Extended ecosystem signatures with application to Eos synergism requirements

The primary objective is to define the advantages of synergistically combining optical and microwave remote sensing measurements for the determination of biophysical properties important in ecosystem modeling. This objective was approached in a stepwise fashion starting with ground-based observations of controlled agricultural and orchard canopies and progressing to airborne observations of more natural forest ecosystems. This observational program is complemented by a parallel effort to model the visible reflectance and microwave scattering properties of composite vegetation canopies. The goals of the modeling studies are to verify our basic understanding of the sensor-scene interaction physics and to provide the basis for development of inverse models optimized for retrieval of key biophysical properties. These retrieval algorithms can then be used to simulate the expected performance of various aspects of Eos including the need for simultaneous SAR and HIRIS observations or justification for other (non-synchronous) relative timing constraints and the frequency, polarization, and angle of incidence requirements for accurate biophysical parameter extractions. This program completed a very successful series of truck-mounted experiments, made remarkable progress in development and validation of optical reflectance and microwave scattering models for vegetation, extended the scattering models to accommodate discontinuous and periodic canopies, developed inversion approaches for surface and canopy properties, and disseminated these results widely through symposia and journal publications. In addition, the third generation of the computer code for the microwave scattering models was provided to a number of other US, Canadian, Australian, and European investigators who are currently presenting and publishing results using the MIMICS research code

In situ sensing of leaf cuticular wax, pecan yield and pecan leaf nitrogen concentration

Scope and Method of Study:The objectives of this study were to develop technologies to enable in situ sensing of plant physiological conditions.Cuticular wax on spinach leaves was quantified by applying an empirically developed regression relationship to Fourier transform infrared attenuated total reflectance (FTIRATR) spectra of fresh plant material.In the second study, the backscatter response of microwaves from pecan tree canopy samples was investigated to assess the ability of short range radar to estimate nut yield in pecan orchards prior to harvest.Finally, two methods to assess concentration of nitrogen in pecan leaves were developed. The first method extracted data from high resolution camera images in the green, red and near-infrared bands to calculate foliar nitrogen levels. In the second investigation, regression analysis was used to find relationships between chlorophyll meter measurements and chemical nitrogen analysis.Findings and Conclusions:Linear regression models derived from FTIR-ATR spectra were able to predict greater than 86% of wax variation on leaves using 4 or 5 frequencies. DSC did not provide reliable predictions of cuticular wax.Measurements of short range microwave radiation from 1 to 18 GHz reflected from pecan tree canopy samples resulted in linear regression models that predicted total water and dry mass of the samples over a wide range of frequencies with R2 >0.63 and 0.78 respectively.Normalized difference vegetative index (NDVI) and reflectance data extracted from the camera images were significantly correlated to foliar N in both months of the study on 'Pawnee' pecans but only in one month 'Kanza'. The various relationships had R2 between 0.21 and 0.51. Correlation of foliar N to chlorophyll meter readings was poor in May for all cultivars but distinct significant linear relationships were found for 'Maramec' and 'Pawnee' for each of the other months tested with R2 ranging from 0.40 to 0.87. Data from 'Kanza' had significant relationships in June and October with R2 of 0.39 and 0.72, respectively

Goddard Visiting Scientist Program for the Space and Earth Sciences Directorate

Progress reports of the Visiting Scientist Program covering the period from 1 Jul. - 30 Sep. 1992 are included. Topics covered include space science and earth science. Other topics covered include cosmic rays, magnetic clouds, solar wind, satellite data, high resolution radiometer, and microwave scattering

Radar backscatter modelling of forests using a macroecological approach

This thesis provides a new explanation for the behaviour of radar backscatter of forests using vegetation structure models from the field of macroecology. The forests modelled in this work are produced using allometry-based ecological models with backscatter derived from the parameterisation of a radiative transfer model. This work is produced as a series of papers, each portraying the importance of macroecology in defining the forest radar response. Each contribution does so by incorporating structural and dynamic effects of forest growth using one of two allometric models to expose variations in backscatter as a response to vertical and horizontal forest profiles. The major findings of these studies concern the origin of backscatter saturation effects from forest SAR surveys. In each work the importance of transition from Rayleigh to Optical scattering, combined with the scaling effects of forest structure, is emphasised. These findings are administered through evidence including the transition’s emergence as the region of dominant backscatter in a vertical profile (according to a dominant canopy scattering layer), also through the existence of a two trend backscatter relationship with volume in the shape of the typical “saturation curve” (in the absence of additional attenuating factors). The importance of scattering regime change is also demonstrated through the relationships with volume, basal area and thinning. This work’s findings are reinforced by the examination of the relationships between forest height and volume, as collective values, providing evidence to suggest the non-uniqueness of volume-toheight relationships. Each of the studies refer to growing forest communities not single trees, so that unlike typical studies of radar remote sensing of forests the impact of the macroecological structural aspects are more explicit. This study emphasises the importance of the overall forest structure in producing SAR backscatter and how backscatter is not solely influenced by electrical properties of scatteres or the singular aspects of a tree but also by the collective forest parameters defining a dynamically changing forest

Apports des données radar à haute répétitivité et à haute résolution du capteur Sentinel-1 pour la caractérisation de l'état hydrique des surfaces agricoles dans les régions sud-méditerranéennes

Le suivi de l'irrigation est un enjeu important pour l'optimisation de l'irrigation. L'humidité superficielle (SSM) est une variable clé pour la gestion de l'irrigation. De plus, la détection précoce du stress hydrique peut contribuer à une utilisation optimale de l'eau agricole. Les données radar en bande C ont montré un grand potentiel pour le suivi des conditions hydriques du sol et de la végétation. Dans ce contexte, cette thèse a pour objectif général d'évaluer les potentialités des données radar bande C pour suivre le fonctionnement hydrique des céréales irriguées. Nos objectifs spécifiques sont : (1) développer une nouvelle approche pour l'inversion de la SSM en utilisant uniquement les données radar ; (2) proposer une méthodologie pour l'estimation des quantités et des dates d'irrigation à l'échelle de la parcelle sur la base de ces nouveaux produits de SSM ; (3) étudier les potentialités de la réponse radar bande C pour le suivi du fonctionnement physiologique et, in fine, la détection du stress hydrique. En préliminaire à l'inversion, les séries temporelles de données Sentinel-1, notamment le coefficient de rétrodiffusion (sigma^0), le rapport de polarisation (PR) et la cohérence interférométrique (rho) sont interprétées à l'aide de données expérimentales collectées sur des parcelles de blé irriguées au Maroc. Les résultats montrent que rho et PR sont fortement liés au développement de la végétation alors que la dynamique de sigma^0 suit les variations de SSM pendant les premiers stades de croissance du blé. En outre, les changements drastiques de la géométrie du couvert associés à la phase d'épiaison ont un fort impact sur sigma^0. Les résultats montrent que le modèle Water Cloud (WCM) est capable de reproduire le cycle saisonnier de Sentinel-1. Grâce à une configuration multicouche du modèle Karam, le 2ème cycle est attribué à la diffusion de volume au sein de la couche des épis. Dans un 2ème temps, une nouvelle approche basée sur l'inversion du WCM pour estimer la SSM a été proposée en utilisant uniquement les données radar Sentinel-1. Dans ce but, les descripteurs de la végétation : la biomasse aérienne (AGB) et le contenu en eau de la végétation ont été estimés à partir de rho et PR. Les meilleurs résultats d'inversion de SSM sont obtenus en utilisant la relation entre rho_VV et l'AGB (R = 0.82 et RMSE = 0.05 m3/m3). Les produits SSM sont assimilés dans la FAO-56 par une technique de filtrage particulaire pour estimer les dates et les quantités d'irrigation. Premièrement, des expériences jumelles sont conçues pour évaluer l'impact de certains paramètres de l'approche. La méthode est ensuite évaluée en utilisant des mesures in situ de SSM avec 3 temps de revisite différents (3, 6 et 12 jours). Enfin, les produits de SSM Sentinel-1 dérivés par l'approche rho_VV-AGB sont utilisés. L'utilisation de données in situ permet d'obtenir de bons résultats. Avec une observation tous les 6 jours, les quantités saisonnières sont inversés avec R > 0.98 et RMSE 0.98 and RMSE < 32 mm. Similarly, over the flood-irrigated fields, more than 70% of the events are correctly detected. Using the SSM products derived from Sentinel-1, the statistics are still acceptable. For the drip-irrigated fields, the 15-day cumulative amounts are estimated with R = 0.64 and RMSE = 28.7 mm; metrics close to those obtained using in situ data (R = 0.74 and RMSE = 24.8 mm). Finally, the last part is devoted to the preliminary analysis of in situ radar acquisition by the C-band antennas installed on a wheat field in Morocco. The analysis of the fully polarimetric acquisitions (sigma^0 and rho) with a time step of 15 min reveals the existence of a diurnal cycle of rho whose amplitude evolves with the development of the canopy. The drop in rho at dawn is concomitant with the increase in evapotranspiration. In contrast, the lowest coherence values at the end of the afternoon are rather related to wind peaks

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied