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Preprint enviat per a la seva publicació en una revista científica: Predictability, Stability, and Chaos in N-Body Dynamical Systems , vol 272. pp 305-309. [https://doi.org/10.1007/978-1-4684-5997-5_26], We consider the motion around an oblate primary, keeping only the J2 term in the expansion of the potential in spherical harmonics. The problem has cylindrical symmetry. It has been suspected for a long time, due to numerical evidences, that the problem is non integrable. This has been proved recently [4]. However, even if the system is non integrable, the size of the stochastic zones can be so small that they can be neglected for all practica! purposes. This is what we study here, and we show that for the case of the Earth and considering possible real orbits, i.e., non colliding with the Earth, the effect of the non integrability can be completely neglected.

The design and performance of a 30-GHz mixer is presented. The mixer is to be used in the RF front end of an earth station for the OPEX experiment with the propagation beacons of the ESA's Olympus satellite. It uses a balanced approach in fin-line technology. Both the RF and OL ports are in waveguide·, which has required in particular the design of a waveguide/microstrip/edge-coupled fin-line transition for the OL injection. A conversion loss below 7.5 dB has been achieved in the 28-33 GHz frequency range .

Els proppassats dies 26 i 27 de maig se celebrà a Avinyó el IV Col·loqui Geopoint 82. El Grup Dupont proposava per enguany la discussió d'un tema que prometia ser molt interessant i suggeridor: Les territoires de la vie quotidienne. A títol introductori inicià les sessions M. Le Berre. Un cop definit el concepte de territori i tenint en compte que aquest terme presenta unes connotacions totalment diferents segons l'epoca (abans del segle XVII territori era sinònim de regne) i segons les diferents escoles geogràfiques, M. Le Berre se, centrà exclusivament en l'anàlisi de 1'ús d'aquest terme en la literatura geogràfica francesa, a partir de la lectura de les tesis regionals i de la Bibliografia Geogràfica Internacional. La conclusió principal a que arribà fou la relativa modernitat en la utilització del terme territori, emprat avui bàsicament de quatre formes diferents.

The concept of Satellite Formation Flying (SFF) means to have two or more satellites in orbit such that their relative positions remain constant or obeying a certain dynamical configuration along the trajectory. This concept involves the control over the coordinated motion of a group of satellites, with the goal of maintaining a specific geometric space configuration between the elements of the cluster. Assume a constellation of satellites is flying close a given nominal trajectory around L 4 or L 5 in the Earth-Moon system, in such a way that, there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, previous studies about triangular libration points have determined the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory that prevent from the expansion or contraction of the constellation. Similarly, these studies have also shown the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory that produce a larger expansion and contraction of the constellation. However, these studies only considered the gravitational force of the Earth and the Moon using as approximation the Circular Restricted Three Body Problem (CRTBP). Although the CRTBP model is a good approximation for the dynamics of spacecraft in the Earth-Moon system, the stability of constellations flying around L4 and L5 is strongly a ff ected when the primary orbit eccentricity and perturbations from the sun (gravity and light pressure) are considered. As consequence, the previous studies show that, using the CRTBP model, the fuel consumption to maintain the geometry of the constellation computed by the residual acceleration is practically zero. In this manner, the goal of this work is the study and analysis of the best regions to place a constellation that is flying close a given nominal trajectory around L 4 or L 5 , involving a linear approximation of the equations of motion relative to the periodic orbits around triangular libration points and taking into account the Moon’s eccentricity and perturbations from the Sun. This model is not only more realistic for practical engineering applications but permits to determine more accurately the fuel consumption to maintain the geometry of the constellation

The present work analyses the requirements related to the orbit and the effects of the space radiation on Polosat, a toy-model satellite whose main goal is to monitor and image the Earth Poles. Our main objective has been to work on the so-called phase A of the design of a space mission, in which a preliminary study of the viability and characteristics of the mission is made. We present this project as a coordinated work due to the fact that its competition required the use of two relatively complex software tools, as well as the achievement of extra theoretical background on orbital mechanics, radiation and its effects. One of the software tools was STK (Satellite Tool Kit). It allows to compute with realism and high degree of accuracy the time evolution of the kinematics of an object in orbit around the Earth. The other tool was SPENVIS (Space Environment Information System). It also computes the time evolution of the orbital parameters of an object -although with less option for realism and accuracy than STK, and the characteristics of the incident radiation and its effects of the orbiting object. Both software tools are used in professional and academic environments and, therefore, becoming familiar with them and their use has been an important and useful part of our work. We compare the results that STK and SPENVIS yield for the computation of the orbital kinematics in the cases where both tools are appropriate (cases with negligible atmospheric drag and limited intervals of time). We check that in such cases STK and SPENVIS results yield a very good agreement and, most importantly, we have found the procedure in which results from STK can be transferred to SPENVIS, in order to model the situations we are interested in. As we show, by using both codes, we can take advantage of both the powerful numerical tools of STK in order to study orbital mechanics, and the capabilities of SPENVIS in order to model the incidence of radiation and its effects on the spacecraft. Finally, we have concluded that both STK and SPENVIS are convenient tools for developing the proposed project and have determined the way in which we can use them in order to accomplish our objectives.

We demonstrate that, for the baseline design of the CORE satellite mission, the polarized foregrounds can be controlled at the level required to allow the detection of the primordial cosmic microwave background (CMB) B-mode polarization with the desired accuracy at both reionization and recombination scales, for tensor-to-scalar ratio values of rgsim 5× 10−3. We consider detailed sky simulations based on state-of-the-art CMB observations that consist of CMB polarization with τ=0.055 and tensor-to-scalar values ranging from r=10−2 to 10−3, Galactic synchrotron, and thermal dust polarization with variable spectral indices over the sky, polarized anomalous microwave emission, polarized infrared and radio sources, and gravitational lensing effects. Using both parametric and blind approaches, we perform full component separation and likelihood analysis of the simulations, allowing us to quantify both uncertainties and biases on the reconstructed primordial B-modes. Under the assumption of perfect control of lensing effects, CORE would measure an unbiased estimate of r=(5 ± 0.4)× 10−3 after foreground cleaning. In the presence of both gravitational lensing effects and astrophysical foregrounds, the significance of the detection is lowered, with CORE achieving a 4σ-measurement of r=5× 10−3 after foreground cleaning and 60% delensing. For lower tensor-to-scalar ratios (r=10−3) the overall uncertainty on r is dominated by foreground residuals, not by the 40% residual of lensing cosmic variance. Moreover, the residual contribution of unprocessed polarized point-sources can be the dominant foreground contamination to primordial B-modes at this r level, even on relatively large angular scales, ℓ ~ 50. Finally, we report two sources of potential bias for the detection of the primordial B-modes by future CMB experiments: (i) the use of incorrect foreground models, e.g. a modelling error of Δβs = 0.02 on the synchrotron spectral indices may result in an excess in the recovered reionization peak corresponding to an effective Δ r > 10−3; (ii) the average of the foreground line-of-sight spectral indices by the combined effects of pixelization and beam convolution, which adds an effective curvature to the foreground spectral energy distribution and may cause spectral degeneracies with the CMB in the frequency range probed by the experiment.

Surface soil moisture is a critical climate variable and strongly influences water and energy cycles at the surface-atmosphere interface. It is widely used to improve numerical climate and weather models, rainfall and drough estimation, vegetation monitoring, among others. Traditionally, there were two main ways to retrieve soil moisture data. On one hand, soil moisture sensors networks placed and maintained in situ to obtain long term distributed measurements, which is expensive and time-consuming. On the other hand, soil moisture data could be obtained by using numerical model products combined with ground observations. But, in both cases, the data resolution provided was not enough to characterize soil moisture at large scale. Nowadays, microwave remote sensing allows the global monitoring of soil moisture. SMOS (Soil Moisture and Ocean Salinity) mission, launched in 2009, was the first mission with this objective and providing an acceptable spatial resolution. It aims to monitor soil moisture over land surfaces, surface salinity over the oceans, and surfaces covered by snow and ice, by performing microwave radiometric measurements at L-band, characterized by being unaffected by cloud cover and variable surface solar illumination. The SMOS soil moisture data has a spatial resolution of 35-50 km, which is enough for global applications. But, local applications such as hydrological, fire prevention, agricultural and water management, require higher soil moisture resolution. In order to cover this necessity, several downscaling methodologies have been developed to improve the spatial resolution. The Department of Signal Theory in the UPC developed a downscaling algorithm based on the synergistic usage of low resolution soil moisture map and data provided by other satellites, that computed soil moisture maps at 1 km resolution (Maria Piles, 2010 [32]). This algorithm combines the SMOS soil moisture with NDVI and LST measurements from Aqua and Terra missions obtained by MODIS instrument. Later, this algorithm was improved by using an adaptive sliding window, which is the version we will use in this project (Gerard Portal, 2017 [24]). The aim of this project is to substitute the NDVI and LST measurements from MODIS used as ancillary data in the downscaling algorithm by the ones provided by Sentinel 3, comparing its differences and the variation of the high resolution soil moisture maps (SM HR maps) obtained. Also, it will include the evaluation of the data download and preparation process workflow.

Actualment existeixen programes capaços de treballar amb imatges de satèl·lit, però molts en forma de software propietari i subjectes, per tant, al pagament de llicències i als criteris de desenvolupament dels seus fabricants. El CMIMA (Centre Mediterrani d’Investigacions Marítimes i Ambientals), el centre de recerca per el qual es realitza aquest projecte, està interessat en un software capaç de realitzar les mateixes tasques que aquests programes però que es pugui adaptar millor a les seves necessitats, tant econòmiques com de disseny. La complexitat de generar aquest software és tal que no pot ésser assolida en un sol TFC (Treball de Fi de Carrera) donada la seva extensió, i és per això que aquest pretén ser sols un pas intermig. L’objectiu del projecte no serà el de crear aquest software, sinó el d’elaborar una documentació suficient a partir de la qual es pugui produir posteriorment, proporcionant una base solida sobre la que començar a programar. El sistema que es vol crear haurà de tenir en compte les característiques pròpies de les imatges de satèl·lit i els seus formats, i haurà de permetre realitzar les operacions de processat habituals que es fan amb elles, com ara la composició d’imatges multiespectrals o el reconeixement de superfícies. El punt de partida per al software és FWTools, un paquet de programes de lliure distribució que conté entre altres coses un visor de dades multiespectrals anomenat OpenEV. Aquest visor incorpora algunes de les funcions i estructures bàsiques per treballar amb imatges i és capaç d’incorporar nous mòduls en llenguatge Python. La plataforma compleix els requisits tant econòmics com de disseny, i és millor que altres opcions perquè implementa moltes de les estructures i funcions necessàries. Lamentablement, la manca d’informació disponible al respecte en dificulta el procés d’aprenentatge. A més, és obligatori el coneixement del llenguatge de programació Python, fet que en complica encara més l’adaptació. La realització del treball consta de tres fases. En la primera, és necessària una important tasca de documentació sobre FWTools i Python. Per tal d’aconseguir una millor familiarització amb els dos sistemes també es realitzaran algunes proves, com ara la programació de bucles o la lectura/escriptura de fitxers. En la segona fase es creen quatre aplicacions senzilles, destinades a servir d’exemple per a realitzar-ne de més complexes. S’ha intentat que les funcions implementessin les estructures i funcions més típiques, a fi de poder ser de màxima utilitat per al futur. La fase final ha consistit en l’elaboració del document que recull la informació recollida, intentant que pugui ser de màxima utilitat per als futurs projectes. També s’ha generat un document en format .html amb enllaços d’Internet per ésser penjat a la xarxa. El cos d’aquest document està dividit en tres parts. En la primera es situa al lector amb una breu explicació sobre les imatges de satèl·lit, la plataforma FWTools i les tasques concretes a realitzar en el projecte. En la segona part es presenta la informació sobre l’estructura i el funcionament útils per a la programació que s’ha obtingut de Python i FWTools. La tercera part consisteix en l’explicació dels passos que segueixen les quatre aplicacions d’exemple que s’han creat. Finalment, un breu apartat finalitza el document amb els resultats i les conclusions extretes. El text resultant del projecte ha resultat ser un bon punt de partida per a desenvolupar futures aplicacions, però la manca d’informació disponible sobre OpenEV ha fet allargar massa la primera fase, provocant que les quatre aplicacions creades a la segona fase no siguin excessivament complicades, tot i que assoleixen els objectius marcats prèviament. L’objectiu d’aquest treball és generar una documentació suficient com per poder crear, en posteriors projectes, un software a través del qual es pugui treballar amb dades generades a partir d’imatges de satèl·lit. El sistema haurà de tenir en compte les característiques pròpies d’aquestes imatges i permetre realitzar les operacions de processat habituals que es fan amb elles, com ara la composició d’imatges multiespectrals o el reconeixement de superfícies. Durant el treball realitzarem a més petites aplicacions d’exemple, però sempre prioritzant la generació de documentació a l’obtenció de resultats tècnics. El punt de partida per al projecte és FWTools, un paquet de programes de lliure distribució que conté entre altres coses un visor de dades multiespectrals anomenat OpenEV. Aquest visor incorpora algunes de les funcions i estructures bàsiques per treballar amb imatges i és capaç d’incorporar nous mòduls en llenguatge Python. Per tal d’assolir els objectius, el primer que serà necessari és una fase de documentació, en la qual ens haurem de familiaritzar tant amb l’entorn OpenEV com amb el llenguatge de programació Python. En la següent fase es realitzaran unes petites aplicacions que puguin servir d’exemple, on s’intentarà que apareguin les estructures i funcions més útils per a la programació de mòduls d’OpenEV. En la darrera fase es generarà un document que reculli tota la informació obtinguda, i que pugui servir com a punt de partida per posteriors projectes basats en l’OpenEV. També es crearà una versió del document en format .html que contingui enllaços d’Internet i que es pugui penjar a la xarxa. El document resultant del projecte ha resultat ser un bon punt de partida per a desenvolupar aplicacions, però la manca d’informació disponible sobre OpenEV ha fet allargar massa la primera fase, provocant que les dues aplicacions creades a la segona fase no siguin excessivament complicades, tot i que assoleixen els objectius marcats prèviament.

Multibeam satellite systems have been recently studied in order to provide broadband services to their coverage area by employing fractional frequency reuse pattern. Towards a more spectrally efficient system, the designer can resort to full frequency reuse among beams with on-ground extra signal processing as a precoding or detecting scheme for limiting the interbeam interference. These techniques have shown great potential in the multibeam system architecture. However, feeding all these data from a single gateway is not feasible based on the current frequency bandwidth resources utilized on the feeder link. In this paper, the focus is set on the forward link of a multibeam satellite system where full frequency reuse among beams with linear precoding technique is considered. In this context, we investigate a multiple gateway scenario where each gateway is serving a cluster of adjacent beams. Note that with a multiple gateway architecture, the feeder link spectral resources can be shared by all the gateways since they use directive antennas so that interference is minimized and the spectral efficieny of the feeder link system is increased. We present a novel multiple gateway Zero Forcing (ZF) precoder design which mitigates both the inter and intra-cluster interference. The provided simulation results quantify the performance gain obtained by our method.

The purpose of this design is a new type of planar antenna with hi gh-efficency and large-bandwidth requirements of TVRO. A low loss suspended substrate line (SSL ) has been developed and optimisated for feed network.

[ANGLÈS] Several correlation algorithms for satellite and aerial images are studied in this project to detect homologous key-points. These key-points are used to georeference images. Particularly, of a metric based on information theory is used to correlate images of different nature (optical spectrum, infrared, SAR, etc..). [CASTELLÀ] En este proyecto se estudian diferentes métodos de correlación de imágenes satelitales y aéreas para la detección de puntos homólogos. Estos puntos se utilizan en la georeferenciación de las imágenes. En particular se estudia la utilidad de una métrica basada en la teoría de la información para correlar imágenes de diferente naturaleza (imágenes en espectro visible, espectro infrarrojo, SAR, etc). [CATALÀ] En aquest projecte s'estudien diferent mètodes de correlació d'imatges de satèl·lit i aèries per a la detecció de punts homòlegs. Aquests punts s'utilitzen per a la georefenciació de les imatges. En particular s'estudia la utilitat d'una mètrica basada en la teoria de la informació per correlar imatges de diferent natura (imatges en espectre visible, infraroig, SAR, etc).