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In the present thesis, a MatLab simulator originally designed to calculate connections between satellites and ground stations has been expanded to include airplane routes and their respective connections. The goal is to provide an accurate and efficient ground-air-space simulation tool for monitoring air connections, which will allow for improved air traffic efficiency and safety. Air transportation is one of the most widely used modes of transportation worldwide, and its efficiency and safety are of vital importance. Using satellites for monitoring airplanes is of utmost importance due to several reasons, including the ability to provide continuous global coverage, real-time data on aircraft parameters, improved air traffic management, and enhanced safety. The designed tool allows for the simulation of multiple aeroplanes and satellites, and automatically calculates the connections between aircraft and satellites and between satellites and ground stations. In addition, a module has been added to simulate and calculate connections between aircraft and ground stations. This project is part of the PLATHON project of the Polytechnic University of Catalonia, which aims to develop a simulator to study the communications between constellations of cubes and the Earth. The simulator developed in this thesis will be used as a basis for the study of the communication between cubes, airplanes and ground in the PLATHON project. Testing and validation of the simulator have been conducted, and it has been demonstrated to be an effective tool for simulating and monitoring air connections. In conclusion, this project represents a significant advance within the PLATHON project in the monitoring of air connections, and has proven to be a very useful and necessary tool for monitoring aircraft routes across the globe.

Aquest treball ha rebut finançament del programa europeu DISCOVERER (Disruptive Technologies for Very Low Earth Orbit Platforms, EC-H2020-737183) This thesis studies the complementarity of VLEO satellite technologies with existing solutions in the telecommunications market, both in the space and terrestrial sectors. All the characteristics and particularities of VLEO orbits are defined and explained in detail, showing advantages and disadvantages compared to traditional higher orbits. Study of the deployment of the satellite constellation concept within the New Space framework. Next, the business opportunities that can be generated by the introduction of VLEO technologies in the telecommunications market are studied, analysing the possible reshaping of each vertical market and how can they be most benefited. Finally, a business opportunity is proposed and qualitatively analysed in detail using the Value Proposition Canvas methodology.

Recently, there has been a paradigm shift in space missions. They no longer rely on a single satellite to achieve all the objectives of a mission. Responsibility is shared between devices that can communicate and share resources to achieve these objectives. This paradigm shift has increased the need to assess communication performance within FSS. Despite proposals for simulators and emulators to achieve this goal, none of them integrates the dynamics of satellites with their communications. This thesis presents two proposals and the implementation of one of them to extend the capabilities of the communication channel of the simulator developed by the NanoSat Lab of the UPC. Additionally, following the lines of the i2Cat Space Communications research group, a test bench is also presented to demonstrate the feasibility of a satellite contact emulator. As it will be demonstrated, developing such an emulator has not been possible. Finally, it is concluded that both parts of this thesis may converge. Thus, combining the possibilities offered by the current simulator with those available in the emulator under development. En el transcurso de los últimos años se ha observado un cambio en el paradigma en las misiones espaciales. Éstas ya no cuentan sólo con un único satélite que tenga que alcanzar todos los objetivos de una misión. Se reparte la responsabilidad entre diferentes dispositivos que son capaces de comunicarse y compartir recursos para alcanzar tales objetivos. De ese cambio de paradigma nace la necesidad de poder evaluar el comportamiento de las comunicaciones dentro de un FSS. A pesar de la existencia de simuladores y propuestas de emuladores para alcanzar tal objetivo, ninguno de ellos integra las dinámicas de los satélites con sus comunicaciones. En esta tesis, se presentan dos propuestas y la implementación de una de ellas para ampliar las capacidades del canal de comunicaciones del simulador desarrollado por NanoSat Lab de la UPC. Además, siguiendo las líneas del grupo de investigación de Comunicaciones Espaciales de i2Cat también se presenta un test-bed para demostrar la viabilidad de un emulador de contactos de satélites. Pues, como se va a demostrar, el desarrollador de uno como tal no ha sido posible. Por último, se concluirá que ambas partes de esta tesis puedan converger en algún momento combinando así las posibilidades que ofrece el actual simulador con las de un emulador que está en desarrollo. En el transcurs dels últims anys s’ha observat un canvi en el paradigma de les missions espacials. Aquestes ja no compten només d’un únic satèl·lit que hagi d’assolir tots els objectius d’una missió. Es reparteix la responsabilitat entre diferents dispositius els quals són capaços de comunicar-se i compartir recursos per tal d’assolir tals objectius. D’aquest canvi de paradigma neix la necessitat de poder avaluar el comportament de les comunicacions dins d’un FSS. Tot i l’existència de simuladors i propostes d’emuladors per assolir tal objectiu, cap d’ells integra les dinàmiques dels satèl·lits amb les seves comunicacions. En aquesta tesi, es presenten dues propostes i la implementació d’una d’elles per tal d’ampliar les capacitats del canal de comunicacions del simulador desenvolupat pel NanoSat Lab de la UPC. A més a més, seguint les línies del grup de recerca de Comunicacions Espacials d'i2Cat també es presenta un test-bed per tal de poder demostrar la viabilitat d’un emulador de contactes de satèl·lits. Doncs, com es demostrarà, el desenvolupant d’un com a tal no ha estat possible. Finalment, es conclourà que ambdues parts d'aquesta tesi puguin convergir en algun moment combinant així les possibilitat que ofereix l'actual simulador amb les d’un emulador que està en desenvolupament

We have recently been able to witness how large companies have set themselves the goal of launching fleets of hundreds or even thousands of satellites to offer different services. This new generation of satellites is marking a clear trend to reduce their size and cost. However, this also leads to increasingly demanding challenges and constraints that require innovative solutions in the design of small-size, high-capacity communications systems. The present work offers the complete process from the design, to the implementation and test of a communications system for PocketQube picosatellites. The proposed solution benefits from LoRa technology, and includes both the hardware part of the communications subsystem and software for its configuration and operation according to the defined protocol. Finally, this project has been designed and integrated, and its compatibility and cooperation with the rest of the subsystems has been tested, for the PoCAT picosatellites developed at the UPC NanoSat Lab. Recientemente hemos podido presenciar como grandes compañías se han marcado el objetivo de lanzar flotas de cientos o incluso miles de satélites para ofrecer diferentes servicios. Esta nueva generación de satelites está marcando una clara tendencia a reducir el tamaño y coste de éstos. Sin embargo, esto también conlleva retos y restricciones cada vez más exigentes que necesitan soluciones inovadoras en el diseño de sistemas de comunicaciones de tamaño reducido y alta capacidad. El presente trabajo ofrece el proceso completo desde el diseño, pasando por la implemetación y test, de un sistema de comunicaciones para picosatelites PocketQube. La solución propuesta se beneficia de la tecnología LoRa, y comprende tanto la parte de hardware del subsistema de comunicaciones, como el software para su configuración y funcionamiento según el protocolo definido. Finalmente, este proyecto ha sido diseñado e integrado, y se ha probado su compatibilidad y cooperación con el resto de subsistemas, para los picosatellites PoCAT desarrollados por el UPC NanoSat Lab. Recentment, hem pogut presenciar com grans companyies s'han marcat l'objectiu de llançar flotes de centenars o fins i tot milers de satèl·lits per oferir diferents serveis. Aquesta nova generació de satèl·lits està marcant una clara tendència a reduir-ne la mida i el cost. No obstant, això també comporta reptes i restriccions cada vegada més exigents que necessiten solucions innovadores en el disseny de sistemes de comunicacions de mida reduïda i alta capacitat. Aquest treball ofereix el procés complet des del disseny, passant per la implementació i test, d'un sistema de comunicacions per a picosatèl·lits PocketQube. La solució proposada es beneficia de la tecnologia LoRa, i comprèn tant la part de hardware del subsistema de comunicacions, com el software per a la seva configuració i funcionament segons el protocol definit. Finalment, aquest projecte ha estat dissenyat i integrat, i s’ha provat la seva compatibilitat i cooperació amb la resta de subsistemes, pels picosatèl·lits PoCAT desenvolupats per l'UPC NanoSat Lab.

UPC NanoSat Lab is a laboratory located in the Universitat Politècnica de Catalunya, which is focused on the design and development of nano and picosatellite spacecrafts. This type of platforms have significant limitations in dimensions and structure. Nevertheless, due to its reduced cost, there is a high momentum as many companies and universities are investing their resources in innovative applications for Earth observation and communications. This thesis is part of a UPC NanoSat Lab project for the IEEE Geoscience and Remote Sensing Society called "Open PocketQube Kit". It aims at developing different educational PocketQubes, a type of picosatellite with a 5 cm cube size, which will be integrated in the 3Cat-8 mission. Precisely, this final degree thesis is focused on the design and implementation of the electrical power supply for these spacecrafts as well as a thermal analysis study for the whole of the structure. El UPC NanoSat Lab es un laboratorio de la Universidad Politécnica de Cataluña, que se centra en el diseño y desarrollo de nano y picosatélites. Este tipo de plataformes tienen limitaciones significativas en dimensiones y potencia. Sin embargo, debido a su coste reducido, existe un impulso creciente por parte de muchas empresas y universidades que estan invirtiendo sus recursos en aplicaciones innovadoras de observación terrestre y comunicaciones. Este trabajo de final de grado forma parte de un proyecto del UPC NanoSat Lab para la IEEE Geoscience and Remote Sensing Society titulado "Open PocketQube Kit" que tiene como objectivo desarrollar diferentes PocketQubes educativos, un tipo de picosatélites con forma de cubo de 5 cm de tamaño, los cuales irán integrados dentro de la misión del 3Cat-8. Precisamente, este trabajo de final de grado está centrado en el diseño e implementación del subsistema de alimentación eléctrica de estas plataformas así como un análisis térmico del conjunto de toda la misión. L'UPC NanoSat Lab és un laboratori de la Universitat Politècnica de Catalunya, focalitzat en el disseny i desenvolupament de nano i picosatèl·lits. Aquest tipus de plataformes tenen limitacions significatives en dimensions i potència. Tanmateix, degut al seu reduït cost, existeix un impuls creixent per part de moltes empreses i universitats que estan invertint els seus recursos en aplicacions innovadores d'observació terrestre i comunicacions. Aquesta treball de fi de grau forma part d'un projecte de l'UPC NanoSat Lab per l'IEEE Geoscience and Remote Sensing Society titulat "Open PocketQube Kit". Aquest projecte té com a objectiu desenvolupar diferents PocketQubes educatius, un tipus de picosatèl·lits, amb forma de cub de 5 cm de mida, que aniran integrats dins de la missió del 3Cat-8. Precisament, aquest treball de fi de grau està centrat en el disseny i implementació del subsistema d'al·limentació elèctrica d'aquestes plataformes així com un anàlisi tèrmic pel conjunt de tota la missió.

NASA JPL ha dissenyat un nou model numèric determinístic de propagació per carac- teritzar el canal entre un transmissor a la Lluna i un receptor a la Terra. En concret, el transmissor pot ser un rover o una estació base a la superfície i el receptor serà generalment una antena de la Deep Space Network (DSN). El model té en compte les reflexions provo- cades per la superfície lunar i obté la caracterització completa de la propagació del retard i del Doppler, entre d’altres aspectes d’interès com la potència rebuda total de les reflexions, etc. Les entrades del model són la definició de la superfície lunar amb un Digital Elevation Map i de la rugositat del sòl amb els paràmetres del RMS del pendent, entre d’altres. El càlcul de les reflexions multicamí es duu a terme a través d’una discretització del mapa en facetes i amb l’aproximació de rajos de Geometria Òptica. Seguidament, es valida el model en dos passos. El primer, veure l’ajust entre la simplifi- cació teòrica d’un model de dos rajos (raig directe en línia de visió i un únic raig reflectit) modelant la Lluna com una esfera perfecta i llisa. El segon, verificar els resultats del model en un cas real comparant-los amb les dades empíriques disponibles mesurades a través de la DSN i el Lunar Reconaissance Orbiter (LRO). Els resultats obtinguts es mostren en gràfiques comparatives i amb mètriques com ara el progrés de la propagació del Doppler en funció del temps. NASA JPL ha diseñado un nuevo modelo numérico determinístico de propagación para caracterizar el canal entre un transmisor en la Luna y un receptor en la Tierra. En concreto, el transmisor puede ser un rover o una estación base en la superficie y el receptor será generalmente una antena de la Deep Space Network. El modelo contempla las reflexiones provocadas por la superficie lunar y obtiene la caracterización completa de la propagación del retraso y del Doppler, entre otros aspectos de interés como la potencia recibida total de las reflexiones, etc. Las entradas del modelo son la definición de la superficie lunar con un Digital Elevation Map y de la rugosidad del suelo con los parámetros del RMS de la pendiente, entre otros. El cálculo de las reflexiones multicamino se realiza a través de una discretización del mapa en facetas y con la aproximación de rayos de Geometría Óptica. Seguidamente, se valida el modelo en dos pasos. El primero, ver el ajuste entre la simplificación teórica de un modelo de dos rayos (rayo directo en línea de visión y un único rayo reflejado) modelando la Luna como una esfera perfecta y lisa. El segundo, verificar los resultados del modelo en un caso real comparándolos con los datos empíricos disponibles medidos a través de la DSN i el Lunar Reconaissance Orbiter (LRO) Los resultados obtenidos se muestran en gráficas comparativas y con métricas como el progreso de la propagación del Doppler en función del tiempo. NASA JPL designed a new deterministic numerical propagation model to characterize the channel between a transmitter on the Moon and a receiver on Earth. Specifically, the transmitter may be a rover or a surface base station, and the receiver will generally be a Deep Space Network (DSN) antenna. The model takes into account the reflections caused by the lunar limb and obtains the complete characterization of the delay and Doppler spread, among other aspects of interest such as the total received power of the reflections, etc. The model inputs are the definition of the lunar surface with a Digital Elevation Map, and the roughness of the ground specified using parameter such as the slope Root Mean Square, among others. The calculation of the multipath reflections is carried out through a discretization of the map in facets and using the Geometric Optics approximation. The model is validated in two steps. First, it is compared the fit between the theoretical simplification of a two-ray model (direct ray in line of sight and a single reflected ray) assuming the Moon is a perfect, smooth sphere. Second, the results of the model are verified in a real case by comparing them with the available empirical data measured using the DSN and the Lunar Reconaissance Orbiter (LRO). The results obtained are shown in comparative graphs and with metrics such as the evolution of the Doppler spread as a function of time.

With the entry barrier for conventional small satellites continuously increasing for uni- versities and researches, this thesis means to promote a more accessible option in the form of a single unit picosatellite (1P). In this report, the design, implementation and testing procedures, alongside with the general mode of operation of these otherwise called PocketQubes will be presented. Three different configurations will be defined by means of three payloads: a VGA camera and two RFI Monitoring Receivers, at L-band and K-band. The avionics, constituting of an EPS, OBC, COMMS and an ADCS will remain mostly unchanged between the three variants. An IEEE GRSS initiative, the project has taken place, from designing to implementation and testing, within UPC?s NanoSat Lab, and is scheduled to be delivered in the shape of a kit, containing the Flight Models fully equipped with a set of manuals and tutorials for assembly, testing and operation, at the end of 2022. Additionally, a flight opportunity is envisioned for two of these PocketQubes aboard the NanoSat Lab?s future 3Cat-8 mission. Con la barrera de entrada de los pequeños satélites convencionales en continuo aumento para las universidades e investigadores, esta tesis pretende promover una opción más accesible en forma de un picosatélite de una sola unidad (1P). En este informe, el diseño, la implementación y los procedimientos de prueba, junto con el modo general de funcionamiento de estos, también llamados PocketQubes, serán presentados. Se definirán tres configuraciones diferentes mediante tres cargas útiles: una cámara VGA y dos receptores de monitorización RFI, uno en banda L y otro en banda K. La aviónica, constituida por los subsistemas EPS, OBC, COMMS y ADCS, permanecer a prácticamente sin cambios entre las tres variantes. El proyecto, una iniciativa del GRSS del IEEE, se ha llevado a cabo desde el diseño hasta la implementación y las pruebas en el NanoSat Lab de la UPC, y está previsto que se entregue en forma de kit, conformado por los modelos de vuelo Amb la barrera d’entrada als petits satèl·lits convencionals en augment continu per a les universitats i investigadors, aquesta tesi tracta de facilitar l’accés a una opció més assequible, en forma d’un picosatèl·lit d’1P. En aquest treball es presenten els procediments de disseny, implementació i proves realitzades, conjuntament amb els modes generals de funcionament d’aquests satèl·lits, anomenats PocketQubes. Es definiran tres configuracions diferents, segons la carrega útil a bord: una càmera VGA i dos sensors de RFI, un en banda L i l’altre en banda K. L’aviònica, constituïda per una EPS, una OBC, un sistema COMMS i el mòdul ADCS, romandrà pràcticament sense alteracions entre els tres models. Aquest projecte és una iniciativa del GRSS de l’IEE, i s’ha executat, des del disseny fins a la implementació i verificació, a les instal·lacions del NanoSat Lab de la UPC, i està pendent de ser entregat com a kit complet, incloent-hi els models de vol i el conjunt de manuals i tutorials de muntatge, proves i la operació, a finals de 2022. A més, es preveu una oportunitat de vol per a dos d’aquests PocketQubes a bord de la futura missió 3Cat-8 del NanoSat Lab.

Els nivells de flexibilitat i escalabilitat mai vistos de la propera generació de sistemes de comunicació per satèl·lit exigeixen nous algorismes de gestió de recursos que s'adaptin a contextos dinàmics. El futur entorn dels serveis de comunicació per satèl·lit estarà definit per un nombre més gran d'usuaris, una gran part dels quals correspondrà a usuaris mòbils com avions o vaixells. El repte addicional que introdueixen aquests usuaris és abordar la incertesa espai-temporal que es presenta en forma de retards, canvis en la seva trajectòria, o tots dos. Atès que els usuaris mòbils constituiran un segment important del mercat, els operadors de satèl·lits prioritzen l'aprofitament dels avançats sistemes digitals per desenvolupar estratègies flexibles d'assignació de recursos que siguin robustes davant de les bases d'usuaris dinàmiques. Un dels problemes clau en aquest context és com gestionar l'espectre de freqüències de manera eficient. Mentre que nombroses solucions aborden escenaris d'assignació de dinàmica freqüències, el nivell addicional de complexitat que presenten els usuaris mòbils no ha estat prou estudiat, i no és clar si els nous algorismes d'assignació de freqüències poden abordar la incertesa espai-temporal. Concretament, sostenim que els canvis inesperats en la posició dels usuaris introdueixen noves restriccions en l'assignació de freqüències que els algoritmes la literatura podrien no ser capaços de complir, especialment si les decisions s'han de prendre en temps real i a escala. Per solucionar aquesta limitació, proposem un algorisme de gestió dinàmica de freqüències basat en programació lineal entera que assigna recursos a escenaris amb usuaris tant fixos com mòbils, tenint en compte la incertesa espai-temporal d'aquests últims. El nostre mètode inclou tant la planificació a llarg termini com l'operació en temps real, una sinergia que no ha estat prou explorada per a les comunicacions per satèl·lit i que és crítica quan s'opera sota incertesa. P Los niveles de flexibilidad y escalabilidad nunca vistos de la próxima generación de sistemas de comunicación por satélite exigen nuevos algoritmos de gestión de recursos que se adapten a contextos dinámicos. El futuro entorno de los servicios de comunicación por satélite estará definido por un mayor número de usuarios, una gran parte de los cuales corresponderá a usuarios móviles como aviones o barcos. El reto adicional que introducen estos usuarios es abordar la incertidumbre espacio-temporal que se presenta en forma de retrasos, cambios en su trayectoria, o ambos. Dado que los usuarios móviles constituirán un segmento importante del mercado, los operadores de satélites dan prioridad al aprovechamiento de los avanzadas sistemas digitales para desarrollar estrategias flexibles de asignación de recursos que sean robustas frente a las bases de usuarios dinámicas. Uno de los problemas clave en este contexto es cómo gestionar el espectro de frecuencias de forma eficiente. Mientras que numerosas soluciones abordan escenarios de asignación dinámica de frecuencias, el nivel adicional de complejidad que presentan los usuarios móviles no ha sido suficientemente estudiado, y no está claro si los nuevos algoritmos de asignación de frecuencias pueden abordar la incertidumbre espacio-temporal. En concreto, sostenemos que los cambios inesperados en la posición de los usuarios introducen nuevas restricciones en la asignación de frecuencias que los algoritmos la literatura podrían no ser capaces de cumplir, especialmente si las decisiones deben tomarse en tiempo real y a escala. Para solventar esta limitación, proponemos un algoritmo de gestión dinámica de frecuencias basado en la programación lineal entera que asigna recursos en escenarios con usuarios tanto fijos como móviles, teniendo en cuenta la incertidumbre espacio-temporal de estos últimos. Nuestro método incluye tanto la planificación a largo plazo como la operación en tiempo real, una sinergia que no ha sido suficient The unprecedented levels of flexibility and scalability of the next generation of communication satellite systems call for new resource management algorithms that adapt to dynamic environments. The upcoming landscape of satellite communication services will be defined by an increased number of unique users, a large portion of which will correspond to mobile users such as planes or ships. The additional challenge introduced by these users is addressing the spatiotemporal uncertainty that comes in the form of delays, changes in their trajectory, or both. Given that mobile users will constitute an important segment of the market, satellite operators prioritize leveraging modern digital payloads to develop flexible resource allocation strategies that are robust against dynamic user bases. One of the key problems in this context is how to manage the frequency spectrum efficiently. While numerous solutions address dynamic frequency assignment scenarios, the additional layer of complexity presented by mobile users has not been sufficiently studied, and it is unclear whether novel frequency assignment algorithms can address spatiotemporal uncertainty. Specifically, we argue that unexpected changes in the position of users introduce new restrictions into the frequency assignment, which previous algorithms in the literature might not be able to meet, especially if decisions need to be made in real-time and at scale. To address this gap, we propose a dynamic frequency management algorithm based on integer linear programming that assigns resources in scenarios with both fixed and mobile users, accounting for the spatiotemporal uncertainty of the latter. Our method includes both long-term planning and real-time operation, a synergy that has not been sufficiently explored for satellite communications and proves to be critical when operating under uncertainty. To fulfill the problem’s scope, we propose different strategies that extend a state-of-the-art frequency management alg Outgoing

