution will be 300 × 300 m 2. The satellite will fly in tandem with Sentinel-3 providing different and complementary measurements with a temporal collocation of 6 to 15 s. The FLEX launch is scheduled for 2022.
2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016
The Fluorescence Explorer (FLEX) mission has been recently selected as the 8th Earth Explorer by ... more The Fluorescence Explorer (FLEX) mission has been recently selected as the 8th Earth Explorer by the European Space Agency (ESA). It will be the first mission specifically designed to measure from space vegetation fluorescence emission, by making use of very high spectral resolution imaging spectroscopy techniques. Vegetation fluorescence is the best proxy to actual vegetation photosynthesis which can be measurable from space, allowing an improved quantification of vegetation carbon assimilation and vegetation stress conditions, thus having key relevance for global mapping of ecosystems dynamics and aspects related with agricultural production and food security. The FLEX mission carries the FLORIS spectrometer, with a spectral resolution in the range of 0.3 nm, and is designed to fly in tandem with Copernicus Sentinel-3, in order to provide all the necessary spectral / angular information to disentangle emitted fluorescence from reflected radiance, and to allow proper interpretation of the observed fluorescence spatial and temporal dynamics.
In addition to the widely known leaf chlorophyll (Chl) detection by absorbance or reflectance, we... more In addition to the widely known leaf chlorophyll (Chl) detection by absorbance or reflectance, we propose here to use optical assessment of leaf polyphenolics content (Phen) as an indicator of crop nitrogen (N) status. We developed a portable instrument based on chlorophyll fluorescence excitation spectra, the Dualex®, adapted to measurements of leaf Phen content in the field. It operates in full daylight with a UV beam at 375 nm and a red reference beam at 650 nm. Thanks to the use of a patented feedback loop, measurements take less than a second. We used the Dualex® to follow the dynamics of wheat-leaf Phen in fields that had received different N fertilisation rates. We showed that wheat crops under N deficiency accumulate more Phen. Thus, Phen responded in an opposite manner to Chl. We propose the use of the Chl to Phen ratio as an indicator of crop N status. This new indicator is more sensitive than Chl or Phen alone, and alleviates, at least partially, the problem of gradients ...
IEEE Transactions on Geoscience and Remote Sensing, 2012
A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monit... more A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monitor the fluorescence emission of a sorghum field during its growing period. The measurements were performed continuously at the canopy level, from seeding to maturity. A passive instrument based on three spectrometers was used to monitor the evolution of fluorescence fluxes and vegetation indexes such as Photochemical Reflectance Index (PRI) and Normalized Difference Vegetation Index (NDVI). Fluorescence fluxes were retrieved from radiances, using the filling-in of the atmospheric oxygen absorption bands, at 687 and 760 nm. In parallel, leaf fluorescence spectra, canopy height, and leaf chlorophyll contents were acquired during the growth. Both PRI and NDVI indexes varied with the development of the sorghum field: we observed that NDVI was more sensitive during the early stage of the growth. However, NDVI saturates before the PRI index. Fluorescence fluxes at 687 nm (Fs687) and 760 nm (Fs760) showed an overall increase: Fs687 increased more rapidly at the beginning of growth but trends to saturate while Fs760 still increase. During the growth, the Fs687/Fs760 ratio at the canopy level is found lower than at leaf level. At canopy level, the ratio decreased when the leaf chlorophyll content increases. A decrease was also observed at leaf level with a lower extend. This more important decrease of the fluorescence ratio at canopy level is attributed to a reabsorption of red fluorescence (Fs687) during its transfer through the canopy layers. In the context of forthcoming large-scale remote sensing application, the modification of the leaf level fluorescence emission by the structure of the canopy observed in this article is one of the major issues that must be addressed to interpret the fluorescence signal.
The invention relates to a method and device for determining the chlorophyll content ratio and a ... more The invention relates to a method and device for determining the chlorophyll content ratio and a non-fluorescent chromophore compound in the fluorescence band of the chlorophyll of a plant tissue, without the determination of said contents. The method comprises: - an emission of two fluorescence excitation radiation of chlorophyll, one of the excitation radiation being absorbed by the chromophoric compound and the other not, - a measurement of the induced fluorescence radiation, fluorescence radiation induced by the excitation radiation absorbed by the chromophore compound being measured outside the chlorophyll absorption spectrum and the fluorescence radiation induced by the excitation radiation not absorbed by the chromophore compound being measured in the spectrum absorption of chlorophyll, - the ratio of the contents is determined by the ratio of the fluorescence radiation mesures.L'invention can be implemented for measuring an indicator, called NBI (nitrogen Balance Index),...
Current techniques for large scale remote sensing of fluorescence aim at quantifying the sun-indu... more Current techniques for large scale remote sensing of fluorescence aim at quantifying the sun-induced fluorescence (SIF) in absorption features present in the incoming radiation. However, these techniques allow measurement of the emitted fluorescence flux but do not provide a direct assessment of the fluorescence yield, which is the true variable linked to the physiological status of the plant. To overcome these limitations, the authors initiated, with the support from CNES and ANR, the CALSIF project whose main purpose is to build an airborne instrument for simultaneous measurement of laser induced fluorescence (LIF) and SIF. By combining fluorescence yield and radiance measurements over different vegetation types, a partitioning of structure and physiological effects on fluorescence can be derived. Additionally, by analyzing the lidar waveform, the vertical structure of the canopy will also be resolved. In parallel, a new fluorescence canopy model is developed. The new model will s...
Sun-induced chlorophyll fluorescence (SIF) is a promising new tool for remotely estimating photos... more Sun-induced chlorophyll fluorescence (SIF) is a promising new tool for remotely estimating photosynthesis. However, the degree to which incoming sunlight and the structure of the canopy rather than leaf physiology contribute to SIF variations is still not well characterized. Here we demonstrate that the canopy structure-related near-infrared reflectance of vegetation multiplied by incoming sunlight (NIRvP) is a robust proxy of far-red SIF across a wide range of spatial and temporal scales. Our findings indicate that contributions from leaf physiology to SIF variability are small compared to its structure and radiation components. NIRvP captured spatio-temporal patterns of photosynthesis better than SIF, which seems to be mostly due to the retrieval noise of SIF. Our results highlight the promise of using widely available NIRvP data for vegetation monitoring and also indicate the potential of using SIF and NIRvP in combination to extract physiological information from SIF.
(54%) were imaged following NAC. Mastectomy was performed on 17 (49%) tumours and breast conserva... more (54%) were imaged following NAC. Mastectomy was performed on 17 (49%) tumours and breast conservation (BC) on 18 (51%). Median tumour size on final pathology was 28 mm (7-60mm). 18 (51%) tumours had positive axillary nodes on imaging. pCR was achieved in 22 (63%) tumours; 12 (79%) within the mastectomy and 10 (56%) within the BC group. Higher pCR rates were seen in ER negative 9/13 (69%) compared to ER positive 13/ 22 (59%) tumours. Conclusion: Our pCR rates were comparable to the Neosphere trial results. We recommend Pertuzumab-based NAC for HER2 positive patients as this is associated with higher pCR rates and would make breast conservation surgery more amenable.
Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing pr... more Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing proxies. Solarinduced chlorophyll fluorescence (SIF) has been shown to be a good indicator of photosynthetic activity across various spatial scales. However, a global and spatially challenging estimate of terrestrial gross primary production (GPP) based on satellite SIF remains unresolved due to the confounding effects of species-specific physical and physiological traits and external factors, such as canopy structure or photosynthetic pathway (C 3 or C 4). Here we analyze an ensemble of far-red SIF data from OCO-2 satellite and ground observations at multiple sites, using the spectral invariant theory to reduce the effects of canopy structure and to retrieve a structurecorrected total canopy SIF emission (SIF total). We find that the relationships between observed canopy-leaving SIF and ecosystem GPP vary significantly among biomes. In contrast, the relationships between SIF total and GPP converge around two unique models, one for C 3 and one for C 4 plants. We show that the two single empirical models can be used to globally scale satellite SIF observations to terrestrial GPP. We obtain an independent estimate of global terrestrial GPP of 129.56 ± 6.54 PgC/year for the 2015-2017 period, which is consistent with the state-of-the-art data-and process-oriented models. The new GPP product shows improved sensitivity to previously undetected 'hotspots' of productivity, being able to resolve the double-peak in GPP due to rotational cropping systems. We suggest that the direct scheme to estimate GPP presented here, which is based on satellite SIF, may open up new possibilities to resolve the dynamics of global terrestrial GPP across space and time.
Remote sensing of far-red sun-induced chlorophyll fluorescence (SIF) has emerged as an important ... more Remote sensing of far-red sun-induced chlorophyll fluorescence (SIF) has emerged as an important tool for studying gross primary productivity (GPP) at the global scale. However, the relationship between SIF and GPP at the canopy scale lacks a clear mechanistic explanation. This is largely due to the poorly characterized role of the relative contributions from light absorption, leaf physiology and canopy scattering to the variability of the top-of-canopy, observed SIF signal. In particular, the effect of the canopy structure beyond light absorption is that only a fraction (fesc) of the SIF emitted from all leaves in the canopy can escape from the canopy due to the strong scattering of near-infrared radiation. We combined rice, wheat and corn canopy-level in-situ datasets to study how the physiological and structural components of SIF individually relate to GPP. At seasonal time scales, we found that the structural component of SIF, defined as the product of APAR and fesc, explained t...
The interest of the scientific community on the remote observation of sun‐induced chlorophyll flu... more The interest of the scientific community on the remote observation of sun‐induced chlorophyll fluorescence (SIF) has increased in the recent years. In this context, hyperspectral ground measurements play a crucial role in the calibration and validation of future satellite missions. For this reason, the European cooperation in science and technology (COST) Action ES1309 OPTIMISE has compiled three papers on instrument characterization, measurement setups and protocols, and retrieval methods (current paper). This study is divided in two sections; first, we evaluated the uncertainties in SIF retrieval methods (e.g., Fraunhofer line depth (FLD) approaches and spectral fitting method (SFM)) for a combination of off-the-shelf commercial spectrometers. Secondly, we evaluated how an erroneous implementation of the retrieval methods increases the uncertainty in the estimated SIF values. Results show that the SFM approach applied to high-resolution spectra provided the most reliable SIF retri...
Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used t... more Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with other vegetation information derived from spectral data) and low signal intensity, several environmental, physiological, and experimental aspects have to be considered during signal acquisition and are key for its reliable interpretation. The European Cooperation in Science and Technology (COST) Actio...
Vegetation transpiration (T) is the process of plant water loss through the stomata on the leaf s... more Vegetation transpiration (T) is the process of plant water loss through the stomata on the leaf surface and plays a key role in the energy and water balance of the land surface, especially with dense vegetation cover. To date, however, estimation of ecosystem-scale T is still rather uncertain mainly due to errors in modeling canopy resistance or conductance. Considering the intrinsic link between photosynthesis and chlorophyll fluorescence, the recent available remote sensing of solar-induced chlorophyll fluorescence (SIF) provides a valuable opportunity to estimate plants T at large scales. In this study, we demonstrate how remote sensing of SIF relates to canopy stomatal conductance and transpiration at diurnal and seasonal scales with continuous ground measurements of SIF at three flux sites in forest, cropland and grassland ecosystems. The results show that both ground and spaceborne SIF observations are good indicators of canopy conductance at both diurnal and seasonal scales (R 2 = 0.57 and 0.74 for forest, R 2 = 0.62 and 0.80 for cropland, R 2 = 0.52 and 0.63 for grassland, respectively). Then, empirical SIF-based canopy conductance models are employed to estimate hourly and daily transpiration. We evaluate our ecosystem T estimations against latent heat fluxes measured by eddy covariance systems with more satisfactory results for forest (R 2 = 0.57 and 0.71), and cropland (R 2 = 0.77 and 0.83) than for grassland (R 2 = 0.13 and 0.22) at hourly and daily time scales. Our results suggest the potential of remotelysensed SIF for estimating canopy conductance and plant transpiration, but a more mechanistic understanding is needed for their link. Penman-Monteith model or empirical relations driven by RS-derived indices are widely used to estimate ET (
L'arrivée de nouvelles données satellitaires en accès libre (notamment du programme européen Sent... more L'arrivée de nouvelles données satellitaires en accès libre (notamment du programme européen Sentinel de Copernicus) fait avancer la caractérisation de l'occupation des sols et des cycles de l'eau et du carbone. La résolution spatiale décamétrique de ces données, disponibles à une fréquence élevée, permet de produire des variables biogéophysiques à l'échelle des parcelles agricoles. Des applications en agrométéorologie sont possibles, mais également pour la validation et l'amélioration des modèles des surfaces terrestres utilisés en météorologie et en climat. Deux nouvelles missions de l'Agence spatiale européenne, Biomass et Flex, dont les lancements sont programmés respectivement pour 2021 et 2022, vont apporter des connaissances nouvelles sur la photosynthèse et le stockage de carbone par les forêts.
