Dissertationen zum Thema „Observation satellite“

A new range of multi-plankton biogeochemical models have recently been developed, designed to advance our understanding of the ocean carbon cycle to improve predictions of its future influence on climate. Synoptic measurements of the different phytoplankton communities are required to validate and ultimately improve such models. Measuring ocean colour from satellite is the only method currently available for synoptically monitoring wide-area properties of ocean ecosystems, such as phytoplankton chlorophyll biomass. Recently, a variety of bio-optical methods have been established that use satellite data to identify and differentiate between either phytoplankton functional types (PFTs) or phytoplankton size classes (PSCs). In this thesis, several of these techniques were evaluated against in situ observations (6504 samples) to determine their ability to detect dominant phytoplankton size classes (micro-, nano- and picoplankton). Results show that spectral-response, ecological and abundance-based approaches can all perform with similar accuracy. However, abundance-based approaches provide better spatial retrieval of PSCs. Based on insights into the abundance-based models, and by utilising a large pigment database, a new three-component model was developed which calculates the fractional contributions of three phytoplankton size classes (micro-, nano- and picoplankton) to the overall chlorophyll-a concentration. Using a globally representative, independent, coupled pigment and satellite dataset the model estimates fractional contributions with a mean accuracy of 9.2 % for microplankton, 17.1 % for nanoplankton and 16.1 % for picoplankton. The effect of optical depth on the model parameters was also investigated and explicitly incorporated into the model. Using the three-component model, the two-component absorption model of Sathyendranath et al. (2001) and Devred et al. (2006) was extended to three-component populations of phytoplankton, namely, pico-, nano- and microplankton. The new model infers total and size-dependent phytoplankton absorption as a function of the total chlorophyll-a concentration. A main characteristic of the model is that all the parameters that describe it have biological or optical interpretation. The three-component model performs better than the two-component model, at retrieving total phytoplankton absorption. Accounting for the contribution of pico- and nanoplankton, rather than the combination of both used in the two-component model, improved significantly the retrieval of phytoplankton absorption at low chlorophyll-a concentrations. The three-component model was applied to a decade of ocean colour observations. In the equatorial region of the Pacific and Indian Oceans, phytoplankton size class anomalies (% total chlorophyll-a) were highly correlated with indices of both the El Niño (La Niña) Southern Oscillation and the Indian Ocean Dipole. Furthermore, in these regions, micro- and nanoplankton size class anomalies were negatively correlated with anomalies of the sea surface temperature, sea surface height and stratification. Whereas, the picoplankton size class anomalies were positively correlated with these physical variables. Results from this thesis indicate that phytoplankton size class can be retrieved from Earth Observation with reasonable accuracy. It is recommended that such information can now be assimilated into multi-plankton biogeochemical models, or alternatively, verify them.

This thesis is directed toward the feasibility of observing satellites on the nano scale and determining an accurate propagated orbit using a Meade LX600-ACF 14” diameter aperture telescope currently located on the California Polytechnic State University campus. The optical telescope is fitted with an f/6.3 focal reducer, SBIG ST-10XME CCD camera and Optec TCF-S Focuser. This instrumentation allowed for a 22’ X 15’ arcminute FOV in order to accurately image passing LEO satellites. Through the use of the Double-r and Gauss Initial Orbit Determination methods as well as Least Squared Differential Correction and Extended Kalman Filter Orbit Determination methods, an accurate predicted orbit can be determined. These calculated values from observational data of satellites within the Globalstar system are compared against the most updated TLEs for each satellite at the time of observation. The determined differential errors from the well-defined TLEs acquired via online database were used to verify the feasibility of the accuracy which can be obtained from independent observations. Through minimization of error caused from imaging noise, pointing error, and timing error, the main determination of accurate orbital determination lies in the instrumentation mechanical capabilities itself. With the ability to acquire up to 7 individual satellite observations during a single transit, the use of both IOD and OD methods, and the recently acquired Cal Poly telescope with an increased 14” aperture, the feasibility of imaging and orbital determination of nanosatellites is greatly improved.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 399-412).
System architecting is concerned with exploring the tradespace of early, high-level, system design decisions with a holistic, value-centric view. In the last few years, several tools and methods have been developed to support the system architecting process, focusing on the representation of an architecture as a set of interrelated decisions. These tools are best suited for applications that focus on breadth - i.e., enumerating a large and representative part of the architectural tradespace -as opposed to depth - modeling fidelity. However, some problems in system architecting require good modeling depth in order to provide useful results. In some cases, a very large body of expert knowledge is required. Current tools are not designed to handle such large bodies of knowledge because they lack scalability and traceability. As the size of the knowledge base increases, it becomes harder: a) to modify existing knowledge or add new knowledge; b) to trace the results of the tool to the model assumptions or knowledge base. This thesis proposes a holistic framework for architecture tradespace exploration of large complex systems that require a large body of expert knowledge. It physically separates the different bodies of knowledge required to solve a system architecting problem (i.e., knowledge about the domain, knowledge about the class of optimization or search problem, knowledge about the particular instance of problem) by using a rule-based expert system. It provides a generic population-based heuristic algorithm for search, which can be augmented with rules that encode knowledge about the domain, or about the optimization problem or class of problems. It identifies five major classes of system architecting problems from the perspective of optimization and search, and provides rules to enumerate architectures and search through the architectural tradespace of each class. A methodology is also defined to assess the value of an architecture using a rule-based approach. This methodology is based on a decomposition of stakeholder needs into requirements and a systematic comparison between system requirements and system capabilities using the rules engine. The framework is applied to the domain of Earth observing satellite systems (EOSS). Three EOSS are studied in depth: the NASA Earth Observing System, the NRC Earth Science Decadal Survey, and the Iridium GEOscan program. The ability of the framework to produce useful results is shown, and specific insights and recommendations are drawn.
by Daniel Selva Valero.
Ph.D.

The PhD research activity has taken place in the space debris field. In detail, it is focused on the possibility of detecting space debris from the space based platform. The research is focused at the same time on the software and the hardware of this detection system. For the software, a program has been developed for being able to detect an object in space and locate it in the sky solving the star field. For the hardware, the possibility of adapting a ground telescope for space activity has been considered and it has been tested on a possible electronic board.

The PhD research activity has taken place in the space debris field. In detail, it is focused on the possibility of detecting space debris from the space based platform. The research is focused at the same time on the software and the hardware of this detection system. For the software, a program has been developed for being able to detect an object in space and locate it in the sky solving the star field. For the hardware, the possibility of adapting a ground telescope for space activity has been considered and it has been tested on a possible electronic board.

Earth observation satellites provide useful information for early warnings of coming disasters. Theoretically, Principle XI in the Principles Relating to Remote Sensing of the Earth from Outer Space posits that states having access to information about potential natural disasters should promptly transmit this data and its related information to states endangered by the disaster. This thesis analyzes the legal issues related to this duty, liability, remuneration, and the status of international organizations and private entities. It concludes that liability and remuneration issues are unclear. However, due to the time needed to finalize a legally-binding treaty, a United Nations resolution is the way to formulate the regime. Furthermore, the United Nations can promote cooperation between the have and have-not countries, not only in the legal context but also by raising awareness; promoting standardized, compatible data; and supporting the expense of providing remote sensing data to countries without satellites.
Les satellites d'observation de la terre fournissent des informations utiles pour détecter en avance les catastrophes éventuelles. Théoriquement, le principe XI, un des principes sur la télédétection, impose particulièrement que les états ayant accès aux informations sur des catastrophes naturelles potentielles devraient promptement transmettre ces données et son information relative aux états mis en danger par le désastre. Ce mémoire analyse les problématiques liées à ce devoir, à la responsabilité, à la rémunération, et au statut des organismes internationaux et des entités privées. Elle conclut que la responsabilité et la rémunération sont peu claires. Cependant, en raison du temps nécessaire pour conclure un traité juridiquement contraignant, une résolution des Nations Unies paraît comme la manière souhaitable pour formuler ce régime. En outre, les Nations Unies peuvent promouvoir la coopération entre les pays ayant les capacités technologiques et ceux qui ne l’ont pas, non seulement dans le contexte juridique mais également en soulevant la conscience ; en promouvant l’uniformisation et les données compatibles ; et en accordant des aides financières pour les dépenses à fournir des données de télédétection aux pays privés de satellites.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 145-151).
Continuously increasing demand for Earth observation in atmospheric research, disaster monitoring, and intelligence, surveillance and reconnaissance (ISR) has been met by responsive architectures such as unmanned aerial systems (UAS) or artificial satellites. Space-based architectures can provide non-dominated design solutions on the utility-cost curve compared to alternate architectures through the use of two approaches: (1) reducing satellite manufacturing and launch costs and (2) introducing reconfigurability to the satellite constellations. Reconfigurable constellations (ReCons) enable fast responses to access targets of interest while providing global monitoring capability from space. The wide-area coverage and fast responses provided ReCon can complement high-resolution imagery provided by UAS. A newly proposed ReCon framework improves the model fidelity of previous approaches by utilizing Satellite Tool Kit (STK) simulations and Earth observation mission databases. This thesis investigates the design and optimization of ReCon in low Earth orbits. A multidisciplinary simulation model is developed, to which optimization techniques are applied for both single-objective and multi-objective problems. In addition to the optimized baseline ReCon design, its variants are also considered as case studies. Future work will potentially co-optimize ReCon and UAS-like systems.
by Sung Wook Paek.
S.M.

Ce travail est composé de deux parties. La première partie concerne l'étude de l'amas de galaxies Abell 85 en utilisant les données en rayons x du satellite Rosat ainsi que des données optiques et radio. Plusieurs méthodes d'analyse ont été appliquées aux données. Nous avons ainsi pu étudier des régions particulières de l'amas comme la partie centrale, siège des courants de refroidissement ou la région de la radiosource 0038-096 ou la mesure des flux x et radio a permis d'obtenir la valeur du champ magnétique. Une seconde partie du travail a consisté à étudier les caractéristiques des courants de refroidissement ainsi que la masse de gaz et de matière noire dans 11 amas de galaxies, grâce à un programme conçu pour ajuster les données de Rosat. Nous avons également obtenu la fraction de baryons de ces amas et discuté les conséquences cosmologiques des valeurs obtenues.

Approved for public release; distribution is unlimited
Coastal bathymetry was measured using wave motion as observed by a commercial satellite imaging system. The linear finite depth dispersion relation for surface gravity waves was used to determine nearshore ocean depth from successive images acquired by the WorldView-2 satellite of the coastal area near Camp Pendleton, California. Principal component transforms were performed on co-registered images and principal component four was found to very effectively highlight wave crests in the surf zone. Change detection images, which included principal component four from successive images, contained both spatial and temporal information. From these change detection images, wave celerity could be determined and depth inversion could be performed. For waves farther from shore, principal component four no longer highlighted wave crests. Waves could be resolved within a single RGB composite image with equalization enhancement. The wavelength of a wave above a known depth was measured and the wave period method was used to determine depth for other waves in the propagation direction of this wave. Our depth calculations compared favorably to our reference bathymetry. The spatial resolution for this method of determining depth is higher and perhaps more accurate than our reference bathymetry, particularly in the surf zone.

The principal objective of this research is to identify typical cloud-top signatures of incipient thunderstorms and its early electrification process in satellite multi-channel observations as means of building a conceptual model of thunderstorm detection based on brightness temperature and electrification life cycle association. The methods toward the principal objective analyzed the data set of CHUVA-Vale field campaign from 01 November 2011 to 31 March 2012, including multi-channel observations from the SEVIRI infrared fields, a radar-lightning co-located data set and a sample of 40 compact isolated thunderstorms. The sequence for each infrared field comprises the parallax correction in satellite observations; the co-location of satellite and radar-lightning data; the selection of an evaluation area for thunderstorm detection, and the construction of brightness temperature relative cumulative-frequency distributions along with respective thresholds analysis and validation. Consequently, 4 thunderstorm predictors used in tandem to detect the largest differentiation among the lightning time steps and significant cumulus cloud and electrification intensification, resulted throughout parameters in corresponding brightness temperature histograms whose thresholds are as follows: IF1 or Predictor 1= Ch05-Ch06: (6.2 − 7.3) $\mu$m: Tbd $\geq$ −14.0 K; IF2 or Predictor 2= 10.8 $\mu$m: Tb $\leq$ +263.0 K, IF3 or Predictor 3= (6.2 − 10.8) $\mu$m: Tbd $\geq$ −14.0 K and IF4 or Predictor 4= (8.7−10.8)−(10.8−12.0) $\mu$m: Tbd $\geq$ 0 K. Additionally, an independent 2-day validation test indicated that the conceptual model has a higher probability of lightning detection for the interval of index sums from 16 to 12 because of the higher POD and lower FAR. Also the results indicated that the conceptual model has a lower probability of lightning detection for the interval of index sums from 8 to 4 because of the lower POD and higher FAR. This representative behavior of the thunderstorm electrification life cycle in geostationary satellite multi-channel observations will allow a potential development of nowcasting tools at the boundary of subtropical regions using data from the Meteosat Second Generation Satellite, and with the perspective to use in the near future, the data from the Geostationary Operational Environmental Satellite-R and the imminent Meteosat Third Generation Satellite.
O objetivo principal desta pesquisa é identificar um conjunto de assinaturas típicas do topo das nuvens que permitam prever o processo de eletrificação quando as nuvens se transformam em tempestades. Através das combinações de canais dos imageadores de satélites geoestacionários este trabalho visa construir um modelo conceitual de detecção de início dos processos de eletrificação de tempestades utilizando a tendência dos histogramas de temperatura de brilho (ou diferença de canais). Para construção deste modelo conceitual foram utilizadas observações em diferentes canais infravermelhos co-localizados com observações de radar polarimétrico banda X e de medidas do LMA (Lightning Mapping Array) que consiste de fontes emitidas pelos relâmpagos em Very Higher Frequency. Foram selecionadas 40 tempestades compactas durante a campanha CHUVA-Vale para a elaboração do modelo conceitual e posteriormente os resultados foram testados em casos independentes. A sequência dos procedimentos metodológicos para campo de interesse compreende a correção da paralaxe nas observações de satélite; a co-localização com os dados de radar e descargas elétricas; a seleção de uma área de avaliação para detecção das tempestades e a construção de distribuições de frequência relativa-cumulativa de temperatura de brilho (ou diferenças) e a definição de limiares para a construção das frequências cumuladas. Quatro canais ou diferença de canais foram selecionados para detectar o processo de eletrificação da nuvem. Os seguintes preditores foram utilizados: IF1 or Predictor 1= (6.2 − 7.3) $\mu$m: Tbd $\geq$−14.0 K; IF2 or Predictor 2= 10.8 $\mu$m: Tb $\leq$+223.0 K, IF3 or Predictor 3= (6.2 − 10.8) $\mu$m: Tbd $\geq$−14.0 K and IF4 or Predictor 4= (8.7 − 10.8) − (10.8 − 12.0) $\mu$m: Tbd $\geq$ 0 K. Esse conjunto de preditores foi utilizado em função das propriedades que esses canais têm para descrever os processos microfísicos das nuvens. Após a definição do modelo, um teste de validação independente de 2 dias permitiu definir as incertezas do modelo conceitual. O emprego dos campos selecionados quando empregados juntos melhoram significativamente a previsibilidade do processo de eletrificação da nuvem. Este comportamento representativo do ciclo de vida da eletrificação das tempestades através de combinações de canais de satélite geoestacionário permitirá o desenvolvimento de ferramentas de previsão a curtíssimo prazo nas regiões tropicais e subtropicais usando dados do Meteosat Second Generation e, em breve, do Geostationary Operational Environmental Satellite-R e do futuro Meteosat Third Generation Satellite.

My Master Thesis takes place in the context of the MicroCarb mission. The goal of this mission is to identify the sinks and the sources of carbon dioxide on Earth in order to map them and to improve the knowledge of its cycle. To fulfill this mission, some particular guidance modes must be implemented in order to study their feasibility. My thesis consisted in defining and enriching the algorithms used to define the guidance laws, by implementing new tools and a new guidance law, and studying the induced performances in terms of data acquisition and with respect to the constraints related to the satellite. Alongside with this mission, the implementation of those elements support the development of the guidance library POLARIS, actual in its early phase, which is at first only dedicated to MicroCarb but which is intended to become multimissions. First, I describe the CNES as well as the guidance team I worked in. Then, the context of the Master Thesis is introduced. Once the context is established we will focus on the first elements I have been working on, as part of the Dazzling studies. Indeed, the spectrometer used in MicroCarb is very sensitive and has to be maintained at very low temperature. Thus the passive cooling mechanism must be protected from the Sunlight and from the light reflected by the Earth. I had to use a class of the Space mechanics library PATRIUS, called Assembly, in order to materialize the satellite and its numerous parts. Once implemented, I was able to perform some Dazzling Studies, highlighting some issues with the various strategies that were considered, and opening new perspectives. Moreover, a problem was detected on a crucial function of the guidance laws calculator. Once a new function was compiled, I had to made a cross validation using Scilab, and results were positive. This part will end with a Geometric Cape study, realized in order to quantify the influence of the satellite, and the MCV roll, over the Geometric Shifting. In the second part, we will introduce a guidance law which was not implemented initially, and on which I had to work during the last weeks of the thesis: The City mode. Although this mode is similar to an existing calibration mode, it has its own characteristics I had to take into account. The code for this acquisition mode worked well, but the results were not satisfying, considering the Dazzling problem and the kinematic constraints. Thus new strategies had to be considered, and more particularly the 2-scans mode. This mode brought a lot of satisfactions, but there is still more work to be done. This report ends with a general conclusion about my work and some perspectives which could be considered for future studies. I also present my personal contribution and some encountered difficulties I had to deal with.
Examensarbetet fokuserade på rymduppdraget MicroCarb. Målet med detta uppdrag är att identifiera koldioxidsänkor och -källor på jorden för att kartlägga dem och förbättra kunskapen om deras cykler. För att uppfylla detta uppdrag måste vissa specifika styrningsmoder implementeras för att studera uppdragets genomförbarhet. Detta bestod i att definiera och förfina de algoritmer som användes för att definiera siktningslinjer, genom att implementera nya verktyg och en ny styrning samt studera prestandan när det gäller datainsamling och utifrån begränsningar hos satelliten. Detta uppdrag stöder utvecklingen av vägledningsbiblioteket POLARIS, i dess tidiga fas, som i första hand är avsedd för MicroCarb men som också är avsett att användas i flera kommande uppdrag. Arbetet inleds med en beskrivning av CNES, där examensarbetet utfördes, samt den grupp jag arbetade inom. Därefter presenteras motivation och sammanhanget. Sedan inriktas fokus mot de första elementen jag har arbetat med som en del av de bländande studierna. Spektrometern som används i MicroCarb är mycket temperaturkänslig och måste hållas vid mycket låg temperatur. Således måste den passiva kylmekanismen skyddas mot solljus samt från det ljus som reflekteras från jorden. En klass inom rymdmekanikbiblioteket PATRIUS, kallad Assembly, användes för att modellera satelliten och dess många delar. Därefter utfördes preliminära bländande studier, med fokus på några problem med de olika styrningsstrategier som föreslagits, vilket öppnade nya perspektiv. Dessutom upptäcktes ett problem med en avgörande funktion i siktlinjens räknare. När en korrigerad funktion sammanställts, utfördes en korsvalidering med mjukvaran Scilab, och resultaten var positiva. Denna del avslutas med en geometrisk studie för att kvantifiera påverkan av satelliten och instrumentrullningen på den geometriska skiftningen. Den andra fasen i arbetet var implementering av en ny funktionalitet kallad Stadsläget. Även om det här läget liknar ett befintligt kalibreringsläge, har det egna egenskaper som måste tas hänsyn till. Beräkningskoden för detta läge fungerade bra, men resultaten var inte tillfredsställande utifrån bländningsproblemet och kinematiska begränsningar. Därför beaktades nya strategier, i synnerhet ett nytt skanningsläget med två avskanningar. Detta läge gav bättre resultat, men behöver utvecklas ytterligare. Rapporten avslutas med förslag på fortsatt arbete och personliga reflektioner.

L'éclairement du Soleil à la surface de la Terre est reconnu comme une variable climatique essentielle par l'Organisation Météorologique Mondiale. Sa connaissance est aussi précieuse pour les sciences du climat que pour le développement d'énergies alternatives aux combustibles fossiles, comme le solaire photovoltaïque. La mesure au sol de ce rayonnement est très clairsemée sur la Terre, d'où l'intérêt de méthodes d'estimation basées sur la télédétection par satellite. Combiner les estimations produites à partir de différents satellites en orbite est une voie pour couvrir au mieux l'information sur tout le globe terrestre. De plus, différentes générations de satellites ont produit une imagerie de la Terre depuis plusieurs décennies, permettant d'estimer de longues séries temporelles du rayonnement solaire, voire d'identifier des variations long terme, un objectif récurrent dans l'étude du changement climatique. Depuis plus de trente ans, les méthodes Heliosat permettent cette estimation, mais elles ont été conçues pour être appliquées à un capteur spécifique en orbite géostationnaire et ont des contraintes limitant leurs champs d'application : la nécessité d'utiliser une longue série temporelle passée (Heliosat, Heliosat-2), ou le besoin de mesures multispectrales (Heliosat-4). Ce travail sur le développement d'une méthode Heliosat-V apporte des éléments de polyvalence à l'estimation satellite par les méthodes dites à "indice d'ennuagement", dans l'objectif de tendre vers une donnée homogène du rayonnement solaire issue de mesures de différents instruments satellites. Deux problèmes sont en particulier considérés pour parvenir à cette estimation : la diversité des capteurs en termes de sensibilités spectrales, et l'influence des géométries de visée et d'éclairement solaire sur les mesures satellites. La méthode s'appuie extensivement sur la modélisation du transfert radiatif dans l'atmosphère dans la gamme spectrale 400-1000 nm pour simuler d'une part les mesures de radiomètres satellites en conditions de ciel clair et d'autre part celles en présence d'un nuage optiquement épais. La méthode est testée sur l'imagerie d'un instrument satellite géostationnaire, Meteosat-9/SEVIRI, et de manière plus exploratoire sur celle d'un non géostationnaire, DSCOVR/EPIC. Les résultats sont comparés à des mesures de référence au sol de l'éclairement, et montrent des performances similaires à celles de produits opérationnels d'éclairement solaire. La qualité des estimations dépend cependant du canal spectral utilisé, en particulier de la présence de diffusion ou d'absorption de l'atmosphère claire dans le signal mesuré par satellite. L'accent est aussi mis sur le besoin d'un étalonnage absolu précis des mesures radiométriques satellites pour produire des séries temporelles d'éclairement de surface avec des biais et une dérive temporelle les plus faibles possibles
Solar irradiance at the surface of the Earth is recognized as an essential climate variable by the World Meteorological Organization. Its knowledge is as much important for climate sciences as for the development of energy alternatives to fossil fuels, like solar photovoltaic. Ground measurements of this radiation are very sparse on Earth, explaining the interest for satellite-based remote sensing to estimate it. Combining estimations from different satellites in orbit is a pathway to cover the information on the whole globe. Different generations of satellites also produced a multidecadal imagery of the Earth, making it conceivable to estimate long time series of solar radiation, or even to identify long-term variations, a recurrent objective in the study of climate change. For more than 30 years, Heliosat methods estimate surface solar irradiance from satellite imagery, but they have been designed to be applied to a specific sensor on a geostationary orbit, and have limitations in their scope : the need for a long archive of satellite imagery (Heliosat, Heliosat-2), or else the need for multispectral measurements (Heliosat-4). This work dedicated to the development of a Heliosat-V method brings elements of versatility to the satellite-based estimation from so-called "cloud-index" methods, with the ultimate goal to reach homogeneous data of solar radiation derived from measurements made by different satellite instruments. Two issues are in particular considered here to reach such an estimation: the diversity of sensors in terms of spectral sensitivities, and the influence of viewing and solar geometries on spaceborne measurements. The method extensively deals with radiative transfer modeling in the spectral range 400-1000 nm to simulate on one hand satellite measurements in clear-sky conditions, and on the other hand satellite measurements in the presence of an optically thick cloud. The method is tested on the imagery of a geostationary satellite instrument, Meteosat-9/SEVIRI, and in a more exploratory way, on the non geostationary sensor DSCOVR/EPIC. Results are compared to high quality ground-based measurements of irradiance, and show performances similar to operational satellite products. However, the quality of estimates depends on the spectral channel used, and especially of the presence of clear-sky atmospheric scattering or absorption in the signal measured by the satellite instrument. The accent is also put on the need for an accurate absolute calibration of satellite radiometric measurements in order to produce time series of surface solar irradiance with the smallest biases and temporal drift possible

The main objective of this thesis is obtaining data on gravity waves from images taken by the NTNU Test Satellite (NUTS). The satellite's main payload consists of a camera intended to capture images of gravity waves in the atmosphere. A limitation of the satellite is its ability to transmit data. Two separate approaches have been investigated to limit the amount of data that needs to be sent. One is the degree of image and video compression that can be applied to a series of images before data is corrupted. The second is implementing a 3D-Fast Fourier Transform (FFT) method that obtains the relevant data in the image series directly and only sends these. The NUTS-satellite is a project still in the making with a preliminary launch date in 2014. Currently there are no comparable, usable images of the wave phenomenon captured from space. Ground based images taken with fish-eye lenses are therefore used as a basis to make emulate satellite images. These are used to test how satellite images will be influenced by compression and how the 3D-FFT can extract the data. We found the 3D-FFT able to extract wave parameters from the images, providing significant reduction in the need for transmission of data compared to sending compressed images. In addition we found that the compression-approach corrupts data before a considerable reduction in transmitted data is achieved.

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Subaqueous beach profiles are obtained for littoral regions near Camp Pendleton, CA, using observations of wave motion. Imagery was acquired from WorldView2 Satellite on 24 March 2010. Two sequential images taken 10 seconds apart are used for the analyses herein. Water depths were calculated using linear dispersion relationship for surface gravity waves. Depth profiles were established from shoreline out to 1 kilometer offshore and depths of up to 15 meters. Comparisons with USGS DEM values show agreement within five percent in the surf zone (shoreline to wave breaking) and one percent outside the surf zone (offshore of wave breaking).

La surface de neige sur le Plateau Antarctique joue un rôle important dans l'étude du bilan de masse et d'énergie de surface. Ses caractéristiques dépendent des interactions entre les conditions atmosphériques et le haut du manteau neigeux, à travers notamment les précipitations, la redistribution de neige par le vent et le métamorphisme. L'ensemble des aspects de la surface, i.e. le type de cristaux, la rugosité, la densité, l'albédo ..., sont regroupés sous la formule état de surface. L'objectif de cette thèse est l'étude de l'état de surface et de son évolution, en fonction des conditions atmosphériques, à l'aide d'observations in situ et satellite. L'analyse conjointe d'observations in situ, essentiellement à partir de photographies infrarouges de la surface (développement d'un algorithme examinant la texture des images), et satellite, principalement l'émission micro-onde du manteau neigeux (utilisation du rapport de polarisation sensible à la densité proche de la surface), a permis de montrer une dynamique rapide de la surface à Dôme C. En particulier, des périodes où le givre recouvre entièrement la surface sont observées et représentent environ 45% du temps. Cette dynamique est aussi caractérisée par des élévations rapides et importantes de la surface, pouvant être largement supérieures à l'accumulation annuelle moyenne de 8 cm (jusqu'à 20 cm en 2 heures). Le vent est déterminant dans l'évolution de la surface. Plus particulièrement, ces travaux ont montrés l'importance de la direction du vent pour la disparition du givre (perpendiculaire à la direction dominante, i.e. le sud-ouest). Enfin, la corrélation entre présence de givre et rapport de polarisation a permis d'étendre ces résultats sur les 10 années d'observation du satellite et ouvre la voie à la détection des précipitations par télédétection. La modélisation de l'émission micro-onde à 19 et 37 GHz a ensuite été menée à Dôme C à l'aide d'un modèle de transfert radiatif (DMRT-ML). Les propriétés du manteau neigeux (taille des grains, densité et température), utilisées en entrée du modèle, ont été mesurées durant la campagne d'été 2010 - 2011. Les résultats des simulations montrent que la densité de la neige proche de la surface est principalement responsable des variations du rapport de polarisation. Cette densité a ainsi été " inversée " à Dôme C sur 10 ans. Elle montre une tendance pluriannuelle à la baisse de 10 kg m-3 a-1, superposée à un cycle annuel et à des variations journalières / hebdomadaires. La mesure in situ de la densité et l'observation du givre coïncident avec les variations rapides de la densité estimée. L'évolution pluriannuelle conséquente mérite d'être prise en compte pour l'étude du bilan de masse de surface, les causes probables étant une hausse des précipitations ou une baisse de l'intensité du vent. Suivant une méthodologie similaire, l'évolution de la densité de surface a été déduite pour l'ensemble de l'Antarctique. Les variations spatiales mettent en évidence une tendance claire à la diminution de la densité sur une grande région entre Dôme C et Vostok et une région à l'est de Dôme C où elle augmente. À plus grande échelle, le rapport de polarisation moyen montre de grandes variations, signatures de la stratification en densité du manteau neigeux. L'étude de l'altimétrie satellite permettrat de corroborer ces résultats.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.
Vita.
Includes bibliographical references (p. 233-240).
Atmospheric density mismodeling is a large source of errors in satellite orbit determination and prediction in the 200-600 kilometer range. Algorithms for correcting or "calibrating" an existing atmospheric density model to improve accuracy have been seen as a major way to reduce these errors. This thesis examines one particular algorithm, which does not require launching special "calibration satellites" or new sensor platforms. It relies solely on the large quantity of observations of existing satellites, which are already being made for space catalog maintenance. By processing these satellite observations in near real-time, a linear correction factor can be determined and forecasted into the near future. As a side benefit, improved estimates of the ballistic coefficients of some satellites are also produced. Also, statistics concerning the accuracy of the underlying density model can also be extracted from the correction. This algorithm had previously been implemented and the implementation had been partially validated using simulated data. This thesis describes the completion of the validation process using simulated data and the beginning of the real data validation process. It is also intended to serve as a manual for using and modifying the implementation of the algorithm.
by Sarah Elizabeth Bergstrom.
S.M.

The demand of space applications has been increasing over the years. This has derivedin new satellites structures that required from precise and robust control management.The satellite design is evolving towards the development of lighter structures. The combinationof lighter structures with precise and robust control has arisen the problem ofstructure vibration control. The control design of structures with large appendages likeantennas, booms or solar panels has become a challenge. The flexible dynamics of theappendages needs to be considered when performing the attitude analysis of the satellite,since these parts can be easily excited by the environment perturbations such us gravity,gravity gradient or solar wind. The objective of these research project is to develop ahigh-fidelity model plant of a satellite with flexible panels and review different systemidentification techniques used to observe the states of the system. The equations of themodel are reviewed and the model is verified against a multi-body software, Adams. Thesensors and actuators are selected and modelled for the control of the rigid body and theobservation of the rigid and flexible body. For the implementation of the flexible structureobservations a technique based in Genetic Algorithm is applied for optimal sensor location.Finally, different system identification techniques are reviewed for the identificationof modal parameters and rigid body parameters. The results illustrate the performanceof the model and how the different system identification techniques are performed whenobserving the model states.

La télédétection par satellite est couramment utilisée pour observer le cycle hydrologique à des échelles spatiales allant des bassins fluviaux au globe terrestre. Pourtant, il reste difficile d'obtenir un bilan hydrique équilibré en utilisant des données de télédétection, ce qui met en évidence les erreurs et les incertitudes des données d'observation de la Terre. Cette recherche visait à améliorer les estimations des précipitations, de l'évapotranspiration, de l'écoulement, et du changement du stockage total de l'eau à l'échelle mondiale en utilisant une combinaison de méthodes analytiques (interpolation optimale, OI) et de méthodes de modélisation statistique, y compris les réseaux neuronaux (NN). Les modèles ont été entraînés sur un ensemble de 1 358 bassins fluviaux et validés sur un ensemble indépendant de 340 bassins et sur des observations in situ des précipitations, de l'évapotranspiration et du débit des cours d'eau. Les modèles sont étendus pour faire des prévisions à l'échelle du pixel dans des cellules de grille de 0,5° pour une couverture quasi mondiale. Les ensembles de données calibrées donnent des résidus de bilan hydrique plus faibles dans les bassins de validation : la moyenne et l'écart-type du déséquilibre sont de 11±44 mm/mo lorsqu'ils sont calculés avec des données non corrigées et de 0,03±24 mm/mo après calibrage par les modèles NN. Les résultats nous permettent de faire des estimations plus précises des composantes manquantes du cycle de l'eau, par exemple pour estimer l'évapotranspiration dans les zones non instrumentées, ou pour prédire le débit dans les bassins non jaugés. Les résultats peuvent également indiquer aux producteurs de données où leurs produits semblent incohérents par rapport à d'autres ensembles de données et où un étalonnage plus poussé pourrait apporter des améliorations. Enfin, cette recherche démontre l'utilisation des réseaux neuronaux et de l'intelligence artificielle pour l'intégration des données satellitaires et pour l'étude du cycle de l'eau
Satellite remote sensing is commonly used to observe the hydrologic cycle at spatial scales ranging from river basins to the globe. Yet, it remains difficult to obtain a balanced water budget using remote sensing data, which highlights the errors and uncertainties in earth observation (EO) data. This research aimed to improve estimates of precipitation, evapotranspiration, runoff, and total water storage change at the global scale using a combination of analytical methods (optimal interpolation, OI) and statistical modeling methods including neural networks (NN). Models were trained on a set of 1,358~river basins and validated them on an independent set of 340~basins and in-situ observations of precipitation, evapotranspiration, and river discharge. The models are extended to make pixel-scale predictions in 0.5° grid cells for near-global coverage. Calibrated datasets result in lower water budget residuals in validation basins: the mean and standard deviation of the imbalance is 11±44 mm/mo when calculated with uncorrected EO data and 0.03±24 mm/mo after calibration by the NN models. The results allow us to make more accurate estimates of missing water cycle components, for example to estimate evapotranspiration in un-instrumented areas, or to predict discharge in ungaged basins. The results can also indicate to data producers where their products seem incoherent with other datasets and where enhanced calibration could lead to improvements. Finally, this research demonstrates the use of neural networks and machine learning for the integration of satellite data and for the study of the water cycle

The Scintillation Prediction Observation Research Task (SPORT) is a joint United States of America (USA) and Brazil small satellite mission to address the further under-standing of the preconditions leading to equatorial plasma bubbles. Utah State University (USU) is supplying four instruments towards this SPORT mission. These four instruments will allow measurements of the electric field and plasma density in the ionosphere which will help understand what gives rise to plasma bubbles in the ionosphere. This thesis will discuss the command, control, and telemetry communications needed to operate the SPORT USU instruments. It will cover an overview of the instruments involved, how the instruments are controlled specifically, what commands were needed to run the instruments, what telemetry data was produced and how it was transmitted to the ground station, and how the data is made useful. The design process, challenges, and solutions to this system and project will also be discussed.

The snow cover plays an important role not only for the whole climate system but also for tourism and economy in the Lapland winter (e.g. dog sledding, snow mobile, etc). Snow constitutes a shelter for animals and plants during the winter due to thermal isolation, but, on the range of this investigation, it can make grazing difficult for reindeers, if the conditions are not favorable. Different approaches to the study have been made; the first and most important part of the investigation was a campaign in Järämä, in Swedish Lapland. During 3 days (between the 3rd and 5th of March 2009), a series of snow pits were done, recording snow grain size, snow layers depth, snow hardness/compactness, density and temperature. The hardness in the snow was evaluated through ram penetration tests. It was additionally studied the correspondence between the snow layers found in situ and the Sámi terminology. Another approach of the study consisted of satellite observations during the winter season 2008/2009 with day light in the region. The type of imagery used was MODIS (The Moderate Resolution Imaging Spectroradiometer) daily snow albedo and 8-day surface reflectance products. Measurements of temperature, precipitation, snow depth were used to cover the polar night time when satellite images were missing. According to these weather observations some snow metamorphisms were also studied, and their influence on the snowpack conditions. Through the comparison between all these forms of data it was found that in the winter season 2008/2009 the conditions for reindeers grazing were not good due to the formation of ice encapsulating the lichens and grass. Additionally several hard snow layers have been found in the snowpack which increase the difficulty to dig in the snow and may cause problems to the reindeers’ digestion. Snow hardness measurements with a ram penetrometer, manual tests and visual grain size observation proved these discovers. Several periods of positive temperature may cause melting/refreezing cycles contributing to the formation of hard snow layers. These conclusions are supported by the snow albedo and surface reflectance satellite imagery. In these images is visible a period with snow albedo decreasing a lot in the beginning of autumn, after the first lasting snowfall. The weather conditions in early fall, when the first durable snow occurs, are of extreme importance for the reindeers’ grazing, and in the case of the studied winter season, the conditions were not favorable.

Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The ability of satellites to actively control their attitude has changed the way we live. Navigation systems, satellite television, and weather forecasting, for example, all rely on satellites which are able to determine and control their attitude accurately. This project was aimed at designing and analysing an attitude determination and control system (ADCS) for a 20 kg Earth observation satellite by means of simulation. A realistic simulation toolset, which includes the space environment, sensor, and actuator models, was created using MATLAB and Simulink. An ADCS hardware suite was selected for the satellite based on a given set of pointing and stability requirements, as well as current trends in the small satellite industry. The hardware suite consists of among others a star tracker and three reaction wheels. A variety of estimators and controllers were investigated, after which an application specific ADCS state machine was defined. The state machine included a Safe Mode for de-tumbling, a Nominal Mode for normal operation, a Forward Motion Compensation (FMC) Imaging Mode for Earth observation, and a Target Tracking Mode for ground station tracking. Simulation results indicated that de-tumbling, coarse and fine sun tracking, FMC factor 4 imaging, and target tracking were successfully implemented. Lastly, the satellite’s pointing error and stability were determined to be less than 70 arcseconds and 7 arcseconds per second respectively, both values well within the given requirements.
AFRIKAANSE OPSOMMING: Satelliete se vermoë om hul oriëntasie aktief te beheer, het die manier waarop ons lewe, verander. Navigasiestelsels, satelliettelevisie en weervoorspelling, byvoorbeeld, maak staat op satelliete wat hul oriëntasie akkuraat kan bepaal en beheer. Die mikpunt van hierdie projek was die ontwerp en analise van ’n oriëntasiebepaling- en -beheerstelsel (ADCS) vir ’n 20 kg aardwaarnemingsatelliet deur middel van simulasie. ’n Realistiese simulasieopstelling, wat modelle van die ruimteomgewing, sensore en aktueerders insluit, was ontwikkel deur gebruik te maak van MATLAB en Simulink. ’n ADCS hardewarestel was gekies vir die satelliet op grond van ’n stel rig- en stabiliteitsvereistes, sowel as die huidige tendense in die klein-satellietbedryf. Die hardewarestel bestaan onder andere uit ’n stervolger en drie reaksiewiele. Nadat verskeie afskatters en beheerders ondersoek was, was ’n toepassingspesifieke ADCS toestandmasjien gedefinieer. Die toestandmasjien het ’n Veilige Modus vir onttuimelling, ’n Nominale Modus vir normale operasie, ’n Vorentoe-bewegingskompensering (FMC) Beeldskandeermodus vir aardwaarneming en ’n Teikenvolgmodus vir grondstasie volging ingesluit. Simulasieresultate het aangedui dat onttuimeling, growwe- en fyn sonvolging, FMC faktor 4 beeldskandering en teikenvolging suksesvol geïmplementeer was. Laastens was die satelliet se rigfout en stabiliteit bepaal as minder as 70 boogsekondes en 7 boogsekondes per sekonde onderskeidelik, albei waardes gemaklik binne die vereistes.

Cette étude est basée sur les mesures collectées pendant la période d'observation de l'Expérience INDOEX (Indian Ocean Experiment) pendant l'hiver 1999. Le but de ce travail est premièrement d'examiner les propriétés des systèmes convectifs à mesoéchelle (MCSs) à l'aide des images METEOSAT-5 infrarouge; deuxièmement, d'étudier les précipitations en employant les données micro-ondes de DMSP-SSM/I et de TRMM-TMI; troisièmement, de présenter une comparaison des échantillonnages des données obtenus pour les orbites de différents satellites et de présenter un des avantages du nouveau satellite Megha-Tropiques. Dans la première partie, un algorithme de suivi des nuages sur les images Meteosat-5 IR a été appliqué pour calculer les paramètres radiatifs et morphologiques de chaque MCS. Les trajectoires de chaque MCS ont été construites, et les situations de dissipation, division et fusion des systèmes identifiées. La carte de fréquence d'occurrence montre que la plupart des systèmes se produisent dans la zone intertropicale de convergence (ITCZ) distribuée de l'Indonésie jusqu'au nord de Madagascar, deux autres secteurs distincts apparaissant au sud du Golfe du Bengale et au sud de Madagascar. Les résultats montrent que les MCSs qui ont un cycle de vie long sont fortement associés aux températures de brillance les plus froides, moins de 210 K, et à une surface énorme de couverture nuageuse, supérieure à 105 km2. Une autre étude porte sur l'orientation du mouvement de chaque MCS pour différentes durées de vie; elle indique les différentes directions préférentielles de propagation des MCSs dans chaque zone subdivisée: par exemple environ 63% des MCSs au sud de Madagascar vont vers l'est. La deuxième partie de l'étude a pour but de caractériser la relation entre la précipitation régionale et la distribution des MCSs. Les données SSM/I des trois satellites DMSP présents à cette période ont été employées pour estimer les précipitations. Le taux de pluie au-dessus de l'océan est dérivé à partir de l'algorithme de Scattering Index (SI) de Grody [1991]. Ces résultats sont comparés aux estimations de taux de pluie de TRMM TMI et au produit cumul de pluie mensuel et quotidien du Global Precipitation Climatology Project (GPCP). Une carte de taux de pluie moyen mensuel montre la corrélation élevée entre les précipitations et la fréquence de distribution des MCSs. Les variations journalières des précipitations montrent que la pluie a tendance à tomber le matin près des secteurs côtiers tandis qu'il n'y a pas de période préférencielle sur l'océan ouvert. Le dernier sujet concerne le rôle de l'amélioration de l'échantillonnage des mesures journalières sur un secteur spécifique de la région tropicale. Par comparaison avec les satellites DMSP et TRMM qui fournissent en moyenne une seule observation par jour, le futur satellite Megha-Tropiques fournira 3 à 6 observations par jour pour n'importe quel point entre 23°N à 23°S. Cela sera très utile pour les études des MCSs et des précipitations associées dans différentes phases de leur développement.

La banquise joue un rôle majeur dans la circulation océanique ainsi que dans le système climatique et météorologique. Dans un contexte de réchauffement climatique, où l’étendue de la banquise arctique ne cesse de décroître depuis les 40 dernières années, le suivi et la surveillance de l’Arctique est essentiel. Les instruments micro-ondes à bord de satellites permettent l’étude de cette région terrestre par tous les temps, indépendamment du cycle jour/nuit. Particulièrement adaptées à l’observation des régions polaires où la présence de nuages est importante et où la nuit polaire dure six mois, les observations satellites micro-ondes sont la pierre angulaire des estimations des paramètres géophysiques de la banquise. Néanmoins, la compréhension de la physique sous-jacente aux signatures micro-ondes observées est encore partielle. Cette thèse a pour but d’améliorer notre compréhension des signaux micro-ondes de la banquise et se place dans le cadre de la préparation de deux prochaines missions d’observation de la Terre menée par l’Agence Saptiale Européenne : le Copernicus Imager Microwave Radiometer (CIMR) et le Copernicus polaR Ice and Snow Topography ALtimeter (CRISTAL). Dans une première partie, les covariabilités des signaux micro-ondes passifs, mis en avant par une technique de classification non supervisée, seront analysées et interprétées conjointement avec des signaux micro-ondes actifs à l’aide d’un modèle de transfert radiatif micro-onde spécifique à la banquise. Les résultats ont montré qu’il est possible d’identifier les comportements spécifiques de la concentration et de l’épaisseur de la glace de mer, et de la structure de la neige. L’importance du métamorphisme au sein du manteau neigeux pour l’interprétation des signaux micro-ondes passifs a été mis en évidence. Dans une deuxième partie, un algorithme d’estimation de l’épaisseur de la glace de mer à partir d’observations micro-ondes passives a été développé en utilisant une technique d’intelligence artificielle. Les résultats ont été comparés à des mesures in situ d’épaisseur de glace de mer et ont aussi montré de bonnes performances en comparaison à d’autres produits satellitaires d’épaisseur de glace de mer. En appliquant l’algorithme à une longue collection de données satellitaires intercalibrées, une série temporelle d’épaisseur de glace de mer arctique a été construite entre 1992 et 2020, ce qui en fait la plus longue à ce jour. Une dernière partie traite des techniques altimétriques micro-ondes pour la mesure des paramètres géophysique de la banquise. Une analyse de la sensibilité des formes d’ondes altimétriques micro-ondes à l’épaisseur du manteau neigeux de la banquise arctique est menée
Sea ice plays a major role in ocean circulation as well as in the climate and weather system. In the context of global warming, the extent of the Arctic sea ice has been decreasing steadily over the last 40 years and monitoring of the Arctic is essential. Microwave instruments on board satellites allow the study of this region of the Earth under all weather conditions, and regardless of the day/night cycle. Particularly suited over polar regions with high cloud cover and a six-month polar night, microwave satellite provide key observations for estimating geophysical parameters of the sea ice. Nevertheless, the understanding of the physics underlying the observed microwave signatures is still partial. This thesis aims at improving our understanding of the microwave signals of the sea ice and is part of the preparation of two upcoming Earth observation missions led by the European Space Agency: the Copernicus Imager Microwave Radiometer (CIMR) and the Copernicus Polar Ice and Snow Topography ALtimeter (CRISTAL). In a first part, the covariabilities of passive microwave signals, highlighted by an unsupervised classification technique, will be analyzed and interpreted jointly with active microwave signals, using a microwave radiative transfer model. The results showed that it is possible to identify specific behaviors of sea ice concentration and thickness, and snow structure. The importance of metamorphism within the snowpack for the interpretation of passive microwave signals was highlighted. In a second part, an algorithm for estimating sea ice thickness from passive microwave observations was developed using an artificial intelligence technique. The results were compared to in situ sea ice thickness measurements and also showed good performance compared to other satellite-based sea ice thickness products. By applying the algorithm to a long collection of intercalibrated satellite data, a time series of Arctic sea ice thickness was constructed between 1992 and 2020, making it the longest to date. A final section deals with microwave altimetry techniques for measuring geophysical parameters of the sea ice. The sensitivity of microwave altimetry waveforms to the thickness of the snow cover of the Arctic sea ice is analyzed

Магістерська робота на тему «Розробка системи моніторингу положення штучних супутників Землі на основі мови Python» Лещука Назарія Віталійовича. – Тернопільський національний технічний університет імені Івана Пулюя, Факультет комп'ютерно-інформаційних систем і програмної інженерії, Кафедра програмної інженерії, група СПм–61 // Тернопіль, 2019. C. – 103, рис. – 23, табл. – 4, слайдів. – 12, додат. – 3, бібліогр. – 38. Метою роботи є аналіз та реалізація найновішої ревізії математичної моделі спрощених загальних збурень №4 на мові програмування Python, яка є важливою для моніторингу положення навколоземних об’єктів на їх орбітах в довільний момент часу, з використанням сучасних інструментів розробки та тестування. Методи та програмні - засоби, використані при виконанні розробки системи: мова програмування Python та її бібліотеки, середовище розробки JetBrains PyCharm, модифікація водоспадної методології розробки програмного забезпечення Сашімі. Результатом роботи є пакет бібліотек мови програмування Python з системою придатною для моніторингу положення штучних супутників чи навколоземних об’єктів як ближнього так і дальнього космосу. Ключові слова: СУПУТНИКИ, МАТЕМАТИЧНА МОДЕЛЬ, СИСТЕМА МОНІТОРИНГУ, ЗБУРЕННЯ, ЕЛЕМЕНТИ ОРБІТИ, АЛГОРИТМ, РІВНЯННЯ КЕПЛЕРА.

Le plateau des Guyanes est une région qui est caractérisée à 90% d’une forêt tropicale primaire et compte pour environ 20% des réserves mondiales d’eau douce. Ce territoire naturel, au vaste réseau hydrographique, montre des intensités pluviométriques annuelles atteignant 4000 mm/an ; ce qui fait de ce plateau une des régions les plus arrosées du monde. De plus les précipitations tropicales sont caractérisées par une variabilité spatiale et temporelle importante. Outre les aspects liés au climat, l’impact des précipitations dans cette région du globe est important en termes d’alimentation énergétique (barrages hydroélectriques). Il est donc important de développer des outils permettant d’estimer quantitativement et qualitativement et à haute résolution spatiale et temporelle les précipitations dans cette zone. Cependant ce vaste espace géographique est caractérisé par un réseau de stations pluviométriques peu développé et hétérogène, ce qui a pour conséquence une méconnaissance de la répartition spatio-temporelle précise des précipitations et de leurs dynamiques.Les travaux réalisées dans cette thèse visent à améliorer la connaissance des précipitations sur le plateau des Guyanes grâce à l’utilisation des données de précipitations satellites (Satellite Precipitation Product : SPP) qui offrent dans cette zone une meilleure résolution spatiale et temporelle que les mesures in situ, au prix d’une qualité moindre en terme de précision.Cette thèse se divise en 3 parties. La première partie compare les performances de quatre produits d’estimations satellitaires sur la zone d’étude et tente de répondre à la question : quelle est la qualité de ces produits au Nord de l’Amazone et sur la Guyane française dans les dimensions spatiales et temporelles ? La seconde partie propose une nouvelle technique de correction de biais des SPP qui procède en trois étapes : i) utiliser les mesures in situ de précipitations pour décomposer la zone étudiée en aires hydro-climatiques ii) paramétrer une méthode de correction de biais appelée quantile mapping sur chacune de ces aires iii) appliquer la méthode de correction aux données satellitaires relatives à chaque aire hydro-climatique. On cherche alors à répondre à la question suivante : est-ce que le paramétrage de la méthode quantile mapping sur différentes aires hydro-climatiques permet de corriger les données satellitaires de précipitations sur la zone d’étude ? Après avoir montré l’intérêt de prendre en compte les différents régimes pluviométriques pour mettre en œuvre la méthode de correction QM sur des données SPP, la troisième partie analyse l’impact de la résolution temporelle des données de précipitations utilisées sur la qualité de la correction et sur l’étendue spatiale des données SPP potentiellement corrigeables (données SPP sur lesquelles la méthode de correction peut s’appliquer avec efficacité). Concrètement l’objectif de cette partie est d’évaluer la capacité de notre méthode à corriger sur une large échelle spatiale le biais des données TRMM-TMPA 3B42V7 en vue de rendre pertinente l’exploitation de ce produit pour différentes applications hydrologiques.Ce travail a permis de corriger les séries satellites journalières à haute résolution spatiale et temporelle sur le plateau des Guyanes selon une approche nouvelle qui utilise la définition de zones hydro-climatiques. Les résultats positifs en terme de réduction du biais et du RMSE obtenus grâce à cette nouvelle approche, rendent possible la généralisation de cette nouvelle méthode dans des zones peu équipées en pluviomètres
The Guiana Shield is a region that is characterized by 90% of a primary rainforest and about 20% of the world’s freshwater reserves. This natural territory, with its vast hydrographic network, shows annual rainfall intensities up to 4000 mm/year; making this plateau one of the most watered regions in the world. In addition, tropical rainfall is characterized by significant spatial and temporal variability. In addition to climate-related aspects, the impact of rainfall in this region of the world is significant in terms of energy supply (hydroelectric dams). It is therefore important to develop tools to estimate quantitatively and qualitatively and at high spatial and temporal resolution the precipitation in this area. However, this vast geographical area is characterized by a network of poorly developed and heterogeneous rain gauges, which results in a lack of knowledge of the precise spatio-temporal distribution of precipitation and their dynamics.The work carried out in this thesis aims to improve the knowledge of precipitation on the Guiana Shield by using Satellite Precipitation Product (SPP) data that offer better spatial and temporal resolution in this area than the in situ measurements, at the cost of poor quality in terms of precision.This thesis is divided into 3 parts. The first part compares the performance of four products of satellite estimates on the study area and attempts to answer the question : what is the quality of these products in the Northern Amazon and French Guiana in spatial and time dimensions ? The second part proposes a new SPP bias correction technique that proceeds in three steps: i) using rain gauges measurements to decompose the studied area into hydro climatic areas ii) parameterizing a bias correction method called quantile mapping on each of these areas iii) apply the correction method to the satellite data for each hydro-climatic area. We then try to answer the following question : does the parameterization of the quantile mapping method on different hydro-climatic areas make it possible to correct the precipitation satellite data on the study area ? After showing the interest of taking into account the different rainfall regimes to implement the QM correction method on SPP data, the third part analyzes the impact of the temporal resolution of the precipitation data used on the quality of the correction and the spatial extent of potentially correctable SPP data (SPP data on which the correction method can be applied effectively). In summary, the objective of this section is to evaluate the ability of our method to correct on a large spatial scale the bias of the TRMM-TMPA 3B42V7 data in order to make the exploitation of this product relevant for different hydrological applications.This work made it possible to correct the daily satellite series with high spatial and temporal resolution on the Guiana Shield using a new approach that uses the definition of hydro-climatic areas. The positive results in terms of reduction of the bias and the RMSE obtained, thanks to this new approach, makes possible the generalization of this new method in sparselygauged areas

The line-of-sight (LoS) pointing and stability requirements of Earth observation satellites are becoming increasingly stringent. The microvibrations that disturb the LoS are therefore no longer negligible, and many studies are focusing on the estimation of these microvibrations and on mitigation strategies, on platform and payload levels. Disturbances of the LoS can be seen by image processing algorithms that provide high-frequency information. In this paper, a novel method is proposed to fuse these optical data with inertial data using a Kalman filter to obtain the best LoS estimation. To demonstrate the performances of this fusion, a simulation tool is developed on Matlab/Simulink and three estimators, corresponding to three image processing techniques (fixed scene, scrolling scene and scene tracking) are tested. The stabilization of the LoS is performed by adding a fast-steering mirror in the optic path of the telescope. Results indicate that the fusion with optical data enables to include in the LoS estimation the instrument motion, which can differ from the platform motion at high frequencies. Using this estimation, stabilization results are approaching the challenging pointing requirements.
Siktlinjens (LoS) peknoggrannhet och stabilitetskrav för jordobservationssatelliter blir allt striktare. Mikrovibrationerna som stör LoS är därför inte längre försumbara, och många studier fokuserar på uppskattningen av dessa mikrovibrationer samt på strategier för att minska dessa, både plattforms- och nyttolastnivåerna. Störningar i LoS kan ses av bildbehandlingsalgoritmer som ger högfrekvent information. I detta arbete föreslås en ny metod för att slå samman optiska data med tröghetsdata med hjälp av ett Kalman-filter för att uppnå bästa LoS-uppskattning. För att visa prestandan för denna datasammanslagning utvecklades ett simuleringsverktyg i Matlab/Simulink och tre uppskattningsalgoritmer, motsvarande tre bildbehandlingstekniker (fast scen, rullningsbild och scenspårning), testades. Stabiliseringen av LoS utförs genom att lägga till en snabbspegel i teleskopets optiska väg. Resultaten visar att sammanslagningen med optisk data gör det möjligt att inkludera instrumentets rörelse i LoS-uppskattningen, som kan skilja sig från plattformens rörelse vid höga frekvenser. Med hjälp av denna uppskattning närmar sig stabiliseringsresultaten de utmanande pekkraven.

The aim of this thesis is to evaluate the capability of radio detection and ranging (radar) data collected by the Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture radar (PALSAR), supported by field measurements obtained through ground survey, to predict and map Above Ground Woody Biomass (AGWB) in the tropical savannas of the developing country of Belize, and to understand how the forest structure may influence the backscatter observed. Firstly, an extensive inventory of the woody vegetation of the tropical savannas of Belize was created by measuring the diameter at breast height (dbh), the total height (ht) and the location of 6547 trees in plots covering a total woodland area of 30.8 hectares, located within four protected areas (the Rio Bravo Conservation and Management Area (11×1ha), Deep River (108×0.1ha) and Manatee Forest Reserve (1ha) and the Bladen Nature Reserve (1ha) and also from plots located in unprotected areas (7×1ha). These measurements of forest structure, when combined with information about forest management practices obtained from local organisations revealed that different forms of protection and management may lead to the development of pine woodlands with different structural characteristics in these savannas. Secondly, a case-study was conducted to establish the sensitivity of the ALOS PALSAR backscatter data to AGWB and determine the effect of sample plot size to their relationship. The findings of this case-study show that the L-band backscatter in these low density pine woodlands is a possible predictor of AGWB and confirm that the appropriate sample plot size for predicting AGWB is one hectare; while the sensitivity degrades significantly with decreasing sample plot size. Taken together, the findings described above were combined to assess the capability of ALOS PALSAR backscatter to predict AGWB in these woodlands. A semi-empirical Water Cloud Model (WCM) describing the interaction between the backscatter and vegetation was re-arranged to enable the prediction of AGWB. Non-linear regression analysis revealed that the ALOS PALSAR backscatter predicted AGWB with an R2=0.92; an external validation conducted with additional ground reference data estimated this AGWB prediction to have an RMSE ~13 t/ha. The form of the regression model linking backscatter to AGWB appears to be particularly influenced by sample plots with higher tree numbers and by plots in which the trees were more homogeneous. The presence of many similar sized individuals within some plots is postulated as one explanation for the elevated saturation level for predictions in this study (> 100 t/ha) compared to other models. The model developed here predicts complete saturation in the backscatter - AGWB relationship to occur primarily as a result of increases in the tree number density and often concurrently in basal area, two parameters which are usually strongly correlated with AGWB in these woodlands. Thirdly, the locally validated relationship between ALOS PALSAR backscatter and AGWB is used to map AGWB for the lowland pine savannas of Belize at a spatial resolution of 100m. The mapping estimates that over 90% of these pine woodlands have an AGWB below 60 t/ha, with the average woody biomass estimated at 23.5 t/ha. When these new predictions are mapped and aggregated over the extents of two protected areas (Rio Bravo and Deep River), the totals obtained agree closely (error ≤20%) with previous estimates of AGWB obtained from ground data and previous research. The combined evidence suggests that woodland protection may produce a small, positive effect upon AGWB, with the mean of the AGWB/ha predictions higher in areas that are protected and managed for biodiversity (29.55 ± 0.84 t/ha) than in other areas that are not protected (23.29 ± 0.19 t/ha). When the fine scale local AGWB mapping produced using ALOS PALSAR is compared cell-by-cell with global biomass products at coarser spatial resolutions (500m and 1000m), the AGWB differences observed range from 115-120%. When the coarser AGWB estimates are aggregated over the extents of Deep River and Rio Bravo, the AGWB totals obtained differ significantly (~280 – 300%) from AGWB estimates from ground data and previous research. Overall, these findings suggest that where sufficient ground data exists to build a reliable local relationship to radar backscatter, more detailed biomass mapping can be produced from ALOS and similar satellite sensor data at resolutions of ~100m. This more accurate and spatially detailed information about the distribution of woody biomass within tropical lowland savannas is more appropriate for monitoring local changes in forest cover and for supporting management decisions for forested areas of around ~10,000ha than estimates based upon previously available, but coarser scale, global biomass products.

Etablir le meilleur plan pour l'usinage d'un produit, le meilleur ordonnancement des activités de construction d'un bâtiment ou la meilleure tournée de véhicules pour la livraison des commandes, en prenant en compte diverses contraintes économiques, temporelles, humaines, ou même météorologiques : dans cette diversité d'applications, optimiser la planification est une tâche complexe par le grand nombre d'entités hétérogènes en interaction, la forte dynamique, les objectifs contradictoires à atteindre, etc. La planification de missions pour des constellations de satellites en est un exemple majeur : beaucoup de paramètres et de contraintes, souvent antagonistes, doivent être pris en compte, entraînant une importante combinatoire. Actuellement, en Europe, les plans de missions sont élaborés au sol, juste avant que le satellite ne soit visible par la station d'émission. Les requêtes arrivant durant la planification ne peuvent être traitées, et sont mises en attente. De plus, la complexité de ce problème croit drastiquement : le nombre de constellations et les satellites les composant augmentent, ainsi que le nombre de requêtes journalières. Les approches actuelles montrent leurs limites. Pour pallier à ces inconvénients, de nouveaux systèmes basés sur la décentralisation et la distribution inhérentes à ce genre de problèmes, sont nécessaires. La théorie des systèmes multi-agents adaptatifs (AMAS) et notamment le modèle AMAS4Opt (AMAS for Optimisation) ont montré leur adéquation pour la résolution de problèmes d'optimisation complexes sous contraintes. Le comportement local et coopératif des agents AMAS permet au système de s'auto-adapter à la forte dynamique et de fournir des solutions adéquates rapidement. Dans cette thèse, nous adressons la résolution de la planification des missions de satellites par AMAS. Pour cela, nous avons complété et enrichi les modèles d'agents proposés par AMAS4Opt. Nous avons ainsi développé le système de planification dynamique de missions ATLAS. Pour valider ATLAS sur divers critères, nous avons utilisé un grand nombre de données hétérogènes. Enfin, ce travail a été comparé à un système " opérationnel' " standard sur des scénarios réels, mettant en valeur les apports de notre système
Building the best plan in product treatment, the best schedule to a building construction or the best route for a salesman in order to visit a maximum of cities in the time allowed while taking into account different constraints (economic, temporal, humans or meteorological ): in all of those variety of applications, optimizing the planning is a complex task including a huge number of heterogeneous entities in interaction, the strong dynamics, multiple contradictory objectives, etc. Mission planning for constellations of satellites is a major example: a lot of parameters and constraints, often antagonists must be integrated, leading to an important combinatorial search space. Currently, in Europe, plans are built on ground, just before the satellite is visible by the ground stations. Any request coming during the planning process must wait for the next period. Moreover, the complexity of this problem grows drastically: the number of constellations and satellites increases, as the number of daily requests. Current approaches have shown their limits. To overcome those drawbacks, new systems based on decentralization and distribution inherent to this problem, are needed. The adaptive multi-agent systems (AMAS) theory and especially the AMAS4Opt (AMAS For Optimization) model have shown their adequacy in complex optimization problems solving. The local and cooperative behavior of agents allows the system to self-adapt to highly dynamic environments and to quickly deliver adequate solutions. In this thesis, we focus on solving mission planning for satellite constellations using AMAS. Thus, we propose several enhancement for the agent models proposed by AMAS4Opt. Then, we design the ATLAS dynamic mission planning system. To validate ATLAS on several criteria, we rely on huge sets of heterogeneous data. Finally, this work is compared to an operational and standard system on real scenarios, highlighting the value of our system

La qualité de l’air est un enjeu environnemental majeur de notre société. Cette thèse se focalise sur l’observation depuis l’espace du polluant gazeux majeur, l’ozone troposphérique. Les instruments satellitaires de nouvelle génération permettent de le mesurer journalièrement aux échelles régionales à globale. Cependant, les mesures d’un seul domaine spectral n’amène pas d’information suffisante pour quantifier les concentrations de l’ozone dans la couche limite atmosphérique, où se situe l’air que nous respirons. Le couplage des mesures de multiples domaines spectraux offre un fort potentiel pour mieux caractériser la pollution à l’ozone. La première approche multispectrale à 2 bandes combinant les mesures de l’infrarouge (IR) de IASI et l’ultraviolet (UV) de GOME-2 a été développée au laboratoire LISA, que j’ai intégré dans le cadre de ma thèse. L’objectif de mon travail de thèse est de franchir un pas supplémentaire dans la quantification de la pollution à l’ozone en incluant la bande visible (VIS) de Chappuis, afin de développer un couplage multispectral inédit à trois bandes spectrales UV+VIS+IR. Premièrement, j’ai mis au point une approche pour extraire l’information sur l’ozone des spectres VIS de GOME-2, en sélectionnant les longueurs d’onde affectées majoritairement par l’absorption à l’ozone et rejetant celles avec des absorptions d’autres gaz, ainsi que déterminant les variables d’ajustement conjoint de l’approche (profil vertical d’ozone, albédo de surface, shifts spectraux, etc) et les bases de données nécessaires pour simuler les spectres VIS (albédo de surface, spectroscopie).Ensuite, j’ai mis en œuvre la méthode multispectrale à trois bandes UV+VIS+IR, premièrement sur des observations simulées défilantes de IASI et GOME-2 et géostationnaires de MAGEAQ afin d’estimer l’amélioration en terme de sensibilité et précision, par rapport aux méthodes existantes. Dernièrement, j’ai appliqué l’approche multispectrale à 3 bandes à des observations satellitaires réelles de IASI et GOME-2. Des comparaisons avec d’autres données montrent des meilleures performances des nouvelles observations UV+VIS+IR pour caractériser des évènements de pollution à l’ozone, par rapport à l’approche à 2 bandes
Air quality is a major environmental issue for our society. This PhD thesis focuses on space borne observation of the major gaseous pollutant. Tropospheric ozone. New generation satellite instruments allow measuring it daily at regional to global scales. However, single spectral domain measurements do not provide enough information for quantifying ozone concentrations at the atmospheric boundary layer, where the air we breathe is located. Synergism of measurements from multiple spectral domains offers a great potential for better characterizing ozone pollution. The first 2-band multispectral approach combining infrared (IR) measurements of IASI and the ultraviolet (UV) of GOME-2 was developed at LISA laboratory, where I conducted my thesis. The goal of my thesis is to go a step further in the quantification of ozone pollution by including the visible (VIS) Chappuis band, in order to develop an unprecedented 3-band multispectral synergism UV+VIS+IR. First, I developed a approach for extracting ozone information from GOME-2 VIS spectra, by selecting the wavelengths mostly affected by ozone absorption and rejecting those with absorptions from other gases, as well as determining the joint adjustment variables of the approach (vertical ozone profile, surface albedo, spectral shifts, etc) and the databases needed to simulate the spectra VIS (surface albedo, spectroscopy).Then, I implemented the multispectral method with three bands UV+VIS+IR, first on simulated low-orbit and geostationary observations from respectively IASI and GOME-2 and MAGEAQ to estimate the improvement in terms of sensitivity and precision, as compared to existing methods. Last, I applied the 3-band multispectral approach to real satellite observations of IASI and GOME-2. Comparisons with other data shows enhanced performances of the new UV+VIS+IR observations to characterize ozone pollution events, with respect to the 2-band approach

Among natural disasters floods are the most common and widespread hazards worldwide (CRED and UNISDR, 2018). Thus, making communities more resilient to flood is a priority, particularly in large flood-prone areas located in emerging countries, because the effects of extreme events severely setback the development process (Wright, 2013). In this context, operational flood preparedness requires novel modeling approaches for a fast delineation of flooding in riverine environments. Starting from a review of advances in the flood modeling domain and a selection of the more suitable open toolsets available in the literature, a new method for the Rapid Estimation of FLood EXtent (REFLEX) at multiple scales (Arcorace et al., 2019) is proposed. The simplified hydraulic modeling adopted in this method consists of a hydro-geomorphological approach based on the Height Above the Nearest Drainage (HAND) model (Nobre et al., 2015). The hydraulic component of this method employs a simplified version of fluid mechanic equations for natural river channels. The input runoff volume is distributed from channel to hillslope cells of the DEM by using an iterative flood volume optimization based on Manning’s equation. The model also includes a GIS-based method to expand HAND contours across neighbor watersheds in flat areas, particularly useful in flood modeling expansion over coastal zones. REFLEX’s flood modeling has been applied in multiple case studies in both surveyed and ungauged river basins. The development and the implementation of the whole modeling chain have enabled a rapid estimation of flood extent over multiple basins at different scales. When possible, flood modeling results are compared with reference flood hazard maps or with detailed flood simulations. Despite the limitations of the method due to the employed simplified hydraulic modeling approach, obtained results are promising in terms of flood extent and water depth. Given the geomorphological nature of the method, it does not require initial and boundary conditions as it is in traditional 1D/2D hydraulic modeling. Therefore, its usage fits better in data-poor environments or large-scale flood modeling. An extensive employment of this slim method has been adopted by CIMA Research Foundation researchers for flood hazard mapping purposes over multiple African countries. As collateral research, multiple types of Earth observation (EO) data have been employed in the REFLEX modeling chain. Remotely sensed data from the satellites, in fact, are not only a source to obtain input digital terrain models but also to map flooded areas. Thus, in this work, different EO data exploitation methods are used for estimating water extent and surface height. Preliminary results by using Copernicus’s Sentinel-1 SAR and Sentinel-3 radar altimetry data highlighted their potential mainly for model calibration and validation. In conclusion, REFLEX combines the advantages of geomorphological models with the ones of traditional hydraulic modeling to ensure a simplified steady flow computation of flooding in open channels. This work highlights the pros and cons of the method and indicates the way forward for future research in the hydro-geomorphological domain.

Afin d'etablir des cartes des champs thermiques de surface de la mer aussi precises que possible, des observations in situ sont melees a des images obtenues par teledetection. Les structures de la temperature de surface de la mer sont etudiees saisonnierement et modelisees par des variogrammes. Si les donnees in situ provenant des nombreux navires collaborant au reseau meteorologique mondial sont entachees d'erreurs importantes, elles sont cependant a la base des atlas climatiques et utilisees de ce fait en tant que reference. Plus precises dans le temps et l'espace les observations des satellites tiros (defilant de la national oceanographic and atmospheric administration) et meteosat (geostationnaire de l'agence spatiale europeenne) sont cependant soumises a des effets de surface et a l'absorption atmospherique. L'effet des erreurs est discute et une methode, basee sur les techniques de krigeage, est proposee pour cartographier au mieux les isothermes en incorporant l'ensemble des informations

Inadequate economic data makes it more difficult for its incorporation in security-policy related prediction and there is a need for alternative datasets. Satellite data, more specifically nighttime lights data, can be used as a proxy for the economy. In this project, the correlation between nighttime lights and the economy between 1992 and 2018 is explored for five countries in Africa: Nigeria, Libya, the Central African Republic, the Republic of the Congo and Ghana. Data from two different satellite series, DMSP-OLS and VIIRS-DNB are used, and the extracted datasets are calibrated for the differences or intercalibrated. There was found to be a high correlation for two of the countries, the Republic of the Congo and Ghana. The biggest improvement can be made by developing the intercalibration method. A pitfall of the method is that it is not generally applicable as unique circumstances seen for Nigeria show in the correlation results.

During years a number of satellites have been developed to remotely sense Earth geophysical parameters for weather forecasting and other climate studies. In recent years the use of reflected Global Navigation Satellite System Signals (GNSS-R) has shown its potential to retrieve geophysical parameters over the ocean, mainly altimetry and sea state, and over land, mainly soil moisture. It is known that sea roughness has an impact on L-band radiometric measurements, and therefore on the retrieved sea surface salinity (SSS). GNSS-R is an interesting tool to help improving the sea state effect correction to reduce the final SSS retrieval error. To demonstrate this idea the Passive Advanced Unit (PAU) project was proposed to the European Scienc Foundation (ESF) under the EURYI 2004 call. The main objective was the study of the direct relationship between the radiometric brightness temperatures and some GNSS-R observables to perform the state correction without using emission/scattering models. Once this goal was successfully addressed, the PAU objectives were broaden including the development of new GNSS-R instruments and techniques, and the study of retrieving geophysical parameters from different surfaces. The present Ph.D. dissertation describes one of the research lines of the the PAU project, undertaken between February 2007 and December 2011, within the Passive Remote Sensing Group of the Remote Sensing Lab, at the Department of Signal Theory and Communications of the Universitat Politènica de Catalunya. The present Ph.D. dissertation focuses on GNSS-R techniques applied to the observation of different types of scattering surfaces (land surfaces: bare soils, vegetation-covered soils, snow-covered soils; inland-water surfaces and ocean surfaces) and the retrieval of different geophysical parameters. Two main GNSS-R techniques have been studied and applied to real data obtained during seven field experiments, the Delay-Doppler Map (DDM) processing technique and the Interference-Pattern Technique (IPT), selecting the one most appropriate to the observed surface. Furthermore, in the context of this Ph.D dissertation a new type of GNSS-R instrument has been developed, being the main tool for the application of the IPT and the retrieval of several geophysical parameters over land and inland-water surfaces. After an introduction on GNSS-R and the PAU-project, the methodology, the instruments and the techniques used to retrieve soil moisture, vegetation height and topography in agricultural areas, snow thickness, water level in reservoirs, and wind speed in ocean surfaces, are described. These retrievals show the potential that these opportunity signals have for monitoring a broad kind of effects. After that, some studies related to space-borne GNSS-R techniques are summarized. Finally a summary of the work performed in this Ph. D. dissertation, the main conclusions and the future work lines are presented. The presented results contribute to promote the use of the GNSS opportunity signals for monitoring geophysical parameters to increase the understanding of the Earth¿s water cycle, and position these techniques as suitable tools that enhance water resources management.

Cette thèse s'intéresse au développement de nouvelles méthodes d’observation spatiale des aérosols sulfatés volcaniques, dans l’infrarouge thermique. Les premiers travaux ont débouché sur l’importance de considérer les interférences radiatives entre les aérosols sulfatés et le SO₂ afin d’optimiser les observations satellitaires des deux espèces dans cette région spectrale. Pour une éruption volcanique simulée, le signal des aérosols sulfatés domine dans le spectre infrarouge à partir de 3 à 5 jours de l’éruption volcanique, entrainant des surestimations sur les observations du SO₂. Observées conjointement avec des capteurs infrarouges à haute résolution spectrale, comme MetOp-IASI, les deux espèces peuvent être restituées indépendamment. À la lumière de ces observations, un algorithme d'inversion appelé AEROIASI-Sulphates a été développé afin de restituer des profils verticaux d’extinctions et de concentration massiques des aérosols sulfatés à partir des mesures IASI. AEROIASI-Sulphates identifie correctement la morphologie du panache volcanique horizontalement ainsi que verticalement après un jour de l’éruption du volcan Etna (Mars 2012) et ceci est confirmé à travers la comparaison avec les observations et les simulations du panache de SO₂. Pour une quantité de soufre initiale de 1.5 kT, 60 % de la masse de soufre injectée est convertie en particules après 24h de l'éruption. Un forçage radiatif direct en ondes courtes, calculé à l'échelle régionale pour la zone Méditerranéenne occidentale, a été estimé à -0.8 W/m². Il s’agit de la première quantification des aérosols sulfatés à partir d’un instrument spatial en géométrie nadir, ce qui présente une grande importance pour mieux comprendre les processus de dégazage volcanique et pour évaluer l’impact climatique des éruptions volcaniques à l’échelle régionale
The main objective of this thesis is to develop new satellite observations of volcanic sulphate aerosols, in the Thermal InfraRed (TIR). We found, as first results, that it is important to consider the radiative interference between sulphate aerosols and SO₂ in order to optimize satellite retrievals of the two species. For a simulated volcanic eruption, the mutual effect of SO₂ and sulphate aerosols on the TIR outgoing radiation is evident after three to five days from the eruption. Significant overestimations may be introduced in SO₂ retrievals if the presence of sulphate aerosols is not taken into account. The high spectral resolution of IASI instrument allows the observation of these two effluents as independent quantities with limited uncertainties. Based on these results, we developed a new retrieval algorithm using IASI observations, called AEROIASI-Sulphates, to measure vertically-resolved sulphates aerosols extinctions and mass concentration profiles. The algorithm is applied to a moderate eruption of Mount Etna volcano. AEROIASI-Sulphates correctly identifies the volcanic sulphate aerosols plume morphology both horizontally and vertically after comparisons with SO₂ plume observations and simulations. For an initial sulphur mass of 1.5 kT, 60 % of the injected sulphur mass is converted to particulate matter after 24 h from the beginning of the eruption. A shortwave and direct radiative forcing of -0.8 W/m² is exerted at the regional scale in the western Mediterranean area. This is the first time that sulphate aerosols are quantitatively observed from space-based instruments in the nadir geometry, which is of great importance to monitor and quantify volcanic emissions, their evolution and impacts at the regional scale

Surface wind speeds are an important and revealing component of the structure of tropical cyclones (TCs). To understand the asymmetric structure of surface winds in TCs associated with differences in formation region, environmental wind shear, storm forward motion, and TC strength and intensification, a twelve year database of satellite scatterometer data are utilized to produce composite total wind speed and Fourier-derived, low wavenumber analyses. A quantified asymmetry is determined as a function of TC intensity and reveals the tropical storms are influenced by wind shear at all TC-centric radii but only for areas away from the radius of maximum wind in hurricanes. Additionally, an increase of absolute angular momentum flux has a preference for the downshear-right quadrant, and the low wavenumber maximum develops downwind of this momentum transport. Further evaluation of the asymmetric structure with respect to wind shear’s relation to motion and impacts during TC intensity change are also considered. A composite rapid intensification event is produced and compared to overlapping satellite rain estimates. Results indicate that the TC becomes more symmetric during intensification and the phase of the maximum asymmetry rotates from a downshear-left direction to upshear-left direction after the intensification slows. The rain or convective maximum is generally located upwind of the surface wind maximum at the early stages of intensification and is coincident with the region of large angular momentum transport, which supports the idea that the surface wind asymmetry is likely a consequence of convective or other processes. Using data from a regional TC model, it is also determined that the scatterometer data are useful for model verification of tropical storms and non-major hurricanes and performs similar to or better than the standard tool at forecast lead times up to 60 hours. Preliminary comparisons of model-derived surface wind asymmetry relative to rain generally confirm the observational results.

Land use and land cover maps can support our understanding of coupled human- environment systems and provide important information for environmental modelling and water resource management. Satellite data are a valuable source for land use and land cover mapping. However, cloud-free or weather independent data are necessary to map cloud-prone regions. Merging radar with optical images would increase the accuracy of the study. Agricultural land cover is characterized by strong variations within relatively short time intervals. These dynamics are challenging for land cover classifications on the one hand, but deliver crucial information that can be used to improve the machine learning classifier’s performance on the other hand. A parcel-based map of the main crop classes of the Netherlands was produced implementing a script on GEE and using Copernicus data. The machine-learning model used is a Random Forest Classifier. This was done by combining time series of radar and multispectral images from Sentinel 1 and Sentinel 2 satellites, respectively. The results show the potential of providing useful information delivered by entirely open source data and uses a cloud computing-based approach. The algorithm combines the two satellites data of one year in a multibands image to feed in the classifier. Standard deviation and several vegetation indexes were added in order to have more variables for each 15-day-median image composite. The process paid particular attention to time variability of mean values of each field. This will provide useful information both for understanding differences among crops and variability over the phenology of the plant. The accuracy assessment demonstrates that several crop types (i.e. corn, tulip) can be better classified with both radar and optical images while others (i.e. sugar beet, barley) have an increased accuracy with only radar. The overall accuracy of RFC with optical and radar is 76% while it is 74% if only radar is used.

Synthetic aperture radar imaging is an effective tool for imaging the sea surface because of its response to changes in sea surface roughness. This allows for the remote sensing of features on the sea surface, which modulate se surface roughness. In this work, 18 synthetic aperture radar images were collected from the TerraSAR-X and RADARSAT-2 satellites in the Port Everglades, Florida area. In-situ measurements were collected in conjunction with the satellite images in order to provide more information on the features visible in the imagery, and aid in identification of the origin of the features. Information on ships in the area of the satellite image footprints was collected using an automatic information system. Weather conditions were recorded by a meteorological station and a National Oceanic and Atmospheric Administration weather radar station. Waves and currents in the observational area were recorded with acoustic Doppler current profilers and wave gauges. Sonar systems and conductivity, depth, and salinity profilers were used to identify stratification in the water column. Surfactant release experiments were also conducted to explore the affects of surface active materials. Results of the experiment show the manifestation of atmospheric effects, oceanic fronts and eddies, wind shadowing, natural and artificial slicks, and ships and ship wakes on the synthetic aperture radar imagery. Atmospheric conditions were found to play a significant role in the visibility of features on the sea surface, and sometimes masked the appearance of features on the ocean surface. Overall the most reliable feature capable of being imaged on the sea surface by the synthetic aperture radar satellites was the signatures of ships and their wakes.

Satellite Image Time Series (SITS) are becoming available at high spatial, spectral and temporal resolutions across the globe by the latest remote sensing sensors. These series of images can be highly valuable when exploited by classification systems to produce frequently updated and accurate land cover maps. The richness of spectral, spatial and temporal features in SITS is a promising source of data for developing better classification algorithms. However, machine learning methods such as Random Forests (RFs), despite their fruitful application to SITS to produce land cover maps, are structurally unable to properly handle intertwined spatial, spectral and temporal dynamics without breaking the structure of the data. Therefore, the present work proposes a comparative study of various deep learning algorithms from the Convolutional Neural Network (CNN) family and evaluate their performance on SITS classification. They are compared to the processing chain coined iota2, developed by the CESBIO and based on a RF model. Experiments are carried out in an operational context using with sparse annotations from 290 labeled polygons. Less than 80 000 pixel time series belonging to 8 land cover classes from a year of Sentinel- 2 monthly syntheses are used. Results show on a test set of 131 polygons that CNNs using 3D convolutions in space and time are more accurate than 1D temporal, stacked 2D and RF approaches. Best-performing models are CNNs using spatio-temporal features, namely 3D-CNN, 2D-CNN and SpatioTempCNN, a two-stream model using both 1D and 3D convolutions.
Tidsserier av satellitbilder (SITS) blir tillgängliga med hög rumslig, spektral och tidsmässig upplösning över hela världen med hjälp av de senaste fjärranalyssensorerna. Dessa bildserier kan vara mycket värdefulla när de utnyttjas av klassificeringssystem för att ta fram ofta uppdaterade och exakta kartor över marktäcken. Den stora mängden spektrala, rumsliga och tidsmässiga egenskaper i SITS är en lovande datakälla för utveckling av bättre algoritmer. Metoder för maskininlärning som Random Forests (RF), trots att de har tillämpats på SITS för att ta fram kartor över landtäckning, är strukturellt sett oförmögna att hantera den sammanflätade rumsliga, spektrala och temporala dynamiken utan att bryta sönder datastrukturen. I detta arbete föreslås därför en jämförande studie av olika algoritmer från Konvolutionellt Neuralt Nätverk (CNN) -familjen och en utvärdering av deras prestanda för SITS-klassificering. De jämförs med behandlingskedjan iota2, som utvecklats av CESBIO och bygger på en RF-modell. Försöken utförs i ett operativt sammanhang med glesa annotationer från 290 märkta polygoner. Mindre än 80 000 pixeltidsserier som tillhör 8 marktäckeklasser från ett års månatliga Sentinel-2-synteser används. Resultaten visar att CNNs som använder 3D-falsningar i tid och rum är mer exakta än 1D temporala, staplade 2D- och RF-metoder. Bäst presterande modeller är CNNs som använder spatiotemporala egenskaper, nämligen 3D-CNN, 2D-CNN och SpatioTempCNN, en modell med två flöden som använder både 1D- och 3D-falsningar.

The work presented in this Thesis has been carried out for the MAGIC experiment during three years of PhD student-ship at the University of Padova, Department of Physics G. Galilei, in association with the Padova section of National Institute of Nuclear Physics (Istituto Nazionale di Fisica Nucleare, INFN), under the supervision of Professor M. Mariotti, PhD Michele Doro and PhD Villi Scalzotto. The two MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, located in the Canary Island of La Palma (Spain), are a stereoscopic system based on the IAC (Imaging Atmospheric Cherenkov) technique and detect Cherenkov light emitted by atmospheric showers of charged particles that originate in the Earth’s atmosphere. These showers are predominantly generated by charged primary cosmic rays, such as protons and light isotopes, which impinge the Earth’s atmosphere isotropically, and by a percentage of gamma–rays, whose direction points back to the region of the cosmic emission. Thanks to sophisticated data reduction algorithms it is possible to efficiently extract the gamma–ray signal of the observed sources from the hadronic background in the energy range between ∼50 GeV and ∼20 TeV, allowing studies in different scientific fields such as galactic and extragalactic high energy Astrophysics, Cosmology and Particle Physics. The scientific activities of the MAGIC experiment are carried out in synergy and complementarity with satellite experiments, like AGILE and FERMI, and ground-based experiments, like H.E.S.S., VERITAS, and Milagro. The MAGIC telescopes, operated by a collaboration of about 150 physicists in more than 20 institutes, spread in several European countries, belong to the second generation of Cherenkov telescopes and have innovative features compared to previous IAC experiments related for example to the size of the reflecting surface area (about 250 square meters), to the lower energy threshold (below 100 GeV) and to the tracking velocity in case of observations of transient phenomena such as the Gamma Ray Bursts. In particular, the start of the operations of the second telescope MAGIC-II and the possibility to perform stereoscopic observations allow a lower energy threshold and a better sensitivity (by a factor ∼2) compared to the single MAGIC-I telescope observations. Currently, the MAGIC telescopes represent the more sensitive world-wide ground-based detector for gamma-rays in the energy range between ∼50 GeV and ∼150 GeV. During the PhD student-ship, my research activity focused on two principal occupations. The first one, orientated on technical issues, concerned the upgrade of a specific part of the software of the MAGIC experiment required for the stereoscopic data taking (which started since fall 2009), i.e. the calculation of the Effective Collection Area. The second one, more focused on scientific topics, was addressed to the possible indirect detection of dark matter with the MAGIC-I telescope. In particular, I contributed to the analysis data and to the related publications of the observations of interesting sources for possible detection of gamma–ray signal from self-annihilation processes of dark matter, like the dwarf spheroidal galaxies (satellite of the Milky Way) Draco and Willman 1 and the galaxy cluster Perseus. During the three years of PhD student-ship, I spent, on a whole, 4 months in the site of the MAGIC telescopes, as data taking operator and shift leader. I also contributed in June 2009 to the commissioning of the second telescope MAGIC-II for a period of 4 weeks. This Thesis is divided into eight chapters. Chapter 1 will be dedicated to a brief introduction on the physics of cosmic–rays and of astrophysical gamma-rays, on the current experimental methods for their detection, on the main mechanisms active in the Universe for the production of very high energy gamma-rays and on the main astronomical objects known as gamma-ray emitters. In chapter 2, a description of the main physical characteristics of the hadronic and electromagnetic atmospheric showers, the subsequent Cherenkov light emission and the Imaging Atmospheric Cherenkov technique will be given. In chapter 3, the main hardware components of the MAGIC telescopes will be illustrated, together with the main innovations introduced for the second telescope. In chapter 4, the standard analysis chain of the MAGIC-I telescope finalized to the extraction of the physical quantities of main interest, such as the significance and the gamma-ray flux of a given source, will be described. Subsequently, the new tools required for the stereo analysis of the MAGIC telescopes data will be introduced. The current performance of the stereoscopic system (whose commissioning phase was successfully accomplished during 2009) will be also shown. Chapter 5 will be dedicated to the alt-azimuth dependence of one of the main quantities which characterize the detection of Cherenkov light by the MAGIC telescopes, i.e. the Effective Collection Area. Indeed, while the Zenith effect on this quantity is well known and related to the increased atmospheric depth the atmospheric showers must pass through for increasing Zenith angles of observation, a possible Azimuth dependence is associated to the geomagnetic effects induced to the development of the showers and to the particular geometric configuration of the two telescopes system. The fixed direction between them, in fact, breaks the circular symmetry typical for the observations performed with a single telescope. In view of the start of the operations of the second MAGIC telescope and of the stereoscopic observations, the introduction of the Azimuth dependence of the Effective Collection Area has been therefore systematically taken into account and successfully implemented in the analysis software of the experiment. The results of tests performed on both Monte Carlo simulated data and real data will be shown. In chapter 6, a brief introduction on the dark matter topic will be reported: the main experimental evidences and some of the models and candidates proposed in literature to describe the dark matter nature will be discussed. In particular, the attention will be focused on the indirect dark matter search which is based on the possibility for MAGIC to detect gamma–rays as a result of annihilation or decay of dark matter particles. Gamma–ray signals are searched for in places where dark matter is concentrated, like, for example, the dwarf spheroidal galaxies satellite of the Milky Way. Chapter 7 will be dedicated to the data analysis of the observation carried out by the MAGIC-I telescope of Segue 1, a source considered to be a dwarf spheroidal galaxy satellite of the Milky Way, whose stellar kinematics seems to indicate a high mass–to–light ratio, making this celestial object extremely interesting from the point of view of indirect dark matter searches. The data of this source required particular cares due to the fact that a 3.5 apparent magnitude star was present in the field of view of the source during the whole survey. The adopted techniques used to face the problems related to the light of that star will be illustrated. This analysis allowed to determine, for energies above 100 GeV, upper limits on the flux emission derived form different assumed power law spectra. A paper on Segue 1 observation carried out by the MAGIC-I telescope, based on the results achieved by this analysis, is in preparation. Finally, in chapter 8, the general conclusions of the work presented in this Thesis will be given.
Il lavoro presentato in questa Tesi è stato svolto nell’ambito dell’esperimento MAGIC durante i tre anni di Scuola di Dottorato all’Università degli Studi di Padova, Dipartimento di Fisica G. Galilei, in associazione con l’Instituto Nazionale di Fisica Nucleare, sezione di Padova, sotto la supervisione del Professor M. Mariotti, del Dott. Michele Doro e del Dott. Villi Scalzotto. Il sistema stereoscopico di due telescopi MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov), situato nell’isola canaria di La Palma (Spagna), è basato sulla tecnica IAC (Imaging Atmospheric Cherenkov) per la rivelazione della luce Cherenkov emessa da cascate di particelle cariche che si originano nell’atmosfera terrestre. Tali cascate atmosferiche sono generate preminentemente dai raggi cosmici carichi, quali protoni e isotopi leggeri, che entrano isotropicamente nell’atmosfera terrestre, e da una percentuale di raggi gamma, la cui direzione di provenienza punta direttamente alla regione cosmica di emissione. Grazie a sofisticati algoritmi di riduzione dei dati è possibile estrarre efficacemente il segnale di natura gamma dal quello di natura adronica per energie comprese tra ∼50 GeV e ∼20 TeV, permettendo studi in diversi settori scientifici quali l’Astrofisica galattica ed extragalattica delle alte energie, la Cosmologia e la Fisica delle Particelle Elementari. Le attività scientifiche dell’esperimento MAGIC vengono portate avanti in sinergia e complementarità con gli esperimenti gamma posti su satellite, quali AGILE e FERMI, e quelli posti a terra, quali H.E.S.S., VERITAS eMilagro. I telescopi MAGIC, realizzati da una collaborazione internazionale di circa 150 fisici appartenenti ad una ventina di istituzioni di diversi paesi della comunità europea, rientrano nella seconda generazione di telescopi Cherenkov e presentano rispetto ai precedenti delle caratteristiche innovative legate per esempio alla grandezza della superficie riflettente (circa 250 metri quadri), all’abbassamento della soglia energetica al di sotto dei 100 GeV e alla velocità di puntamento nel caso dell’osservazione di fenomeni improvvisi, come ad esempio l’esplosione di raggi gamma (Gamma Ray Bursts). In particolare, la messa in opera del secondo telescopio MAGIC-II e la possibilità di condurre osservazioni stereoscopiche permettono un abbassamento della soglia energetica ed una sensibilità di circa un fattore 2 superiore a quella ottenuta con il singolo telescopio MAGIC-I. Attualmente, i telescopi MAGIC rappresentano il rivelatore posto a terra più sensibile al mondo per raggi gamma di energie comprese tra ∼50 GeV e ∼150 GeV. Durante il lavoro di dottorato ho svolto la mia ricerca in due principali attività. La prima, di tipo tecnico, ha riguardato l’aggiornamento di una specifica parte del software dell’esperimento MAGIC necessario in vista della presa dati stereoscopica dei telescopi MAGIC (iniziata alla fine del 2009), ovvero il calcolo dell’area efficace collettrice. La seconda, di tipo più prettamente scientifico, è stata rivolta alla possibile rivelazione indiretta di materia oscura con il telescopio MAGIC-I. In particolare, ho contribuito all’analisi dati e alle relative pubblicazioni delle sorgenti osservate dal telescopio MAGIC-I candidate per la ricerca di possibili segnali gamma dovuti ad auto annichilazione di materia oscura, quali le galassie nane satelliti della Via Lattea Draco e Willman 1 e il cluster galattico Perseus. Durante i tre anni di dottorato ho passato complessivamente 4 mesi a La Palma, nel sito dei telescopi MAGIC, come operatore di presa dati. Inoltre nel mese di Giugno del 2009 ho partecipato per 4 settimane alla fase di commissioning del secondo telescopio MAGIC-II. Questo lavoro di Tesi è suddiviso in otto capitoli. Nel capitolo 1 verranno brevemente introdotti la fisica dei raggi cosmici e dei raggi gamma di natura astrofisica, gli attuali metodi sperimentali per la loro rivelazione, i meccanismi attivi nell’Universo per la produzione di raggi gamma di alte energie e le principali sorgenti cosmiche note di raggi gamma. Il capitolo 2 sarà dedicato alla descrizione delle principali caratteristiche fisiche degli sciami atmosferici di natura adronica ed elettromagnetica, alla susseguente emissione di luce Cherenkov prodotta da essi e alla tecnica di rivelazione IAC, su cui i telescopi MAGIC sono basati. Nel capitolo 3 verranno descritte le principali componenti hardware dei due telescopi MAGIC e le innovazioni introdotte per il secondo telescopio. Nel capitolo 4 si discuterà la catena di analisi standard del telescopio MAGIC-I per l’estrazione delle principali quantità fisiche di interesse, quali la significanza del segnale proveniente da una data sorgente e il suo flusso. Successivamente verranno brevemente descritte le principali novità introdotte per la corrente analisi delle sorgenti osservate stereoscopicamente. Le attuali performance del sistema stereoscopico (la cui fase di commissioning è stata portata a termine con successo durante il 2009) saranno inoltre presentate. Nel capitolo 5 verrà introdotta la tematica riguardante la dipendenza alt-azimutale di una delle principali quantità che caratterizzano la rivelazione di luce Cherenkov da parte dei telescopi MAGIC ovvero l’area efficace collettrice. Infatti, se da un lato l’effetto zenitale su tale quantità è ben noto e correlato alla maggiore profondità atmosferica che gli sciami percorrono nel loro sviluppo per angoli zenitali via via maggiori, una possibile dipendenza azimutale è associata agli effetti che il campo geomagnetico induce sullo sviluppo degli sciami stessi e alla particolare configurazione geometrica del sistema di telescopi. La direzione fissa tra di essi, infatti, rompe la simmetria circolare di osservazione tipica delle osservazioni effettuate con un singolo telescopio. Alla luce della messa in funzione del secondo telescopio MAGIC-II e della osservazione stereoscopica delle sorgenti, l’introduzione della dipendenza azimutale dell’area efficace colletrice è stata dunque presa sistematicamente in considerazione e implementata efficacemente nel software di analisi dati dell’esperimento. Saranno riportati inoltre i risultati di test effettuati su campioni di dati Monte Carlo e di dati reali. Nel capitolo 6 verrà fatta una breve introduzione sulla materia oscura: saranno discusse le principali evidenze sperimentali, alcuni modelli che la descrivono e i principali candidati proposti in letteratura per spiegarne la natura. L’attenzione sarà focalizzata sulla ricerca indiretta di materia oscura che si basa sulla possibilità per i telescopi MAGIC di poter rivelare segnali indiretti sotto forma di raggi gamma, provenienti da annichilazione o decadimento di particelle di materia oscura, da parte di sorgenti caratterizzate da alte densità di tale tipo di materia quali, per esempio, galassie nane sferoidali satelliti della Via Lattea. Il capitolo 7 sarà dedicato all’analisi dati dell’osservazione effettuata da parte del telescopio MAGIC-I della sorgente Segue 1, ritenuta essere una galassia nana sferoidale satellite della Via Lattea, la cui cinematica stellare sembra indicare un elevato rapporto massa–luminosità, rendendo tale oggetto celeste estremamente interessante dal punto di vista della recerca indiretta di materia oscura. I dati di tale sorgente hanno richiesto particolare attenzione dovuta al fatto della presenza di una stella di magnitudo apparente 3.5 nel campo di vista della sorgente durante l’intera osservazione. Le tecniche adottate per trattare i problemi legati alla presenza di tale stella saranno illustrati. L’analisi ha permesso di determinare, per energie maggiori di 100 GeV, limiti superiori sul flusso della sorgente assumendo diversi generici spettri di potenza. Un articolo sull’osservazione della sorgente Segue 1 condotta dal telescopio MAGIC-I, basato sui risultati di questa analisi, è in fase di preparazione. Infine, nel capitolo 8, verranno riportate le conclusioni generali su questo lavoro di Tesi.

The main purpose of my thesis has been the analysis of the space debris environment and their characterization through optical measurements. In particular I had the opportunity to contribute to the Italian Space Agency activities in space debris optical observation campaign and I cooperated directly with NASA Orbital Debris Program Office by working at the Astronomy Department of the University of Michigan for six months.