Satellite simulators, such as STK, implement accurate models of the spacecrafts astrodynamics, which is crucial for some analyses. However, these simulators are insufficient simulating the networking aspects of satellites. For that reason the Distributed Satellite Systems (DSS) simulator has been implemented. The DSS is based on Network Simulator-3 (NS-3),and it is used to simulate communications of spacecrafts and constellations. The simulator allows to obtain metrics of contacts between the ground station and the satellite, and also of communications between satellites. I Distributed Satellite Systems (DSS), composed of multiple spacecraft units orbiting around the Earth, are becoming increasingly popular due to their ability to satisfy short revisit times and responsiveness. Furthermore, these DSS may be equipped with inter satellite communications and networking capabilities. Simulation techniques and computational support are required to develop and optimize such satellite structures. As a result, the major goal of the "DSS-Sim" (Distributed Satellite Systems Simulator), a project currently under development at the UPC NanoSat Lab, is to replicate all parts of this type of in-orbit architecture and analyse a variety of system-level properties. In this regard, this thesis describes the design and implementation in the DSS-Sim of two additional MAC protocols: an Aloha and a CSMA/CA MAC protocol. This thesis presents the design and implementation of the MAC protocols mentioned above, and a test section that describes the validation procedures for these protocols implemented on the DSS-Sim. Los Sistemas de Satélites Distribuidos (DSS), están compuestos por múltiples unidades de satélites que orbitan alrededor de la Tierra. Estos DSS se están volviendo cada vez más populares debido a su capacidad para satisfacer tiempos de revisita cortos y su capacidad de respuesta. Además, estos DSS pueden estar equipados con comunicaciones internas por satélite y disponer de sistemas con capacidades de red. Sin embargo, se requieren técnicas de simulación y soporte computacional para desarrollar y optimizar dichas estructuras de satélites. Por ello, el gran objetivo del "DSS-Sim" (del inglés ‘Distributed Satellite Systems Simulator’), proyecto actualmente en desarrollo en el NanoSat Lab de la UPC, es replicar todas las partes de este tipo de arquitectura en órbita y analizar una variedad de propiedades a nivel del sistema. En este sentido, esta tesis describe el diseño e implementación en el DSS-Sim de dos protocolos MAC adicionales: el Aloha y un protocolo MAC CSMA/CA. Esta tesis presenta el diseño e implementación de los protocolos MAC mencionados anteriormente, y una sección de pruebas que describe los procedimientos de validación para estos protocolos implementados en el DSS-Sim. Els Sistemes de Satèl·lits Distribuïts (DSS), estan formats per múltiples satèl·lits que orbiten al voltant de la Terra. Aquests DSS s’estan tornant cada cop més populars a causa de la seva capacitat per satisfer temps de revisita curts i la seva gran capacitat de resposta. A més, aquests DSS poden estar equipats amb comunicacions per satèl·lit internes i sistemes amb capacitats de xarxa. Tanmateix es requereixen tècniques de simulació i suport computacional per desenvolupar i optimitzar aquestes estructures de satèl·lits. Com a resultat, el principal objectiu del ‘DSS-Sim’ (de l’anglès ‘Distributed Satellite Systems Simulator’), un projecte que actualment està en desenvolupament al NanoSat Lab de la UPC, és replicar les parts d’aquest tipus d’arquitectura en òrbita i analitzar una varietat de propietats a nivell del sistema. En aquest sentit, aquesta tesi descriu el disseny i la implementació en el DSS-Sim de dos protocols MAC addicionals: l’Aloha i un protocol MAC CSMA/CA. Aquesta tesi presenta el disseny i implementació dels protocols MAC esmentats anteriorment, i una secció de proves que descriu els procediments de validació d’aquests protocols implementats al DSS-Sim.

Having a quality connectivity service is key in the economic, educational and health development of today’s society. However, current communication systems are not capable of providing full community connectivity, leaving the most remote areas underserved. This project analyzes how the Telesat satellite operator, through its Telesat Lightspeed constellation, proposes a business model based on deploying 298 satellites in low Earth orbits (LEO) to face the most demanding telecommunications challenges, and close the digital divide between urban and rural communities by delivering a universal, fast and affordable internet service. Therefore, studying the benefits and applications of low Earth orbits, analyzing the characteristics of Telesat and its constellation of satellites, as well as examining how it intends to carry out its value proposition and the risks it faces, are the main points on which this thesis is based.

The use of Signals of Opportunity for Earth Observation is a hot topic nowadays. It consists of using signals already used for some purposes for other purposes, like remote sensing or navigation. The thesis mixes this concept with signals from P-band, a really interesting band because they can penetrate more than 20 cm in the soil, before being reflected, allowing us to estimate root-zone soil moisture values. The main objective of the project is to design a receiving system for Signals of Opportunity at P-band based on Software Defined Radio. This thesis reviews all the necessary parts of the whole system and the necessary software setup to have a complete receiver. On the other hand it has some results recorded for testing the receiving system and results of the process of finding suitable signals of Opportunity to develop our reflectometry studies with also a curious report on Intermodulation Distortion components being surprisingly well received. Results indicate that the receiving system works, but that the received interferences are a problem for the thesis objective, and further tests on different locations with different setups are needed to start having a first estimation of the root-zone soil moisture. El uso de Señales de Oportunidad para la teledetección es un tema de relevancia actualmente, consiste en usar señales preconcebidas para otras finalidades para tus propies intereses, como teledetección o para usar de señal de navegación. La tesis mezcla ese concepto con señales de banda P, una banda de frecuencias realmente interesante por el hecho de que las frecuencias que pertenecen a la banda son capaces de penetrar unos 20 cm en la tierra antes de reflejarse, permitiéndonos estimar valores de humedad en las raíces de la vegetación. El objetivo principal del proyecto es diseñar un sistema de recepción para señales de oportunidad en la banda P basado en una Radio Definida por Software (SDR). La tesis repasa todas las partes necesarias que componen el sistema entero y el software necesario para tener el setup del sistema de recepción completo. Por otro lado, incluye resultados grabados para probar el funcionamiento del sistema de recepción y el resultado del proceso de encontrar señales de oportunidad adecuadas para desarrollar estudios de reflectometría. La tesis también incluye un reporte curioso sobre Productos de Intermodulación siendo recibidos correctamente. Los resultados indican que el sistema de recepción funciona, pero las interferencias recibidas son un problema para los objetivos del proyecto. También indican que más test en diferentes localizaciones con diferentes configuraciones son necesarios para empezar a tener estimaciones de valores de humedad en las raíces de vegetación. L'ús de Senyals d'Oportunitat per a la teledetecció és un tema de rellevància actualment, consisteix a utilitzar senyals preconcebuts per altres finalitats pels teus propis interessos, com teledetecció o per utilitzar de senyals de navegació. La tesi combina aquest concepte amb senyals de banda P, una banda de freqüències realment interessants pel fet que les freqüències que pertanyen a aquesta banda estan capacitades de penetrar uns 20 cm a la terra abans de reflectir-se, permetent estimar valors d'humitat a les arrels de la vegetació. L'objectiu principal del projecte és dissenyar un sistema de recepció per senyals d'oportunitat a la banda P basat en una Ràdio Definida per Software (SDR). La tesi repassa totes les parts necessàries que componen el sistema sencer i el software necessari per tenir el "setup" del sistema de recepció complet. Per altra banda, inclou resultats gravats per provar el funcionament del sistema de recepció i el resultat del procés de trobar senyals d'oportunitat adequats per desenvolupar estudis de reflectometria. La tesis també aporta un informe curiós sobre Productes d'Intermodulació sent rebuts correctament. Els resultats indiquen que el sistema de recepció funciona, però les interferències rebudes són un problema pels propòsits del projecte. També indiquen que més test a diferents localitzacions amb diferents configuracions són necessaris per començar a tenir estimacions de valors d'humitat en les arrels de la vegetació.

