Finalized PhD theses

Número de entradas: 76

Thermal Diagnostics in the LISA Technology Package Experiment

Estado: defended (13/12/2007)
Estudiante: Miquel Nofrarias Serra
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

The LISA Pathfinder mission (LPF) is an ESA mission, with NASA contributions, planned to fly in 2010. The LPF is a technology readiness mission devoted to pave the way to the future spaceborne gravitational wave observatory LISA. The LISA Technology Package (LTP) experiment in the LPF mission will measure…
Estado: defended (13/12/2007)
Estudiante: Miquel Nofrarias Serra
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

The LISA Pathfinder mission (LPF) is an ESA mission, with NASA contributions, planned to fly in 2010. The LPF is a technology readiness mission devoted to pave the way to the future spaceborne gravitational wave observatory LISA. The LISA Technology Package (LTP) experiment in the LPF mission will measure the relative distance between two free falling test masses to the picometer resolution by using both masses as end mirrors of an interferometer together with an active control loop, known as drag-free, that will act to keep the spacecraft centered around the geodetic motion of the masses. The work in this thesis deals with the thermal diagnostics subsystem, intended to measure and characterise the thermal noise contribution to the instrument performance: from the qualification of the high stability electronics designed to measure temperature fluctuations onboard the satellite to the characterisation of heaters aimed to generate controlled perturbation during mission operations. Analytic solutions together with simulations and experimental results have been used to this end. The results obtained have allowed the characterisation of the temperature subsystem and, also, to define a methodology to deal with the thermal data that will be obtained from the satellite during flight operations.

Dark energy problem in Friedmann cosmology with ideal fluid and in modified gravity

Estado: defended (30/10/2007)
Estudiante: O.G. Gorbunova
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

DE problem is investigated
Estado: defended (30/10/2007)
Estudiante: O.G. Gorbunova
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

DE problem is investigated

Cosmology and structure formation

Estado: defended (26/06/2007)
Estudiante: Marc Manera Miret
Supervisada por: Enrique Gaztañaga

In the rst part of this thesis we look at several non-standard cosmological models. These models have been introduced in the literature mainly to explain the accelerated expansion that we see the universe is currently undertaken. We want to study if they can also reproduce the observations of the…
Estado: defended (26/06/2007)
Estudiante: Marc Manera Miret
Supervisada por: Enrique Gaztañaga

In the rst part of this thesis we look at several non-standard cosmological models. These models have been introduced in the literature mainly to explain the accelerated expansion that we see the universe is currently undertaken. We want to study if they can also reproduce the observations of the large scale structure and its evolution. For doing so we t introduce a formalism to compute the growth of structure in non-standard cosmologies. Then, for each of these non-standard models, we will focus in computing observables like the linear growth, the skewness, or the cluster number counts. In the second part of this thesis we will look at the cross-correlation between CMB-temperature maps and galaxy (or other dark matter tracers ) surveys maps. This cross-correlation is a way to measure the Integrated Sachs Wolfe (ISW) e ect, which can be directly related to the growth of structure. We will use the ISW signal dependence in redshift and in angular scale to constrain and the equation of state parameter w. In this part of the thesis we will also focus on studying di erent error estimators for the sky maps cross-correlation measurements. We will actually present a new method, which estimate the errors in the con guration space. This method will be compared with other error estimators widely used in the literature: the Jack-knife, the Monte Carlo errors and the theoretical harmonic space errors. The problem of bias. In order to compare models to observations we need to address a crucial point: does light trace mass? In other words: how well the structure we see traces the dark matter we can't see?. Are the observations biased tracers of the mass?. This is a key point to be abble to compare models of growth of structure with observations in the real world. Unfortunately in detail, this requires understanding how star's and galaxies form and shine. As the the universe expands, the dark matter clumps into halos and lamentary structure. This can be very clearly seen in dark matter cosmological simulations, which allow us to study the gravitational clustering separately from other (but also interesting) physical e ects. Like galaxies, halos are not perfect traces of the underlying dark matter uctuations, but biased ones. In fact, we believe that galaxies form inside dark matter halos, so that understanding halo bias is the rst step towards understanding galaxy bias. In part three of this thesis we will use a cosmological dark matter simulation to study the halo clustering and bias. More speci cally, we wonder to what extend the the local bias model could be applied to the predictions and analyses of the two and three point halo correlation functions.

Gamma-ray emission from regions of star formation: theory and first observations with the MAGIC telescope

Estado: defended (03/03/2006)
Estudiante: Eva Domingo-Santamaria
Supervisada por: Cortina, J.; Diego F. Torres
Universidad: Universitat Autònoma de Barcelona

See the link below for a full copy (there go to Fermilab Library Server).
Estado: defended (03/03/2006)
Estudiante: Eva Domingo-Santamaria
Supervisada por: Cortina, J.; Diego F. Torres
Universidad: Universitat Autònoma de Barcelona

See the link below for a full copy (there go to Fermilab Library Server).

The Friedmann cosmological models in dilatation and modified gravity and account of quantum effects.

Estado: defended (26/02/2006)
Estudiante: Yu.Shaido
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

The study of Friedmann universe in modified gravity with account of quantum effects is presented. The conformal anomaly effects are taken into account. The new model of dark energy as modified gravity with ideal fluid described by equation of state with bulk viscosity is suggested. The scalar-tensor…
Estado: defended (26/02/2006)
Estudiante: Yu.Shaido
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

The study of Friedmann universe in modified gravity with account of quantum effects is presented. The conformal anomaly effects are taken into account. The new model of dark energy as modified gravity with ideal fluid described by equation of state with bulk viscosity is suggested. The scalar-tensor friedmann cosmology is investigated.

Calibration, Validation and Polarimetry in 2D Aperture Synthesis: Application to MIRAS

Estado: defended (30/06/2005)
Estudiante: Serni Ribó
Supervisada por: Martín-Neira, M.; Torres, F.
Universidad: Universitat Politècnica de Catalunya

The SMOS mission of the European Space Agency (scheduled 2007) is devoted to measure Soil Moisture and Ocean Salinity, which are key parameters on the understanding of global climate change. The single instrument of this mission is the MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), a…
Estado: defended (30/06/2005)
Estudiante: Serni Ribó
Supervisada por: Martín-Neira, M.; Torres, F.
Universidad: Universitat Politècnica de Catalunya

The SMOS mission of the European Space Agency (scheduled 2007) is devoted to measure Soil Moisture and Ocean Salinity, which are key parameters on the understanding of global climate change. The single instrument of this mission is the MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), a new kind of instrument devoted to Earth observation. It is a thinned Y-shaped array with 21 elements per arm. With this technique a large synthetic aperture antenna with relative low weight can be obtained. This novel technique has been selected for the SMOS mission in order to fulfil both criteria ground resolution (35-50km) and revisit time (3 days). Similar instruments to MIRAS have already been used for radio astronomy but in that case only sources with a narrow angular size (stars and galaxies) were observed. In the case of MIRAS, the Earth is an extended source of thermal radiation, which almost fills up the complete field of view of MIRAS. The consequence of it is that the calibration techniques developed for radio astronomy may not be used in the SMOS mission. This thesis is mainly focused to experimentally test several calibration techniques and to prove the imaging properties of MIRAS. A second part is devoted to the polarimetric mode of MIRAS and its capability to improve its performance. This thesis was started thanks to a two year grant (from summer 2000 to summer 2002) at the ESTEC centre of the European Space Agency in the Netherlands. During this time the first experimental campaigns aimed to test calibration methods and imaging capabilities of MIRAS were done. In these so called image validation tests a first MIRAS prototype was used. The planning, preparation, execution and data processing for different tests was done. The capability of the calibration methods was demonstrated, showing also in which direction further research should be undertaken in order to refine them. The imaging properties of MIRAS were also demonstrated with the measurement of its impulsional response. The most important results are presented here. At the ESTEC centre theoretical work and simulations on polarimetric interferometry have also been done. This research contributed to the formulation of the polarimetric visibility function and the definition of the polarimetric operation mode of MIRAS. After the two years stage at ESTEC, the thesis was continued at the Laboratory of Space Technology (LST) of the Helsinki University of Technology (HUT) for three months (August 2002 to October 2002), as an invited researcher. There the HUT-2D interferometric radiometer, an airborne demonstrator instrument for MIRAS, was being constructed. The experience gained in the previous campaigns was shared with the HUT-2D team and the calibration methods were tested in a different instrument, confirming the previous results. In February 2003 this thesis was continued at the Institut d'Estudis Espacials de Catalunya (IEEC) under a research contract of the Spanish ministry of research. There the effect of Faraday rotation on MIRAS was studied. A solution for compensating it was proposed, making use of the polarimteric operation mode of MIRAS. The thesis was continued at IEEC, designing and manufacturing the Electrical Ground Support Equipment (EGSE) of an airborne demonstrator of MIRAS, known as SAM (Small Airborne MIRAS). This work was done for ESA. This instrument implements the complete calibration scheme with two-level noise injection, which is arefinement of the calibration schemes used in previous MIRAS prototypes. Preliminary experimental results of this novel calibration technique are also presented in this thesis.

X-ray emission from classical novae

Estado: defended (22/09/2004)
Estudiante: Sala, G.
Supervisada por: Margarita Hernanz
Universidad: Universitat de Barcelona

To be included shortly
Estado: defended (22/09/2004)
Estudiante: Sala, G.
Supervisada por: Margarita Hernanz
Universidad: Universitat de Barcelona

To be included shortly

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function

Estado: defended (26/06/2002)
Estudiante: Barriga Carrasco, Jose
Supervisada por: Enrique Gaztañaga

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function. We present a new algorithm to compare the 3-point correlation function in theory and in N-body simulations. We also present a comparison of the power spectrum as measure…
Estado: defended (26/06/2002)
Estudiante: Barriga Carrasco, Jose
Supervisada por: Enrique Gaztañaga

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function. We present a new algorithm to compare the 3-point correlation function in theory and in N-body simulations. We also present a comparison of the power spectrum as measure by CMB and galaxy observations to test the the ci

Gravitational lensing with relativistic objects

Estado: defended (27/05/2002)
Estudiante: Ernesto Eiroa
Supervisada por: Diego F. Torres ; Romero, G.
Universidad: Universidad Nacional de Buenos Aires, Argentina

See the full record in the link below (from Fermilab library)
Estado: defended (27/05/2002)
Estudiante: Ernesto Eiroa
Supervisada por: Diego F. Torres ; Romero, G.
Universidad: Universidad Nacional de Buenos Aires, Argentina

See the full record in the link below (from Fermilab library)

Sea Surface Determination Using GNSS Reflected Signals

Estado: defended (08/03/2002)
Estudiante: Estel Cardellach Galí
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GNSS) are large, stable and calibrated sets of spaceborne L-band microwave transmitters with very well characterized properties. They provide global and permanent coverage as required by the meteorological, oceanographical and climate scientist. All these features…
Estado: defended (08/03/2002)
Estudiante: Estel Cardellach Galí
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GNSS) are large, stable and calibrated sets of spaceborne L-band microwave transmitters with very well characterized properties. They provide global and permanent coverage as required by the meteorological, oceanographical and climate scientist. All these features make the GNSS signal an appropriate candidate to be an excellent source of opportunity for bistatic monitoring of the Oceans' surface.

The dissertation 'Sea Surface Determination Using GNSS Reflected Signals' tackles the question of how the GNSS signal scattered off the ocean surface can be used to obtain geophysical information about the sea-air interface. The focus is put on the retrieval of the surface roughness and/or the wind.

The thesis defends a scatterometric approach where the distribution of the scattered power crosswise the illuminated area is used to infer the roughness of the surface. The distribution or mapping is achieved by parceling the sea area in cells whose scattered signal has different delay and frequency properties. This information is gathered in anobservable called waveform.

The structure of the thesis has been divided in three main parts: (a) the modeling of the scattered GNSS signal (GNSSr); (b) the feasibility study; and (c) the experimental validation.

The scatterometric GNSSr forward and backward models are presented. The former generates the waveform of the reflected signal as a function of the geometry of the scattering, instrumental parameters, as well as the roughness of the sea surface. The backward approach proposed at this level tries to infer the sea surface roughness characteristics of the illuminated area through the inversion of the waveform.

The expected performance of the scatterometric-GNSSr system is analyzed as a first order examination of its capabilities in terms of resolution and accuracy of the wind measurements. The aim of this part of the study is to determine how precisely can the wind be measured by the GPSr techniques proposed in the backward model, as wellas how can these observations cover the Oceans.
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya