Design, implementation and verification of CubeSat systems for Earth Observation

In recent years, Earth Observation (EO) technologies have surged in an attempt to better understand the world we live in, and exploit the vast amount of data that can be collected to improve our lives. The field of EO encompasses a broad array of technologies capable of extracting information remotely, in a process called Remote Sensing (RS). CubeSats are causing a revolution in the RS field, and are becoming a really important contribution to it. The lack of testing and preparation are common in CubeSat EO missions due to the low budgets they usually suffer from. A successful CubeSat EO mission must supply the lack of size or funding with properly tested components and environments. In this document, emphasis will be given to preemptive approaches such as studying the performance of Commercial Off-The-Shelf (COTS) Global Positioning System (GPS) receivers and the development of simulators for highly dynamic environments This topic will be expanded upon by introducing the problematic of simulating such signals for testing, and the possible countermeasures to Radio-Frequency Interference (RFI) that threatens the success of the mission. Finally, a new S-Band Ground Station will be built to provide access to this band for future CubeSat missions. All of the above will provide a holistic view on some of the hot challenges that EO faces, and multiple future research paths that open with the recent rise of New Space technologies

New instrument concepts for ocean sensing: analysis of the PAU-radiometer

Sea surface salinity can be remotely measured by means of L-band microwave radiometry. However, the brightness temperature also depends on the sea surface temperature and on the sea state, which is probably today one of the driving factors in the salinity retrieval error budgets of the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission and the NASA-Comision Nacional de Actividades Espaciales Aquarius/SAC-D mission. This paper describes the Passive Advanced Unit (PAU) for ocean monitoring. PAU combines in a single instrument three different sensors: an L-band radiometer with digital beamforming (DBF) (PAU-RAD) to measure the brightness temperature of the sea at different incidence angles simultaneously, a global positioning system (GPS) reflectometer [PAU-reflectometer of Global Navigation Satellite Signals (GNSS-R)] also with DBF to measure the sea state from the delay-Doppler maps, and two infrared radiometers to provide sea surface temperature estimates. The key characteristic of this instrument is that both PAU-RAD and the PAU-GNSS/R share completely the RF/IF front-end, and analog-to-digital converters. Since in order to track the GPS-reflected signal, it is not possible to chop the antenna signal as in a Dicke radiometer, a new radiometer topology has been devised which makes uses of two receiving chains and a correlator, which has the additional advantage that both PAU-RAD and PAU-GNSS/R can be operated continuously and simultaneously to perform the sea-state corrections of the brightness temperature. This paper presents the main characteristics of the different PAU subsystems, and analyzes in detail the PAU-radiometer concept.Peer Reviewe

Implementation of a GNSS-R payload based on software defined radio for the 3CAT-2 mission

©2016 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.The 3CAT-2 nanosatellite aims at demonstrating global navigation satellite system reflectometry (GNSS-R) techniques for spaceborne applications in the small form of a six-unit CubeSat. There are many challenges involved from a size, processing, and power perspectives. The proposed solution for the payload uses a software-defined radio (SDR) connected to a nadir looking array of dual-band and dual-frequency and dual-polarization antennas to capture the reflected GNSS signals and to a zenith looking patch antenna to capture the direct ones. The SDR is controlled by the payload computer, which retrieves the binary samples and processes the raw data to obtain delay-doppler maps (DDMs) via various techniques. DDMs are then compressed using the fully adaptive prediction error coder algorithm, producing an output more suitable for the limited downlink capabilities of these small platforms.Peer ReviewedPostprint (author's final draft

New Passive Instruments Developed for Ocean Monitoring at the Remote Sensing Lab—Universitat Politècnica de Catalunya