Currently, about 40% of the world’s population has limited or no access to high-speed Internet. Especially in rural, hard-to-reach areas, there is a challenge in terms of infrastructure to guarantee a quality connection.The need for global coverage has led telecommunications service providers to explore new alternatives to traditional communication. This search has led to the development of a multitude of projects related to satellite constellations in LEO orbits, where a more economical business model has been found, capable of providing global coverage and high-speed connection. The growing interest in LEO communications has motivated this project. The objective of this thesis is to study communication links in a LEO constellation through link budget calculations. Both inter-satellite links and ground-satellite links will be evaluated in order to study the characteristics of each one. For this purpose, an orbit simulator has been used, where the necessary calculations have been introduced to evaluate the links according to parameters such as received power and SNR, among others. The results of this project are expected to determine the viability of communications in a constellation and the effect of the link budget parameters on the communications performance.

El present treball ha estat realitzat durant una estància de pràctiques a Sener Aeroespacial, una empresa del sector espacial que es dedica al desenvolupament de subsistemes de comunicacions per a satèl·lits científics i comercials. En aquest es descriu el disseny, anàlisi, mesures y resultats d’un generador de polsos de corrent que permet la commutació de circuladors amb guia de ferrita, i el disseny i anàlisi de circuits que permeten alimentar els dissenys de radiofreqüència. Ambdós formen tota la PCB d’alimentació i control del radiòmetre que s’embarcarà a la missió espacial CIMR (Copernicus Imaging Microwave Radiometer). El document comença amb una primera introducció a la missió i el satèl·lit, seguit d’un resum dels diferents commutadors de radiofreqüència utilitzats actualment. A continuació, es mostren tres blocs: el disseny electrònic, els anàlisi del disseny segons els estàndards de l’Agència Espacial Europea, i el disseny de la PCB. Finalment, el disseny final del generador de polsos és implementat i, al mateix temps, es detallen els procediments de mesura i els resultats obtinguts. El presente trabajo ha sido realizado durante una estancia de prácticas en Sener Aeroespacial, una compañía del sector espacial que se dedica al desarrollo de subsistemas de comunicaciones para satélites científicos y comerciales. En él se describe el diseño, análisis, medida y resultados de un generador de pulsos de corriente que permite la conmutación de circuladores en guía de ferrita, y el diseño y análisis de la circuitería que permite alimentar los diseños de radiofrecuencia. Ambos forman toda la PCB de alimentación y control del radiómetro que se embarcará en la misión espacial CIMR (Copernicus Imaging Microwave Radiometer). El documento comienza con una primera introducción a la misión y al satélite, seguido de un resumen de los diferentes conmutadores de radiofrecuencia usados actualmente. A continuación, se muestran tres bloques: el diseño electrónico, los análisis del diseño según los estándares de la Agencia Espacial Europea, y el diseño de la PCB. Finalmente, el diseño final del generador de pulsos es implementado y, al mismo tiempo, se detallan los procedimientos de medida y los resultados obtenidos. This work has been carried out during an internship at Sener Aeroespacial, a space dedicated company that deals with the development of communications subsystems for scientific and commercial satellites. It describes the design, analysis, measurements, and results of a current pulse generator that enables the switching of waveguide ferrite circulators, and the circuitry design and analysis to correctly bias the Radio Frequency equipment. Both form the entire power and control PCB for the radiometer that will be embarked on the CIMR (Copernicus Imaging Microwave Radiometer) space mission. The document starts with a first introduction to the mission and the satellite, followed by a brief summary of the different RF switches currently in use. Next, three blocks are shown: the electronic design, the design analyses according to European Space Agency standards, and the PCB design. Finally, the final design of the pulse generator is implemented, and the measurement procedures, as well as the results obtained, are detailed and discussed.

This project aims to study the quality of communication using nanosatellites in LEO orbits. The objective is to study the signal attenuation by radio frequency (RF) antennas between a nanosatellite and a ground station, or another nanosatellite. For this purpose, a MATLAB simulator is developed that allows the modeling of satellite orbits by using TLEs, orbital elements or Walker constellations. As for the communication parameters, different transmission frequencies and atmospheric propagation models can be used. As for the antennas, two different types are used: parabolic reflectors for ground stations and patch antennas for satellites. The quality of a communication link is determined by two different methods: using the received power or the signal-to-noise ratio in reception. In the case of received power, this should be higher than the sensitivity of the transceiver under study, while signal-to-noise takes into account different digital modulations that determine the probability of message loss. Thanks to this simulator, it is possible to obtain results that determine the visibility times between satellites and/or ground stations, and to determine if the communication for a given link meets the minimum communication requirements, as well as to calculate the transmission power necessary to meet these requirements. It also performs a 3D representation in which the orbits of the satellites as well as the ground stations can be observed.

The Global Satellite Tracking Initiative aims to support international students and young professionals to set up ground stations to download real-time data and images from satellites orbiting above their regions. The objective is to empower and build capabilities among space enthusiasts around the world and to promote the space sector through hands-on activities and real space technologies related to satellite communications. The Space Generation Advisory Council, together with SatNOGS as an integral part of the Libre Space Foundation, have been supporting the initiative to enhance the development of a global open source network of satellite ground stations. The initiative will be providing all the resources, hardware, and know-how that is needed to set up ground stations. A competition was launched by the end of 2021 to select teams of space enthusiasts and supply them with a kit and step-by-step instructions on how to build their own ground stations. By setting up ground stations in backyards, local universities, or maker clubs, teams are not only self-learning about telecommunications and satellite technologies, but they are creating a meaningful impact in their local communities by bringing the broad society closer to science, technology, engineering, mathematics and, in particular, space. The initiative also intends to support space missions while engaging local communities from different regions around the world in the space sector through appealing imagery and tools. After closing the Call for Applications in this pilot initiative, 10 winning teams were selected upon receiving almost 200 applications from more than 60 countries. The selected winners are based in the following emerging space faring nations: Benin, Bolivia, Egypt, Ethiopia, Nepal, Peru, Philippines, Rwanda, Vietnam, and Zimbabwe. They are being supplied with a basic Ground Station Kit and instructions on how to receive live images and data from different space missions, starting with the following frequency bands: - 137 megahertz: To receive images from National Oceanic & Atmospheric Administration satellites. - 144-146 megahertz: To receive images and data from the International Space Station. - 440 megahertz: To receive data from numerous scientific and educational small satellites. Those teams that manage to set up the basic ground station kits and conduct some outreach and educational activities will receive a more advanced system. This paper captures the process to be followed by the selected teams, from the unboxing of the hardware to the reception and processing of data from operational space missions.

This article addresses the problem of energy and code allocation to many users accessing, under spreading-based nonorthogonal multiple access, a wireless node set up with a successive interference cancellation architecture aided by redundancy-check error control. As an application, we consider the asynchronous access of a delay-tolerant satellite system, where users employ finite-length channel codes and are subject to a known power unbalance induced by the known distribution of the channel’s attenuation. The article develops, as a mathematically tractable approximation to massively populated systems, a unified framework to compute the best energy and code allocation rules that maximize the spectral efficiency of a network that handles asymptotically many users. Concretely, the presented approach circumvents the exponential complexity in the number of users when modeling the propagation of packet decoding failures through the receiver’s decoding scheme. It also enables a deterministic analysis of the more complex features affecting the receiver, making the related performance optimization problem amenable to systematic tools from differential and variational calculus. The derived expressions evidence the most favorable three-way unbalance between energy, rate, and reliability for receiver performance. Low-level system simulations are carried out for validation. This work was supported in part by the Spanish Ministry of Science and Innovation through project RODIN (PID2019-105717RB-C22/AEI/10.13039/501100011033) and in part by Grant 2017 SGR 578.

This paper addresses general space education for interdisciplinary audiences. In particular, this paper considers education in the field of Satellite Telecommunications (Sat-Comms). The challenge in presenting the field of sat-comms for effective learning is two-fold. Firstly, this field is interdisciplinary, the disciplines are coupled, and it is complex. Secondly, the typical audiences for this subject often have diverse backgrounds. Hence, a suitable teaching strategy is required, so that all students can learn from a training session. Publicly available sat-comms training is largely engineering focused. This study could not find suitable training for the purpose of interdisciplinary sat-comms education. Hence, to address this absence in available training, the author has created a workshop, which provides sat-comms education to interdisciplinary audiences. The workshop was empirically developed from the author’s experience at Inmarsat and at the International Space University. The workshop uses elements from Constructivist, Behaviourism, Cognitive, Connectivism, and Experiential learning theories. Furthermore, it was designed to be taught in person and online. The Sat-Comms Game was first trialled in an online format in 2021. The workshop worked well in engaging the participants during the session. Additionally, feedback on the workshop was positive. Hence, this trial indicated that the workshop could function logistically and engage people pedagogically. The author intends to conduct further trials and corresponding assessment methods to gauge the pedagogic effectiveness

The ESA ESEO Mission [1] included an amateur radio payload [2]. The results of which included the development of radio technologies that utilised final year student projects over a 5 year period. Many lessons regarding compliance and process enabled a new payload to follow: the Student Ranging Transponder Radio for X-band and L-band (or STAR-XL). The STAR-XL design leverages key aspects of the ESEO payload design for a generic CubeSat platform; including TT&C voltage and current sense circuitry, receiver circuitry, and flight software. But instead of a maximum 4800 bps telemetry and transponder system - the STAR- XL targets a 100 kHz bandwidth system that will allow faster downlink rates that are forward error correction, link margin and modulation order dependent. With 100 kHz bandwidth, the linear receiver is designed to also operate as a transponder - enabling ranging and navigation applications such as orbit determination and further experiments from amateur radio groundstations. This paper details the recent student project efforts in three key areas: a new STM32-based on-board computer, an X-band up-converter board and dual X/L band patch (as shown in Fig. 1). The new OBC includes an IQ modulator for transmitting complex waveforms and an optimised flight software suite that takes advantage of dual DMA hardware on-chip to reduce overheads. The X-band upconverter board required the development of new safety interlock and RF chain circuitry on a Rogers (RO4350B) PCB material. A new dual X/L-band patch antenna and filter circuit is also built and measured. Each of these projects has led to new lessons and increased the real-world case studies used to teach spacecraft avionics.

Communication links over satellites allow interconnecting very distant regions to provide service where the terrestrial networks are limited. In this scenario, it is of major importance to devise mechanisms accounting for the improved freshness of packets given the impact of large distances. Their analysis is particularly important when considering the deployment of sensors in remote areas, where satellite links may introduce a high delay in the communication system. In this respect, we report the use of age of information (AoI) metrics to evaluate users' allocation mechanisms. We use power-domain non-orthogonal multiple access (NOMA) as an alternative to orthogonal multiple access (OMA) to optimally reduce the age of received packets. We derive the proper formulation to account for a fairness condition when pairing users accounting for both; the user's needs to transmit information and the allowable link rate. Comparative results are provided by numerically evaluating the solution for NOMA and OMA accounting for the peak age of information (PAoI) metric. We show that the resource allocation mechanisms in NOMA results in less PAoI (40%) compared to OMA. We remark this result through extensive numerical simulations based on actual uplink satellite communication links accounting for 500 users. This work has been supported by the Spanish National Project IRENE (PID2020-115323RB-C31, PID2020- 115323RB-C33 / AEI / 10.13039/501100011033).

Next-generation satellite systems require more flexibility in resource management such that available radio resources can be dynamically allocated to meet time-varying and non-uniform traffic demands. Considering potential benefits of beam hopping (BH) and non-orthogonal multiple access (NOMA), we exploit the time-domain flexibility in multi-beam satellite systems by optimizing BH design, and enhance the power-domain flexibility via NOMA. In this paper, we investigate the synergy and mutual influence of beam hopping and NOMA. We jointly optimize power allocation, beam scheduling, and terminal-timeslot assignment to minimize the gap between requested traffic demand and offered capacity. In the solution development, we formally prove the NP-hardness of the optimization problem. Next, we develop a bounding scheme to tightly gauge the global optimum and propose a suboptimal algorithm to enable efficient resource assignment. Numerical results demonstrate the benefits of combining NOMA and BH, and validate the superiority of the proposed BH-NOMA schemes over benchmarks. This work was supported in part by the Luxembourg National Research Fund (FNR) CORE projects ROSETTA (under grant C17/IS/11632107) and FlexSAT (under grant C19/IS/13696663).

Zero-Forcing (ZF) and Regularized Zero-Forcing (RZF) precoding are low-complexity sub-optimal solutions widely accepted in the satellite communications community to mitigate the resulting co-channel interference caused by aggressive frequency reuse. However, both are sensitive to the conditioning of the channel matrix, which can greatly reduce the achievable gains. This paper brings the attention to the benefits of a design that allows some residual received interference power at the co-channel users. The motivation behind this approach is to relax the dependence on the matrix inversion procedure involved in conventional precoding schemes. In particular, the proposed scheme aims to be less sensitive to the user scheduling, which is one of the key limiting factors for the practical implementation of precoding. Furthermore, the proposed technique can also cope with more users than satellite beams. In fact, the proposed precoder can be tuned to control the interference towards the co-channel beams, which is a desirable feature that is not met by the existing RZF solutions. The design is formulated as a non-convex optimization and we study various algorithms in order to obtain a practical solution. Supporting results based on numerical simulations show that the proposed precoding implementations are able to outperform the conventional ZF and RZF schemes. This work has been partially supported by the Luxembourg National Research Fund (FNR) under the project FlexSAT (C19/IS/13696663) and by the ministry of Science, Innovation and Universities, Spain, under project TERESA-TEC2017-90093- C3-1-R (AEI/FEDER, UE).

The space market is experiencing a tremendous transformation with private companies taking the lead and launching an increasing number of satellites. Up until recently, geostationary orbits were the most used for commercial exploitation, however, in recent years Low and Very Low Earth Orbits have been playing a very important role in the evolution of the space market. While the Earth Observation industry has continued developing, the last couple of years have seen the focus shifting towards telecommunications. As part of the Discoverer project, which is developing terrestrial observation satellites for Very Low Earth Orbits, this study aims to look beyond observation satellites to propose a market for satellites in the Internet of Tomorrow technologies. During the course of this project the American company Starlink has been gaining traction in their goal to create a constellation of satellites in Low and Very Low Earth Orbits to provide internet in all remote parts of the planet, A business plan has been made in which Discoverer could develop satellites for low and very low orbits with a focus on telecommunications use. As part of the study, business opportunities have been proposed and, above all, the greatest emerging competitor, Starlink, has been analyzed.

This paper proposes a hybrid network architecture combining a cell-free Massive MIMO terrestrial layout with a low Earth orbit satellite segment jointly targeting the maximization of the minimum per-user rate in the coverage area. Towards this end, an optimization framework is proposed, alongside a greedy solution, that diverts the terrestrial users experiencing poor propagation conditions to the satellite segment. Simulation results show the substantial benefits this integrated approach brings along, very specially when the terrestrial segment operates single-antenna access points or is sparsely deployed., Grant numbers : TERESA - Hybrid TERrEstrial/Satellite Air Interface for 5G and Beyond (TEC2017-90093-C3-1-R).

During the last years, satellite systems have evolved from monolithic spacecraft to distributed architectures. These new architectures are based on a group of satellites that works to achieve a common goal or mission. Among the different distributed architectures, the Federated Satellite System concept is the more promising one for Earth Observation. This novel concept aims at establishing win-win collaborations between the satellites to share unallocated resources, such storage capacity or downlink opportunities. The deployment of this concept requires the development of new technologies and the necessary equipment to perform it. In particular, a simulation engine that represents the interaction between the satellites becomes a crucial facility. Among the different simulation engines, no one is able to integrate satellite dynamics and communications interaction. These two features are essential to correctly represent the interaction of the satellites in a federation. For this reason, a dedicated simulator was developed by the NanoSat Lab research group in UPC. This engine provides a simulation framework in which satellites can be defined with different modules that represents the satellite resources, and the corresponding protocols to interact between them. The simulator remains still under development, and new features must still be implemented. Among the different ones, the development of a viewer that is able to represent the status of the interactions in the satellite trajectory becomes an interesting feature to understand the nature of federations. This dissertation addresses this new feature, implementing a dedicated viewer using current technologies. The development has addressed the different challenges associated to integrating a new viewer in the simulator, and in the standard visualization tool. The resulting implementation is able to represent the satellite interaction using a temperature representation in which more transmission heat the communication link. This resulting viewer will contribute in the future research associated to the Federated Satellite Systems. En els últims anys, els sistemes de satèl·lits han evolucionat, passant de ser naus monolítiques a tractar-se d'arquitectures distribuïdes. Aquestes noves arquitectures es basen en grups de satèl·lits que treballen en poder assolir un objectiu o missió comuna. Entre els diferents tipus d'arquitectures distribuïdes, el concepte de les Federated Satellite System és el més prometedor de cara a l'Observació terrestre. Aquest concepte innovador mira d'establir col·laboracions win-win entre els satèl·lits i compartir d'aquesta manera recursos que no es troben en ús, tals com l'emmagatzematge o l'opció de Downlink. El desplegament d'aquest concepte requereix el desenvolupament de noves tecnologies i d'un equipament necessari per a realitzar-ho. En particular, un simulador que representi la interacció entre satèl·lits esdevé un bé fonamental. Entre els diferents sistemes de simulació, cap és capaç d'integrar dinàmiques dels satèl·lits i comunicacions. Aquestes dos característiques són essencials per a representar correctament la interacció entre satèl·lits en una FSS. Per aquest motiu, un simulador dedicat estava sent desenvolupat pel grup de recerca del NanoSat Lab de la UPC. Aquest motor proporciona un entorn de simulació en el qual els satèl·lits poden ser definits amb diferents mòduls que representin els seus recursos, i els corresponents protocols per a poder interactuar entre ells. El simulador és encara en fase de desenvolupament, i noves característiques necessiten ser implementades. Entre aquestes característiques, el desenvolupament d'un visor que permeti representar l'estat de les interaccions en la trajectòria d'un satèl·lit és una característica que pot ser important de cara a entendre el funcionament de les federacions de satèl·lits. Aquesta dissertació tracta aquesta nova característica, implementant un visor dedicat utilitzant tecnologies actuals. El desenvolupament enfoca diferents reptes associats a integrar una now viewer en el simulador, i en l'estàndard de visualització. La implementació resultada és capaç de representar la interacció entre satèl·lits mostrant en una escala de calor l'activitat d'un enllaç. Aquesta viewer contribuirà en el futur de la recerca associada a les Federated Satellite Systems..

​© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Adopting satellite constellations to provide global Internet access services has recently drawn increasing attention. A Low Earth Orbit (LEO) satellite network with multiple satellites has global coverage ability, low latency and independent operation, so it can be an effective complement to terrestrial IP networks. Satellite gateways are placed on the ground and can serve as data exchange points between satellite networks and the Internet. As the placement scheme can affect the network performance, it is a fundamental problem to find appropriate sites for gateways. In this paper, a Gateway Placement Optimization (GPO) method in LEO satellite networks is proposed to solve the problem, which is modeled as a combination optimization problem. Our aim is to select the best places for gateways that can balance the traffic loads with as few gateways as possible. The constraints come from the physical links between gateways and satellites including the link interference, the satellite bandwidth and the number of satellite antennas. The gravity model is used to estimate the traffic matrix from/to gateways and satellites, and then the discrete Particle Swarm Optimization (PSO) algorithm is adopted and modified to solve this problem. Finally, the GPO method is applied to numerical tests involving real satellite constellation networks. Results indicate that our method has good performance and effectiveness. Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.1 - Desenvolupar infraestructures fiables, sostenibles, resilients i de qualitat, incloent infraestructures regionals i transfrontereres, per tal de donar suport al desenvolupament econòmic i al benestar humà, amb especial atenció a l’accés assequible i equitatiu per a totes les persones Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.c - Augmentar de forma significativa l’accés a les tecnologies de la informació i la comunicació i esforçar-se a proporcionar accés universal i assequible a Internet als països menys avançats a tot tardar el 2020

CubeSats are no longer just an academic exercise, but they have become a commercial and technical solution in the space field. Improvements in miniaturization, electronics and energy have made it possible to reduce the dimensions of the spacecraft, and therefore, their antennas size. This document shows first the design and simulation of a deployable Fresnel Zone Plate type antenna. In a second stage, the manufacturing and testing is presented in two ways, using two configurations: a heavier and more robust one with a paint-based conductor and a lighter one with a silver adhesive tape-based conductor. Both results are positive, the second one being especially satisfactory and leading to subsequent studies that further improve the system.

