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  • Real-time RFI detection and mitigation system for microwave radiometers

     Forte Veliz, Giuseppe Francesco; Querol Borras, Jorge; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-10
    Journal article

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    Microwave radiometers are very sensitive passive sensors that measure the power of the thermal noise within a determined bandwidth. Therefore, any other signal present in the band modifies the value of the measured power, and the corresponding estimated antenna temperature, from which the geophysical parameters are retrieved. Due to the high sensitivity and accuracy required for these instruments, radio frequency interference (RFI) is becoming more and more a serious problem. On one hand, ground-based or global RFI surveys are helping to understand the occurrence and types of RFI sources. If RFI does not necessarily affect the whole bandwidth, or it is not present during the whole integration time, the application of either frequency blanking, time blanking or signal spectrogram techniques can be applied. However, it would be desirable to apply techniques to estimate the RFI signal so that it can be subtracted from the received signal itself so that some useful measurements are still possible. Such a real-time system is currently being developed for RFI detection and mitigation. This work focuses however in the description and performance of a wavelet-based RFI-mitigation technique implemented in a FPGA hardware back-end. The interfering signal is estimated by using the powerful denoising capabilities of the wavelet transform, and it is then subtracted from the total received signal to obtain a RFI-mitigated noise signal. © 2012 IEEE.

  • Inter-comparison of SMOS and aquarius brightness temperatures at L-band over selected targets

     Pablos Hernandez, Miriam; Piles Guillem, Maria; Gonzalez Gambau, Verónica; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    The spectral window at L-band (1.400 - 1.427 GHz) is reserved for passive microwave remote sensing. This band is well-suited to retrieve soil moisture and ocean salinity due to emissivity of soil and seawater decreases with moisture and salinity, respectively, affecting microwave radiation of the Earth's surface. Nowadays, there are two space missions devoted to Earth observation with L-band radiometers on-board: the SMOS mission from the ESA and the Aquarius/SAC-D mission from the NASA and CONAE. Both missions are providing the first TB measurements of the Earth's surface at 1.413 GHz. Thus, it is a great opportunity to compare SMOS and Aquarius TBs and verify the continuity and consistency of the data. This inter-comparison is a key requirement needed to use data of both radiometers for meteorological, hydrological and climatological studies on a long term.

  • Study of radio frequency interference effects on radiometry bands in urban environments

     Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Tarongí Bauzá, José Miguel; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Microwave radiometers are very accurate passive sensors that have been successfully used in Earth remote sensing during the last decades. Microwave radiometers measure thermal noise, therefore any other signal (radio-frequency interference or RFI) present in the band modifies the value of the measured power, and the corresponding estimated antenna temperature, from which the geophysical parameters will be retrieved. An on-going RFI survey shows how corrupted is the spectrum “protected” L-band in the city of Barcelona. This type of studies should help to validate or discard the measurements made there, and in other locations, and also to take further actions against RFI. Detection and mitigation techniques are used to validate results.

  • UPCSAT-1, demostrador CubeSat para observación terrestre

     Jove Casulleras, Roger; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Bou Balust, Elisenda; Ramos Castro, Juan Jose; Alarcon Cot, Eduardo Jose; Alonso Arroyo, Alberto
    Congreso de la Asociación Española de Teledetección
    Presentation's date: 2013-10
    Presentation of work at congresses

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    UPCSat-1, es el primer proyecto de la Universitat Politécnica de Catalunya para construir y lanzar un pico- satélite. El objetivo principal de este proyecto es construir, ensamblar, testear y poner en órbita baja terrestre (LEO) un sensor óptico y un sensor de oxígeno monoatómico entre otros demostradores tecnológicos. Empezado en 2007 y actualmente en fase de integración, el satélite UPCSat-1 pretende demostrar la validez de la plataforma y las tecnologías que incorpora. Su objetivo es adquirir el know-how para la fabricación de CubeSats para preparar misiones más complejas en un futuro cercano. Por otro lado el proyecto tiene un fuerte componente educacional puesto que algunos de los subsistemas han sido desarrollados por nuestros estudiantes a través de sus proyectos finales de carrera. Se espera el lanzamiento para antes de 2015.

