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  • Radiometric performance of SMOS full polarimetric imaging

     Wu, Lin; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Duran Martinez, Israel; Vall-llossera Ferran, Mercedes Magdalena; Camps, Adiano; Delwart, Steven; Martín Neira, Manuel
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2013-11
    Journal article

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    This work has been conducted in the framework of several projects devoted to assess the performance of the Soil Moisture and Ocean Salinity (SMOS) mission full-pol measurement mode. Since its launch in November 2009, SMOS is producing dual-polarization brightness temperature synthesized images that are yielding a high scientific return. However, these images are affected by a non-negligible spatial amplitude error, the so-called spatial bias (SB), that degrades geophysical parameter retrieval. This effect is particularly detrimental in SMOS polarimetric images where spatial bias is masking the polarimetric physical signature to a large extend. This paper presents a method to mitigate SMOS spatial bias by taking into account the co-and cross-polar antenna patterns in the image reconstruction algorithm through the, so called, full-pol G-matrix (FPG). The method is validated by producing spatial bias maps out of the comparison between SMOS full-pol images and an accurate polarimetric brightness temperature model of the ocean. This model has been provided to SMOS ESLs (Expert Support Laboratories) by LOCEAN (Laboratoire d'Océanographie et du Climat, France) as a test bench to validate and improve SMOS Level 1 (L1) data. Finally, a radiometric performance summary table comparing spatial bias and radiometric sensitivity between this new FPG approach and SMOS current co-polar G-matrix approach (CPG) is provided. This paper presents the best quality SMOS polarimetric images, which may lead a breakthrough in the science returns of the mission.

  • Spatial biases analysis and mitigation methods in SMOS images

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Wu, Lin; Duffo Ubeda, Nuria; Duran Martinez, Israel; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-22
    Presentation of work at congresses

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    SMOS brightness temperature images show some residual artifacts as a function of spatial directions. Due to having different antenna patterns in each element, even if knowing them perfectly, a minimum reconstruction error inherent to the inversion algorithm exists. On top of that, antenna patterns measurement errors and other effects such as cross-polarization terms, increase the spatial biases. Accurate characterization of these sources of error allows improving the quality of the SMOS images. Good results in this direction are reported.

  • In-orbit validations of SMOS full polarimetric equations

     Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Wu, Lin; Duffo Ubeda, Nuria; Delwart, Steven; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-22
    Presentation of work at congresses

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    This paper analyzes the consistency of SMOS fully polarimetric measurement mode by comparing measured data over the ocean with the expected results. These last are based on an accurate ocean model provided by LOCEAN and simulated taking into account both the co- and cross-polar field antenna patterns. The successful image reconstruction by means of the so-called model full-pol G matrix (M-FPG) method validates SMOS main full-pol features: the full-pol switching scheme, the accuracy of the full-pol antenna pattern measurements and the full-polarimetric visibility equations.

  • Spatial decorrelation of radiometric noise in SMOS measurements

     Torres Torres, Francisco; Wu, Lin; Duffo Ubeda, Nuria; Corbella Sanahuja, Ignasi; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-22
    Presentation of work at congresses

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  • Stability of the MIRAS amplitude calibration

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2012
    Presentation of work at congresses

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    Efficient methods to characterize and mitigate longand short- term drifts in SMOS data have been developed after careful analysis of the external and internal calibration parameters and by accurate modeling of the individual receiver frontends. A method to characterize this drift has been successfully developed and used to reduce the measured antenna temperature variations.

    Efficient methods to characterize and mitigate long-and short- term drifts in SMOS data have been developed after careful analysis of the external and internal calibration parameters and by accurate modeling of the individual receiver front-ends. A method to characterize this drift has been successfully developed and used to reduce the measured antenna temperature variations.

  • Supermiras instrument development, technology and calibration

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-22
    Presentation of work at congresses

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  • Enhanced SMOS amplitude calibration using external target

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Duran, Israel; Pablos, Miriam; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-22
    Presentation of work at congresses

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  • Performance of a spatial error correction technique in SMOS brightness temperature images

     Wu, Lin; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Martín Neira, Manuel
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2012-03-05
    Presentation of work at congresses

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    Soil Moisture and Ocean Salinity (SMOS) brightness temperature synthesized images are obtained after a comprehensive calibration and error correction procedure. However, the final images are still contaminated by small but non-negligible spatial errors: the so-called pixel bias. These errors have been found to be very stable in the SMOS Alias-Free Field of View (AF-FoV) and can be mitigated, to a large extent, by applying a multiplicative mask to the measured brightness temperatures at the antenna plane. This paper describes the procedure to upgrade this mask to cover SMOS Extended AF­ FoV.

  • Review of the CALIMAS Team Contributions to European Space Agency¿s Soil Moisture and Ocean Salinity Mission Calibration and Validation

     Camps Carmona, Adriano Jose; Font Ferré, Jordi; Corbella Sanahuja, Ignasi; Vall-llossera Ferran, Mercedes Magdalena; Portabella, Marcos; BALLABRERA POY, JOAQUIM; Gonzalez Gambau, Verónica; Piles Guillem, Maria; Aguasca Sole, Alberto; Acevo Herrera, René; Gabarro Prats, Carolina; Duffo Ubeda, Nuria; Bosch, Xavier; Fernández Gallego, Pedro; Gourrion, J.; Guimbard, Sébastien Arnaud; Marín, Anna; Martínez, Justino; Monerris Belda, Alessandra; Pérez, Baptiste; Pérez Villar, Fernando; Salvador, Joaquin; Sabia, Roberto; Talone, Marco; Torres Torres, Francisco; Pablos, Miriam; Martínez-Fernández, José; ANTONIO, TURIEL MARTÍNEZ; Valencia Domenech, Enric; Rodríguez Álvarez, Nereida; Sanchez, Nilda; Pérez Gutiérrez, Carlos; Baroncini Turricchia, Guido; Rius, Antonio; Ribó Vedrilla, Serni
    Remote sensing of environment
    Date of publication: 2012
    Journal article

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  • Reduction of Secondary Lobes in Aperture Synthesis Radiometry

     Corbella Sanahuja, Ignasi; Martín Neira, Manuel; Oliva, R.; Torres Torres, Francisco; Duffo Ubeda, Nuria
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012-09
    Journal article

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  • Minimization of Image Distortion in SMOS Brightness Temperature Maps Over the Ocean

     Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Wu, Lin; Duffo Ubeda, Nuria; Gourrion, J.; Font Ferré, Jordi; Martín Neira, Manuel
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012-01
    Journal article

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  • Contribution to the characterization of interferometric radiometers devoted to Earth observation: application to the MIRAS/SMOS payload  Open access

     González Gambau, Veronica
    Defense's date: 2012-09-05
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The variability of soil moisture and ocean salinity controls the continuous exchange of water between the oceans, the atmosphere and the land. Therefore, the accurate and periodic measurements of these geophysical variables are paramount to improve the climate change prediction and extreme-event forecasting. However, until very recently, global measurements of these parameters with a suitable spatial and temporal resolution have not been available. Real aperture radiometers have been frequently used for Earth observation applications. Nevertheless, for space-borne sensors at a low Earth orbit, the requirements on spatial resolution and coverage, at the operating frequencies (L-band), would require an unfeasibly large antenna. Conversely, synthetic aperture radiometry achieves high resolution using an array of small antennas, becoming a sound alternative to real aperture radiometry at low microwave frequencies. The ESA's SMOS (Soil Moisture and Ocean Salinity) mission, successfully launched on November 2009, is the first mission ever attempted to frequently and globally measure soil moisture over the continents and sea surface salinity over the oceans. The single payload of the mission, the MIRAS (Microwave Imaging Radiometer by Aperture Synthesis) instrument, is the first spaceborne L-band two dimensional synthetic aperture radiometer. This completely new type of instrument implies a technological challenge, for which the development of a detailed error model denition, dedicated calibration and image reconstruction algorithms have been needed. The calibration of MIRAS tackles all activities devoted to retrieve the SMOS scientic products from raw data measurements with the accuracy required by the scientic community. Characterization activities of the MIRAS instrument, mainly performed prior to the beginning of the in-orbit operation, have been required to develop and test the calibration activities. Within the framework of the SMOS mission, this Ph.D. Thesis is focused on the characterization of the interferometric radiometers devoted to Earth observation. The main contributions of this Thesis, which are directly related to the MIRAS payload performance assessment, are: (i) the denition of tests for the characterization campaigns, data processing methods and success criteria and (ii) the development of calibration algorithms and tools to fine-tune the instrument in order to fully achieve the system requirements and therefore the scientific requierements of the mission. Most of the work has been done in the framework of the MIRAS/SMOS Pre-Commissioning Phase activities and it has been completed in the framework of the Commissioning Phase preparatory work. Calibration tools and techniques developed for the MIRAS ground characterization have been adapted to fulfill in-orbit instrument characterization during the first months of the Commissioning Phase and contributed to the development and consolidation of the SMOS operational level-1 processing.

    La variabilidad de la humedad del suelo y de la salinidad de los oc´eanos controla el continuo intercambio de agua entre los oc´eanos, la atm´osfera y la tierra. Por tanto, la obtenci´on de medidas precisas y peri´odicas de estas dos variables geof´ısicas es fundamental para la mejora de la predicci´on del cambio clim´atico y de la previsi´on de desastres naturales. Sin embargo, hasta hace muy poco no se dispon´ıa de medidas globales de estos par´ametros con la resoluci´on temporal y espacial necesaria para este tipo de aplicaciones. Los radi´ometros de apertura real se han utilizado frecuentemente para aplicaciones de observaci´on de la Tierra. Sin embargo, para sensores situados en ´orbitas bajas, los requerimientos de resoluci´on espacial y cobertura, a la frecuencia de trabajo (banda L), implicar´ıan el uso de una antena de unas dimensiones que no son viables tecnol´ogicamente. Por el contrario, la radiometr´ıa de apertura sint´etica permite obtener una alta resoluci´on utilizando un array de peque˜nas antenas, convirti´endose en una s´olida alternativa a la radiometr´ıa de apertura real para frecuencias bajas de microondas. La misi´on SMOS, de la Agencia Espacial Europea, lanzada con ´exito en Noviembre de 2009, es la primera misi´on para la medida frecuente y global de la humedad del suelo y la salinidad de los oc´eanos. La ´unica carga ´util de la misi´on, el instrumento MIRAS, es el primer radi´ometro de apertura sint´etica en dos dimensiones que es lanzado al espacio. Este tipo de instrumento, completamente novedoso, implica todo un reto tecnol´ogico, por lo que han sido necesarios la definici´on de un modelo detallado de errores y el desarrollo de algoritmos espec´ıficos de calibraci´on e inversi´on de imagen. La calibraci´on del radi´ometro MIRAS comprende todas las actividades dedicadas a recuperar los productos cient´ıficos de SMOS a partir de los datos crudos con la precisi´on requerida por la comunidad cient´ıfica. Para poder desarrollar y probar las actividades de calibraci´on ha sido preciso realizar campa˜nas de caracterizaci´on del instrumento, llevadas a cabo en tierra principalmente. En el marco de la misi´on SMOS, esta tesis se centra en la caracterizaci´on de radi´ometros interfer´ometricos para la observaci´on de la Tierra. Las principales contribuciones de esta tesis, relacionadas directamente con la evaluaci´on de las prestaciones del radi´ometro MIRAS, son: (i) la definici´on de las medidas para las campa˜nas de caracterizaci´on, m´etodos de procesado de datos y criterios de ´exito y (ii) el desarrollo de algoritmos de calibraci´on y herramientas que permitan el ajuste del intrumento para cumplir los requerimientos del sistema y por lo tanto, los requerimientos cient´ıficos de la misi´on. La mayor parte de este trabajo se ha realizado en el marco de las actividades previas al lanzamiento de la misi´on y se ha completado en el marco del trabajo preparatorio de la fase de comisionado (primeros meses de medidas en ´orbita). Las herramientas de calibraci´on y las t´ecnicas desarrolladas para la caracterizaci´on en tierra del instrumento se han adaptado para completar la caracterizaci´on del instrumento durante los primeros meses en ´orbita, contribuyendo al procesado de nivel 1 operacional.

  • PAU-SYNTHETIC APERTURE: A NEW INSTRUMENT TO TEST POTENTIAL IMPROVEMENTS FOR FUTURE INTERFEROMETRIC RADIOMETERS  Open access

     Ramos Perez, Isaac
    Defense's date: 2012-02-27
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The Soil Moisture and Ocean Salinity (SMOS) mission is an Earth Explorer Opportunity mission from the European Space Agency (ESA). It was a direct response to the global observations of soil moisture and ocean salinity. Its goal is to produce global of these parameters using a dual-polarization L-band interferometric radiometer the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). This instrument is a new polarimetric two-dimensional (2-D) Y-shaped synthetic aperture interferometric radiometer based on the techniques used in radio-astronomy to obtain high resolution avoiding large antenna structures. MIRAS measures remotely the brightness temperature (TB) emitted by the Earth's surface, which is not isotropic, since it depends on the incidence angle and polarization, the Soil Moisture (SM) or the Sea Surface (SSS), the surface roughness etc. among others. The scope of this doctoral thesis is the study of some potential improvements could eventually be implemented in future interferometric radiometers. To validate improvements a ground-based instrument concept demonstrator the Passive Advanced Unit Synthetic Aperture or (PAU-SA) has being designed and implemented. Both MIRAS and PAU-SA are Y-shaped array, but the receiver topology and the processing unit are different. This Ph.D. thesis has been developed in the frame of The European Investigator Awards (EURYI) 2004 project entitled "Passive Advanced Unit (PAU): Hybrid L-band Radiometer, GNSS Refectometer and IR-Radiometer for Passive Sensing of the Ocean", and supported by the European Science Foundation (ESF).

  • SMOS: Actividades de la fase operacional y futuras misiones

     Duffo Ubeda, Nuria
    Participation in a competitive project

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  • A new space technology for ocean observation: the SMOS mission

     Font Ferré, Jordi; BALLABRERA POY, JOAQUIM; Camps Carmona, Adriano Jose; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Duran Martínez, Israel; Emelianov Kolomitski, Mikhail; Enrique González, Luis; Fernández Gallego, Pedro; Gabarro Prats, Carolina; González, Cristina; Gonzalez Gambau, Verónica; Gourrion, J.; Guimbard, Sébastien Arnaud; Hoareau, N.; Julià, A; Kalaroni, S.; Konstantinidou, Anna; Aretxabaleta, L.; Martínez, Justino; Miranda, Jorge Miguel; Monerris Belda, Alessandra; Montero, Sergio; Mourre, B.; Pablos Hernandez, Miriam; Pérez Villar, Fernando; Piles Guillem, Maria; Portabella, Marcos; Sabia, Roberto; Salvador, Joaquin; Talone, Marco; Torres Torres, Francisco; Turiel Martínez, Antonio; Vall-llossera Ferran, Mercedes Magdalena; Villarino, Ramon
    Scientia marina
    Date of publication: 2012
    Journal article

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    Capability for sea surface salinity observation was an important gap in ocean remote sensing in the last few decades of the 20th century. New technological developments during the 1990s at the European Space Agency led to the proposal of SMOS (Soil Moisture and Ocean Salinity), an Earth explorer opportunity mission based on the use of a microwave interferometric radiometer, MIRAS (Microwave Imaging Radiometer with Aperture Synthesis). SMOS, the first satellite ever addressing the observation of ocean salinity from space, was successfully launched in November 2009. The determination of salinity from the MIRAS radiometric measurements at 1.4 GHz is a complex procedure that requires high performance from the instrument and accurate modelling of several physical processes that impact on the microwave emission of the ocean’s surface. This paper introduces SMOS in the ocean remote sensing context, and summarizes the MIRAS principles of operation and the SMOS salinity retrieval approach. It describes the Spanish SMOS high-level data processing centre (CP34) and the SMOS Barcelona Expert Centre on Radiometric Calibration and Ocean Salinity (SMOS-BEC), and presents a preliminary validation of global sea surface salinity maps operationally produced by CP34.

