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The 2-D frequency-based omega-K method is known to be a suitable algorithm for fully focused SAR (FF-SAR) radar altimeter processors, as its computational efficiency is much higher than equivalent time-based alternatives without much performance degradation. In this article, we provide a closed-form description of a 2-D frequency-domain omega-K algorithm specific for instruments such as Poseidon-4 onboard Sentinel-6. The processor is validated with real data from point targets and over the open ocean. Applications such as ocean swell retrieval and lead detection are demonstrated, showing the potentiality of the processor for future operational global-scale products., This work was supported by the Industrial Doctorates Plan from the Secretary of Universities and Research of the Department of Business and Knowledge of the Government of Catalonia through Project SA.45217 with Expedient Number 094 under Grant Doctorats Industrials 2020., Peer Reviewed, Postprint (published version)

The lack of knowledge of the micromobility regulations by e-scooter users is an important factor behind some of the accidents involving these vehicles. We present two modules that can increase the safety of the users and pedestrians: First, a computer vision model that analyses the video feed captured with a smartphone attached to the e-scooter, and predicts in real-time the type of lane in which the user is riding. This knowledge is used by an application which combines this information with GSNN location information and a database of mobility regulations, and informs the user when he/she is not complying with these regulations. Second, an accident detection system, using the smartphone accelerometer, that detects if there is a fall during the riding, so that the app can contact the authorities to determine the appropriate response. The experimental results show excellent results for both modules., We sincerely acknowledge the financial support that funding bodies have provided for this work. We thank the Spanish Ministry of Science, Innovation and Universities (PID2020-117142GB-I00 [DeeLight project] by MCIN/AEI/10.13039/501100011033). Additionally, we extend our gratitude to the EIT Urban Mobility, an initiative of the European Institute of Innovation and Technology (EIT), a body of the European Union, for their support under the RideSafeUM project, Peer Reviewed, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

(English) Future Geosynchronous Synthetic Aperture Radar (GEOSAR) missions will provide permanent monitoring of continental areas of the planet with revisit times of less than 24 h. Several GEOSAR missions have been studied in the USA, Europe, and China with different applications, including water cycle monitoring and early warning of disasters. GEOSAR missions require unprecedented orbit determination precision in order to form focused SAR images from Geosynchronous Orbits (GEO). A precise orbit determination technique based on microwave interferometry is proposed. An interferometric orbit determination system has been designed and implemented in order to acquire experimental phase observations from which the trajectory of the satellite can be estimated. The technique presents the capacity for tracking illuminators of opportunity, allowing interferometry to be tested without launching any new spacecraft. Multiple experimental campaigns are carried out using the signals of opportunity from the satellites of the Astra 19.2oE constellation. Since the measurement sensitivity of the interferometer increases with the length of the baseline, a signal relay strategy is proposed in order to extend the baseline while keeping all the receivers together, sharing a common clock reference. The use of passive reflectors in the near field of the secondary receivers forms a compact interferometric baseline of 15~m. The interferometer uses correlation techniques to operate with arbitrary transmitted signals. The correlator's high processing gain allows the system to effectively track weak signals well below the noise level. Thus, some buildings found in the vicinity of the campus are used as reflectors of opportunity, providing a weak satellite signal scattered in the direction of the receiver antennas, forming large interferometric baselines of up to 1200 m. An error model is developed in order to estimate the expected orbit determination precision from a set of interferometric pha, (Español) Las futuras misiones de radar geosíncrono de apertura sintética (GEOSAR) permitirán vigilar permanentemente zonas continentales del planeta con tiempos de revisita inferiores a 24 h. En Estados Unidos, Europa y China se han estudiado varias misiones GEOSAR con diferentes aplicaciones, como la vigilancia del ciclo del agua y la alerta temprana de catástrofes. Las misiones GEOSAR requieren una precisión de determinación orbital sin precedentes para obtener imágenes SAR enfocadas desde órbitas geosíncronas (GEO). Se propone una técnica de determinación orbital precisa basada en la interferometría de microondas. Se ha diseñado e implementado un sistema interferométrico de determinación orbital para adquirir observaciones experimentales de fase a partir de las cuales estimar la trayectoria del satélite. La interferometría es capaz de seguir iluminadores de oportunidad, permitiendo evaluar la técnica sin necesidad de lanzar ningún satélite nuevo. Se han llevado a cabo varias campañas experimentales utilizando las señales de oportunidad de los satélites de la constelación Astra 19.2oE. Dado que la sensibilidad de medida del interferómetro aumenta con la longitud de la línea de base, se propone una estrategia de retransmisión de señales con el fin de extender la línea de base manteniendo los receptores juntos para compartir una señal de referencia común. El uso de reflectores pasivos en el campo cercano de los receptores secundarios forma una línea de base interferométrica compacta de 15 m. El interferómetro utiliza técnicas de correlación para operar con señales arbitrarias. La gran ganancia de procesamiento del correlador permite el seguimiento eficaz señales débiles, muy por debajo del nivel de ruido. Así, algunos edificios que se encuentran en las proximidades del campus se utilizan como reflectores de oportunidad, proporcionando una débil señal de satélite reflejada en dirección a las antenas receptoras, formando grandes líneas de base interferométricas de ha, Postprint (published version)

