Dissertations / Theses: 'Microwave observations' – Grafiati (2024)

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Simulations and observations of the microwave sky are of great importance for under- standing the Universe that we reside in. Specifically, knowledge of the Cosmic Microwave Background (CMB) and its foregrounds – including the Sunyaev-Zel’dovich (SZ) effect from clusters of galaxies and radio point sources – tell us about the Universe on its very largest scales, and also what the Universe is made of. We describe the creation of software to carry out large numbers of virtual sky simulations. The simulations include the CMB, SZ effect and point sources, and are designed to examine the effects of point sources and the SZ effect on present and recent observations of the CMB. Utilizing sets of 1,000 simulations, we find that the power spectrum resulting from the SZ effect is expected to have a larger standard deviation by a factor of 3 than would be expected from purely Gaussian realizations. It also has a distribution that is significantly skewed towards increased values for the power spectrum, especially when small map sizes are used. The effects of the clustering of galaxy clusters, residual point sources and uncertainties in the gas physics are also investigated, as are the implications for the excess power measured in the CMB power spectrum by the CBI and BIMA experiments. We also investigate the possibility of using the One Centimetre Receiver Array (OCRA) receivers to observe the CMB and measure this high-multipole excess. An automated data reduction package has been created for the OCRA receivers, which has been used in end-to-end simulations for OCRA-p observations of point sources. We find that these simulations are able to realistically simulate the noise present in real observations, and that the introduction of 1/ f noise into the simulations significantly reduces the predicted ability of the instruments to observe weak sources by measuring the sources for long periods of time. The OCRA-p receiver has been used to observe point sources in the Very Small Array fields so that they can be subtracted from observations of the CMB power spectrumWe find that these point sources are split between steep and flat spectrum sources. We have also observed 550 CRATES flat spectrum radio sources, which will be useful for comparison to Planck satellite observations. Finally, the assembly and commissioning of the OCRA-F receiver is outlined. This receiver is now installed on the Torun ́ 32-m telescope, and is currently being calibrated prior to starting observations in the next few months.

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La humedad del suelo es la variable que regula los intercambios de agua, energía, y carbono entre la tierra y la atmósfera. Mediciones precisas de humedad son necesarias para una gestión sostenible de los recursos hídricos, para mejorar las predicciones meteorológicas y climáticas, y para la detección y monitorización de sequías e inundaciones. Esta tesis se centra en la medición de la humedad superficial de la Tierra desde el espacio, a escalas global y regional. Estudios teóricos y experimentales han demostrado que la teledetección pasiva de microondas en banda L es optima para la medición de humedad del suelo, debido a que la atmósfera es transparente a estas frecuencias, y a la relación directa de la emisividad del suelo con su contenido de agua. Sin embargo, el uso de la teledetección pasiva en banda L ha sido cuestionado en las últimas décadas, pues para conseguir la resolución temporal y espacial requeridas, un radiómetro convencional necesitaría una gran antena rotatoria, difícil de implementar en un satélite. Actualmente, hay tres principales propuestas para abordar este problema: (i) el uso de un radiómetro de apertura sintética, que es la solución implementada en la misión Soil Moisture and Ocean Salinity (SMOS) de la ESA, en órbita desde noviembre del 2009; (ii) el uso de un radiómetro ligero de grandes dimensiones y un rádar operando en banda L, que es la solución que ha adoptado la misión Soil Moisture Active Passive (SMAP) de la NASA, con lanzamiento previsto en 2014; (iii) el desarrollo de técnicas de desagregación de píxel que permitan mejorar la resolución espacial de las observaciones. La primera parte de la tesis se centra en el estudio del algoritmo de recuperación de humedad del suelo a partir de datos SMOS, que es esencial para obtener estimaciones de humedad con alta precisión. Se analizan diferentes configuraciones con datos simulados, considerando (i) la opción de añadir información a priori de los parámetros que dominan la emisión del suelo en banda L —humedad, rugosidad, temperatura del suelo, albedo y opacidad de la vegetación— con diferentes incertidumbres asociadas, y (ii) el uso de la polarización vertical y horizontal por separado, o del primer parámetro de Stokes. Se propone una configuración de recuperación de humedad óptima para SMOS.La resolución espacial de los radiómetros de SMOS y SMAP (40-50 km) es adecuada para aplicaciones globales, pero limita la aplicación de los datos en estudios regionales, donde se requiere una resolución de 1-10 km. La segunda parte de esta tesis contiene tres novedosas propuestas de mejora de resolución espacial de estos datos:•Se ha desarrollado un algoritmo basado en la deconvolución de los datos SMOS que permite mejorar la resolución espacial de las medidas. Los resultados de su aplicación a datos simulados y a datos obtenidos con un radiómetro aerotransportado muestran que es posible mejorar el producto de resolución espacial y resolución radiométrica de los datos.•Se presenta un algoritmo para mejorar la resolución espacial de las estimaciones de humedad de SMOS utilizando datos MODIS en el visible/infrarrojo. Los resultados de su aplicación a algunas de las primeras imágenes de SMOS indican que la variabilidad espacial de la humedad del suelo se puede capturar a 32, 16 y 8 km. •Un algoritmo basado en detección de cambios para combinar los datos del radiómetro y el rádar de SMAP en un producto de humedad a 10 km ha sido desarrollado y validado utilizando datos simulados y datos experimentales aerotransportados. Este trabajo se ha desarrollado en el marco de las actividades preparatorias de SMOS y SMAP, los dos primeros satélites dedicados a la monitorización de la variación temporal y espacial de la humedad de la Tierra. Los resultados presentados contribuyen a la obtención de estimaciones de humedad del suelo con la precisión y la resolución espacial necesarias para un mejor conocimiento del ciclo del agua y una mejor gestión de los recursos hídricos.
Soil moisture is a key state variable of the Earth's system; it is the main variable that links the Earth's water, energy and carbon cycles. Accurate observations of the Earth's changing soil moisture are needed to achieve sustainable land and water management, and to enhance weather and climate forecasting skill, flood prediction and drought monitoring. This Thesis focuses on measuring the Earth's surface soil moisture from space at global and regional scales.Theoretical and experimental studies have proven that L-band passive remote sensing is optimal for soil moisture sensing due to its all-weather capabilities and the direct relationship between soil emissivity and soil water content under most vegetation covers. However, achieving a temporal and spatial resolution that could satisfy land applications has been a challenge to passive microwave remote sensing in the last decades, since real aperture radiometers would need a large rotating antenna, which is difficult to implement on a spacecraft. Currently, there are three main approaches to solving this problem: (i) the use of an L-band synthetic aperture radiometer, which is the solution implemented in the ESA Soil Moisture and Ocean Salinity (SMOS) mission, launched in November 2009; (ii) the use of a large lightweight radiometer and a radar operating at L-band, which is the solution adopted by the NASA Soil Moisture Active Passive (SMAP) mission, scheduled for launch in 2014; (iii) the development of pixel disaggregation techniques that could enhance the spatial resolution of the radiometric observations.The first part of this work focuses on the analysis of the SMOS soil moisture inversion algorithm, which is crucial to retrieve accurate soil moisture estimations from SMOS measurements. Different retrieval configurations have been examined using simulated SMOS data, considering (i) the option of adding a priori information from parameters dominating the land emission at L-band —soil moisture, roughness, and temperature, vegetation albedo and opacity— with different associated uncertainties and (ii) the use of vertical and horizontal polarizations separately, or the first Stokes parameter. An optimal retrieval configuration for SMOS is suggested.The spatial resolution of SMOS and SMAP radiometers (~ 40-50 km) is adequate for global applications, but is a limiting factor to its application in regional studies, where a resolution of 1-10 km is needed. The second part of this Thesis contains three novel downscaling approaches for SMOS and SMAP:•A deconvolution scheme for the improvement of the spatial resolution of SMOS observations has been developed, and results of its application to simulated SMOS data and airborne field experimental data show that it is feasible to improve the product of the spatial resolution and the radiometric sensitivity of the observations by 49% over land pixels and by 30% over sea pixels.•A downscaling algorithm for improving the spatial resolution of SMOS-derived soil moisture estimates using higher resolution MODIS visible/infrared data is presented. Results of its application to some of the first SMOS images show the spatial variability of SMOS-derived soil moisture observations is effectively captured at the spatial resolutions of 32, 16, and 8 km.• A change detection approach for combining SMAP radar and radiometer observations into a 10 km soil moisture product has been developed and validated using SMAP-like observations and airborne field experimental data. This work has been developed within the preparatory activities of SMOS and SMAP, the two first-ever satellites dedicated to monitoring the temporal and spatial variation on the Earth's soil moisture. The results presented contribute to get the most out of these vital observations, that will further our understanding of the Earth's water cycle, and will lead to a better water resources management.