Non-Orthogonal Multiple Access (NOMA) has potentials to improve the performance of multi-beam satellite systems. The performance optimization in satellite-NOMA systems can be different from that in terrestrial-NOMA systems, e.g., considering distinctive channel models, performance metrics, power constraints, and limited flexibility in resource management. In this paper, we adopt a metric, Offered Capacity to requested Traffic Ratio (OCTR), to measure the requested-offered data (or rate) mismatch in multi-beam satellite systems. In the considered system, NOMA is applied to mitigate intra-beam interference while precoding is implemented to reduce inter-beam interference. We jointly optimize power, decoding orders, and terminal-timeslot assignment to improve the max-min fairness of OCTR. The problem is inherently difficult due to the presence of combinatorial and non-convex aspects. We first fix the terminal-timeslot assignment, and develop an optimal fast-convergence algorithmic framework based on Perron-Frobenius theory (PF) for the remaining joint power-allocation and decoding-order optimization problem. Under this framework, we propose a heuristic algorithm for the original problem, which iteratively updates the terminal-timeslot assignment and improves the overall OCTR performance. Numerical results verify that max-min OCTR is a suitable metric to address the mismatch issue, and is able to improve the fairness among terminals. In average, the proposed algorithm improves the max-min OCTR by 40.2% over Orthogonal Multiple Access (OMA)., Comment: 11 pages, 5 figures

The energy allocation problem in a massive access setting under iterative successive interference cancellation (SIC) is undertaken in this work. The classic one-iteration SIC still has room for improvement when the channel coding schemes adopted are non-error free. In this work, we investigate a satellite return link in which transmitters employ the same physical layer and transmission protocol: a given encoder, and spreading-based nonorthogonal multiple access. Leveraging iterative SIC, the gateway is endowed with strong interference suppression potential to deal with many uncoordinated transmissions. We elaborate on the interplay between energy and reliability for all users by designing an energy allocation with minimum energy expenditure when the iterative SIC receiver performs two decoding attempts per user. We resort to the user-asymptotic regime to address the randomness in the multi-feature system model of two-iteration SIC, which has turned the analysis into a deterministic one. We formulate our final design as a vector optimization aided by tools from the calculus of variations. We show the competitive performance achieved by the designed allocation, specially under encoders associated with short-length codes. We also assess our analysis by simulating a low-level SIC implementation. Work supported in part by Agencia Estatal de Investigacion (AEI, Spain) and by European Regional Development Fund (ERDF) through project RODIN (PID2019-105717RB-C22), and in part by the Catalan administration (AGAUR) under Grant 2017 SGR 578 and Fellowship 2020FI B2 00062.

Secure and reliable exchange of data and information plays a crucial role in our society, for example protecting money transfers, commercial transactions, medical data, remote control of sensible infrastructures, etc. Efforts are striving towards achieving global network coverage even in remote geographical areas. In this context, the QUANGO (cubesat for QUANtum and 5G cOmmunication) project, started in January 2021 under the EU Horizon 2020 Research and Innovation program, is aimed at designing and prototyping the key elements of a satellite mission that targets the delivery of both IoT services and Quantum Key Distribution (QKD) services, implemented using a constellation of CubeSats that operate in LEO. The rationale behind this vision is to address the growing need for the safe, reliable, and ubiquitous exchange of data in our society that is becoming of paramount importance for a plethora of activities. The implementation of this project can provide a new paradigm to share the satellite infrastructure required for secure communication based on quantum technologies and for 5G communication. The spacecraft will carry two interconnected payloads: 1. A 5G IoT radio, called access network payload, based on a flexible software-defined radio (SDR). 2. A secure communication system based on a quantum link to distribute quantum keys to the ground. The combination of these two payloads allows for the implementation of a QKD service where the 5G IoT payload in addition to the delivery of IoT services, is intended to be used as an integral part of the envisioned QKD solution. Moreover, the combination of these two payloads will contribute to reduce the cost of both services by sharing the satellite platform and study how these two technologies can further improve synergically, getting benefits from each other’s ecosystem. The project is being developed by a consortium of European universities, research centres and SME with a strong heritage in areas such as quantum cryptography, optical communication, microsatellites development and 5G networks. The objective of the paper is to present an overview of the QUANGO project along with preliminary design considerations of the mission and platform to be developed. This work was supported by the QUANGO project (see https://quango.dei.unipd.it/), funded by the EU in the frame of Horizon 2020 programme. Peer Reviewed Article signat per 17 autors/es: D. Sarica (a), A. Balossino (a), S. Simonetti (a), G. Vallone (b), P. Villoresi (b), F. Berra (b), M. Guadalupi (c), J. Ferrer (c), I. Llorens (c), R. Ferrús (c), A. Francesconi (d), F. Sansone (d), E. Birello (d), V. Pruneri (e), I. H. L. Grande (e), E. Diamanti (f), M. Schiavon (f) (a) Argotec Srl, Via Cervino 52, 10155, Torino, Italy, {danilo.sarica, alessandro.balossino, simone.simonetti} @argotecgroup.com / (b) Department of Information Engineering, University of Padova, I-35131 Padova, Italy, {vallone, paolo.villoresi,} @dei.unipd.it, federico.berra@phd.unipd.it / (c) Sateliot, Rambla de Catalunya 124, 08008, Barcelona, Spain, {marco, josep.ferrer, isaac.llorens, ramon.ferrus} @sateliot.space / (d) Stellar Project, Via Niccolò Tommaseo, 69/D, 35131, Padova, Italy, {alessandro.francesconi, francesco.sansone, edoardo.birello} @stellarproject.space / (e) ICFO, Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain, {Valerio.Pruneri, Ignacio.Lopez} @icfo.eu / (f) Sorbonne Université, 4 place Jussieu, 75005, Paris, France, {eleni.diamanti, matteo.schiavon} @lip6.fr

Low-complexity suboptimal solutions are widely accepted to design spatial precoders that mitigate the resulting co-channel interference in multibeam high throughput satellites, which is caused by the aggressive frequency reuse. The most widely accepted solution, due to its simplicity and robustness to different channel conditions, is the so-called minimum Mean Square Error (MMSE) precoder. This work reviews the different rationals that support this technique and presents an alternative that maximizes the directivity. With this new point of view we propose a solution that is suitable for both the unicast and the multicast scenario. The latter is quite unexplored in the existing literature, partly explained by its loss of performance with respect to the unicast case. The proposed technique presents a practical and more clear design than the MSE, and the numerical simulations proof its gains compared to the benchmark. © VDE VERLAG GMBH · Berlin · Offenbach., This work is supported by the Spanish ministry of science and innovation under project IRENE (PID2020-115323RB-C31 / AEI / 10.13039/501100011033) and from the Catalan Government (2017-SGR-1479). © 2021, IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work.

Cellular networks play a very important role in nowadays paradigm which goal is to establish connectivity all around the world. Low power wide area networks (LPWAN) seem to fit well within low-cost devices, which constitute a great part of the electronics market. In this context, the narrowband internet of things (NB-IoT) protocol specified by the 3GPP is consolidating as one of the most adopted technologies in the field of LPWAN, together with LoRaWAN. With the goal of reaching global coverage, the NB-IoT protocol, which was mainly designed for terrestrial cellular networks, is now being extended to be able to work also on satellite networks. The support of satellite access is seen as the enabler of truly massive machine-type communications (mMTC) into areas that cellular connectivity is limited or inexistent (remote areas, air and sea communications). This thesis provides a performance assessment of the NB-IoT protocol under different satellite link conditions and transmission modes. The assessment is conducted using the MATLAB LTE Toolbox. Las redes móviles tienen un papel muy importante en la actualidad, puesto que tienen como objetivo establecer conectividad en todo el mundo. Las redes de bajo consumo y largo alcance (LPWAN) parecen encajar bien en un entorno donde los dispositivos de bajo coste constituyen una gran parte del mercado de la electrónica. En este contexto, el protocolo NB-IoT especificado por el 3GPP se consolida como una de las tecnologías más adoptadas en el contexto de LPWAN, junto con LoRaWAN. Con el objetivo de conseguir una cobertura global, el protocolo NB-IoT, que fue diseñado principalmente para redes de telefonía terrestre, ahora se está ampliando para poder trabajar también en redes de satélite. El acceso por satélite es visto como la puerta hacia las comunicaciones de tipos máquina masiva (mMTC) en áreas donde la conectividad celular es limitada o inexistente (áreas remotas, comunicaciones aéreas y marítimas). Esta tesis proporciona una evaluación del rendimiento del protocolo NB-IoT bajo diferentes condiciones de enlace por satélite y modos de transmisión. La evaluación se realiza utilizando la caja de herramientas MATLAB LTE. Les xarxes mòbils tenen un paper molt important en l'actualitat, ja que tenen com a objectiu establir connectivitat a tot el món. Les xarxes de baix consum i llarg abast (LPWAN) semblen encaixar bé en un entorn on els dispositius de baix cost constitueixen una gran part del mercat de l'electrònica. En aquest context, el protocol NB-IoT especificat pel 3GPP es consolida com una de les tecnologies més adoptades en el context de LPWAN, juntament amb LoRaWAN. Amb l'objectiu d'aconseguir una cobertura global, el protocol NB-IoT, que va ser dissenyat principalment per a xarxes de telefonia terrestre, ara s'està ampliant per poder treballar també en xarxes de satèl·lit. L'accés per satèl·lit és vist com la porta cap a comunicacions de tipus màquina massiva (mMTC) en àrees on la connectivitat cel·lular és limitada o inexistent (àrees remotes, comunicacions aèries i marítimes). Aquesta tesi proporciona una avaluació del rendiment del protocol NB-IoT sota diferents condicions d'enllaç per satèl·lit i modes de transmissió. L'avaluació es realitza utilitzant la caixa d'eines MATLAB LTE.