  • On the synergy of SMOS and Terra/Aqua MODIS: high resolution soil moisture maps in near real-time

     Piles Guillem, Maria; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose; Sanchez, Nilda; Martinez Fernandez, Jose; Martinez, Justino; Gonzalez Gambau, Verónica; Riera, R.
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    An innovative downscaling approach to obtain fine-scale soil moisture estimates from 40 km SMOS observations has been developed. It optimally blends SMOS multi-angular and full-polarimetric information with MODIS visible/data into high resolution soil moisture maps. The core of the algorithm is a model that linksmicrowave/optical sensitivity to soilmoisture and linearly relates the two instruments across spatial scales. This algorithm has been implemented at SMOS-BEC facilities and near real-time maps of disaggregated soil moisture over the Iberian Peninsula are being distributed. In this work, the temporal and spatial variability of these maps is evaluated through comparison with ground-basedmesurements acquired at the REMEDHUS soil moisture network, in the central part of the Duero basin, Spain. Results from a two-year time-series comparison show that downscaled soil moisture maps compare well with in situ data and nicely reproduce soil moisture dynamics at a 1 km spatial scale.

  • Experimental study on the performance of RFI detection algorithms in microwave radiometry: Toward an optimum combined test

     Forte Veliz, Giuseppe Francesco; Tarongí Bauzá, José Miguel; Depau, Veronica; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-10
    Journal article

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    Radio-frequency interference (RFI) is probably today's most serious limitation to the accurate retrieval of geophysical parameters from microwave radiometric measurements. Strong RFI inducing a change in the detected power larger than the natural variability is simple to detect. Moderate or weak RFI can be masked by the natural variability of the measurements, passing undetected and corrupting them. A number of techniques have been devised in the past years to detect and, eventually, mitigate RFI present in microwave radiometry measurements: 1) time domain; 2) frequency domain; 3) spectrogram techniques looking for anomalously high power peaks; 4) statistical techniques testing the hypothesis of Gaussianity of the received signal; 5) polarimetric techniques looking for anomalous signatures in the third and fourth Stokes parameters; or 6) wavelet techniques to estimate the RFI signal and cancel it (if any). In this paper, the first four techniques are evaluated with real data gathered with a multifrequency microwave radiometer. It will be shown how spectrogram techniques can detect RFI signals concentrated in narrow frequency bands and/or time intervals that may pass undetected with time-domain and/or frequency-domain techniques alone or with statistical methods. A combined approach is proposed to take advantage of the best performance of each technique. On one side, for strong localized RFI, the approach is spectrogram blanking or, if it is too demanding in terms of computational resources, simple time- and frequency-domain blanking. On the other side, for weak RFI, the approach is the Kurtosis statistical test, which exhibits the best performance among the ten normality tests evaluated, in conjunction with the Anderson-Darling test to detect potential RFI in the blind spots of the Kurtosis test. © 2012 IEEE.

  • 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.

  • PRODUCTOS Y APLICACIONES AVANZADOS DE SMOS Y FUTURAS MISIONES. PARTE UPC

     Vall-llossera Ferran, Mercedes Magdalena
    Participation in a competitive project

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    PAU-SA: a synthetic aperture interferometric radiometer test bed for potential improvements in future missions  Open access

     Ramos Perez, Isaac; Camps Carmona, Adriano Jose; Bosch Lluis, Xavier; Rodríguez Álvarez, Nereida; Valencia Domenech, Enric; Park, Hyuk; Forte Veliz, Giuseppe Francesco; Vall-llossera Ferran, Mercedes Magdalena
    Sensors
    Date of publication: 2012-06
    Journal article

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    The Soil Moisture and Ocean Salinity (SMOS) mission is an Earth Explorer Opportunity mission from the European Space Agency (ESA). Its goal is to produce global maps of soil moisture and ocean salinity using the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). The purpose of the Passive Advanced Unit Synthetic Aperture (PAU-SA) instrument is to study and test some potential improvements that could eventually be implemented in future missions using interferometric radiometers such as the Geoestacionary Atmosferic Sounder (GAS), the Precipitation and All-weather Temperature and Humidity (PATH) and the Geostationary Interferometric Microwave Sounder (GIMS). Both MIRAS and PAU-SA are Y-shaped arrays with uniformly distributed antennas, but the receiver topology and the processing unit are quite different. The purpose of this work is to identify the elements in the MIRAS’s design susceptible of improvement and apply them in the PAU-SA instrument demonstrator, to test them in view of these future interferometric radiometer missions.

  • Validation and experimental tests of the PAU-synthetic aperture radiometer

     Ramos Perez, Isaac; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Bosch Lluis, Xavier; Rodríguez Álvarez, Nereida; Valencia Domenech, Enric; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper presents calibration and the radiometric performance of the Passive Advanced Unit Synthetic Aperture (PAU-SA) in order to verify the instrument's characterization.

  • A downscaling approach to combine SMOS multi-angular and full-polarimetric observations with MODIS VIS/IR data into high resolution soil moisture maps

     Piles Guillem, Maria; Vall-llossera Ferran, Mercedes Magdalena; Laguna, Laia; Camps Carmona, Adriano Jose
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    A downscaling algorithmfor SMOS which combines MODIS Visible/Infrared data and SMOS horizontal brightness temperatures at 42.5◦ incidence angle into high-resolution soil moisture maps has been shown to nicely reproduce soil moisture dynamics at a 1 km spatial scale. The core of this algorithm is a linking model that depicts the synergy between SMOS and MODIS observations and their sensitivity to soil moisture. In this work, the impact of adding SMOS observations at horizontal and vertical polarizations and at multiple incidence angles to this linking model has been evaluated using 6 months of observations over the Murrumbidgee catchment, South-East Australia, and a robust alternative formulation is proposed. Results show that adding SMOS observations at multiple incidence angles and both polarizations the algorithm is more stable over time and its minimization error is reduced. By comparing with in situ data, a remarkable improvement of the linear regression between downscaled and in situ data is also observed (slope of 0.95).

  • Digital back-end for RFI detection and mitigation in microwave radiometers

     Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Ramos, I.; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Radio-frequency interference (RFI) is a serious problem in microwave radiometry. In order to process the received data in real time, a powerful back-end for RFI detection and mitigation system must be implemented. This system includes many techniques against RFI, like time, frequency domain and spectrogram analysis. A wavelet-based RFI-mitigation technique is implemented in hardware. The interfering signal is estimated by using the powerful denoising capabilities of the wavelet transform. Then, this estimate of the RFI signal is subtracted from the total received signal to obtain a RFI-mitigated noise signal. Statistical analysis helps to validate the mentioned methods.

  • Spatial patterns of SMOS downscaled soil moisture maps over the remedhus network (Spain)

     Sanchez, Nilda; Piles Guillem, Maria; Scaini, Anna; Martinez Fernandez, Jose; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper describes the relationships found between remotely sensed soil moisture, in situ observed soil moisture, and spatial distribution of soil and climatic factors. For the comparison between remote and in situ soil moisture, soil moisture map series at high resolution, obtained by applying a downscaling approach that combines Soil Moisture and Ocean Salinity (SMOS) and MODIS imagery is extracted. The in situ soil moisture series are obtained from the Soil Moisture Measurement Stations Network (REMEDHUS) in Spain. For the spatial analysis, factors such as topography, precipitation, and land uses were mapped from the climatic and cartographic database of REMEDHUS. The comparison between downscaled and in situ soil moisture data resulted in correlation coefficient (R) values between 0.40 and 0.70, bias between -0.04 and 0.16 m3m-3, and root mean squared difference (RMSD) between 0.07 and 0.19 m3m-3. Regarding the spatial correlations between downscaled and spatial factors, no clear patterns were found when considering the topography (Topographic Wetness Index, TWI), and the land uses (Landsat classification). Nevertheless, the downscaled soil moisture was more related with the spatial distribution of precipitation (Antecedent Precipitation Index, API), with significant correlations varying between 0.24 and 0.55.