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Le interazioni tra neutrini oltre il modello standard della fisica delle particelle sonoun campo aperto sia dal punto di vista teorico che sperimentale. In questa tesipresentiamo come le proprietà non standard dei neutrini possano essere vincolateusando le osservazioni cosmologiche e in particolare i dati della radiazione di fondocosmica, come i dati di Planck. Considereremo la possibilità che i neutrini possegganointerazioni segrete scalari o pseudoscalari mediate da un bosone Nambu-Goldstonedi una simmetria globale spontaneamente rotta U (1) ancora sconosciuta, come adesempio i modelli che includono i Majoroni oppure quelle interazioni segrete di contattotra neutrini sterili leggeri (∼ 1 eV), mediati da un bosone di gauge massivo X (conM X M W ). Presenteremo vincoli sulla forza di interazione e sulla massa di neutriniconsentita dai dati cosmologici o in combinazione con osservazioni astrofisiche, infinediscuteremo la fattibilità dei modelli considerati.
Neutrino interactions beyond the standard model of particle physics are an open fieldboth from theoretical and experimental point of view. In this thesis we present how non-standard neutrino properties can be constrained using cosmological observations and inparticular cosmic microwave background data like those of the Planck satellites. We willconsider the possibility that neutrinos possess secret scalar or pseudoscalar interactionsmediated by the Nambu-Goldstone boson of a still unknown spontaneously brokenglobal U (1) symmetry, as in, e.g., Majoron models or that secret contact interactionsamong eV sterile neutrinos, mediated by a massive gauge boson X (with M X M W )exist. We will present constraints on the interaction strength and on the neutrino massallowed by cosmological data alone or in combination with astrophysical observationsand we will discuss the feasibility of the considered models.

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Thesis (Ph. D.)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xv,110 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Robert J. Scherrer, Dept. of Physics. Includes bibliographical references (p. 106-110).

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Famennian (Upper Devonian) ammonoids and their biostratigraphy are reviewed with particular reference to the Sauerland and Oberfranken, West Germany. Host european species of the Order Clymeniida are described. The Famennian ammonoid zonal scheme is rationalised and within it 23 faunal levels are proposed. Ammonoid Zones and conodont zones are correlated, and the rhomboidea (conodont) Zone is newly recognised to be coeval with the curvispina Zone. The fOllowing genera and subgenera are dealt with in detail: Progonioclyrnenia, Endosiphonites, Sellaclymenia, Biloclymenia, Gonioclymenia (Gon.), Gonioclymenia (Kalloclymenia), Sphenocl~enia, Platycl~enia (Plat.), Plat. (Pleuroclymenia), Plat. (TrigonocIYmenia), Sulcoclymenia, Piricclymenia, Ornatoclymenia, Cyrto- clyymenia, Protactoclymenia, Carinoclymenia, Clymenia, protoxyclymenia , Kosmoclymenia, Genuclymenia, fymaclymenia, Genn. Nov. D, E, and F. In most cases the types of the type species are illustrated photographically for the first time. The following generic names are recognised to have been wrongly interpreted in the past, and, where necessary new names have been proposed. Kalloclymenia, Biloclymenia, Rectoclymenia and Falciclmenia. Two new subgenera and one new genus are proposed, and two generic names, Protactoclymenia and Endosiphonites, have been revived. Kosmoclymenia is split into four species groups by its ornament and Cymaclymenia bas been split into three species groups. Two widely used specific names are recognised to have been placed in the wrong genus; sedgwicki Munster is a pseudoclymenia (a goniatite), and ~pentina MUnster is a Protoxyclymenia.

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The cosmic microwave background (CMB) temperature and polarisation anisotropies contain a wealth of cosmological information concerning the formation and evolution of the universe. Upcoming CMB experiments targeting measurements of the B-mode polarisation pattern of the CMB face a major challenge both in terms of experimental design and data analysis due to the small amplitude of the signal and the presence of experimental systematic effects and polarised foregrounds. This thesis focuses on aspects of preparation for the Spider experiment. Spider is a balloon-borne polarimeter targeting CMB polarisation, it will launch in the Austral summer of 2013 for a long duration flight from Antarctica. It consists of large arrays of 512 detectors in each receiver, creating a large volume of data that is a challenge to analyse, especially when taking into account noise correlations between detectors. We develop SPIMPI, a mapmaking algorithm for estimating temperature and polarisation maps from Time Ordered Data (TOD). To test the mapmaker, realistic TOD containing signal and noise components are generated from the simulated Spider scan strategy. We use an iterative scheme for solving linear systems (the Preconditioned Conjugate Gradient method) to produce optimal estimates of temperature and polarisation. We present templates of the intensity and polarisation of emission from two of the main polarised Galactic foregrounds, interstellar dust and synchrotron radiation. We present estimates of the level of polarised foregrounds expected, focusing on high galactic latitudes and patches that will be targeted by upcoming experiments. We describe details of a model for the 3D Galactic magnetic field, examining both large and small scales. We include details of the dust and cosmic ray electron density distributions, grain alignment, the intrinsic polarisation of the emission from an individual grain and details of synchrotron emission mechanisms. We compare the templates with WMAP MCMC best-fit templates for these foreground components.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
Includes bibliographical references (p. 299-307).
This thesis addresses the problem of retrieving the temperature profile of the Earth's atmosphere from overhead infrared and microwave observations of spectral radiance in cloudy conditions. The contributions of the thesis are twofold: improvements in 1) microwave instrumentation and 2) hyperspectral signal processing and estimation algorithms. The NPOESS Aircraft Sounder Testbed-Microwave (NAST-M) passive spectrometer was designed, fabricated and deployed. NAST-M provides accurate brightness temperature measurements in 16 channels near the oxygen absorption lines at 50-57 GHz and 118.75 GHz, permitting the first reliably accurate retrieval images of temperature profiles and precipitation structure in cloudy areas. The correlation structure of the NPOESS Aircraft Sounder Testbed-Infrared (NAST-I) instrument noise was analyzed in the spectral and spatial domains using the Iterated Order-Noise (ION) algorithm [1] for two representative flights. Results indicate that vibration-induced noise was the dominant component, but that it could be significantly reduced by filtering in the spatial domain. Novel multi-pixel cloud clearing and temperature profile retrieval algorithms were developed for simulated Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) radiances using neural networks. RMS temperature profile retrieval errors of -0.5 K were obtained for all levels of the atmosphere from 0-15 km in clear air at a horizontal resolution of 2000 km2 and a vertical resolution of 1 km. RMS radiance errors under cloudy conditions for altitudes from 0 to 10 kilometers ranged from 1.25 K to 0.1 K for radiance retrievals near 15 microns, and from 0.8 K to 0.05 K for radiance retrievals near 4 microns.
(cont.) Validation of the simulation results with NAST observations was hampered by the lack of a statistically-diverse data set accompanied by cloud truth. An upper bound on cloud-clearing performance (NEAT) was estimated to be approximately a factor of two worse than the simulation results accompanied by ground truth. An improvement of approximately 25 percent in RMS radiance cloud-clearing performance was realized by rejecting 20 percent of soundings based on a neural network-derived metric.
by William Joseph Blackwell.
Sc.D.

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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, March 1998.
"March 1998." Thesis advisor(s): Russell L. Elsberry, Patrick A. Harr. Includes bibliographical references (p. 91-93). Also available online.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.
Vita.
Includes bibliographical references (p. 123-127).
by William Joseph Blackwell.
M.S.

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The study and characterization of the Cosmic Microwave Background (CMB) polarized signal represent, nowadays, one of the most im- portant branches of observational cosmology. In the curl component of the CMB polarization (also known as “B-modes”) it is thought to be hiding the imprint of primordial gravitational waves generated during the inflationary epoch. The observation of this signal would therefore open the door to the study of the physics of the very early universe. The CMB B-modes signal is extremely faint, at the level of fraction of µK, and sophisticated experiments with high sensitivity are needed to detect it. Moreover, the control of instrumental systematic effects and the characterization of foreground emission represent important challenges for this kind of measurements. In this thesis we investigated these two issues focusing on two specific and explicatory experimental cases. By analyzing the multi-frequency polarized observations of the Planck satellite, we studied the contamination arising from the Galactic foreground emission in the CMB observation carried out by the BICEP2 experiment. We showed how the polarized thermal dust emission dominates over the CMB B-modes signal at frequencies as low as 150 GHz and even at high Galactic latitudes. For what concern the instrumental systematic effects we developed a simulation pipeline for the LSPE (Large Scale Polarization Explorer) low frequency instrument. LSPE is a future balloon-borne experiment, aimed at observing the CMB polarized signal on the very large angular scales. Our pipeline simulates the sky observation of the STRIP instrument allowing to understand the expected scientific performance. The presence of possible sources of instrumental systematic effects is also considered and their expected impact on final scientific results is determined.

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Au cours de ma thèse, mes recherches ont porté sur le développement des projets futurs de mesure de la polarisation du fond diffus cosmologique (CMB) visant à sonder les modes B primordiaux. Pour atteindre cet objectif, il faudra non seulement une sensibilité suffisante des matrices de détecteurs, mais également un contrôle sans précédent de toutes les erreurs systématiques inhérentes aux mesures de polarisation du CMB. Une source importante d’erreur systématique est la non-uniformité ou la non-concordance des filtres passe-bande des différents détecteurs. Cet effet induit des fuites de l’intensité vers la polarisation après l’étalonnage des données. J'ai estimé le niveau de fuite pour une configuration réaliste de la prochaine mission LiteBIRD de la JAXA à l’aide de simulations et montré que l'amplitude de la fuite dépendait de la stratégie de balayage du satellite paramétrée par l'angle de rotation du satellite, l’angle de précession et les vitesses de précession et de rotation. En conclusion de cette étude, j’ai proposé des configurations quasi optimales pour LiteBIRD permettant d’atteindre l’objectif sur le rapport tenseur sur scalaire r. Le biais dû à la fuite des avant-plans dans l’intervalle 2≤l≤10 (bosse de réionisation) est de l’ordre de 5×〖10〗^(-4) et dans l’intervalle 10≤l≤200 (bosse de recombinaison) de l’ordre de 5×〖10〗^(-5). Le deuxième sujet de ma thèse était une étude instrumentale : l’interaction des particules avec une matrice de TES. Pour ce faire, j’ai utilisé le plan focal de l’expérience QUBIC (interféromètre bolométrique Q U pour la cosmologie). Le but de ce travail était de tester le comportement des détecteurs aux rayons cosmiques (tels que les constantes de temps et la diaphonie entre détecteurs). J'ai placé une source radioactive d'américium 241 devant un réseau de 256 TES à l'intérieur d'un cryostat. Lorsque les particules interagissent avec l’un des composants d’un pixel (ex: thermomètre, grille absorbante, substrat), l’énergie déposée provoque une élévation de la température d’un composant et éventuellement celui d’un pixel voisin. Cela pourrait fournir une évaluation de la diaphonie entre pixels. De plus, cette étude nous permet de comprendre les constantes de temps du système de lecture thermique et électronique d'un TES
During my Ph.D., my research focused on the development of future projects for the measurement of Cosmic Microwave Background (CMB) polarization aimed to probe primordial B mode. Achieving this goal will not only require sufficient detector array sensitivity but also unprecedented control of all systematic errors inherent to CMB polarization measurements. One of the important effects is the bandpass mismatch error which is the effect of non-uniformity or mismatch of the bandpass filters for different detectors inducing leakage from foreground intensity to polarization after calibrating the data on CMB. I estimated the level of the leakage for a realistic configuration of the forthcoming LiteBIRD JAXA mission with simulation and found that the amplitude of leakage depends on the scanning strategy of the satellite parameterized with precession angle, spin angle, precession and rotation velocities. After the study, I proposed some nearly optimal configurations to archive the target of tensor-to-scalar ratio r. The bias from foreground leakage in the range 2≤l≤10 (reionization bump) is of the order of about 5×〖10〗^(-4) and in the range 10≤l≤200 (recombination bump) of the order of about 5×〖10〗^(-5). The second topic of my thesis was an instrumental study: the interaction of particles with a Transition Edge Sensors (TES) array using the focal plane of the ground-based QUBIC (Q U Bolometric Interferometer for Cosmology) experiment. The goal of this work was to test the behaviour of detectors to cosmic rays (such as time-constants and cross-talk). I placed an Americium 241 radioactive source in front of a 256 TESs array inside a cryostat. When particles hit one of the components of a pixel (eg: Thermometer, absorbing grid, substrate), the deposited energy induced temperature elevation among components and possibly to the neighbor pixels. This could provide an evaluation of the cross-talk between pixels. Moreover, this study allows us to understand the thermal and electronic readout system time constants of a TES

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This thesis describes the analysis of pointed thermal Sunyaev-Zel'dovich (SZ) effect data from observations using the Cosmic Background Imager 2 (CBI2). CBI2 is an upgrade to the original Cosmic Background Imager, with antennas that have twice the effective collecting area, and hence provide greater sensitivity on longer baselines. Observations of the thermal SZ effect constrain the line-of-sight integrated gas pressure within clusters of galaxies and, when combined with X-ray data, provide an excellent tool for deriving the physical properties of these large structures. The CBI2 SZ data combine relatively low-resolution with a large field-of-view, and can therefore be used to constrain the gas properties of medium-redshift clusters out to the virial radius. By jointly fitting a suitable analytical model to SZ data and X-ray surface brightness data, it is possible to obtain constraints on the temperature and total mass of the cluster. For the analysis work presented in this thesis I choose to parametrise the gas based upon the known behaviour of the entropy, and the total mass by the Navarro, Frenk and White (NFW) prescription. This model is tested against Hydrodynamic/N-body simulations and is found to reproduce the radial behaviour of key cluster properties. The CBI2 observations presented in this work focus on the REFLEX-DXL clusters, an X-ray luminous sub-sample of the REFLEX survey at z ~ 0.3, which have previously published X-ray surface brightness data. The Bullet Cluster, a significant merger system, is a member of this sample and is presented here as a case study for use of the entropy-based model. The derived total mass and gas mass fraction of this cluster are found to be consistent with results from previous X-ray observations. The derived properties from the REFLEX-DXL sample are used to construct a preliminary set of SZ scaling relations out to the virial radius, and are found to be consistent with the self-similar model for massive clusters.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.
Includes bibliographical references (p. 469-488).
Soil moisture is a critical hydrosphere state variable that links the global water, energy, and carbon cycles. Knowledge of soil moisture at scales of individual hillslopes (10's to 100's of meters) is critical to advancing applications such as landslide prediction, rainfall-runoff modeling, and wildland fire fuel load assessment. This thesis develops a data assimilation framework that employs the ensemble Kalman Filter (EnKF) to estimate the spatial distribution of soil moisture at hillslope scales by combining uncertain model estimates with noisy active and passive L-band microwave observations. Uncertainty in the modeled soil moisture state is estimated through Monte Carlo simulations with an existing spatially distributed ecohydrology model. Application of the EnKF to estimate hillslope-scale soil moisture in a watershed critically depends on: (1) identification of factors contributing to uncertainty in soil moisture, (2) adequate representation of the sources of uncertainty in soil moisture, and (3) formulation of an observing system to estimate the geophysically observable quantities based on the modeled soil moisture. Uncertainty in the modeled soil moisture distribution arises principally from uncertainty in the hydrometeorological forcings and imperfect knowledge of the soil parameters required as input to the model. Three stochastic models are used in combination to simulate uncertain hourly hydrometeorological forcings for the model. Soil parameter sets are generated using a stochastic approach that samples low probability but potentially high consequence parameter values and preserves correlation among the parameters. The observing system recognizes the role of the model in organizing the factors effecting emission and reflection of L-band microwave energy and emphasizes the role of topography in determining the satellite viewing geometry at hillslope scales.
(cont.) Experiments in which true soil moisture conditions were simulated by the model and used to produce synthetic observations at spatial scales significantly coarser than the model resolution reveal that sequential assimilation of observations improves the hillslope-scale near-surface moisture estimate. Results suggest that the data assimilation framework is an effective means of disaggregating coarse-scale observations according to the model physics represented by the ecohydrology model. The thesis concludes with a discussion of contributions, implications, and future directions of this work.
by Alejandro Nicolas Flores.
Ph.D.

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Progress in our understanding of the chemical composition of the interstellar medium leans both on laboratory analyses of high resolution rotational spectra from molecules that may be present in these regions, and on radio astronomical observations of molecular tracers to constrain astrochemical models. Due to the thermodynamic conditions in outer space, some molecules likely to be found in interstellar regions in relevant abundances are open shell radicals. In a series of laboratory studies, the pure rotational spectra of the transition metal containing radicals sulfur species ScS, YS, VS and ZnSH were obtained for the first time. In addition to accurate and precise rest frequencies for these species, bonding characteristics were determined from fine and hyperfine molecular parameters. It was found that these sulfides have a higher degree of covalent bonding than their mostly ionic oxide counterparts. Isomers and isotope ratios are excellent diagnostic tools for a variety of astrochemical models. From radio observations of isotopes of nitrile species, the galactic gradient of ¹⁴N/¹⁵N was accurately established. A further study of this ratio in carbon rich asymptotic giant branch stars provided observational evidence for an unknown process in J type carbon stars, and highlighted the need to update stellar nucleosynthesis models. Proper radiative transfer modeling of the emission spectra of interstellar molecules can yield a wealth of information about the abundance and distribution of these species within the observed sources. To model the asymmetric emission of SO and SO₂ in oxygen-rich supergiants, an in-house code was developed, and successfully applied to gain insight into circ*mstellar sulfur chemistry of VY Canis Majoris. It was concluded that current astrochemistry kinetic models, based on spherical symmetry assumptions, need to be revisited.

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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

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La température de surface des continents est une variable essentielle dans la modélisation du bilan énergétique global. Les mesures effectuées par les imageurs microondes passifs en orbite permettent d’estimer la température de la surface quelle que soit la couverture nuageuse contrairement aux mesures dans l'infrarouge qui ne sont pas utilisables sous les nuages. Néanmoins, plusieurs difficultés surviennent lors de l'utilisation de ces observations. Parmi celles-ci, la correction des écarts entre des observations provenant d’instruments différents par un inter-étalonnage des mesures, la détection des observations contaminées par des nuages en fonction de la fréquence d'observation et du type de nuage sont abordées dans cette thèse. Ou encore la création de cartes recensant les zones arides dans lesquelles la température en microondes correspond à celle de la sub-surface qui peut être différente de la température à la surface. Une méthode pour augmenter la résolution spatiale des températures de surface en se basant sur des relations statistiques avec d’autres variables est aussi présentée
Land surface temperature is an essential variable in modeling the global energy budget. Passive microwave imagers aboard satellite provide global observations that can be used to estimate the land surface temperature in all-sky conditions contrary to infrared observations that cannot be used to estimate surface temperatures under overcast conditons. Nevertheless, a few challenges arise when using these observations that are addressed in this thesis. Among them, the correction of observations coming from different instruments through inter-calibration, the detection of cloud-contaminated signal with changing cloud type and frequency. Also, maps of arid areas with high penetration depth where microwave temperature comes from the sub-surface with a temperature that can be different from the skin temperature are created. A downscaling methodology to increase the spatial resolution of land surface temperature using statistical relationship with ancillary variables is also introduced

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L'optimisation de la gestion de l'eau en agriculture est essentielle dans les zones semi-arides afin de préserver les ressources en eau qui sont déjà faibles et erratiques dues à des actions humaines et au changement climatique. Cette thèse vise à utiliser la synergie des observations de télédétection multispectrales (données radar, optiques et thermiques) pour un suivi à haute résolution spatio-temporelle des besoins en eau des cultures. Dans ce contexte, différentes approches utilisant divers capteurs (Landsat-7/8, Sentinel-1 et MODIS) ont été developpées pour apporter une information sur l'humidité du sol (SM) et le stress hydrique des cultures à une échelle spatio-temporelle pertinente pour la gestion de l'irrigation. Ce travail va parfaitement dans le sens des objectifs du projet REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) qui visent à estimer l'humidité du sol dans la zone racinaire (RZSM) afin d'optimiser la gestion de l'eau d'irrigation. Des approches innovantes et prometteuses sont mises en place pour estimer l'évapotranspiration (ET), RZSM, la température de surface du sol (LST) et le stress hydrique de la végétation à travers des indices de SM dérivés des observations multispectrales à haute résolution spatio-temporelle. Les méthodologies proposées reposent sur des méthodes basées sur l'imagerie, la modélisation du transfert radiatif et la modélisation du bilan hydrique et d'énergie et sont appliquées dans une région à climat semi-aride (centre du Maroc). Dans le cadre de ma thèse, trois axes ont été explorés. Dans le premier axe, un indice de RZSM dérivé de LST-Landsat est utilisé pour estimer l'ET sur des parcelles de blé et des sols nus. L'estimation par modélisation de ET a été explorée en utilisant l'équation de Penman-monteith modifiée obtenue en introduisant une relation empirique simple entre la résistance de surface (rc) et l'indice de RZSM. Ce dernier est estimé à partir de la température de surface (LST) dérivée de Landsat, combinée avec les températures extrêmes (en conditions humides et sèches) simulée par un modèle de bilan d'énergie de surface piloté par le forçage météorologique et la fraction de couverture végétale dérivée de Landsat. La méthode utilisée est calibrée et validée sur deux parcelles de blé situées dans la même zone près de Marrakech au Maroc. Dans l'axe suivant, une méthode permettant de récupérer la SM de la surface (0-5 cm) à une résolution spatiale et temporelle élevée est développée à partir d'une synergie entre données radar (Sentinel-1) et thermique (Landsat) et en utilisant un modèle de bilan d'énergie du sol. L'approche développée a été validée sur des parcelles agricoles en sol nu et elle donne une estimation précise de la SM avec une différence quadratique moyenne en comparant à la SM in situ, égale à 0,03 m3 m-3. Dans le dernier axe, une nouvelle méthode est développée pour désagréger la MODIS LST de 1 km à 100 m de résolution en intégrant le SM proche de la surface dérivée des données radar Sentinel-1 et l'indice de végétation optique dérivé des observations Landsat. Le nouvel algorithme, qui inclut la rétrodiffusion S-1 en tant qu'entrée dans la désagrégation, produit des résultats plus stables et robustes au cours de l'année sélectionnée. Dont, 3,35 °C était le RMSE le plus bas et 0,75 le coefficient de corrélation le plus élevé évalués en utilisant le nouvel algorithme
Optimizing water management in agriculture is essential over semi-arid areas in order to preserve water resources which are already low and erratic due to human actions and climate change. This thesis aims to use the synergy of multispectral remote sensing observations (radar, optical and thermal data) for high spatio-temporal resolution monitoring of crops water needs. In this context, different approaches using various sensors (Landsat-7/8, Sentinel-1 and MODIS) have been developed to provide information on the crop Soil Moisture (SM) and water stress at a spatio-temporal scale relevant to irrigation management. This work fits well the REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) project objectives, which aim to estimate the Root Zone Soil Moisture (RZSM) for optimizing the management of irrigation water. Innovative and promising approaches are set up to estimate evapotranspiration (ET), RZSM, land surface temperature (LST) and vegetation water stress through SM indices derived from multispectral observations with high spatio-temporal resolution. The proposed methodologies rely on image-based methods, radiative transfer modelling and water and energy balance modelling and are applied in a semi-arid climate region (central Morocco). In the frame of my PhD thesis, three axes have been investigated. In the first axis, a Landsat LST-derived RZSM index is used to estimate the ET over wheat parcels and bare soil. The ET modelling estimation is explored using a modified Penman-Monteith equation obtained by introducing a simple empirical relationship between surface resistance (rc) and a RZSM index. The later is estimated from Landsat-derived land surface temperature (LST) combined with the LST endmembers (in wet and dry conditions) simulated by a surface energy balance model driven by meteorological forcing and Landsat-derived fractional vegetation cover. The investigated method is calibrated and validated over two wheat parcels located in the same area near Marrakech City in Morocco. In the next axis, a method to retrieve near surface (0-5 cm) SM at high spatial and temporal resolution is developed from a synergy between radar (Sentinel-1) and thermal (Landsat) data and by using a soil energy balance model. The developed approach is validated over bare soil agricultural fields and gives an accurate estimates of near surface SM with a root mean square difference compared to in situ SM equal to 0.03 m3 m-3. In the final axis a new method is developed to disaggregate the 1 km resolution MODIS LST at 100 m resolution by integrating the near surface SM derived from Sentinel-1 radar data and the optical-vegetation index derived from Landsat observations. The new algorithm including the S-1 backscatter as input to the disaggregation, produces more stable and robust results during the selected year. Where, 3.35 °C and 0.75 were the lowest RMSE and the highest correlation coefficient assessed using the new algorithm

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Les océans et la banquise jouent un rôle important dans le système climatique et météorologique. Une future mission satellite en micro-ondes passives basses fréquences, conçue pour observer les régions polaires est actuellement à l’étude à l’Agence Spatiale Européenne pour l’expansion du programme Copernicus. Les observations satellites en micro-ondes passives permettent une observation de la surface de la Terre par tous temps, aussi bien de jour que de nuit. Dans cette thèse, nous nous intéressons à l’estimation des paramètres de surface de l’océan et de la banquise à partir des observations satellites micro-ondes passives basses fréquences. L’objectif est de développer de nouvelles méthodes d’estimation de ces paramètres qui soient plus efficaces et adaptées à la future mission satellite micro-onde passive CIMR (Copernicus Imaging Microwave Radiometer). La première partie de la thèse traite de l’estimation des paramètres océaniques tels que la température de la surface de la mer, la salinité et la vitesse du vent océanique. La deuxième partie traite de l’estimation des paramètres de la banquise tels que la concentration en glace, l’épaisseur de neige et la température d’interface neige-glace. Enfin, avec les méthodes développées dans cette thèse les performances de la mission CIMR sont évaluées et comparées à celles des missions actuelles
The oceans and sea ice play an important role in the climate and weather system. A future low-frequency passive microwave satellite mission designed to observe the polar regions is currently under study at the European Space Agency for the expansion of the Copernicus programme. Passive microwave satellite observations provide all-weather observation of the Earth surface, both day and night. In this thesis, we are interested in estimating ocean and ice surface parameters from low-frequency passive microwave satellite observations. The objective is to develop new methods for estimating these parameters that are more efficient and adapted to the future passive microwave satellite mission CIMR (Copernicus Imaging Microwave Radiometer). The first part of the thesis deals with the estimation of ocean parameters such as sea surface temperature, salinity and ocean wind speed. The second part deals with the estimation of sea ice parameters such as sea ice concentration, snow depth and snow-ice interface temperature. Finally, with the methods developed in this thesis, the performances of the CIMR mission are evaluated and compared with the current missions

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An electromagnetic model is developed for predicting the microwave blackbody emission from the ocean surface over a wide range of frequencies, incidence angles, and wind vector (speed and direction) for both horizontal and vertical polarizations. This ocean surface emissivity model is intended to be incorporated into an oceanic radiative transfer model to be used for microwave radiometric applications including geophysical retrievals over oceans. The model development is based on a collection of published ocean emissivity measurements obtained from satellites, aircraft, field experiments, and laboratory measurements. This dissertation presents the details of methods used in the ocean surface emissivity model development and comparisons with current emissivity models and aircraft radiometric measurements in hurricanes. Especially, this empirically derived ocean emissivity model relates changes in vertical and horizontal polarized ocean microwave brightness temperature measurements over a wide range of observation frequencies and incidence angles to physical roughness changes in the ocean surface, which are the result of the air/sea interaction with surface winds. Of primary importance are the Stepped Frequency Microwave Radiometer (SFMR) brightness temperature measurements from hurricane flights and independent measurements of surface wind speed that are used to define empirical relationships between C-band (4 Â 7 GHz) microwave brightness temperature and surface wind speed. By employing statistical regression techniques, we develop a physical-based ocean emissivity model with empirical coefficients that depends on geophysical parameters, such as wind speed, wind direction, sea surface temperature, and observational parameters, such as electromagnetic frequency, electromagnetic polarization, and incidence angle.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD

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Cette thèse décrit la réalisation et l’étude de réseaux bidimensionnels de résonateurs supraconducteurs en nid d’abeille. Ce travail constitue un premier pas vers la simulation de systèmes de la matière condensée avec des circuits supraconducteurs. Ces réseaux sont micro-fabriqués et sont constitués de plusieurs centaines de sites. Afin d’observer les modes propres qui y apparaissent dans une gamme de fréquence entre 4 et 8 GHz, nous avons mis au point une technique d’imagerie. Celle-ci utilise la dissipation locale créée par un laser avec lequel nous pouvons adresser chaque site du réseau. Nous avons ainsi pu mesurer la structure de bande et caractériser les états de bord de nos réseaux. En particulier, nous avons observé les états localisés qui apparaissent à l'interface entre deux isolants de sem*noff ayant des masses opposées. Ces états, dits de sem*noff, sont d'origine topologique. Nos observations sont en excellent accord avec des simulations électromagnétiques ab initio
This thesis describes the realization and study of honeycomb lattices of superconducting resonators. This work is a first step towards the simulation of condensed matter systems with superconducting circuits. Our lattices are micro-fabricated and typically contains a few hundred sites. In order to observe the eigen-modes that appear between 4 and 8 GHz, we have developed a mode imaging technique based on the local dissipation introduced by a laser spot that we can move across the lattice. We have been able to measure the band structure and to characterize the edge states of our lattices. In particular, we observe localized states that appear at the interface between two sem*noff insulators with opposite masses. These states, called sem*noff states, have a topological origin. Our observations are in good agreement with ab initio electromagnetic simulations

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This dissertation presents results for an end-to-end computer simulation of a new airborne microwave remote sensor, the Hurricane Imaging Radiometer, HIRAD, which will provide improved hurricane surveillance. The emphasis of this research is the retrieval of hurricane-force wind speeds in the presence of intense rain and over long atmospheric slant path lengths that are encountered across its wide swath. Brightness temperature (Tb) simulations are performed using a forward microwave radiative transfer model (RTM) that includes an ocean surface emissivity model at high wind speeds developed especially for HIRAD high incidence angle measurements and a rain model for the hurricane environment. Also included are realistic sources of errors (e.g., instrument NEDT, antenna pattern convolution of scene Tb, etc.), which are expected in airborne hurricane observations. Case studies are performed using 3D environmental parameters produced by numerical hurricane models for actual hurricanes. These provide realistic  nature runs of rain, water vapor, clouds and surface winds from which simulated HIRAD Tb s are derived for various flight tracks from a high altitude aircraft. Using these simulated HIRAD measurements, Monte Carlo retrievals of wind speed and rain rate are performed using available databases of sea surface temperatures and climatological hurricane atmospheric parameters (excluding rain) as a priori information. Examples of retrieved hurricane wind speed and rain rate images are presented, and comparisons of the retrieved parameters with the numerical model data are made. Statistical results are presented over a broad range of wind and rain conditions and as a function of path length over the full swath.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD

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This Thesis is written in three parts. The first part describes the analytic calculation of the unequal-time correlator of cosmic strings and superstrings. The first efficient constraint analysis of all string and superstring network parameters is performed. By studying the effect of cosmic strings on the cosmic microwave background (CMB) radiation it is discovered that cosmic strings must make up a vanishingly small proportion of the energy density of the universe. The constraints on string network parameters are all skewed toward reducing the magnitude of energy density arising from strings. Also in this Part, a better comprehension of the unconnected segment model (USM) was gained. In particular, a greater understanding of the string scaling parameter $L_f$ was garnered, as well as finding the reason why the USM tends to provide greater power than simulations of Nambu-Goto cosmic strings. The second part contains a detailed description of statistical cosmology and how differences between parameter constraints from different data sets can lead to misleading quantification of discordance. The majority of this part describes different methods of quantifying differences between probability distributions and how these can be interpreted. In particular, using the most up-to-date data possible, differences between parameter constraints using the CMB and probes of large scale structure (LSS) in the universe can be measured. With current data the discordance can be interpreted as a low level of disagreement, but the application of prior ranges on well known parameters can force the tension to be greater. Using data from earlier work, this issue is considered in greater detail, with extensions to the accepted LCDM model added to test if the discordance can be alleviated. These extensions include the addition of active or sterile neutrinos and even ad-hoc changes to the primordial power spectrum. Although there are slight hints that these may help, when considering only the new data it might be unwise to believe that the discordance between parameter distributions from different data sets exists to a degree where the modifications are necessary. Finally, application of deep learning to astrophysical observations is discussed. Using neural networks to learn about specific problems is de rigueur and their use in astronomy and cosmology is a promising field of study. In particular, applying raw data to neural networks can often outperform, or add enhanced features, to what is possible with current, non-empirical feature detection. The classification of supernovae from their light curves can be achieved using a specific machine learning architecture called a recurrent neural network (RNN). Using the raw data from supernova light curves, the RNN is able to learn about features in sequences which can be used to classify types of supernova. Although a large training set is needed to perform as well as current techniques, one major advantage the RNN method has is the possibility of early detection. Rather than needing the entire light curve to perform statistical fits to categorise the supernova type, relatively little information from the early observation data is needed to classify using the RNN. Installing RNN on machinery for observation would save a vast amount of time by early classification since only supernovae of interest can be concentrated on.

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This thesis reports the first observation of the resonant electric dipole-dipole interaction between cold Rydberg atoms using microwave spectroscopy, the observation of the magnetic field suppression of resonant interactions, and the development of a unique technique for precise magnetic field measurements.

A Rydberg state 46d_5/2 of laser cooled ⁸⁵Rb atoms has been optically excited. A fraction of these atoms has been transferred to another Rydberg state 47p_3/2 or 45f_5/2,7/2 to introduce resonant electric dipole-dipole interactions. The line broadening of the two-photon 46d_5/2-47d_5/2 microwave transition due to the interaction of 46d_5/2 with 47p_3/2 or 45f_5/2,7/2 atoms has been used as a probe of the interatomic interactions. This experiment has been repeated with a DC magnetic field applied. The application of a weak magnetic field (≤0. 6G) has reduced the line broadening due to the resonant electric dipole-dipole interaction, indicating that the interactions are suppressed by the field. Theoretical models have been developed that predict the energy shifts due to the resonant electric dipole-dipole interaction, and the suppression of interactions by magnetic fields. A novel technique for sensitive measurement of magnetic fields using the 34s_1/2-34p_1/2 one-photon microwave transition has also been presented. Using this technique, it has been possible to calibrate magnetic fields in the magneto-optical trap (MOT) apparatus to less than 10mG, and put an upper bound of 17mG on any remaining field inhom*ogeneity.

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In this dissertation, techniques of high-resolution rotational spectroscopy have been used to measure the spectra of molecules in both laboratory and astronomical settings. In the laboratory, small metal-bearing molecules containing zinc, iron, nickel, titanium, yttrium, and scandium have been studied at microwave and millimeter/submillimeter wavelengths in order to determine their rotational, fine, and hyperfine constants. These molecules were synthesized in situ in direct-absorption and Fourier-transform microwave spectrometers using Broida-type ovens and laser ablation methods. From the spectroscopic parameters, information about fundamental physical propertes and electronic character could be obtained. Radio telescopes were used to measure the spectra of molecules in different interstellar environments. A new molecule, FeCN, was detected toward the circ*mstellar envelope of the carbon-rich asymtotic giant branch star, IRC+10216, marking the first iron-bearing molecule detected in the interstellar medium. The telescopes were also used to conduct a study of the evolved planetary nebula, NGC 7293, or the Helix Nebula. In the Helix, CO, HCO⁺, and H₂CO were observed at several positions offset from the central star to obtain densities and kinetic temperatures throughout the Helix. A map of the HCO⁺ J = 1→ 0 transition was also constructed, showing that HCO⁺ is widespread throughout the Helix, instead of being photodissociated and destroyed, as theoretical models of planetary nebulae predict.

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Actualment, la comunitat científica ja disposa de les primeres mesures radiomètriques a banda L, polarimètriques i multi-angulars fetes de l’espai. Això és gràcies al recent llançament de la missió de la Eurepean Space Agency (ESA) anomenada Soil Moisture and Ocean Salinity (SMOS). Es sabut que a partir de la temperatura d’antena es possible recuperar salinitat superficial marina (Sea Surface Salinity, (SSS)) i humitat del sòl (Soil Moisture (SM)). Els beneficis de mesurar aquests dos paràmetres geofísics son múltiples, essent especialment profitosos en els camps de la oceanografia i la climatologia. La raó principal que va motivar la presentació del projecte Passive Advanced Unit (PAU) a la European Science Foundantion (ESF) va ser per estudiar la relació entre brillantor de temperatura i observables Global Navigation Satellite System Reflectometry (GNSS/R) per a millorar la recuperació de la SSS i SM. A més a més, els objectius tècnics del projecte PAU incloïen el desenvolupament de nous conceptes de radiòmetres en banda L, com a base tecnològica per a nous sistemes radiomètrics.La present tesi doctoral estén el coneixement adquirit en els últims anys en el desenvolupament del radiòmetre SMOS i és una contribució al desenvolupament d'una nova generació de sensors passius. Per primera vegada – pel que fa els coneixements de l'autor – s’ha desenvolupat amb èxit un radiòmetre amb una agrupació d’antenes capaç de formar feixos en temps real. Aquest sistema és capaç de dirigir múltiples i simultanis feixos en diferents angle d'incidència, sense cap m moviment mecànic, proporcionant així un nou mètode per a obtenir mesures multi-angulars.El projecte PAU ha estat desenvolupat en el Remote Sensing Lab, del Departament de Teoria del Senyal i Comunicacions de la Universitat Politècnica de Catalunya. La present tesi doctoral descriu la tasca realitzada entre 2005 i 2010, tant en aspectes teòrics i de hardware com en el camp de la radiometria de banda L. Aquesta tesi consisteix en un estudi teòric realitzat en radiòmetres correlació amb la formació de feix digital des del punt de vista dels radiòmetres d'obertura sintètica i una anàlisi exhaustiva del impacte del sistema de digitalització. D'altra banda, han estat definits els requisits per a construir un radiòmetre de correlació amb la formació de feix digital en temps real i amb síntesi de la polarització. Un instrument amb aquestes característiques s'ha construït, a nivell intern va igualar per l'amplitud i fase de cada receptor, provat i es caracteritza a la cambra anecoica, i, finalment, s’ha realitzat campanya de camp per obtenir valors de l'emissivitat del sòl per a una gamma d’angles d'incidència.
With the recent launch of the ESA’s Soil Moisture and Ocean Salinity (SMOS) mission the scientific community is provided with the first polarimetric and multi-angular L-band radiometric measurements from the space. From the antenna temperature is possible to retrieve Sea Surface Salinity (SSS) and Soil Moisture (SM), which benefits both the oceanographic and climatologic studies. It is well known that it exists angular and polarization dependence for the radiometric measurements. Using this dependence, it is possible to use multi-angular and polarimetric measurements to retrieve geophysical parameters. The main rationale that motivated the submission of the Passive Advanced Unit (PAU) project to the European Science Foundation (ESF) was to study the relationship between the brightness temperatures and some Global Navigation Satellite System Reflectometry (GNSS/R) observables, so as to improve the SSS retrievals. Also, the technical objectives of the PAU project included the development of new L-band radiometer concepts, such as a technological bed for providing new radiometer systems.The present PhD dissertation extends the knowledge acquired in the recent years in the development of the SMOS radiometer, and is a contribution to the development of a new generation of passive sensors. For the first time – to author’s knowledge – real-time digital beamforming and polarization synthesis have been successfully implemented in a real system. The system is able to steer multiple and simultaneous beams in different incidence angles without mechanical scan of the antenna, providing a new method to obtain multi-angular measurements combining an L-band radiometer with the concept of digital beamformer.The PAU project has been developed by the Passive Remote Sensing Group of the Remote Sensing Lab, at the Department of Signal Theory and Communications of the Universitat Politècnica de Catalunya. The present PhD dissertation describes the work undertaken between 2005 and 2010 in both theoretical and hardware issues within the field of L-band radiometry with real-time digital beamforming with polarization synthesis. This dissertation consists of a theoretical study performed on digital correlation radiometers with beamforming from the point of view of the synthetic aperture radiometers and an extended analysis of the impact of the digitization scheme. Moreover, the requirements to build a correlation radiometer with real-time digital beamforming and polarization synthesis have been stated. The new concept instrument has been built, internally equalized for the amplitude and phase of each receiver, tested and characterized in the anechoic chamber, and in a field campaign obtaining soil emissivity values for a range of incidence angles.

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Abstract:

In this work we analyze two possible observational manifestations of gravitational waves. We consider the effects of gravitational waves on ground based laser interferometric detectors, and the imprints of relic gravitational waves on the Cosmic Microwave Background (CMB) radiation. In order to study the effect of a gravitational wave on a laser interferometer it is crucial to understand the movement of free test particles. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. A gravitational wave bring about the relative motion of free test masses. In particular, analogous to movement of free charges in a field of an electromagnetic wave, a gravitational wave drives the masses in the plane of the wave-front and also, to a smaller extent, back and forth in the direction of the wave's propagation. To describe this motion, we introduce the notion of "electric" and "magnetic" components of the gravitational force. Using different methods, we demonstrate the presence and importance of the "magnetic" component of motion of free masses. We then explicitly derive the full response function of a 2-arm laser interferometer to a gravitational wave of arbitrary polarization. We give a convenient description of the response function in terms of the spin-weighted spherical harmonics. We show that the previously ignored "magnetic" component may provide a correction of up to 10%, or so, to the usual "electric" component of the response function. Another promising venue for detecting gravitational waves are the anisotropics in temperature and polarization of the CMB radiation. A strong variable gravitational field of the very early Universe inevitably generates relic gravitational waves by amplifying their zero-point quantum oscillations. These relic gravitational waves leave their imprint on the anisotropics of the CMB. We explain and summarize the properties of relic gravitational waves that are needed to derive their effects on CMB temperature and polarization anisotropics. Analyzing the radiative transfer equations, we reduce them to a single integral equation of Voltairre type and solve it analytically as well as numerically. We formulate the possible correlation functions Cfx> and derive their amplitudes, shapes and oscillatory features. We show that the TE correlation at lower ts must be negative, if it is caused by gravitational waves, and positive if it is caused by density perturbations. This difference in TE correlation may be a signature more valuable observationally than the lack or presence of the BB correlation, since the TE signal is about 100 times stronger than the expected BB signal. We discuss the detection by WMAP of the TE anti-correlation at t 30 and show that such an anti- correlation is possible only in the presence of a significant amount of relic gravitational waves (within the framework of all other common assumptions). We propose models containing considerable amounts of relic gravitational waves that are consistent with the measured TT, TE and EE correlations.