With the growing concerns regarding the Climate Change phenomenon, the scientific community is putting a lot of effort into establishing empirical means to try and monitor its evolution over time. Specifically, inland waters play a key role not only as a sensitive indicator of the immediate consequences of Climate Change but also in generating educated strategies to improve water management worldwide. For the past years, satellite radar altimetry has been limited to the study of large water bodies such as coastal or open-ocean targets due to the altimeter?s considerably high along-track resolution, which made the analysis of smaller, inland water bodies, not feasible. However, with the introduction of the Fully-Focussed SAR technique, the along-track resolution has been narrowed down to the sub-meter range and, therefore, the analysis of inland waters is finally achievable even for the most remote targets, where the installation of the machinery needed for in-situ monitoring is not deemed as important enough to justify the investment. In this project, we will introduce the capabilities of the Fully-Focussed SAR technique while also conducting multiple water level measurements within the Ebro River Basin to assess the actual measurement quality that can be obtained when putting it into practice., A medida que aumenta la preocupación por el cambio climático, la comunidad científica se está esforzando por establecer una metodología empírica para poder monitorizar la evolución de este fenómeno a lo largo del tiempo. Concretamente, las aguas continentales juegan un papel muy importante tanto en su rol como indicadoras de las consecuencias más directas del cambio climático como para poder crear estrategias de mejora en el tratamiento de agua en todo el mundo. Durante los últimos años, la altimetría radar (en satélites) se ha visto limitada al estudio de masas de agua grandes, como, por ejemplo, el mar y el océano, ya que la resolución 'along- track' es demasiado grande como para ser útil para el estudio de las aguas continentales, que, de forma general, son mucho más pequeñas. Sin embargo, la introducción de la tecnología 'Full-Focussed SAR' consiguió que la resolución 'along-track' se viera reducida hasta quedar por debajo de un metro, y, como consecuencia, el estudio de las aguas continentales es finalmente posible, incluso en las localizaciones más remotas donde la instalación requerida para poder realizar medidas in-situ se considera que es no justificable. En este proyecto, introduciremos las capacidades de la técnica 'Fully-Focussed SAR' a la vez que tomaremos múltiples medidas de altura de aguas continentales próximas a la Cuenca del Ebro para poder analizar la calidad de las medidas obtenidas cuando se implementa esta técnica en la práctica., A mesura que augmenta la preocupació pel canvi climàtic, la comunitat científica s?està esforçant per establir una metodologia empírica per poder monitorar l?evolució d?aquest fenomen al llarg del temps. Concretament, les aigües continentals juguen un paper molt important tant en el seu rol com a indicadors de les conseqüències més directes del canvi climàtic com per poder crear estratègies per millorar el tractament d?aigua arreu del món. Durant els últims anys, l?altimetria radar (en satèl·lits) s?ha vist limitada a l?estudi de masses d?aigua grans, com, per exemple, el mar i l?oceà, ja que la resolució ?along-track? és massa gran per a poder ser útil per l?estudi de les aigües continentals, que, de forma general, són molt més petites. Tot i això, la introducció de la tecnologia ?Full-Focussed SAR? ha aconseguit que la resolució ?along-track? es veiés reduïda fins a quedar per sota d?un metre, i, com a conseqüència, l?estudi de les aigües continentals és finalment possible, fins i tot en localitzacions llunyanes on la instal·lació requerida per poder fer mesures in-situ es considera que és no justificable. En aquest projecte, introduirem les capacitats de la tècnica ?Fully-Focussed SAR? a la vegada que prendrem múltiples mesures d?altura d?aigües continentals pròximes a la Conca de l?Ebre per poder analitzar la qualitat de les mesures quan s?implementa aquesta tècnica a la pràctica.

Future Geosynchronous Synthetic Aperture Radar (GEOSAR) missions will provide permanent monitoring of continental areas of the planet with revisit times of less than 24 h. Several GEOSAR missions have been studied in the USA, Europe, and China with different applications, including water cycle monitoring and early warning of disasters. GEOSAR missions require unprecedented orbit determination precision in order to form focused Synthetic Aperture Radar (SAR) images from Geosynchronous Orbit (GEO). A precise orbit determination technique based on interferometry is proposed, including a proof of concept based on an experimental interferometer using three antennas separated 10–15 m. They provide continuous orbit observations of present communication satellites operating at GEO as illuminators of opportunity. The relative phases measured between the receivers are used to estimate the satellite position. The experimental results prove the interferometer is able to track GEOSAR satellites based on the transmitted signals. This communication demonstrates the consistency and feasibility of the technique in order to foster further research with longer interferometric baselines that provide observables delivering higher orbital precision., This work has been supported by the Spanish Science, Research and Innovation Plan (MICINN) with Project Codes TEC2017-85244-C2-2-P and PID2020-117303GB-C21 and by Unidad de Excelencia Maria de Maeztu MDM-2016-0600 financed by the Agencia Estatal de Investigación, Spain., Peer Reviewed, Postprint (published version)

In the framework of a feasibility study in support of the Hydroterra mission, a high resolution radar has been setup to monitor continuously a crop field with high resolution synthetic aperture radar images. In parallel, ground-truth data is acquired such as soil roughness, soil moisture and crop biological parameters. From this experimental data set the possibility to monitor soil moisture and crop biological parameters from back-scattering radar measurements will be assessed. To use the phase information of SAR images it is interesting to compensate the atmospheric phase screen induced by tropospheric refractive index. The paper presents a study of the atmosphetric phase drift prediction and compensation based on the local measurement of meteorological parameters., Peer Reviewed, Postprint (author's final draft)