Earth observation technologies provide us with a large amount of information and have many diverse applications. In this thesis, we focus on classifying land cover using SAR sensors from the Sentinel-1 satellites. The objective of this study is to use Artificial Intelligence techniques to be able to automatically classify the different regions of an area of interest. For the classification, we will use the Random Forest algorithm that allows us to identify the most relevant features to classify each class, and with which we achieve a classification accuracy of 90%. On the other hand, the importance of certain temporal samples is repeated in all classes, and if we select them as an input subset, we can reduce the number of samples by 80% and maintain a high classification accuracy of 87%. This allows us to simplify the classification problem and reduce the required processing time. Las tecnologías de observación de la tierra nos proporcionan una gran cantidad de información y tienen muchas aplicaciones diversas. En este trabajo nos centramos en clasificar la cobertura de la tierra mediante sensores SAR, de los satélites Sentinel-1. El objetivo de este trabajo es utilizar técnicas de Inteligencia Artificial para poder clasificar automáticamente las diferentes regiones de un área de interés. Para la clasificación utilizaremos el algoritmo de Bosques Aleatorios (Random Forest) que nos permite identificar los parámetros destacados en cada clase, y con el que conseguimos una precisión del 90%. Por otra parte, la importancia de ciertas muestras temporales se repite en todas las clases, y si las seleccionamos como subconjunto de entrada, podemos reducir el número de muestras en un 80% y mantener una precisión elevada, del 87%. Lo que nos permite simplificar el problema y disminuir el tiempo de procesamiento necesario. Les tecnologies d'observació de la terra ens proporcionen una gran quantitat d'informació i tenen moltes aplicacions diverses. En aquest treball ens centrem a classificar la cobertura de la terra mitjançant sensors SAR, dels satèl·lits Sentinel-1. L'objectiu del treball és utilitzar tècniques d'Intel·ligència Artificial per poder classificar automàticament les diferents regions d'una àrea d'interès. Per a la classificació utilitzarem l'algoritme de Boscos Aleatoris (Random Forest) que ens permet identificar els paràmetres que contribueixen a classificar cada classe, i amb el qual aconseguim una preciso de classificació del 90%. Per altra banda, la importància de certes mostres temporals es repeteix en totes les classes, i si les seleccionem com a subconjunt d'entrada podem reduir el nombre de mostres en un 80% i mantenir una precisió de classificació elevada, del 87%. Això, ens permet simplificar el problema i disminuir el temps de processament necessari.

The 3rd Generation Partnership Project (3GPP), the standard development organization in charge of the 5G mobile system specifications, is currently developing the adaption of the NB-IoT protocol for non-terrestrial networks (NTN), referred to as NB-IoT NTN. The NB-IoT NTN protocol is expected to operate, among others, in LEO constellations. To that end, the NB-IoT protocol originally conceived for terrestrial access is being enhanced to address the specific characteristics of LEO satellite channels, including e.g. timing relationship enhancements in random access and scheduling processes to deal with the longer propagation delays of satellite channels and new Doppler precompensation mechanisms. Mobility management improvements to cope with moving satellite cells and noncontinuous operation of the service link are also being worked out, leading to e.g. the specification of new system information messages encoding satellite ephemerides data and specific tracking area management approaches for satellite access. The possibility to use the same protocol NB-IoT for both terrestrial and satellite access offers an unprecedented opportunity for massive IoT services, which will benefit from the global coverage provided by satellites. In this context, this paper describes the key design considerations and main system components of a NB-IoT NTN solution that is being developed for operation with CubeSat platforms in low-density LEO constellations. Results and discussion of technical challenges are provided in the areas of link budget, beam layout configurations, capacity and achievable service performance indicators.

Objectius de Desenvolupament Sostenible::3 - Salut i Benestar Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

As the new space revolution is being led by several operators of large Low Earth Orbit satellite constellations, and research into satellite communications becomes more prevalent, it is increasingly necessary to make access to research in this field as open as possible. This research has been around the development of a satellite networking simulator to enable further research, specially in the satellite-based airborne communications. This simulator has been implemented as flexible as possible to enable further extending features. It ingests real-world data from ground stations, aircraft and satellites, simulates and plans discrete events, and post-processes the network metrics obtained. Several case studies are presented in this thesis for analyzing constellation deployment as well as for exploratory network analysis and validation of the simulator.

Next generation satellite payload technology is expected to provide digital processing capabilities. This will pave the way to regard satellites as flying base stations. However, the initial access procedure must be improved. In this work we focus on non-geostationary earth orbit (NGEO) satellite networks. In this scenario, the random access preamble signal and the detection must be robust to large carrier frequency offsets (CFOs). Towards this end, we investigate the adoption of the pruned discrete Fourier transform spread filter bank multicarrier waveform. The proposed design is suitable for the access scheme of forthcoming 5G-based NGEO satellite communications. The reason is twofold. First, it improves the spectral confinement with respect to the standard single-carrier frequency-division multiplexing (SC-FDM) waveform. Second, it achieves a high level of commonality with 5G new radio, by keeping unchanged the subcarrier spacing, the slot duration and the preamble sequence. Remarkably, the new design allows the straightforward application of non-coherent post detection integration (NCPDI) techniques, which divide the correlation in blocks. Numerical results show that the proposed solution reduces out-of-band emissions and the missed detection probability in presence of CFO, with respect to the conventional approach based on SC-FDM and preamble detection with full-length correlation. This work has received funding from the ministry of Science, Innovation and Universities under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER,UE) and under grant RTI2018-099841-B-I00 and from the Catalan Government (2017-SGR-1479).

Upcoming Low Earth Orbit Satellite Networks will provide low-latency and high downlink capacity necessary for future broadband communications and Earth Observation missions. This architecture was proposed at the beginning of the 90's, although it has just recently re-gained popularity thanks to the so-called Mega-Constellations. This network is composed of satellites that have Inter-Satellite Links (ISL) to communicate between them. Due to the satellite motion, an ISL is a temporal contact between two satellites characterized by a lifetime in which the communication remains feasible. The determination of a route between distant satellites is a challenging problem in this context. However, the satellite follows a well-known deterministic orbit trajectory, being feasible the prediction of its position by propagating a trajectory model over time. The Contact Graph Routing protocol uses this feature to determine the evolution of the routes by pre-computing on-ground a planning of the satellite contacts. This centralized ground-dependent solution cannot be directly applied in the Internet of Satellites paradigm, which proposes the autonomous deployment of heterogeneous satellite networks without pre-assuming any specific satellite system architecture. Following this concept, the present work proposes a distributed algorithm by which a satellite predicts neighbor contacts, and generates a global contact plan without trajectory propagation. To achieve this solution, an ISL has been modeled as a 'close approach' between two satellites, which is characterized by their relative motion. The present work details the predictive algorithm, and evaluates its performance in two scenarios with a hybrid satellite constellation and a mega-constellation., This work was supported in part by the CommSensLab Excellence Research Unit Maria de Maeztu (MINECO) under Grant MDM-2016-0600, in part by the Spanish Ministerio MICINN and EU ERDF Project (Sensing With Pioneering Opportunistic Techniques) under Grant RTI2018-099008-B-C21, in part by the AGAUR—Generalitat de Catalunya (FEDER) under Grant FI-DGR 2015, and in part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya under Grant 2017 SGR 376.

This paper tackles the problem of user scheduling in satellite content delivery networks with precoding. The clustering process has to consider two crucial and independent characteristics of the user terminals. On the one hand, users belonging to the same group shall have a reduced Euclidean norm between their channel vectors in order to obtain the maximum precoding gain. On the other hand, with the aim of exploiting the multicast capabilities of the system, user terminals grouped in the same cluster shall have requested the same content. The resulting clustering problem is formulated as a multigraph (also known as multiview) spectral clustering problem. The paper shows that this unsupervised learning framework is able to capture the different peculiarities of the mentioned problem. Two different techniques are introduced and validated in a close-to-real numerical simulation. This work has received funding from the Spanish ministry of Science, Innovation and Universities under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER,UE), and by the Catalan Government under grant 2017-SGR01479.

Telecom operators are constantly searching for solutions to deal with notable growths on the data demand. One of these options consists in predicting the popularity of content to-be-requested by the subscribers on a daily basis, and store them in advance on the 5G edge nodes during the off-peak hours. To perform this placement, point-to-point optical terrestrial links are conventionally used, transmitting the same content in parallel from the operators' servers to the 5G edge nodes. One simple way to reduce this placing time consists in offloading the terrestrial (optical) network, by multi-casting over satellite (radio) the most popular content. This way, top-ranked files are transmitted only once by the satellite node, and can be received by all 5G edge nodes in coverage range. To implement the satellite segment of such hybrid backhaul solution, two options are considered: A small-sized constellation of low-cost LEO satellites with sporadic contacts with ground points, and a single high-cost GEO satellite that enables continuous pan-European connectivity regardless the location. Simulation results show that the placing time can be notably reduced using the proposed hybrid terrestrial-satellite backhauling. More precisely, the use of few LEO satellites can provide a placing time reduction that is similar to the one with GEO, even though the implementation and operational costs can be much lower with LEOs than with a GEO. This work has received funding from the Ministry of Science, Innovation, and Universities of Spain under Project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER, UE), the Catalan government under grant 2017-SGR-01479, the ERC Advanced Grant 695614 (POWVER), and the DFG Grant 389792660 as part of TRR 248.

The DISCOVERER project is developing technologies to enable commercially-viablesustained-operation of satellites in very low Earth orbitsfor communications and remote sensing applications. Operatingcloser to the surface of the Earthsignificantly reduceslatency for communications applications and improves link budgets, whilstremote sensing also benefitsfrom improved link budgets,the ability to havehigher resolution or smaller instruments, all of which providecost benefits. In addition, all applications benefit from increased launch mass to lower altitudes, whilst end-of-life removal is ensured due to the increased atmospheric drag. However, this drag must also be minimised and compensated for. DISCOVERER is developing several critical technologies to enable commercially-viable operations in at these lower altitudesincluding aerodynamic materials, aerodynamic attitude and orbitcontrol methods, atmosphere breathing electric propulsion and an in-situenvironment monitoring payload. Thecurrentstatus of these developments are summarised, along with the plans for thecoming year. The DISCOVERER project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 737183.

This paper investigates the application of multicast non-orthogonal multiple access (MC-NOMA) schemes to the forward link of a satellite communication system. In multicast transmission each frame contains information of multiple users. To benefit from the theory developed in NOMA, the proposed scheme creates two groups of users within each beam. The analysis conducted in this work reveals that the user grouping has an impact on the performance. In the light of this observation, power allocation and user clustering techniques have been derived to either maximize the sum-rate or achieve max-min fairness. The numerical simulation results show that MC-NOMA outperforms multicast orthogonal multiple access (MC-OMA) schemes, where different groups are served in orthogonal resources. Moreover, the gain of MC-NOMA over the MC-OMA becomes more prominent as number of users per group and the transmit power increases. The results show the minimum-rate and the sum-rate of MC-NOMA can be increased by a factor 2 and 1.45 with respect to MC-OMA, respectively.