  • SMOS brightness temperature measurements and end-to-end calibration

     Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    SMOS is the acronym for the Soil Moisture and Ocean Salinity mission by the European Space Agency (ESA) [1]. Its single payload, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), was launched in November 2009. After a six months Commissioning Phase SMOS entered in operational mode in May 2010. Since then SMOS has been delivering a large amount of data to successfully produce the first relevant scientific results. In order to provide accurate measurements, MIRAS requires a complex multi-step calibration procedure that was successfully tested both during pre-flight ground tests and Commissioning Phase activities. Additionally, an assessment of SMOS system performance in terms of short and long term stability, radiometric sensitivity and radiometric accuracy was also produced. In this context, this work is devoted to provide a high level overview of MIRAS calibration scheme by focusing on the rationale behind it.

  • Correction of spatial errors in SMOS brightness temperature images

     Wu, Lin; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    Systematic spatial errors in SMOS brightness temperature images are successfully estimated by using a statistical analysis of measured data. A constant multiplicative mask is derived by averaging spatial errors of a large number of snapshots over the ocean. The mask has been obtained for the aliasfree field of view region without the need of any geophysical model. It can be considered as part of the instrument characterization and is totally independent of the target to measure. When this mask is applied to regular SMOS brightness temperatures, the spatial artifacts are clearly reduced.

  • Interferometric radiometry measurement concept: The visibility equation

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    The fundamental concept of interferometric aperture synthesis microwave radiometry for Earth observation is reviewed. The measurement principles and a discussion on the signal processing techniques for image reconstruction are briefly summarized. Examples of real measurements from the sensor onboard the ESA SMOS mission are used to illustrate the image reconstruction techniques.

  • Phase error assessment of MIRAS/SMOS by means of the redundant space calibration

     Dávila, Rubén; Torres Torres, Francisco; Duffo Ubeda, Nuria; Corbella Sanahuja, Ignasi; Pablos, Miriam; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07
    Presentation of work at congresses

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    SMOS is the acronym for the Soil Moisture and Ocean Salinity mission by the European Space Agency (ESA) [1]. Its single payload, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), was successfully launched in November 2009. A six months Commissioning Phase was devoted to bring the satellite into a fully operational condition and to characterize the payload using specific orbits to check all instrument modes [2]. An ongoing activity is devoted to analyze the contribution of each single calibration procedure to the overall radiometric accuracy in order to assess the dominant sources of spatial errors. In this framework, this paper is devoted to assess the performance of the phase calibration procedures by means of the so called Redundant Space Calibration (RSC)1.

  • MIRAS calibration and performance: results from the SMOS in-orbit commissioning phase

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; González Gambau, Veronica; Pablos Hernandez, Miriam; Duran Martínez, Israel; Martín Neira, Manuel
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2011-09
    Journal article

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    After the successful launching of the Soil Moisture and Ocean Salinity satellite in November 2009, continuous streams of data started to be regularly downloaded and made available to be processed. The first six months of operation were fully dedicated to the In-Orbit Commissioning Phase, with an intense activity aimed at bringing the satellite and instrument into a fully operational condition. Concerning the payload Microwave Imaging Radiometer with Aperture Synthesis, it was fully characterized using specific orbits dedicated to check all instrument modes. The procedures, already defined during the on-ground characterization, were repeated so as to obtain realistic temperature characterization and updated internal calibration parameters. External calibration maneuvers were tested for the first time and provided absolute instrument calibration, as well as corrections to internal calibration data. Overall, performance parameters, such as stability, radiometric sensitivity and radiometric accuracy were evaluated. The main results of this activity are presented in this paper, showing that the instrument delivers stable and well-calibrated data thanks to the combination of external and internal calibration and to an accurate thermal characterization. Finally, the quality of the visibility calibration is demonstrated by producing brightness temperature images in the alias-free field of view using standard inversion techniques. Images of ocean, ice, and land are given as examples.

  • CONTRIBUTIONS TO EARTH OBSERVATION USING GNSS-R OPPORTUNITY SIGNALS  Open access

     Rodriguez Alvarez, Nereida
    Defense's date: 2011-12-22
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    During years a number of satellites have been developed to remotely sense Earth geophysical parameters for weather forecasting and other climate studies. In recent years the use of reflected Global Navigation Satellite System Signals (GNSS-R) has shown its potential to retrieve geophysical parameters over the ocean, mainly altimetry and sea state, and over land, mainly soil moisture. It is known that sea roughness has an impact on L-band radiometric measurements, and therefore on the retrieved sea surface salinity (SSS). GNSS-R is an interesting tool to help improving the sea state effect correction to reduce the final SSS retrieval error. To demonstrate this idea the Passive Advanced Unit (PAU) project was proposed to the European Scienc Foundation (ESF) under the EURYI 2004 call. The main objective was the study of the direct relationship between the radiometric brightness temperatures and some GNSS-R observables to perform the state correction without using emission/scattering models. Once this goal was successfully addressed, the PAU objectives were broaden including the development of new GNSS-R instruments and techniques, and the study of retrieving geophysical parameters from different surfaces. The present Ph.D. dissertation describes one of the research lines of the the PAU project, undertaken between February 2007 and December 2011, within the Passive Remote Sensing Group of the Remote Sensing Lab, at the Department of Signal Theory and Communications of the Universitat Politènica de Catalunya. The present Ph.D. dissertation focuses on GNSS-R techniques applied to the observation of different types of scattering surfaces (land surfaces: bare soils, vegetation-covered soils, snow-covered soils; inland-water surfaces and ocean surfaces) and the retrieval of different geophysical parameters. Two main GNSS-R techniques have been studied and applied to real data obtained during seven field experiments, the Delay-Doppler Map (DDM) processing technique and the Interference-Pattern Technique (IPT), selecting the one most appropriate to the observed surface. Furthermore, in the context of this Ph.D dissertation a new type of GNSS-R instrument has been developed, being the main tool for the application of the IPT and the retrieval of several geophysical parameters over land and inland-water surfaces. After an introduction on GNSS-R and the PAU-project, the methodology, the instruments and the techniques used to retrieve soil moisture, vegetation height and topography in agricultural areas, snow thickness, water level in reservoirs, and wind speed in ocean surfaces, are described. These retrievals show the potential that these opportunity signals have for monitoring a broad kind of effects. After that, some studies related to space-borne GNSS-R techniques are summarized. Finally a summary of the work performed in this Ph. D. dissertation, the main conclusions and the future work lines are presented. The presented results contribute to promote the use of the GNSS opportunity signals for monitoring geophysical parameters to increase the understanding of the Earth¿s water cycle, and position these techniques as suitable tools that enhance water resources management.

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    Some results on SMOS-MIRAS calibration and Imaging  Open access

     Martín Neira, Manuel; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Cabot, François; Duffo Ubeda, Nuria; Closa Dominguez, Josep M.; Kainulainen, Juha; Castro, R.; Barbosa Torralbo, José; Gutierrez, A.; Martín Porqueras, Fernando; Oliva, R.; Anterrieu, E.; Brown, N.; McMulan, K.
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2010-07-23
    Presentation of work at congresses

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    The performance requirements of the SMOS payload are demanding in terms of spatial resolution, accuracy, stability and precision, all critical to fulfill its scientific objectives. For this reason a commissioning plan for MIRAS was carefully devised to verify, calibrate and characterize all instrument parameters which could have an impact on its performance. This presentation describes the most important results from the instrument commissioning phase.

  • One point calibration in interferometric radiometers: MIRAS/SMOS preliminary results

     Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; González Gambau, Veronica; Pablos Hernandez, Miriam; Duran Martínez, Israel; Martín Neira, Manuel
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2010-03-01
    Presentation of work at congresses

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  • First results on MIRAS calibration and overall SMOS performance

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; González Gambau, Veronica; Pablos Hernandez, Miriam; Duran Martínez, Israel; Martín Neira, Manuel
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2010-03-01
    Presentation of work at congresses

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  • CONTRIBUTION TO THE IMPROVEMENT OF THE SOIL MOISTURE AND OCEAN SALINITY (SMOS) SEA SURFACE SALINITY RETRIEVAL ALGORITHM  Open access  awarded activity

     Talone, Marco
    Defense's date: 2010-11-22
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite was launched on November, 2, 2009 from the Russian cosmodrome of Plesetsk. Its objective is to globally and regularly collect measurements of soil moistre and Sea Surface Salinity (SSS). To do that, a pioneering instru- ment has been developed: the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), the rst space-borne, 2-D interferometric radiometer ever built; it operates at L-band, with a central frequency of 1.4135 GHz, and consists of 69 antennas arranged in a Y shape array. MIRAS' output are brightness temperature maps, from which SSS can be derived through an iterative algorithm, and using auxiliary information. For each overpass of the satellite an SSS map is produced, with an estimated accuracy of 1 psu (rmse). According to the Global Ocean Data Assimilation Experiment (GODAE) the mission requirement is instead speci ed as 0.1 psu after av- eraging in a 10-day and 2 2 spatio-temporal boxes. In previuos works ((Sabia et al., 2010), or more extensively in Dr. Sabia's Ph.D. thesis (Sabia, 2008)) the main error sources in retrieving SSS from SMOS measurements were determined as: 1. Scene-dependent bias in the simulated measurements, 2. L-band forward modeling de nition, 3. Radiometric sensitivity and accuracy, 4. Constraints in the cost function, and 5. Spatio-temporal averaging. This Ph.D. thesis, is an attempt of reducing part of the aforementioned errors (the relative to the one-overpass SSS (1 - 4)) by a more sophisticated data processing. Firstly, quasi-realistic brightness temperatures have been simulated using the SMOS End-to-end Performance Simulator (SEPS) in its full mode and an ocean model, as provider for geophysical parameters. Using this data set the External Brightness Temperature Calibration technique has been tested to mitigate the scene-dependent bias, while the error introduced by inaccuracies in the L-band forward models has been accounted for by the application of the External Sea Surface Salinity Calibration. Apart from simulated brightness temperatures, both External Brightness Temperature Calibration and External Sea Surface Salinity Calibration have been tested using real synthetic-aperture brightness temperatures, collected by the Helsinki University of Technology HUT-2D radiometer during the SMOS Calibration and Validation Rehearsal Campaign in August 2007 and ten days of data acquired by the SMOS satellite between July 10 and 19, 2010. Finally, a study of the cost function used to derive SSS has been performed: the correlation between measurement mis ts has been estimated and the e ect of including it in the processing have been assessed. As an outcome of a 3-month internship at the Laboratoire LOCEAN in Paris, France, a theoretical review of the e ect of the rain on the very top SSS vertical pro le has been carried out and is presented as Appendix.