Lack of frequent and global observations from space is currently a limiting factor in many Earth Observation (EO) missions. Two potential techniques that have been proposed nowadays are: (1) the use of satellite constellations, and (2) the use of Global Navigation Satellite Signals (GNSS) as signals of opportunity (no transmitter required). Reflectometry using GNSS opportunity signals (GNSS-R) was originally proposed in 1993 by Martin-Neira (ESA-ESTEC) for altimetry applications, but later its use for wind speed determination has been proposed, and more recently to perform the sea state correction required in sea surface salinity retrievals by means of L-band microwave radiometry (TB). At present, two EO space-borne missions are currently planned to be launched in the near future: (1) ESA's SMOS mission, using a Y-shaped synthetic aperture radiometer, launch date November 2nd, 2009, and (2) NASA-CONAE AQUARIUS/SAC-D mission, using a three beam push-broom radiometer. In the SMOS mission, the multi-angle observation capabilities allow to simultaneously retrieve not only the surface salinity, but also the surface temperature and an “effective” wind speed that minimizes the differences between observations and models. In AQUARIUS, an L-band scatterometer measuring the radar backscatter (σ0) will be used to perform the necessary sea state corrections. However, none of these approaches are fully satisfactory, since the effective wind speed captures some sea surface roughness effects, at the expense of introducing another variable to be retrieved, and on the other hand the plots (TB-σ0) present a large scattering. In 2003, the Passive Advance Unit for ocean monitoring (PAU) project was proposed to the European Science Foundation in the frame of the EUropean Young Investigator Awards (EURYI) to test the feasibility of GNSS-R over the sea surface to make sea state measurements and perform the correction of the L-band brightness temperature. This paper: (1) provides an overview of the Physics of the L-band radiometric and GNSS reflectometric observations over the ocean, (2) describes the instrumentation that has been (is being) developed in the frame of the EURYI-funded PAU project, (3) the ground-based measurements carried out so far, and their interpretation in view of placing a GNSS-reflectometer as secondary payload in future SMOS follow-on missions

Modification of a FPGA-based GPS receiver for reflectometry applications (GNSS-R)