IEEE Transactions on Geoscience and Remote Sensing, 2017
In November 2015, the FLuorescence EXplorer (FLEX) was selected as the eighth Earth Explorer miss... more In November 2015, the FLuorescence EXplorer (FLEX) was selected as the eighth Earth Explorer mission of the European Space Agency. The tandem mission concept will provide measurements at a spectral and spatial resolution enabling the retrieval and interpretation of the full chlorophyll fluorescence spectrum emitted by the terrestrial vegetation. This paper provides a mission concept overview of the scientific goals, the key objectives related to fluorescence, and the requirements guaranteeing the fitness for purpose of the resulting scientific data set. We present the mission design at the time of selection, i.e., at the end of project phase Phase A/B1, as developed by two independent industrial consortia. The mission concepts both rely on a single payload Fluorescence Imaging Spectrometer, covering the spectral range from 500 to 780 nm. In the oxygen absorption bands, its spectral resolution will be 0.3 nm with a spectral sampling interval of 0.1 nm. The swath width of the spectrometer is 150 km and the spatial resolution will be 300 × 300 m 2. The satellite will fly in tandem with Sentinel-3 providing different and complementary measurements with a temporal collocation of 6 to 15 s. The FLEX launch is scheduled for 2022.
2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016
The Fluorescence Explorer (FLEX) mission has been recently selected as the 8th Earth Explorer by ... more The Fluorescence Explorer (FLEX) mission has been recently selected as the 8th Earth Explorer by the European Space Agency (ESA). It will be the first mission specifically designed to measure from space vegetation fluorescence emission, by making use of very high spectral resolution imaging spectroscopy techniques. Vegetation fluorescence is the best proxy to actual vegetation photosynthesis which can be measurable from space, allowing an improved quantification of vegetation carbon assimilation and vegetation stress conditions, thus having key relevance for global mapping of ecosystems dynamics and aspects related with agricultural production and food security. The FLEX mission carries the FLORIS spectrometer, with a spectral resolution in the range of 0.3 nm, and is designed to fly in tandem with Copernicus Sentinel-3, in order to provide all the necessary spectral / angular information to disentangle emitted fluorescence from reflected radiance, and to allow proper interpretation of the observed fluorescence spatial and temporal dynamics.
In addition to the widely known leaf chlorophyll (Chl) detection by absorbance or reflectance, we... more In addition to the widely known leaf chlorophyll (Chl) detection by absorbance or reflectance, we propose here to use optical assessment of leaf polyphenolics content (Phen) as an indicator of crop nitrogen (N) status. We developed a portable instrument based on chlorophyll fluorescence excitation spectra, the Dualex®, adapted to measurements of leaf Phen content in the field. It operates in full daylight with a UV beam at 375 nm and a red reference beam at 650 nm. Thanks to the use of a patented feedback loop, measurements take less than a second. We used the Dualex® to follow the dynamics of wheat-leaf Phen in fields that had received different N fertilisation rates. We showed that wheat crops under N deficiency accumulate more Phen. Thus, Phen responded in an opposite manner to Chl. We propose the use of the Chl to Phen ratio as an indicator of crop N status. This new indicator is more sensitive than Chl or Phen alone, and alleviates, at least partially, the problem of gradients ...
IEEE Transactions on Geoscience and Remote Sensing, 2012
A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monit... more A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monitor the fluorescence emission of a sorghum field during its growing period. The measurements were performed continuously at the canopy level, from seeding to maturity. A passive instrument based on three spectrometers was used to monitor the evolution of fluorescence fluxes and vegetation indexes such as Photochemical Reflectance Index (PRI) and Normalized Difference Vegetation Index (NDVI). Fluorescence fluxes were retrieved from radiances, using the filling-in of the atmospheric oxygen absorption bands, at 687 and 760 nm. In parallel, leaf fluorescence spectra, canopy height, and leaf chlorophyll contents were acquired during the growth. Both PRI and NDVI indexes varied with the development of the sorghum field: we observed that NDVI was more sensitive during the early stage of the growth. However, NDVI saturates before the PRI index. Fluorescence fluxes at 687 nm (Fs687) and 760 nm (Fs760) showed an overall increase: Fs687 increased more rapidly at the beginning of growth but trends to saturate while Fs760 still increase. During the growth, the Fs687/Fs760 ratio at the canopy level is found lower than at leaf level. At canopy level, the ratio decreased when the leaf chlorophyll content increases. A decrease was also observed at leaf level with a lower extend. This more important decrease of the fluorescence ratio at canopy level is attributed to a reabsorption of red fluorescence (Fs687) during its transfer through the canopy layers. In the context of forthcoming large-scale remote sensing application, the modification of the leaf level fluorescence emission by the structure of the canopy observed in this article is one of the major issues that must be addressed to interpret the fluorescence signal.
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Papers by Yves Goulas