  • Brightness-Temperature Retrieval Methods in Synthetic Aperture Radiometers

     Corbella Sanahuja, Ignasi; Torres, F; Duffo Ubeda, Nuria; Camps Carmona, Adriano Jose; González, A.; Vail-Ilossera, M
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2009-01
    Journal article

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  • Linearity characterization of detectors for interferometric radiometers

     Gonzalez-Haro, Cristina; Torres Torres, Francisco; Duffo Ubeda, Nuria; Corbella Sanahuja, Ignasi; Vilaseca, R; de Paco Sánchez, Pedro Antonio; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2009-07-12
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  • One point calibration in interferometric radiometers: error assessment

     Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; González Gambau, Veronica
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2009-07-12
    Presentation of work at congresses

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  • On-flight characterization of the SMOS payload during the commissioning phase

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; González Gambau, Veronica
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2009-09-12
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  • Experimental estimation of soil emissivity and its application to soil moisture retrieval in the SMOS mission  Open access

     Monerris Belda, Alessandra
    Defense's date: 2009-09-07
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Tot i que l'aigua retinguda pel sòl constitueix una petita fracció del volum total d'aigua que hi ha a la Terra, l'humitat del sòl juga un paper important als models climàtics i hídrics. La radiometria en banda L (1.400 a 1.427 GHz) és la tecnologia més adient per a mesurar l'humitat, no tan sols per la seva gran sensibilitat al contingut d'aigua sinó també perquè proporciona mesures independentment de les condicions meteorològiques. Dues missions espacials mesuraran l'humitat de sòl a escala global: SMOS de l'ESA i SMAP de la NASA. La present tesi doctoral s'ha realitzat dins el marc de les activitats prèvies al llançament de SMOS (Soil Moisture and Ocean Salinity). La càrrega útil de SMOS, anomenada MIRAS, és el primer radiòmetre interferomètric per síntesi d'obertura en dues dimensions aplicat a l'observació de la Terra. Cada pixel de la Terra serà observat sota diversos angles d'incidència, de manera que es disposarà d'informació multiangular per a cadascun d'ells. A aquesta tesi doctoral es presenten en primer lloc els sensors de microones i experiments relacionats amb l'estimació de l'humitat del sòl, a més d'incloure una revisió dels fonaments teòrics de la radiometria i de la física del sòl, i dels models que existeixen en la actualitat per a modelar-ne l'emissió. Després es passa a la part central de la tesi, on es tracten les campanyes de mesura que ha dut a terme el grup de radiometria de la UPC i els resultats i conclusions que s'han derivat de l'estudi de les dades. Les mesures radiomètriques van ser adquirides amb el radiòmetre LAURA (L-band Automatic Radiometer), dissenyat i construït a la UPC. La freqüència de funcionament de LAURA és 1.4 GHz, la mateixa que MIRAS. L'emissivitat del sòl depén de la interacció de molts paràmetres propis del sòl i de la coberta de vegetació que hi ha al damunt, com per exemple la humitat, la temperatura, i la rugositat del sòl, i l'atenuació i la dispersió que introdueix la vegetació. A cadascuna de les campanyes de mesura que es presenten a aquesta tesi doctoral s'ha tractat un d'aquests factors: · MOUSE 2004: efecte de la textura en els perfils d'humitat i temperatura del sòl, en l'emissivitat, i en l'algoritme de recuperació d'humitat del sòl a partir de les mesures multiangulars adquirides per LAURA.· T-REX 2004/2006: efecte de la rugositat en l'emissivitat. Les mesures es comparen amb prediccions teòriques i semi-empíriques dels models existents, els quals tenen en compte de manera diferent l'efecte del paràmetre de rugositat efectiva. · SMOS REFLEX 2003/2006: efectes de les vinyes i de la fracció de pedres. S'estudia la dependència de l'emissivitat amb l'humitat del sòl i amb l'angle d'observació. Aquests experiments es van dur a terme a la Valencia Anchor Station, una regió que ha estat seleccionada per a dur a terme activitats de cal/val de SMOS durant els sis mesos posteriors al llançament.· TuRTLE 2006: efecte de la topografia a les mesures adquirides des d'un sensor a terra.Els resultats mostren que el processador de SMOS hauria de tener en compte un model de constant dielèctrica diferent en funció de la textura, ja que els errors a la recuperació d'humitat poden variar en un 5% segons el tipus de sòl. La rugositat té un impacte important a l'emissivitat, sobre tot a sòls secs. Els models de rugositat segueixen el comportament de les mesures a sòls secs i H-pol, però divergeixen al cas de sòl humit. L'atenuació i dispersió de les vinyes és independent de la polarització. L'error en la recuperació d'humitat sobre camps de vinyes va ser del 2.3%, menor que el 4% requerit per SMOS. L'impacte de la topografia en les mesures és important i no pot modelar-se tenint en compte només la vegetació.

    Although water hold by soils represents a small fraction of the Earth's water budget, soil moisture plays an important role in climate models. In the near future, two space missions will measure soil moisture at global scale: ESA' SMOS and NASA's SMAP. The present Ph.D. Thesis has been performed in the context of the SMOS (Soil Moisture and Ocean Salinity) mission pre-launch activities over land. An important feature of SMOS is that a given pixel on the Earth is imaged at various observation angles as the satellite moves over it, so multi-angular information of each pixel will be available.A description of the field campaigns over land carried out by the Universitat Politècnica de Catalunya and of their results is provided in this PhD Thesis. Radiometric measurements were acquired using the UPC L-band Automatic Radiometer (LAURA), which has a working frequency of 1.4 GHz, the same as SMOS payload MIRAS. The execution of these experiments, the data processing, and the physical interpretation of measurements constitute the core of this PhD Thesis. The emissivity of land surfaces depends upon the interaction of several soil and vegetation characteristics such as soil moisture, roughness, and temperature, and vegetation opacity and albedo. Each of the experiments focused on one of the parameters affecting the emission from soils:· MOUSE 2004: impact of soil texture on soil moisture and temperature profiles, soil emissivity, and the impact on the soil moisture retrieval using multi-angular dual-polarisation radiometric observations.· T-REX 2004/2006: impact of soil roughness on the brightness temperature. Data collected during the T-REX experiments are compared to theoretical simulations using various models for the effective soil roughness.· SMOS REFLEX 2003/2006: effects of rock-fraction and vines. The brightness temperature dependence on soil moisture and observation angle is studied, and soil moisture retrieval is discussed. The experiment site in Valencia has already been selected as a SMOS calibration and validation site.· TuRTLE 2006: impact of topography on soil emissivity at L-band.Results suggest that the SMOS Level 2 soil moisture processor should select the soil dielectric constant model as a function of soil texture, since the root mean squared error can vary from 2% to 7% depending. Soil roughness was found to have a strong impact on land brightness temperature, especially for dry soils. In general, all semi-empirical land emission models follow the trend of dry soils measurements at H-pol, whereas discrepancies exist for wet soils. On the other hand, vines opacity and albedo were found to be independent on the polarisation. The error between ground-truth and estimated soil moisture over vineyards was 2.3%, better than the 4% required for SMOS. Topography effects are important and cannot be accounted for in the models only by the introduction of the vegetation canopy.

  • CONCEPTOS AVANZADOS EN TELEDETECCION ACTIVA Y PASIVA DE MICROONDAS: TECNOLOGIA Y APLICACIONES

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Broquetas Ibars, Antoni; Mallorqui Franquet, Jordi Joan; Duffo Ubeda, Nuria; Aguasca Sole, Alberto; López Martínez, Carlos; Fabregas Canovas, Francisco Javier
    Participation in a competitive project

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    On-ground characterization of the SMOS payload  Open access

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel; González Gambau, Veronica; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2009-09
    Journal article

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    The on-ground characterization of the synthetic aperture radiometer onboard the Soil Moisture and Ocean Salinity mission is described. Characterization includes basic functionality, internal calibration, thermal cycling, response to point and flat sources, self-radio-frequency interference, and others. The description of the different tests performed as well as the detailed results are provided. The results show that the instrument is very stable and has all gains and offsets consistent with the ones obtained at subsystem level. On the other hand, the phase of the visibility has a larger variation with temperature than expected, a small signal leakage from the local oscillators is present, and a small interference from the X-band transmitter during short periods of time has been detected. The implementation of internal-calibration procedures, along with the accurate thermal characterization performed, have been used to produce highly accurate brightness-temperature values well within specifications.

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    Polarimetric emission of rain events: simulation and experimental results at X-Band  Open access

     Duffo Ubeda, Nuria; Vall·Llosera, M; Camps Carmona, Adriano Jose; Corbella Sanahuja, Ignasi; Torres Torres, Francisco
    Remote Sensing
    Date of publication: 2009-06
    Journal article

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    Accurate models are used today for infrared and microwave satellite radiance simulations of the first two Stokes elements in the physical retrieval, data assimilation etc. of surface and atmospheric parameters. Although in the past a number of theoretical and experimental works have studied the polarimetric emission of some natural surfaces, specially the sea surface roughened by the wind (Windsat mission), very limited studies have been conducted on the polarimetric emission of rain cells or other natural surfaces. In this work, the polarimetric emission (four Stokes elements) of a rain cell is computed using the polarimetric radiative transfer equation assuming that raindrops are described by Pruppacher-Pitter shapes and that their size distribution follows the Laws-Parsons law. The Boundary Element Method (BEM) is used to compute the exact bistatic scattering coefficients for each raindrop shape and different canting angles. Numerical results are compared to the Rayleigh or Mie scattering coefficients, and to Oguchi’s ones, showing that above 1-2 mm raindrop size the exact formulation is required to model properly the scattering. Simulation results using BEM are then compared to the experimental data gathered with a X-band polarimetric radiometer. It is found that the depolarization of the radiation caused by the scattering of non-spherical raindrops induces a non-zero third Stokes parameter, and the differential phase of the scattering coefficients induces a non-zero fourth Stokes parameter.

  • Determination of the sea surface emissivity at L-band and application to SMOS salinity retrieval algorithms: Review of the contributions of the UPC-ICM

     Camps Carmona, Adriano Jose; Font, J; Vall-llossera Ferran, Mercedes Magdalena; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Torres Torres, Francisco; Blanch Boris, Sebastian; Aguasca Sole, Alberto; Villarino, R; Gabarro, C; Enrique, L; Miranda, J; Sabia, Roberto
    Radio science
    Date of publication: 2008-06-20
    Journal article

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  • AMIRAS - An Airborne MIRAS Demonstrator

     Martín Neira, Manuel; Cabeza, I; Perez, C; Palacios, M A; Guijarro, M A; Ribó Vedrilla, Serni; Corbella Sanahuja, Ignasi; Blanch Boris, Sebastian; Torres Torres, Francisco; Duffo Ubeda, Nuria; Gonzalez Gambau, Verónica; Beraza, S; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2008-03
    Journal article

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  • Angular and radiometric resolution of Y-shaped non-uniform synthetic aperture radiometers for Earth observation

     Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2008-10
    Journal article

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  • WIND VECTOR RETRIEVAL OVER THE OCEAN BY MEANS OF MICROWAVE RADIOMETRY

     PONS CLARET, JOAN
    Defense's date: 2008-12-03
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Interferometric radiometers: fringe washing function estimation

     Duffo Ubeda, Nuria; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; González Gambau, Veronica; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2008-07-07
    Presentation of work at congresses

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  • Assessment on linearity errors in detectors for interferometric radiometers

     Torres Torres, Francisco; Duffo Ubeda, Nuria; Gonzalez-Haro, Cristina; Vilaseca, R; Sagués, L; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2008-07-06
    Presentation of work at congresses

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    The performance of the power detectors used to denormalize the digital correlations in interferometric radiometers is degraded due to the non-linear behavior of the diode response. This work presents a comprehensive analysis of the impact of detector non-linearity and related correction techniques in the performance of the MIRAS (Microwave Imaging Radiometer with Aperture Synthesis) instrument, which is the single payload of the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) mission.

    The performance of the power detectors used to denormalize the digital correlations in interferometric radiometers is degraded due to the non-linear behavior of the diode response. This work presents a comprehensive analysis of the impact of detector non-linearity and related correction techniques in the performance of the MIRAS (Microwave Imaging Radiometer with Aperture Synthesis) instrument [1], which is the single payload of the European Space Agency (ESA) Soil Moisture and ocean Salinity (SMOS) mission

  • Calibration consistency tool for interferometric radiometers

     Gonzalez Gambau, Verónica; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2008-07-06
    Presentation of work at congresses

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    This paper presents a method to check the consistency of the amplitude calibration in interferometric radiometers devoted to Earth observation This tool is based in the intrinsic properties of the internal calibration scheme and can be used to systematically assess in-orbit the quality of the amplitude calibration coefficients. This technique is illustrated taking into account the results of the validation and system performance tests recently undertaken by the MIRAS instrument, the single payload of the Soil Moisture and Ocean Salinity mission of the European Space Agency.

    This paper presents a method to check the consistency of the amplitude calibration in interferometric radiometers devoted to Earth observation This tool is based in the intrinsic properties of the internal calibration scheme and can be used to systematically assess in-orbit the quality of the amplitude calibration coefficients. This technique is illustrated taking into account the results of the validation and system performance tests recently undertaken by the MIRAS instrument, the single payload of the Soil Moisture and Ocean Salinity mission of the European Space Agency.

  • Phase calibration temperature track in interferometric radiometers devoted to Earth observation

     Gonzalez Gambau, Verónica; Torres Torres, Francisco; Duffo Ubeda, Nuria
    SPIE Europe Remote Sensing
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  • Brightness temperature retrievals from the small airborne MIRAS

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience & Remote Sensing Symposium
    Presentation of work at congresses

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  • Fast processing tool for SMOS data

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Gonzalez Gambau, Verónica; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience & Remote Sensing Symposium
    Presentation's date: 2008-07-07
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  • Improving the spatial resolution of synthetic aperture radiometer imagery using auxiliary information: application to the SMOS mission

     Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Piles Guillem, Maria; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria
    IEEE International Geoscience & Remote Sensing Symposium
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  • MIRAS ground characterization

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Martín Neira, Manuel; Gonzalez Gambau, Verónica; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    Microwave Radiometry and Remote Sensing of the Environment, 2008. MICRORAD 2008
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  • Improved Image Reconstruction Algorithms for Aperture Synthesis Radiometers

     Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Corbella Sanahuja, Ignasi; Duffo Ubeda, Nuria; Torres Torres, Francisco
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2008-01
    Journal article

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  • Some results of the MIRAS-SMOS demonstrator campaigns

     Duffo Ubeda, Nuria; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Gonzalez Gambau, Verónica; Blanch Boris, Sebastian; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Alvarez Muñoz, Jose Luis; Ribó Vedrilla, Serni; Martín Neira, Manuel
    IEEE international Geoscience and Remote Sensing Symposium
    Presentation's date: 2007-06-23
    Presentation of work at congresses

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    In this paper, some results of the MIRAS-SMOS demonstrator campaigns are presented. The follow two campaigns were held: an image validation campaign at IRTA side and a flight demonstrator campaign at Finland. The ultimate objective of the airborne demonstrator is to demonstrate its imaging capabilities by applying improved calibration and inversion algorithms to natural low-contrast targets. © 2007 IEEE.

  • MIRAS in orbit calibration

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Gonzalez Gambau, Verónica
    IEEE international Geoscience and Remote Sensing Symposium
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  • Some results of the MIRAS-SMOS demonstrator campaigns

     Duffo Ubeda, Nuria; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Blanch Boris, Sebastian; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE international Geoscience and Remote Sensing Symposium
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  • MIRAS in-orbit calibration

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Nuria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Gonzalez Gambau, Verónica
    IEEE international Geoscience and Remote Sensing Symposium
    Presentation of work at congresses

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