English: Lack of frequent and global global observations from space is currently a limiting factor Earth observation missions. In recent years, as a low-cost alternative, Global Navigation Satellite System's signals Reflectometry (GNSS-R) has stood a potential powerful remote sensing technique. The existing research has shown that GNSS-R has the potential to give environmental scientist a low-cost, wide-coverage measurement network that will allow to derive geophysical parameters such as ocean altimetry, sea state or soil moisture. This data has the potential to greatly increase our knowledge of the Earth's environmental processes. During the last ten years, the Remote Sensing Laboratory of the Department of Signal Theory and Communications at the Univeristat Politècnica de Catalunya, has worked on the design and implementation of the appropriate receivers in order to track and process this GNSS-R signals in real-time to avoid the storage of huge volumes of raw data. One of its most remarkable efforts is the Passive Advanced Unit for ocean monitoring (PAU) project. In this work, the possibility of adapting an existing Global Position System (GPS) receiver for GNSS-R applications is explored. This GPS receiver is the Namuru-GPL a open source software receiver implemented for the Namuru development platform developed by the University of New South Wales Satellite Navigation and Positioning Laboratory (SNAP). A modified version of the Namuru-GPL has been implemented. This modified version of the receiver has been able to simultaneous track a C/A L1-band signal and a delayed version of it that simulated a reflected signal with the associated longer propagation path. In addition, the receiver has measured pseudorange differences with a tested resolution up 3 m with a single measurment in a controlled experimental scenario, thus validating the Namuru-GPL capabilities for GNSS-R altimetry applications. In addition, a new Acquisition Module has been developed. This module dramatically reduces the Namuru-GPL receiver average acquisition time from a few minutes to 2.5 s approximately, thanks to implementing the parallel code acquisition method. Moreover, the Acquisition Module requires low hardware resources and generates Delay Doppler Maps (DDMs). All the development process stages, including validation through testing of these proposed designs are summarized within this work.Castellano: La falta de observaciones frecuentes y a escala global desde el espacio es actualmente un factor limitador de las misiones de observación de la Tierra. En los últimos años, y como alternativa al uso de constelaciones de satélites de propósito especifico y alto coste, la reflectometría con señales de oportunidad de los sistemas globales de navegación por satélite (GNSS-R) ha demostrado ser una técnica de teledetección con gran potencial. Las investigaciones realizadas hasta ahora demuestran que las técnicas GNSS-R poseen el potencial para obtener datos ambientales de alto interés científico a bajo coste y con una amplia cobertura de las mediciones realizadas. Dichas mediciones permitirían obtener o mejorar la medida de parámetros geofísicos importantes, como el estado del mar, altimetría, o la humedad del suelo. Una mejor medida de dichos parámetros tienen el potencial de aumentar considerablemente nuestro conocimiento de los procesos ambientales de la Tierra. Durante los últimos diez años, el Remote Sesing Lab que pertenece al departamento de Teoría de la Señal y Comunicaciones (TSC) de la UPC, ha trabajado en el diseño y la implementación de receptores adecuados para adquirir y procesar señales GNSS-R en tiempo real para evitar el almacenamiento de enormes volúmenes de datos. Uno de los esfuerzos más notables es el proyecto "Passive Advanced Unit for Ocean monitoring" o proyecto PAU. En este trabajo, se explora la posibilidad de adaptar un receptor GPS para a aplicaciones GNSS-R. Este receptor es el Namuru-GPL, un receptor software open source implementado sobre la plataforma de desarrollo Namuru, desarrollada por el University of New South Wales Satellite Navigation and Positioning Laboratory (SNAP). La versión modificada del receptor Namuru-GPL que se ha implementado, ha sido capaz de seguir una señal GPS C/A en la banda L1 y simultáneamente una versión retardada de la misma que simulaba ser una señal reflejada con un camino de propagación más largo. Además, el receptor ha sido capaz de medir diferencias de pseudorangos con una resolución máxima de hasta 3 m con una única medida, en un escenario experimental controlado, validando así las capacidades del Namuru-GPL para aplicaciones de altimetría mediante GNSS-R. Además, se ha desarrollado un nuevo Módulo de Adquisición. Este módulo es capaz de reducir drásticamente el tiempo medio de adquisición del Namuru-GPL de unos pocos minutos a 2,5 s aproximadamente, gracias al método de adquisición en paralelo. Además, el Módulo de Adquisición necesita relativamente pocos recursos hardware y es capaz de generar "Delay Doppler Maps" (DDMs). Todas las etapas del proceso de desarrollo de los diseños propuestos, incluida la validación experimental se encuentran resumidos en este trabajo.Català: La manca d'observacions freqüents i a escala global des de l'espai és actualment un factor limitador de les missions d'observació de la Terra. En els últims anys, i com a alternativa a l'ús de constel·lacions de satèl·lits de propòsit específic i alt cost, la reflectometría amb senyals d'oportunitat dels sistemes globals de navegació per satèl·lit (GNSS-R) ha demostrat ser una tècnica de teledetecció amb un alt potencial. Les investigacions realitzades fins ara demostren que les tècniques GNSS-R disposen del potencial per obtenir dades ambientals d'alt interès científic a baix cost i amb una àmplia cobertura de les mesures realitzades. Aquestes mesures permetrien obtenir o millorar la mesura de paràmetres geofísics importants, tals com l'estat de la mar, altimetria, o la humitat del sòl. Una millor mesura d'aquests paràmetres té el potencial d'augmentar considerablement el nostre coneixement dels processos ambientals de la Terra. Durant els últims deu anys, el Remote Sesing Lab pertanyent al departament de Teoria del Senyal i Comunicacions (TSC) de la UPC, ha treballat en el disseny i la implementació de receptors adequats per rastrejar i processar senyals GNSS-R en temps real i evitar així haver d'emmagatzemar enormes volums de dades. Un dels seus esforços més rellevants és el projecte "Passive Advanced Unit for Ocean monitoring" o projecte PAU. En aquest treball, s'explora la possibilitat d'adaptar un receptor GPS per aplicacions GNSS-R. Aquest receptor és el Namuru-GPL, un receptor open source implementat sobre la plataforma de desenvolupament Namuru, desenvolupada pel University of New South Wales Satellite Navigation and Positioning Laboratory (SNAP). La versió modificada del receptor Namuru-GPL implementada, ha estat capaç de seguir un senyal GPS C/A a la banda L1 i simultàniament una versió retardada del mateix que simulava ser un senyal reflectit amb un camí de propagació més llarg. A més, el receptor ha estat capaç de mesurar diferències de pseudorangs amb una resolució màxima de fins a 3 m en una única mesura a un escenari experimental controlat, validant així les capacitats del Namuru-GPL per a possibles aplicacions d'altimetria mitjançant GNSS-R. També s'ha desenvolupat un nou Mòdul d'Adquisició. Aquest mòdul és capaç de reduir dràsticament el temps mitjà d'adquisició del Namuru-GPL d'uns pocs minuts a 2,5 s aproximadament, gràcies al mètode d'adquisició en paral·lel. A més, el Mòdul d'Adquisició consumeix relativament pocs recursos hardware i és capaç de generar "Delay Doppler Maps" (DDMs). Totes les etapes del procés de desenvolupament dels dissenys proposats, inclosa la seva validació experimental es troben resumits en aquest treball

The Digital Design and Synthesis of Delay Doppler Maps in GNSS Remote Sensing Receivers

Global Navigation Satellite Systems (GNSS) are satellite based systems primarily capable of determining the location of receivers on the Earth. However, these systems can also receive and process bistatically surface reflected signals, studying the scattering from the signal off the reflection surface. In order to achieve these results, accurate and fast technology are necessary. In this work, a Delay-Doppler mapping module of a GNSS system has been implemented in VHDL and synthesized on FPGA Xilinx-Virtex 6 to map the delay and frequency domains of Earth scattered signals. The designed system presents high timing performance to provide quick and accurate measurements. In this work, a FFT based GNSS mapping algorithms has been designed to process raw samples GNSS data. The remote sensing module has been implemented, generating all the 32 possible C/A codes and then processing the received signal for each of the 32 C/A codes in a pipelined circuit. Once the GNSS power signals have been detected, a final detector is used to compare all the GNSS power signals found with a magnitude twice the noise and with the highest peak to detect the best candidate signal for the Delay Doppler Map (DDM). Different timing delay ranges and Doppler frequency ranges have been considered to compare the performance of the mapping algorithm. The use of an FPGA based algorithm permits significantly higher performance and greater flexibility than software based solutions and opens up the GNSS remote sensing application for integration into real-time instruments

GNSS Application in Retrieving Sea Wind Speed

In traditional Global Navigation Satellite System (GNSS) application, the reflected GNSS signals from Earth’s surface generally are considered as an interference source to be suppressed or removed. Recently, a new idea which treats the reflected GNSS signal as opportunity source of remote sensing has been proposed to monitor Earth’s physical parameters. This technique is called as GNSS-Reflectometry (GNSS-R) which has the advantages of low-power, -mass and -cost. With the development and modernization of GPS, Galileo, GLONASS, and BeiDou system, spaceborne GNSS could significantly improve the temporal-spatial resolution by receiving and processing the reflected signal from multiple satellites. This chapter mainly describes this new bi-static remote sensing technique. First, basic theories of GNSS-R including spatial geometry, polarization, and scattering model of reflected signal are discussed; second, spaceborne receivers and fast-response processing methods are reviewed and analyzed; finally, the empirical models retrieving wind speed are proposed and demonstrated using the DDM data from the UK-TechDomeSat-1 satellite. Based on the discussion of this chapter, it could be concluded that although GNSS-R still has some key challenges which have to be addressed, it could be an optimal choice of remote sensing in some special conditions, such as the tropical cyclone

Development of a drone-based miniaturized Flexible Microwave Payload (FMPL) for GNSS-Reflectometry and L-band radiometry

This project has been developed in collaboration with the NanosatLab UPC, which develops CubeSats for educational and scientific purposes and in-orbit technology demonstration. More specifically, the laboratory is focused on remote sensing systems. In recent years, the NanosatLab UPC has been developing the Flexible Microwave PayLoad (FMPL), the integration of different microwave remote sensing equipment in a single system: reflectometry Global Navigation Satellite System (GNSS) signals (GNSS-R) and microwave radiometry (MWR) in L-band. In 2022, the second version of this system, FMPL-2, is in orbit on board the CubeSat 3Cat5, which has provided precious scientific data on the climate of the earth and the evolution of climate change. The first version, FMPL-1, will be launched in the coming months aboard CubeSat 3Cat4. The third version, FMPL-3, is now ready for launch on board the CubeSat GNSSaS. From space, FMPL has proven to be a very useful tool for studying climate change. This work aims to design, build and test the first FMPL for drones, the FMPL-D. This new platform will be used to evaluate new versions of FMPL. It will also be a valuable tool to study the characteristics of soil, water, ice and vegetation locally and with a spatial resolution much greater than that which can be obtained from a satellite. The results presented in this thesis put the complexity of these systems into perspective. Firstly, in the results of the radiometer, an effect of distortion and destruction of the data obtained due to the radio frequency interference received during the measurement campaigns has been observed, highlighting the need for detection and mitigation systems interference for ground observation missions. For the GNSS reflectometry instrument, multiple flights were conducted in which large amounts of data were collected, the processing of which is still in progress. Preliminary results indicate good characteristics of the radio frequency chain. This Final Degree Project (TFG) is the first version of the FMPL-D, culminating in the system's first version and many lessons learned.Objectius de Desenvolupament Sostenible::13 - Acció per al Clim