This article focuses on mapping tropical deforestation using time series and machine learning algorithms. Before detecting changes in the time series, we reduced seasonality using Photosynthetic Vegetation (PV) index fractions obtained from Landsat images. Single and multi-temporal filters were used to reduce speckle noise from Synthetic Aperture Radar (SAR) images (i.e., ALOS PALSAR and Sentinel-1B) before fusing them with optical images through Principal Component Analysis (PCA). We detected only one change in the two PV series using a non-seasonal detection approach, as well as in the fused images through five machine learning algorithms that were calibrated with Cross-Validation (CV) and Monte Carlo Cross-Validation (MCCV). In total, four categories were obtained: forest, cropland, bare soil, and water. We then compared the change map obtained with time series and that obtained with the classification algorithms with the best calibration performance, revealing an overall accuracy of 92.91% and 91.82%, respectively. For statistical comparisons, we used deforestation reference data. Finally, we conclude with some discussions and reflections on the advantages and disadvantages of the detections made with time series and machine learning algorithms, as well as the contribution of SAR images to the classifications, among other aspects., Cet article porte sur la cartographie de la déforestation tropicale à l’aide de séries chronologiques et d’algorithmes d’apprentissage automatique. Avant de détecter les changements dans les séries temporelles, nous avons réduit la saisonnalité en utilisant les fractions de l’indice de végétation photosynthétique (PV) obtenues à partir des images Landsat. Des filtres mono et multitemporels ont été appliqués pour réduire le bruit de chatoiement des images RSO (Radar à synthèse d’ouverture) (c’est-à-dire ALOS PALSAR et Sentinel-1B) avant de les fusionner avec les images optiques par le biais de l’analyze en composantes principales (ACP). Nous avons détecté un seul changement à la fois dans les séries de PV en utilisant une approche de détection non saisonnière, ainsi que dans les images fusionnées, grâce à cinq algorithmes d’apprentissage automatique qui ont été calibrés par validation croisée (CV) et validation croisée de Monte-Carlo (MCCV). Au total, quatre catégories ont été obtenues: forêt, terres cultivées, sol nu et eau. Ensuite, nous avons comparé la carte des changements obtenue avec les séries temporelles et celle obtenue avec les algorithmes de classification les plus performants en matière de calibration, révélant une précision globale de 92.91% et 91.82% respectivement. Pour les comparaisons statistiques, nous avons utilisé des données de référence sur la déforestation. Enfin, nous concluons par des discussions et des réflexions sur les avantages et les inconvénients des détections effectuées avec les séries temporelles et les algorithmes d’apprentissage automatique, ainsi que sur la contribution des images RSO dans les classifications., The work of Yonatan Tarazona Coronel has been partially funded by American Program in GIS and Remote Sensing and National Program of Scholarships and Educational Credit (PRONABEC–Peru) through RJ: Nº 4276-2018- MINEDU/VMGI-PRONABEC-OBE and RJ: Nº 942-2019- MINEDU/VMGI-PRONABEC-OBE. Xavier Pons is the recipient of an ICREA Academia Excellence in Research Grant. The GRUMETS Research Group is partially supported by the Catalan Government under Grant SGR2017- 1690. This work has also been supported by the Spanish MCIU Ministry through the NEWFORLAND project (RTI2018-099397-B-C21 (MCIU/AEI/ERDF, EU))., Peer Reviewed, Postprint (published version)

Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura

Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura

HydroSoil is a measurement campaign, funded by the European Space Agency (ESA), where the temporal evolutions of two crops, barley and corn, have been continuously monitored during the whole crop period by means of a C-band Fully Polarimetric C-band Ground-Based Synthetic Aperture Radar (GB-SAR). SAR data has been collected together with ancillary data, and both are being processed to demonstrate the retrieval of soil moisture and vegetation parameters in an agricultural field under controlled conditions, to simulate the frequent acquisitions of GeoSAR missions., This work was funded by the European Space Agency (ESA Contract No. 4000132509/20/NL/FF/ab with UPC) and supported by the Spanish MCYT funds Unidad de Excelencia Maria de Maeztu MDM-2016-0600 and under project TEC2017-85244-C2-2-P. Special thanks to the Barcelona School of Agri-Food and Biosystems Engineering (EEABB) for making possible the radar deployment and the use of the experimental field., Peer Reviewed, Postprint (author's final draft)

Earth Observation missions are usually carried out by Low-Earth Orbit (LEO) satellites, which have major drawbacks when it comes to continuous monitoring of certain aspects of the Earth. The European Space Agency is currently in the Phase 0 (feasibility study) of the G-CLASS/Hydroterra mission, which will consist in a Geosynchronous Orbit satellite capable of conducting a continuous monitoring over some areas of the Earth, overcoming all the monitoring problems that the LEO satellites have. A high resolution synthetic aperture radar (GEOSAR) observation of continental areas will require long acquisition times in the order of hours, which can be affected by atmospheric or back-scattering changes of the observed surfaces. The Hydrosoil European Space Agency campaign carried out at Universitat Politecnica de Catalunya (UPC) provides a continuous stream of C-Band SAR polarimetric images of controlled agricultural test fields. The results obtained in the Hydrosoil campaign can be crucial to the future development of the Hydroterra mission as the set-up of the Ground-Based Synthetic Aperture Radar (GBSAR) is very similar to the GEOSAR in terms of the incidence angle. However, the atmosphere plays an important role when trying to monitor certain aspects of the soil such as roughness and moisture, as it modifies the amplitude and phase changes in the images (specially the phase). The main focus of this Master's Thesis is to analyze how the atmosphere really affects to the refractive index - and ultimately, to the phase changes of the SAR images - and how it can be compensated - , as well as to assess how the meteorological parameters and their sudden changes have an effect on other aspects directly related to the SAR images, such as the coherence or the Doppler Spectrum.

HYDROSOIL radar continuous monitoring campaigns over agricultural fields provided relevant data to understand atmospheric conditions impact over radar backscattering and coherence results. Radar backscattering magnitude observations present a daily cycle, with a ripple induced by dew. The interferometric phase results of the field presented an evident correlation with atmospheric humidity. In fact, the atmospheric parameters directly influence the soil permittivity, implying a direct impact on the coherence results that cannot be compensated. From the interferometric coherence modulus evolution analysis, considering different time periods for both barley and corn campaigns, a clear relationship between coherence magnitude decay and plant height is observed, which is almost linear. For this reason, current existing models relating radar observations with crop height can be reviewed to study possible improvements that could be exploited in present and future missions, taking into account the limitations in revisit time and local times of satellite ascending and descending passes., Las campañas de monitorización continua vía radar del proyecto HYDROSOIL sobre campos agrícolas proporcionaron datos relevantes para entender el impacto de las condiciones atmosféricas sobre los resultados de retrodispersión y coherencia del radar. Las observaciones de la magnitud de la retrodispersión del radar presentan un ciclo diario, con una ondulación inducida por el rocío de la madrugada. Los resultados de la fase interferométrica del campo presentan una correlación evidente con la humedad atmosférica. De hecho, los parámetros atmosféricos influyen directamente en la permitividad del suelo, lo que implica un impacto directo en los resultados de coherencia que no puede ser compensado. A partir del análisis de la evolución del módulo de coherencia interferométrica, considerando diferentes periodos de tiempo para las campañas de cebada y maíz, se observa una clara relación entre el decaimiento de la magnitud de coherencia y la altura de la planta, que es casi lineal. Por esta razón, los modelos actuales existentes que relacionan las observaciones de radar con la altura de los cultivos pueden ser revisados para estudiar posibles mejoras que podrían ser aprovechadas en las misiones actuales y futuras, teniendo en cuenta las limitaciones en el tiempo de revisita y los tiempos locales de los pases ascendentes y descendentes del satélite., Les campanyes de monitoratge continu via radar del projecte HYDROSOIL sobre camps agrícoles han proporcionat dades rellevants per a entendre l'impacte de les condicions atmosfèriques sobre els resultats de retrodispersió i coherència de radar. Les observacions de la magnitud de la retrodispersió de radar presenten un cicle diari, amb una ondulació induïda per la rosada de la matinada. Els resultats de la fase interferomètrica de camp presenten una correlació evident amb la humitat atmosfèrica. De fet, els paràmetres atmosfèrics influeixen directament en la permitivitat de terra, la qual cosa implica un impacte directe en els resultats de coherència que no pot ser compensat. A partir d'l'anàlisi de l'evolució de la coherència interferomètrica, considerant diferents períodes de temps per a les campanyes d'ordi i blat de moro, s'observa una clara relació entre el decaïment de la magnitud de coherència i l'alçada de la planta, que és gairebé lineal. Per aquesta raó, els models actuals existents que relacionen les observacions de radar amb l'altura dels cultius poden ser revisats per estudiar possibles millores que podrien ser aprofitades en les missions actuals i futures, tenint en compte les limitacions en el temps de revisita i els temps locals de les passades ascendents i descendents de satèl·lit.