In the past two decades, a silent revolution has taken place in the space domain, leading to what today is known as “New Space.” We have passed from a selected group of countries, space agencies, and big industries building, launching, and operating satellites and other spacecrafts, of a scenario in which many universities and research institutes can do it. The key of this was the definition of the “CubeSat” standard, back to 1999. In 2013, it all took off on the commercial Earth Observation sector with the first launches from two companies that are now running 100+ CubeSat constellations for optical imaging or weather prediction, with very low revisit times. Today, the same revolution is taking place in the fields of Telecommunications, and Astronomical Scientific missions. In this chapter, the evolution of the space sector is briefly revised until the arrival of the CubeSats. Then, the CubeSat intrinsic limitations are discussed as they are key to understand the development and current situation of the CubeSat sector. NASA and ESA strategies are also presented. The chapter concludes with a summary of the technology roadmap to enable the next generation of CubeSat-based missions, including satellite constellations or federations, formation flying, synthetic apertures… This work has been supported by an ICREA Acadèmia award from the Generalitat de Catalunya to Prof. A. Camps. The author wants to express his gratitude to Profs. A. Golkar (Skoltech, Moscow, Russia) and H. Park (Universitat Politècnica de Catalunya, Barcelona, Spain) for the revision of this chapter and useful comments.

Recent studies have shown that using global navigation satellite system reflectometry (GNSS-R) and L-band radiometry it is possible to study soil moisture, biomass and cryospher. 3Cat-4 is an educational and scientific mission that combines the two technologies with the aim of demonstrating the potential of nano-satellites for different earth observation (EO) applications. The manufacture of a satellite consists of different phases before it is ready to be launched. First the mission is conceived, then the design of the components and their manufacture and finally their integration. Integration is the phase in which the components of the satellite as a whole are to be verified and assembled in the structure. A correct integration consists of three phases: a software model of the satellite, a FlatSat and finally the assembly of the entire satellite. These three phases have been applied in the practical case of 3Cat-4. The first of the phases is the analysis of the nano-satellite software model, as a CAD. A CAD model is a representation in dimensions and mass of each of the parts that constitute the nano-satellite. This analysis is essential to be able to predict physical collisions between components of different subsystems that would prevent performing the entire satellite assembly. This thesis presents the process used to keep the CAD model up to date. It shows examples of detected collisions that could be overcome before the day of assembly as well as certain nano-satellite pairs that had to be modified to avoid collisions. The next phase is the FlatSat. The FlatSat is based on positioning all the subsystems of the satellite on a table and by means of an interface the software and the interaction between them is tested. In this way the different parts of the satellite can be validated as a whole and you ensure that there will be no interfering errors once the satellite is integrated. The last of the phases is the assembly itself. In this chapter this document explains the different fit checks that have been carried out to verify that there are no collisions between subsystems, as well as the step-by-step procedure to follow and the equipment necessary to perform the assembly. To synthesize, in this thesis it is stated that a CAD model allows you to anticipate physical collisions between subsystems, with a FlatSat you can anticipate problems at software level and all this together with an assembly procedure that has been validated by fit checks ensures a successful satellite integration. Estudis recents han demostrat que utilitzant reflectometria de senyal de navegaci´o per sat ` el·lit i radi`ometre en banda L es pot estudiar la humitat del terreny, la biomassa i la criosfera. 3Cat-4 es una missi´o educativa i cient´ıfica que combina les dues tecnologies amb l’objectiu de demostrar el potencial dels nano-sat` el·lits per a diferents aplicacions d’observaci ´o terrestre. La fabricaci ´o d’un sat` el·lit t ´e diferents etapes abans d’estar llest per ser llanc¸at. Primer hi ha una concepci´o de la missi´ o, despr´es hi ha el disseny dels components i la seva fabricaci ´ o, i per ´ ultim hi ha la integraci ´ o. La integraci ´o es la fase on s’ah de verificar els components del sat` el·lit en conjunt i s’han d’introduir a dintre de la estructura. Una correcta integraci ´o es composa per tres fases: un model software del sat ` el·lit, un FlatSat i per ´ ultim el muntatge del sat ` el·lit. Aquestes tres fases han sigut estudiades en el cas pr` actic del 3Cat-4. La primera de les fases ´es l’an ` alisi del model software del nano-sat` el·lit, en format CAD. Un model CAD es una representaci´o en dimensions i en massa de cadascuna de les parts que formen el nano-sat` el·lit. Aquest an` alisi ´es essencial per tal d’anticipar les col·lisions f´ısiques entre components de diferents subsistemes que ens impedirien dur a terme la fase de muntatge. Aquesta tesi mostra el proc´es utilitzat per tal de mantenir el model CAD actualitzat, es mostren exemples de col·lisions detectades que es van poder resoldre abans del dia del muntatge aix´ı com determinades parts del nano-sat` el·lit que es van haver de modificar per tal d’evitar aquestes col·lisions. La seg¨uent fase es la del FlatSat. El FlatSat consisteix en posicionar totes les parts del sat ` el·lit a sobre d’una taula i mitjanc¸ant una interf´ıcie es testeja el software i la interacci´o entre subsistemes. D’aquesta manera pots validar les diferents parts del sat` el·lit en conjunt i t’assegures que no hi haur`a errors d’aquest tipus una vegada ha estat integrat el nano-sat` el·lit. L’ ´ ultima de les fases ´es el muntatge en si mateix. En aquest punt aquest document exposa els diferents fit checks que s’han dut a terme per tal de verificar que no hi ha col·lisions entre subsistemes, a m´es dels passos a seguir i l’equipament necessari per tal de realitzar el muntatge. Per sintetitzar, en aquesta tesi es deixa const`ancia que amb el model CAD ets capac¸ d’anticipar col·lisions f´ısiques entre subsistemes, amb el FlatSat pots anticipar problemes a escala de software i interf´ıcies, tot aix `o unit a un procediment de muntatge que hagi estat validat amb diversos fit checks assegura una integraci ´o exitosa.

Scintillation is a disturbance induced by the ionosphere, the farther layer of the atmosphere in which free ions (electrons) are present. These electrons vary in quantity according to many factors related to Solar activity and affect instantaneously and simultaneously both in amplitude and in phase the radio navigation signal. Therefore, the impact of scintillation is typically assessed by means of amplitude and a phase scintillation index. However, multipath reflections induce a signal amplitude variation very similar to what scintillations do, leading to potentially wrong scintillation indices estimations. In the thesis, a technique for clearing out the amplitude scintillation index from the multipath effect is presented and analyzed. The results obtained led by the technique, demonstrate the effect of Multipath in the S4 index and the presence of scintillation masked by it. L'objectiu d'aquest projecte és demostrar la presència d'errors en les mesures d'índexs de scintilaltion en el senyal GPS L1 C / A a causa de la presència de reflexió multipath al receptor i proposar un mètode per reduir aquests errors. La scintilaltion és una perturbació induïda per la ionosfera, la capa més llarga de l'atmosfera en la qual estan presents els ions lliures (electrons). Aquests electrons varien en quantitat segons molts factors relacionats amb l'activitat solar i afecten instantàniament i simultàniament tant en amplitud com en fase de senyal de radiocomunicació. Per tant, l'impacte del scintilaltion sol avaluar-se mitjançant amplitud i un índex de scintilaltion de fase. No obstant això, els reflectors de múltiples vies indueixen una variació d'amplitud de senyal molt similar a la que fan els scintilaltions, donant lloc a estimacions d'índexs de scintilaltion potencialment incorrectes. En la tesi es presenta i analitza una tècnica per eliminar l'índex de scintilaltion d'amplitud de l'efecte multipath. Per a la demostració, es van utilitzar les dades recollides durant els primers deu dies del mes de setembre de 2017, a latituds polars durant una tempesta solar. Les dades es van recollir a un interval d'Hertz (1 Hz) per a períodes de cinquanta (50) minuts; i inclou l'índex de scintilaltion d'amplitud i l'índex de scintilaltion de fase del senyal GPS L1 C / A. Amb aquestes dades, el comportament del senyal s'ha analitzat durant les vint-i-quatre hores del dia i, juntament amb un altre detector de scintilaltion, s'han comparat les dades durant els dies i les hores més concloents de la setmana. Els resultats obtinguts han estat dividits per block de temps i blocs de comportament del senyal, diferenciats en tres blocs diferents segons la quantitat de scintillation present. El processament de dades va confirmar que en els casos seleccionats multipath indueix un creixement considerable del valor de l'índex d'escintilació d'amplitud i que hi ha una correlació en aquesta tendència entre dies consecutius. S'ha demostrat que al alinear correctament les sèries temporals de mesuraments, és possible eliminar la contribució de la ruta múltiple i, per tant, subratllar l'única contribució del scintilaltion real. A més, s'ha enfrontat la necessitat d'un gran enfocament de programació de dades per analitzar totes les dades adquirides. Outgoing

An optimal payload selection conducted in the frame of the H2020 ONION project (id 687490) is presented based on the ability to cover the observation needs of the Copernicus system in the time period 2020–2030. Payload selection is constrained by the variables that can be measured, the power consumption, and weight of the instrument, and the required accuracy and spatial resolution (horizontal or vertical). It involved 20 measurements with observation gaps according to the user requirements that were detected in the top 10 use cases in the scope of Copernicus space infrastructure, 9 potential applied technologies, and 39 available commercial platforms. Additional Earth Observation (EO) infrastructures are proposed to reduce measurements gaps, based on a weighting system that assigned high relevance for measurements associated to Marine for Weather Forecast over Polar Regions. This study concludes with a rank and mapping of the potential technologies and the suitable commercial platforms to cover most of the requirements of the top ten use cases, analyzing the Marine for Weather Forecast, Sea Ice Monitoring, Fishing Pressure, and Agriculture and Forestry: Hydric stress as the priority use cases.

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This TFM is involved in the ³Cat-4 project from the Nano-Satellite and Payload Laboratory. This project is also involved in the Fly Your Satellite! II program of the ESA Academy and will be directed with the colaboration of Joan Adrià Ruiz de Azua Ortega.