Radio frequency interference detection and mitigation techniques for navigation and Earth observation

Radio-Frequency Interference (RFI) signals are undesired signals that degrade or disrupt the performance of a wireless receiver. RFI signals can be troublesome for any receiver, but they are especially threatening for applications that use very low power signals. This is the case of applications that rely on the Global Navigation Satellite Systems (GNSS), or passive microwave remote sensing applications such as Microwave Radiometry (MWR) and GNSS-Reflectometry (GNSS-R). In order to solve the problem of RFI, RFI-countermeasures are under development. This PhD thesis is devoted to the design, implementation and test of innovative RFI-countermeasures in the fields of MWR and GNSS. In the part devoted to RFI-countermeasures for MWR applications, first, this PhD thesis completes the development of the MERITXELL instrument. The MERITXELL is a multi-frequency total-power radiometer conceived to be an outstanding platform to perform detection, characterization, and localization of RFI signals at the most common MWR imaging bands up to 92 GHz. Moreover, a novel RFI mitigation technique is proposed for MWR: the Multiresolution Fourier Transform (MFT). An assessment of the performance of the MFT has been carried out by comparison with other time-frequency mitigation techniques. According to the results, the MFT technique is a good trade-off solution among all other techniques since it can mitigate efficiently all kinds of RFI signals under evaluation. In the part devoted to RFI-countermeasures for GNSS and GNSS-R applications, first, a system for RFI detection and localization at GNSS bands is proposed. This system is able to detect RFI signals at the L1 band with a sensitivity of -108 dBm at full-band, and of -135 dBm for continuous wave and chirp-like signals when using the averaged spectrum technique. Besides, the Generalized Spectral Separation Coefficient (GSSC) is proposed as a figure of merit to evaluate the Signal-to-Noise Ratio (SNR) degradation in the Delay-Doppler Maps (DDMs) due to the external RFI effect. Furthermore, the FENIX system has been conceived as an innovative system for RFI detection and mitigation and anti-jamming for GNSS and GNSS-R applications. FENIX uses the MFT blanking as a pre-correlation excision tool to perform the mitigation. In addition, FENIX has been designed to be cross-GNSS compatible and RFI-independent. The principles of operation of the MFT blanking algorithm are assessed and compared with other techniques for GNSS signals. Its performance as a mitigation tool is proven using GNSS-R data samples from a real airborne campaign. After that, the main building blocks of the patented architecture of FENIX have been described. The FENIX architecture has been implemented in three real-time prototypes. Moreover, a simulator named FENIX-Sim allows for testing its performance under different jamming scenarios. The real-time performance of FENIX prototype has been tested using different setups. First, a customized VNA has been built in order to measure the transfer function of FENIX in the presence of several representative RFI/jamming signals. The results show how the power transfer function adapts itself to mitigate the RFI/jamming signal. Moreover, several real-time tests with GNSS receivers have been performed using GPS L1 C/A, GPS L2C, and Galileo E1OS. The results show that FENIX provides an extra resilience against RFI and jamming signals up to 30 dB. Furthermore, FENIX is tested using a real GNSS timing setup. Under nominal conditions, when no RFI/jamming signal is present, a small additional jitter on the order of 2-4 ns is introduced in the system. Besides, a maximum bias of 45 ns has been measured under strong jamming conditions (-30 dBm), which is acceptable for current timing systems requiring accuracy levels of 100 ns. Finally, the design of a backup system for GNSS