Los radares de apertura sintética (SAR) disponibles actualmente para órbitas LEO tienen un tiempo de revisita muy extenso del orden de semanas, lo que limita las aplicaciones científicas y comerciales, ya que los fenómenos rápidos no pueden monitorearse. Un concepto innovador que aborda este problema es un GeoSynchronous SAR (GEOSAR), utilizando una órbita casi geoestacionaria que permite una observación permanente a escala continental. La investigación sobre este tema requiere la simulación de la adquisición de datos de radar y el posterior procesamiento para evaluar el rendimiento de GEOSAR. Dado que aún no se dispone de satélites GEOSAR, es posible realizar la validación experimental del concepto GEOSAR, utilizando transmisiones de satélites de telecomunicaciones DVB-S1 / S2 como emisores de oportunidad y adquiriendo los ecos producidos con una estación receptora terrestre. Así pues, en este proyecto el objetivo será el estudio de un sistema GEOSAR terrestre formado por un satélite GEO y una estación terrestre que recibe los ecos de una escena urbana. La actividad prevista incluye la generación de datos (señal de eco) y el procesamiento SAR de los ecos para evaluar y mejorar la calidad de la imagen. El objetivo final será utilizar los datos de eco obtenidos por una estación receptora de satélite en el techo del D3 para obtener imágenes reales de SAR., The currently available synthetic aperture radars (SAR) for LEO orbits have a long revisit time in the order of weeks, limiting the scientific and commercial applications of remote sensing since fast phenomena cannot be monitored. An innovative concept addressing this gap is a GeoSynchronous SAR (GEOSAR), which uses an almost GEOstationary orbit allowing a permanent observation at continental scale. The research on this topic requires the simulation of radar data acquisition and subsequent SAR processing to assess GEOSAR performance. Since no GEOSAR satellites are yet available, it is still possible to carry out experimental validation of the GEOSAR concept, using telecommunication satellites DVB-S1/S2 transmissions as emitters of opportunity and acquiring the echoes produced with a ground based receiving station. Thus, in this project the objective will be the study of a ground based GEOSAR system formed by a GEO telecom. satellite and a ground station receiving the echoes from an urban scene. The foreseen activity includes raw data (echo signal) generation and SAR processing of the simulated echoes to evaluate and improve image quality. The final goal will be to use echo data obtained by a satellite receiver station on the D3 roof to obtain real SAR images."

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

The advent of geosynchronous remote sensing missions requires the development of precise orbit determination techniques at high orbits. Geosynchronous satellites require station-keeping manoeuvres to be performed periodically. Dynamical models do not consider artificial forces. Therefore, the tracking system must be able to detect them in order to keep track of the spacecraft autonomously. A compact baseline interferometer is deployed in order to track the signals of opportunity from the ASTRA 19.2?E geostationary constellation. The system is capable of autonomously estimate the trajectory of the satellite for a period of 22 days. Even after artificial orbital manoeuvres are performed. These results show that interferometry is a valid alternative for future geosynchronous remote sensing missions which require precise orbit determination. © 2021 IEEE, This work has been supported by the Spanish Science, Research and Innovation Plan (MINECO) with Project Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P and by Unidad de Excelencia Maria de Maeztu MDM-2016-0600 financed by the Agencia Estatal de Investigacion, Spain., Peer Reviewed, Postprint (published version)

Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

This work has been supported by the Spanish Science, Research and Innovation Plan(MINECO) with Project Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P andby Unidad de Excelencia Maria de Maeztu MDM-2016-0600 financed by the Agencia Es-tatal de Investigaci ́on, Spain.

Evaluation of ice-height change in Antartica, forecasting river discharges or estimating water surface elevation in coastal waters are some of many applications of Altimetry science. The main objective of a satellite Radar Altimeter is to measure the height of reflecting objects on earth. Those reflections are obtained from the echoes of electromagnetic waves, which are continuously sent by the altimeter instrument. The conventional satellite altimeter uses the echo delays to estimate the height. One of the main features to improve in radar altimetry systems is the along-track resolution (i.e. the capacity to distinguish between two point-targets). Along-track resolution improvements can be achieved when using processing algorithms that coherently sum groups of received electromagnetic pulses, which have been reflected by the same target. Nowadays, operational altimeters achieve along-track resolutions over 200 meters thanks to Unfocused Delay-Doppler algorithms. However, Fully-Focused (FF) algorithms can improve the along-track resolution to the order of sub-meter. Two main approaches of Fully-Focused methods have been presented: Fully-Focused in Time Domain and Fully-Focused in Frequency Domain. Although both of them achieve the same along-track resolution, FF in Frequency has demonstrated to be considerably faster than FF in Time. In this thesis, we introduce the theory of both FF methods, and present the results and applications of Fully-Focused in Time Domain algorithm.

In this dissertation, a study and a practical implementation of an acquisition and preprocessing unit are provided for the digitization and suitability of the radar signals. The hardware solution allows the digitization of radar signals at an appropriate speed and subsequently transfers the preprocessed data into a suitable interface. The system must include a memory and a direct connection interface for storage and external communication with a computer, respectively. The final results are obtained by processing the sampled data. This task is performed by a computer with a specific processing software designed by the department. The designed solution must be restrictive in terms of size, weight and portability. A low power hardware is needed in order to feed the unit through external batteries, keeping a suitable performance. From a commercial point of view, a cost effective and high integrated solution is needed.

In the context of preparation of Hydroterra mission by ESA, continuous radar backscattering measurements are required to assess several parameters of interest such as soil moisture and vegetation water content. The project will consist on the characterization, improvement and calibration of a low power ground based synthetic aperture radar that is being developed for continuous polarimetric radar measurements on controlled agricultural fields., As a support of the Hydroterra Mission by ESA, this project consists on the characterization, improvement and calibration of a low power ground based Synthetic Aperture Radar being developed for continuous polarimetric radar measurements on controlled agricultural fields to assess several parameters of interest such as soil moisture and vegetation water content. In such scenario, calibration is required to scale properly the measurements in magnitude and phase in order to be able to interpret the data and build models to retrieve the necessary parameters. A radiometric analysis of the FMCW Radar is developed to build a model describing the field site parameters to validate and aid the calibration procedure. Different measurements have been carried out to collect the ground truth data of the field to study the interaction between the radar and the crop site, like air humidity, temperature, precipitation and pressure. Soil roughness have been characterized after sowing and several soil moisture sensors have been installed at different depths to provide continuous monitoring. Frequent vegetation sampling and processing are performed to obtain data on plant density, leaf area index, phenology stage, water cycle and water content. Two different crops are sown and monitored. In the spring phase, barley, a typical cereal cultivated in southern Europe. Immediately after, corn is monitored through its life cycle until harvesting. The different densities, sizes and water content of both crops will allow the project to assess the radar capabilities to provide soil moisture and crop water content data. The radar and ground truth observations provide results about diurnal water cycle showing water dynamic processes such as precipitation interception, surface soil moisture evolution in the events of rain, dew and evaporation to assess the radar continuous monitoring capabilities.

The orbit accuracy requirements for a Geosynchronous Synthetic Aperture Radar (GEOSAR) are studied. Compared to telecommunication GEO satellites' station keeping needs, focusing the GEOSAR synthetic aperture demands a more accurate orbital determination. For this reason, the most suitable Precise Orbit Observation (POB) techniques are considered. Several radar tracking techniques fulfil the accuracy requirements while presenting a trade-off problem in terms of cost an operation. GNSS allow for precise autonomous navigation even at high orbits like GEO. Optical observation techniques perform well in order to calibrate other tracking systems. Interferometry stands out since it can be used taking advantage of present illuminators of opportunity. A ground interferometer is being designed and built in order to provide experimental measurements which will serve as proof of concept., This work has been supported by the Spanish Science, Re-search and Innovation Plan (MINECO) with Project Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P and by Unidad de Exce-lencia Maria de Maeztu MDM-2016-0600 financed by the AgenciaEstatal de Investigaci ́on, Spain., Peer Reviewed, Objectius de Desenvolupament Sostenible::6 - Aigua Neta i Sanejament, Objectius de Desenvolupament Sostenible::3 - Salut i Benestar, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (published version)

This work has been supported by the Spanish Science, Research and Innovation Plan (MINECO) with Project Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P and by Unidad de Excelencia Maria de Maeztu MDM-2016-0600 financed by the Agencia Estatal de Investigación, Spain., Peer Reviewed, Postprint (author's final draft)

This project consists in designing the work parameters of a new radar system for the ocular detection and in improving a cardio-respiratory radar detection system by implementing a new acquisition subsystem based on a microcontroller STM32F767ZI along with other improvements in signal processing. Both are high-resolution CW-FM radars that use CHIRP signals. The design of the new ocular detection system is based on what is already mounted, the cardiorespiratory detection system. For this reason, these improvements that are achieved for the cardiorespiratory detection system will be expandable to the ocular detection system once they are implemented. The results of the project are positive, as the objectives are achieved: a reliable acquisition of the signal is achieved and a first theoretical design of the new ocular detection radar system has been prepared. In the future it is planned using these prototypes in new configurations of the radar systems enunciated., Este proyecto consiste, por un lado, en diseñar los parámetros de trabajo de un nuevo sistema radar para la detección ocular i, por otro lado, en mejorar un sistema radar de detección cardiorrespiratoria implementando un nuevo subsistema de adquisición basado en un microcontrolador STM32F767ZI junto con otras mejoras en el procesado de señal. Ambos son radares CW-FM de alta resolución que utilizan señales CHIRP. El diseño del nuevo sistema para la detección ocular se basa en el ya montado, el sistema de detección cardiorrespiratoria. Por esta razón las respectivas mejoras que se consiguen para el sistema de detección cardiorrespiratoria serán ampliables al sistema de detección ocular, una vez se proceda a su implementación. Los resultados del proyecto son positivos, puesto que se alcanzan los objetivos: realizar una adquisición de señal fiable y preparar un primer diseño teórico del nuevo sistema radar de detección ocular. En el futuro se planea utilizar estos prototipos en nuevas configuraciones de sistemas radar., Aquest projecte consisteix, per una banda, en dissenyar els paràmetres de treball d'un nou sistema radar per a la detecció ocular i, per altre banda, en millorar un sistema radar de detecció cardiaorespiratòria implementant un nou subsistema d'adquisició basat en un microcontrolador STM32F767ZI junt amb altres millores en el processat de senyal. Ambdós són radars CW-FM d'alta resolució que fan servir senyals CHIRP. El disseny del nou sistema de detecció ocular es basa sobre el que ja hi ha muntat, el sistema de detecció cardiorespiratòria. Per aquest motiu les respectives millores que s'aconsegueixen per al sistema de detecció cardiorespiratori seran ampliables al sistema de detecció ocular una vegada es procedeixi al la seva implementació. Els resultats del projecte són positius, ja que s'assoleixen els objectius: s'aconsegueix realitzar una adquisició fiable del senyal i s'ha preparat un primer disseny teòric del nou sistema radar de detecció ocular. En un futur està planejat utilitzant aquests prototips en noves configuracions dels sistemes radar enunciats.

The mission geosynchronous – continental land atmosphere sensing system (G-CLASS) is designed to study thediurnal water cycle, using geosynchronous radar. Although the water cycle is vital to human society, processes on timescalesless than a day are very poorly observed from space. G-CLASS, using C-band geosynchronous radar, could transform this. Itsscience objectives address intense storms and high resolution weather prediction, and significant diurnal processes such assnow melt and soil moisture change, with societal impacts including agriculture, water resource management, flooding, andlandslides. Secondary objectives relate to ground motion observations for earthquake, volcano, and subsidence monitoring. Theorbit chosen for G-CLASS is designed to avoid the geosynchronous protected region and enables integration times of minutesto an hour to achieve resolutions down to ~20 m. Geosynchronous orbit (GEO) enables high temporal resolution imaging (up toseveral images per hour), rapid response, and very flexible imaging modes which can provide much improved coverage at lowlatitudes. The G-CLASS system design is based on a standard small geosynchronous satellite and meets the requirements ofESA's Earth Explorer 10 call., Peer Reviewed, Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (published version)

A major limitation of current Low Earth Orbit Synthetic Aperture Radars (LEOSAR) is related to their revisit time of several days or weeks. They cannot provide continuous monitoring over the same area of the planet. The introduction of the Geosynchronous Synthetic Aperture Radar (GEOSAR) aims to provide permanent illumination over a wide zone of the planet. This work is performed in the context of the new ESA Earth Explorer pre-selected mission G-CLASS/Hydroterra. It is designed to help scientists unravel the details of the daily water cycle. The orbit determination of a GEOSAR is one of the main challenges of the mission. Previous studies show how the generic sub-wavelength tolerance requirement to build a well focused synthetic aperture can be substantially relaxed up to the sub-meter scale. Several orbit observation techniques are reliable and perform well to this end. Among them, interferometry stands out since it can provide orbit observables coming from current satellites operating in GEO, serving as illuminators of opportunity. The experimental orbit observation data resulting from the validation interferometer built at the campus of the Universitat Politècnica de Catalunya in Barcelona is presented. It depicts the expected motion of the ASTRA 1M satellite, serving as proof of concept for future GEOSAR missions such as G-CLASS/Hydroterra., This work has been supported by the SpanishScience, Research and Innovation Plan (MINECO)withProject Codes TIN2014-55413-C2-1-P and TEC2017-85244-C2-2-P and by Unidad de Excelencia Maria deMaeztu MDM-2016-0600 financed by the AgenciaEstatal de Investigación, Spain., Peer Reviewed, Objectius de Desenvolupament Sostenible::6 - Aigua Neta i Sanejament, Objectius de Desenvolupament Sostenible::3 - Salut i Benestar, Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles, Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (author's final draft)

Aquest projecte consisteix en revisar, caracteritzar i redissenyar si és necessari les diferents parts que componen un prototip biomèdic basat en la tecnologia radar. Mitjançant aquesta tecnologia capaç de detectar moviments és possible monitoritzar constants vitals d'un pacient tals com la respiració o la freqüència cardíaca a partir dels seus desplaçaments toràcics. El radar treballa a alta freqüència (120 GHz) i el sistema s'encarrega de generar el senyal, preparar-lo, transmetre'l i finalment extreure'n informació. El primer capítol del treball és una introducció en la que s'explica el punt de partida: les necessitats del prototip i el primer model que se'n va fer (tot comptant amb la col·laboració de l'Hospital Sant Joan de Déu). En els capítols 2 i 3 es troba una explicació teòrica de les diferents tecnologies implicades: d'una banda una introducció a la tecnologia radar i de l'altra dels diversos components electrònics que conformen aquest disseny. En el quart capítol es tracta la introducció d'un segon canal en el sistema, tot explicant les seves implicacions teòriques, com fer-ne un correcte calibratge i els canvis que això introdueix en el sistema un cop integrat. En el cinquè i en el sisè capítol es revisa, prova i redissenyen dos dels elements principals de la generació de senyal: el DDS i el PLL. Es fa una exhaustiva revisió des del punt de vista tècnic (millores en el rendiment, en el soroll de fase...) i després es proven i presenten els resultats obtinguts. En el capítol 7 es resumeixen els resultats finals amb els valors definitius del prototip i es presenta el conjunt en funcionament. En el capítol 8 es fa un breu resum de l'impacte econòmic que ha tingut la realització d'aquest projecte. Finalment en el capítol 9 es presenten les conclusions extretes en la realització d'aquest projecte i unes possibles línies de treball futures encarades a seguir millorant el prototip., Este proyecto consiste en revisar, caracterizar y rediseñar si es necesario las diferentes partes que componen un prototipo biomédico basado en la tecnología radar. Mediante esta tecnología capaz de detectar movimientos es posible monitorizar constantes vitales de un paciente tales como la respiración o la frecuencia cardíaca a partir de sus movimientos torácicos. El radar trabaja a alta frecuencia (120GHz) y el sistema se encarga de generar la señal, prepararla, transmitirla y finalmente extraer información. El primer capítulo del trabajo es una introducción en la que se explica el punto de partida: las necesidades del prototipo y el primer modelo que se hizo (contando con la colaboración del Hospital Sant Joan de Déu). En los capítulos 2 y 3 se encuentra una explicación teórica de las distintas tecnologías implicadas: por un lado, una introducción a la tecnología radar y por el otro una explicación de los diversos componentes electrónicos que conforman este diseño. En el cuarto capítulo se trata la introducción de un segundo canal en el sistema, hablando de sus implicaciones teóricas, como hacer una correcta calibración y los cambios que esto introduce en el sistema una vez integrado. En el quinto y sexto capítulo se revisa, prueba y rediseñan dos de los elementos principales de la generación de señal: el DDS y el PLL. Se hace una exhaustiva revisión desde el punto de vista técnico (mejoras en el rendimiento, ruido de fase...) y luego se prueban y presentan los resultados obtenidos. En el capítulo 7 se resumen los resultados finales con los valores definitivos del prototipo y se presenta el conjunto en funcionamiento. En el capítulo 8 se hace un breve resumen del impacto económico que ha tenido la realización de este proyecto. Finalmente en el capítulo 9 se presentan las conclusiones extraídas en la realización de este proyecto y unas posibles líneas de trabajo fututas encaradas a seguir mejorando el prototipo., This project consists in reviewing, characterizing and redesigning if needed the different parts that compose a biomedical prototype based on radar technology. By using this technology capable of detecting movement, it is possible to monitor vital constants of a patient such as the breathing pattern or the cardiac frequency by looking at its thoracic movement. The radar works at a high frequency (120GHz) and the system does generate, prepare and transmit the signal while extracting information from it. The first chapter is an introduction in which the starting point is explained: the need of the prototype and the first model that was built (with the collaboration of Hospital Sant Joan de Déu). In the chapters 2 and 3 a theoretical explanation of the different technologies used is found: on the one hand, an approach to radar technology and on the other hand, a brief explanation of the different electronic components that compose the model. The fourth chapter speaks about the introduction of a second channel in the system and it explains its theoretical implications, how to correctly calibrate them and the changes it produces in the system when integrated. In the fifth and sixth chapter, two of the main elements of signal generation are reviewed, tested and redesigned: the DDS and the PLL. An exhaustive revision from the technical point of view (improvements in its performance, phase noise...) is made, and afterwards its tests and results are presented. In chapter 7, the final results and values of the prototype are summarized and presented as a whole system. In chapter 8 a brief review of the economic impact this project has had is made. Finally, in chapter 9, the main ideas and conclusions reached during the making of this project are presented. Also, some future work that could help the development and improvement of this prototype is proposed.

High resolution radar performance is critically affected by the quality of signal acquisition and first level processing subsystems which implement a filter mached to the transmitted waveform. In the case of CW-FM radars, the homodyne configuration allows an efficient implementation of the matched filter based on Fourier Transform techniques. The increasing computing power and versatility of latest microcontrollers allows the design of efficient subsystems including analogue to digital conversion and fast correlation in the Fourier domain. The TFG is focused on the design of a sub-system capable to digitise a base-band radar signals and pre-process them with the use of ADC and DSP modules., Los radares de alta resolución están altamente afectados por la calidad de adquisición de la señal y por los primeros niveles de procesado. En el caso de los CW-FM radares, la configuración permite la eficiente implementación de filtros basados en la transformada de Fourier. El constante incremento de capacidad computacional y versatilidad de los últimos microcontroladores permite diseñar subsistemas que incluyan convertidores analógico-digitales i rápidos cálculos en el dominio de Fourier. El TFG está centrado en el diseño de un subsistema capaz de digitalizar señales radar en banda-base y pre-procesarlas utilizando ADC y módulos DSP., Els radars d'alta resolució estan altament afectats per la qualitat d'adquisició de la senyal i per els primers nivells de processat. En el cas del CW-FM radars, la configuració permet la eficient implementació de filtres basats en la transformada de Fourier. El constant increment de capacitat computacional i versatilitat dels últims microcontroladors permet dissenyar subsistemes que inclouen convertidors analògic-digitals i ràpids càlculs en el domini de Fourier. El TFG està centrat en el disseny d?un subsistema capaç de digitalitzar senyals radar en banda-base i pre-processar-les utilitzant ADC i mòduls DSP.

This project proposes and evaluates a solution to address the existing problem of time synchronization data in the context of precise orbit determination of geostationary satel- lites. For this reason, in this memory a review of the basics of an interferometer and the need of making this accurate time synchronization are done. Then, an introduction to time transference and the method that will be followed are explained as well as the pro- posal of a system design which fulfills the requirements. Furthermore, all the work that has been done in order to develop the time stamp system is expressed in this memory. Finally, the validation of this system using different clocks as time references and other experiments are explained., Este protecto propone y avalua una solución con el fin de solucionar el problema que existe en la sincronización de datos en el contexto de la determinación orbital de satélites geoestacionarios. Por esto, en esta memoria se hace una breve explicación de las bases de la interferometria y de la necesidad de generar una precisa sincronización temporal. Después, se hace una introducción a la transferencia de tiempo y se explica el método que se seguirá asi como la propuesta de diseño del sistema. Además, todo el trabajo que se ha hecho a la hora de desenvolupar el sistema se puede ver en esta memoria. Finalmente se explica la validación del sistema utilizando diferentes relojes como referencias de tiempo y otros experimentos., Aquest projecte proposa i avalua una solució per tal de combatre el problema que existeix en la sincronització de dades en el contexte de la determinació orbital de satèl·lits geostacionaris. Per aquesta raó, en aquesta memòria es fa una breu explicació de les bases de la interferometria i de la necessitat de generar una precisa sincronització temporal. Després, una introducció a la transferència de temps i el mètode que es seguirà són explicats així com la proposta del disseny del sistema. A més a més, tot el treball que s'ha fet a l'hora de desenvolupar el sistema es pot veure en aquesta memòria. Finalment, la validació del sistema utilitzant diferents rellotges com a referències de temps i altres experiments són explicats.

The advancement of RADAR technology has allowed it to expand its use and applications beyond its traditional role. Among them, it highlights its potential as a medical diagnostic tool for biological signals that can allow the development of portable diagnostic systems to improve the speed of diseases detection in its most primitive stages. This thesis is dedicated to the study of various signal processing techniques for respiratory and cardiac signals, as well as to include an initial study on the early detection of epileptic movements. An initial theoretical study of each of the techniques has been carried out, in addition to checking their performance by implementing them in the MATLAB code and carrying out a comparative study to evaluate their possible implementation. It has been used pattern signals extracted from various subjects by a continuous wave radar prototype at 120 GHz developed by the TERAHEALTH team of the Department of Signal Theory and Communications., El avance de la tecnología RADAR ha permitido expandir su uso y aplicaciones más allá de su rol tradicional. Entre ellas, destaca su potencial como herramienta de diagnóstico médico de señales biológicas que puede permitir el desarrollo de sistemas portátiles de diagnóstico para mejorar la velocidad de detección de enfermedades en su estadio más primitivo. Esta tesis está dedicada al estudio de diversas técnicas de procesado de señal para señales respiratorias y cardíacas, además de incluir un estudio inicial sobre la detección temprana de movimientos epilépticos. Se ha realizado un estudio inicial teórico de cada una de las técnicas, además de comprobar sus prestaciones implementándolas en código MATLAB y realizar un estudio comparativo para evaluar su posible implementación. Se ha utilizado señales patrón extraídas de diversos sujetos mediante un prototipo de radar de onda continua a 120 GHz desarrollado por el equipo TERAHEALTH del departamento de Teoría de Señal y Comunicaciones., L'avenç de la tecnologia RADAR ha permès expandir el seu ús i aplicacions més enllà del seu rol tradicional. Entre elles, destaca el seu potencial com a eina de diagnòstic mèdic de senyals biològiques que pot permetre el desenvolupament de sistemes portàtils de diagnòstic per millorar la velocitat de detecció de malalties en el seu estadi més primitiu. Aquesta tesi està dedicada a l'estudi de diverses tècniques de processat de senyal per a senyals respiratòries i cardíaques, a més d'incloure un estudi inicial sobre la detecció primerenca de moviments epilèptics. S'ha realitzat un estudi inicial teòric de cadascuna de les tècniques, a més de comprovar les seves prestacions implementant en codi MATLAB i realitzar un estudi comparatiu per avaluar la seva possible implementació. S'han utilitzat senyals patró estretes de diversos subjectes mitjançant un prototip de radar d'ona contínua a 120 GHz desenvolupat per l'equip TERAHEALTH del departament de Teoria de Senyal i Comunicacions.

The aim of the project is to design and develope a signal generator for high resolution CW-FM radars. The signal is a linear FM called chirp. The object of this generator is to be versatile and reconfigurable, in order to be used in different CW-FM radars and keep the resolution and accuracy being a low-spur linear signal. The signal is generated by the direct digital Synthesis (DDS) technique and two prototypes are built in printed circuit board: the first one is realized with CMOS technology and a microcontroller and the second one uses FPGA/CPLD technology, which offers improvements and more flexibility compared to the first one. The project results are positive, as the objectives are achieved and the generator is able to create different chirp waveforms with the syncronism requiered by the radar to acquiere coherent data. Currently, the first prototype is used in the Vital Sense project radar., Este proyecto consiste en diseñar y desarrollar un generador de señal para radares CW-FM de alta resolución. Se trata de una señal FM lineal llamado chirp. El objetivo es que sea versatil y reconfigurable, para poder implementarse en diferentes radares de este tipo, conservando la alta resolución y precisión siendo el señal lineal y libre de espúrios. La señal se genera mediante la síntesis digital directa (DDS) y se realizan dos prototipos del generador en placas de circuito impreso: el primero utilizando tecnología CMOS y un microcontrolador y el segundo con la tecnología FPGA/CPLD, que añade mejoras y flexibilidad respecto el primero. Los resultados del proyecto son positivos, puesto que se logran los objetivos marcados y el generador permite crear diferentes tipos de señal chirp con el sincronismo requerido por los radares para garantizar la coherencia de los datos adquiridos. Actualmente, el primer prototipo se está utilizando en el radar del proyecto Vital Sense., Aquest projecte consisteix en dissenyar i desenvolupar un generador de senyal per a radars CW-FM d'alta resolució. Es tracta d'un senyal FM lineal anomenat chirp. L'objectiu és que el generador sigui versàtil i reconfigurable, per poder implementar-se en diferents radars d'aquest tipus, conservant l'alta resolució i precisió assegurant que el senyal sigui lineal i lliure d'espuris. El senyal es genera amb la síntesis digital directa (DDS) i es realitzen dos prototips del generador en plaques de circuit imprès: el primer utilitzant tecnologia CMOS i un microcontrolador i el segon amb la tecnologia FPGA/CPLD, que afegeix millores i més flexibilitat respecte el primer. Els resultats del projecte són positius, ja que s'assoleixen els objectius i el generador permet crear diferents tipus de senyals chirp amb el sincronisme requerit pels radars per garantir la coherència de les dades adquirides. Actualment, el primer prototip s'està utilitzant en el radar del projecte Vital Sense.

Conventional radar remote sensing is based on Low Earth Orbit (LEO) satellites with a tytpical revisit time of 10-30 days. To achieve permanent radar monitoring for meteorological applications or natural hazards monitoring a continuous acquisition from Geostationary satellites is required. In the preparation of a future European Geostationary Radar mission new techniques of Synthetic Aperture Radar formation must be studied. The proposed TFG addresses the proposal, simulation and validation of a Geostationary SAR (GEOSAR) Processor. The existing tranmissions of telecommuni, This document is an investigation about GEOSAR technology and possible methods that improve the performance especially by accurately pointing or focusing the antenna towards the target. Results obtained show that this accuracy can be evaluated through several parameters, being the entropy of the SAR image one of the most consistent. A gradient descent is implemented as means to focus the image by optimizing the entropy of the SAR image. The application of this procedure known as ?autofocus? has a wide variety of applications and can be used in different systems if more precision is needed. In this case, the autofocus designed is very forgiving in terms of computational cost, but is very generous with its accuracy., Este documento consiste en una investigación sobre la tecnología GEOSAR y posibles metodologías para obtener un mejor funcionamiento al mejorar el apuntado hacia el objetivo del mismo. Los resutados obtenidos demuestran que dicha precisión se puede medir con buena fidelidad a través de la entropía de la imagen SAR obtenida. Este mismo resultado se utiliza a posteriori para mejorar el apuntado de las antenas del sistema mediante un gradiente descendiente. Dicho apuntado es conocido como "autofocus" o autoapuntado, y varía en función de la aplicación y resultados deseados. En este caso se ha diseñado un autoapuntado muy económico en términos de coste computacional a cosa de pero precisión., Aquest document consisteix en una investigació sobre la tecnologia GEOSAR i possibles mètodes que milloren el seu funcionament millorant l'apuntat de l'antena cap al seu objectiu. Els resultats demostren que la precisió d'aquest apuntat es pot mesurar fidelment amb l'entropia de la imatge SAR generada. Aquest mateix resultat s'utilitza més endavant per implementar un algoritme que millora l'apuntat del sistema. Aquest procediment de millora de l'apuntat es coneix com a "autofocus" o autoapuntat, i canvia en funció de la precisió i cost computacional desitjat. En aquest cas, s'ha dissenyat un sistema que es molt econòmic en termes de cost computacional a canvi de manca de precisió.