in tracking applications that require high reliability against RFI and jamming attacks is proposed.Les interferències de radiofreqüència (RFI) són senyals no desitjades que degraden o interrompen el funcionament dels receptors sense fils. Les RFI poden suposar un problema per qualsevol receptor, però són especialment amenaçadores per les a aplicacions que fan servir senyals de molt baixa potència. Aquest és el cas de les aplicacions que depenen dels sistemes mundials de navegació per satèl·lit (GNSS) o de les aplicacions de teledetecció passiva de microones, com la radiometria de microones (MWR) i la reflectometria GNSS (GNSS-R). Per combatre aquest problema, sistemes anti-RFI s'estan desenvolupament actualment. Aquesta tesi doctoral està dedicada al disseny, la implementació i el test de sistemes anti-RFI innovadors en els camps de MWR i GNSS. A la part dedicada als sistemes anti-RFI en MWR, aquesta tesi doctoral completa el desenvolupament de l'instrument MERITXELL. El MERITXELL és un radiòmetre multifreqüència concebut com una plataforma excepcional per la detecció, caracterització i localització de RFI a les bandes de MWR més utilitzades per sota dels 92 GHz. A més a més, es proposa una nova tècnica de mitigació de RFI per MWR: la Transformada de Fourier amb Multiresolució (MFT). El funcionament de la MFT s'ha comparat amb el d'altres tècniques de mitigació en els dominis del temps i la freqüència. D'acord amb els resultats obtinguts, la MFT és una bona solució de compromís entre les altres tècniques, ja que pot mitigar de manera eficient tots els tipus de senyals RFI considerats. A la part dedicada als sistemes anti-RFI en GNSS i GNSS-R, primer es proposa un sistema per a la detecció i localització de RFI a les bandes GNSS. Aquest sistema és capaç de detectar senyals RFI a la banda L1 amb una sensibilitat de -108 dBm a tota la banda, i de -135 dBm per a senyals d'ona contínua i chirp fen un mitjana de l'espectre. A més a més, el Coeficient de Separació Espectral Generalitzada (GSSC) es proposa com una mesura per avaluar la degradació de la relació senyal a soroll (SNR) en els Mapes de Delay-Doppler (DDM) a causa del impacte de les RFI. La major contribució d'aquesta tesi doctoral és el sistema FENIX. FENIX és un sistema innovador de detecció i mitigació de RFI i inhibidors de freqüència per aplicacions GNSS i GNSS-R. FENIX utilitza la MFT per eliminar la interferència abans del procés de correlació amb el codi GNSS independentment del tipus de RFI. L'algoritme de mitigació de FENIX s'ha avaluat i comparat amb altres tècniques i els principals components de la seva arquitectura patentada es descriuen. Finalment, un simulador anomenat FENIX-Sim permet avaluar el seu rendiment en diferents escenaris d'interferència. El funcionament en temps real del prototip FENIX ha estat provat utilitzant diferents mètodes. En primer lloc, s'ha creat un analitzador de xarxes per a mesurar la funció de transferència del FENIX en presència de diverses RFI representatives. Els resultats mostren com la funció de transferència s'adapta per mitigar el senyal interferent. A més a més, s'han realitzat diferents proves en temps real amb receptors GNSS compatibles amb els senyals GPS L1 C/A, GPS L2C i Galileo E1OS. Els resultats mostren que FENIX proporciona una resistència addicional contra les RFI i els senyals dels inhibidors de freqüència de fins a 30 dB. A més a més, FENIX s'ha provat amb un sistema comercial de temporització basat en GNSS. En condicions nominals, sense RFI, FENIX introdueix un petit error addicional de tan sols 2-4 ns. Per contra, el biaix màxim mesurat en condicions d'alta interferència (-30 dBm) és de 45 ns, el qual és acceptable per als sistemes de temporització actuals que requereixen nivells de precisió d'uns 100 ns. Finalment, es proposa el disseny d'un sistema robust de seguiment, complementari als GNSS, per a aplicacions que requereixen alta fiabilitat contra RFI.Postprint (published version

Advanced GNSS-R instruments for altimetric and scatterometric applications

This work is the result of more than eight years during a bachelor thesis, a master thesis, and the Ph.D. thesis dedicated to the development of the Microwave Interferometric Reflectometer (MIR) instrument. It summarizes all the knowledge acquired during this time, and describes the MIR instrument as detailed as possible. MIR is a Global Navigation Satellite System - Reflectometer (GNSS-R), that is, an instrument that uses Global Navigation Satellite System (GNSS) signals scattered on the Earth's surface to retrieve geophysical parameters. These signals are received below the noise level, but since they have been spread in the frequency domain using spread-spectrum techniques, and in particular using the so-called Pseudo Random Noise (PRN) codes, it is still possible to retrieve them because of the large correlation gain achieved. In GNSS-R, two main techniques are used for this purpose: the conventional technique cGNSS-R and the interferometric one iGNSS-R, each with its pros and cons. In the former technique, the reflected signal is cross-correlated against a locally generated clean-replica of the transmitted signal. In the latter technique the reflected signal is cross-correlated with the direct one. Nowadays multiple GNSS systems coexist, transmitting narrow and wide, open and private signals. A comparison between systems, signals, and techniques in fair conditions is necessary. The MIR instrument has been designed as an airborne instrument for that purpose: the instrument has two arrays, an up-looking one, and a down-looking one, each with 19 dual-band antennas in a hexagonal distribution. The instrument is able to form 2 beams at each frequency band (L1/E1, and L5/E5A), which are pointing continuously to the desired satellites taking into account their position, as well as the instrument's position and attitude. The data is sampled and stored for later post-processing. Last but not least, MIR is auto-calibrated using similar signals to the ones transmitted by the GNSS satellites. During the instrument development, the Distance Measurement Equipment/TACtical Air Navigation (DME/TACAN) signals from the Barcelona airport threatened to disrupt the interferometric technique. These signals were also studied, and it was concluded that the use of a mitigation systems were as strongly recommended. The interferometric technique was also affected by the unwanted contribution of other satellites. The impact of these contributions was studied using real data gathered during this Ph.D. thesis. During these 8 years, the instrument was designed, built, tested, and calibrated. A field campaign was carried out in Australia between May 2018 and June 2018 to determine the instrument's accuracy in sensing soil moisture and sea altimetry. This work describes each of these steps in detail and aims to be helpful for those who decide to continue the legacy of this instrument.Este trabajo es el resultado de más de 8 años de doctorado dedicados al desarrollo del instrumento Microwave Interferometric Reflectometer (MIR). Esta tesis resume todo el conocimiento adquirido durante este tiempo, y describe el MIR lo más detalladamente posible. El MIR es un Reflectómetro de señales de Sistemas Globales de Navegación por Satélite (GNSS-R), es decir, es un instrumento que usa señales de GNSS reflejadas en la superficie de la tierra para obtener parámetros geofísicos. Estas señales son recibidas bajo el nivel de ruido, pero dado que han sido ensanchadas en el dominio frecuencial usando técnicas de espectro ensanchado, y en particular usando códigos Pseudo Random Noise (PRN), es todavía posible recibirlas debido a la elevada ganancia de correlación. En GNSS-R existen dos técnicas para este propósito: la convencional (cGNSS-R), y la interferométrica (iGNSS-R), cada una con sus pros y sus contras. En la primera se calcula la correlación cruzada de la señal reflejada y de una réplica generada del código transmitido. En la segunda técnica se calcula la correlación cruzada de la señal reflejada y de la señal directa. Hoy en día muchos sistemas GNSS coexisten, transmitiendo señales de distintos anchos de banda, algunas públicas y otras privadas. Una comparación entre sistemas, señales, y técnicas en condiciones justas es necesaria. El MIR es un instrumento aerotransportado diseñado como para ese propósito: el instrumento tiene dos arrays de antenas, uno apuntando al cielo, y otro apuntando al suelo, cada uno con 19 antenas doble banda en una distribución hexagonal. El instrumento puede formar 2 haces en cada banda frecuencial (L1/E1 y L5/E5A) que apuntan continuamente a los satélites deseados teniendo en cuenta su posición, y la posición y actitud del instrumento. Los datos son guardados para ser procesados posteriormente. Por último pero no menos importante, el MIR se calibra usando señales similares a las transmitidas por los satélites de GNSS. Durante el desarrollo del instrumento, señales del sistema Distance Measuremt Equi Distance Measurement Equipment/TACtical Air Navigation (DME/TACAN) del aeropuerto de Barcelona mostraron ser una amenaza para la técnica interferométrica. Estas señales fueron estudiadas y se concluyó que era encarecidamente recomendado el uso de sistemas de mitigación de interferencias. La técnica interferométrica también se ve afectada por las contribuciones no deseadas de otros satélites, llamado cross-talk. El impacto del cross-talk fue estudiado usando datos reales tomados durante esta tesis doctoral. A lo largo de estos 8 años el instrumento ha sido diseñado, construido, testeado y calibrado. Una campaña de medidas fue llevada a cabo en Australia entre Mayo de 2018 y Junio de 2018 para determinar la capacidad del instrumento para estimar la humedad del terreno y la altura del mar. Este documento describe cada uno de estos pasos al detalle y espera resultar útil para aquellos que decidan continuar con el legado de este instrumento.Postprint (published version