    This paper describes the relationships found between remotely sensed soil moisture, in situ observed soil moisture, and spatial distribution of soil and climatic factors. For the comparison between remote and in situ soil moisture, soil moisture map series at high resolution, obtained by applying a downscaling approach that combines Soil Moisture and Ocean Salinity (SMOS) and MODIS imagery is extracted. The in situ soil moisture series are obtained from the Soil Moisture Measurement Stations Network (REMEDHUS) in Spain. For the spatial analysis, factors such as topography, precipitation, and land uses were mapped from the climatic and cartographic database of REMEDHUS. The comparison between downscaled and in situ soil moisture data resulted in correlation coefficient (R) values between 0.40 and 0.70, bias between -0.04 and 0.16 m3m-3, and root mean squared difference (RMSD) between 0.07 and 0.19 m3m-3. Regarding the spatial correlations between downscaled and spatial factors, no clear patterns were found when considering the topography (Topographic Wetness Index, TWI), and the land uses (Landsat classification). Nevertheless, the downscaled soil moisture was more related with the spatial distribution of precipitation (Antecedent Precipitation Index, API), with significant correlations varying between 0.24 and 0.55.

  • SMOS CP34 soil moisture and ocean salinity maps

     Font Ferré, Jordi; Gabarró, Carolina; BALLABRERA POY, JOAQUIM; Turiel Martínez, Antonio; Martínez, Justino; Umbert, M.; Pérez, Francisco C.; Hoareau, N.; Portabella, Marcos; González Gambau, Veronica; Gourrion, J.; Guimbard, Sébastien Arnaud; Piles Guillem, Maria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2012
    Presentation of work at congresses

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    This paper presents the soil moisture and ocean salinity maps from the SMOS mission generated operationally by the Spanish SMOS Level 3 and 4 data processing center (CP34) and experimentally by the SMOS Barcelona Expert Center (SMOS-BEC).

  • 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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  • Optimum intercalibration time in synthetic aperture interferometric radiometers: application to SMOS

     Ramos Perez, Isaac; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; González Gambau, Veronica; Valencia Domenech, Enric; Rodríguez Álvarez, Nereida; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena; Forte Veliz, Giuseppe Francesco
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012
    Journal article

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    Interpolation strategies for calibration of the Soil Moisture and Ocean Salinity (SMOS) mission of the European Space Agency are tested and compared. Calibration strategy (how and how often) is critical in achieving the required performance of any instrument, but it is even more important in very complex instruments such as the new family of synthetic aperture interferometric radiometers and, in particular, in the Microwave Imaging Radiometer by Aperture Synthesis instrument aboard the SMOS mission. On one hand, frequent calibration reduces the available observation time. On the other hand, the calibration requirements for soil moisture applications are more relaxed than those for ocean salinity, so the intercalibration time requirements are very different. Since SMOS drifts are stationary, half-orbit information is available to perform different interpolation strategies. In this letter, these approaches are tested to estimate the calibration parameters between consecutive calibrations. The average root-mean-square phase error is then used to find the optimum interpolation strategy and intercalibration time. On the other side, in real-time instruments, the “future” calibration data are not available at the time of taking the measurements, and predictors are required to estimate the evolution of the calibration parameters from past data only. For these systems, the extended Kalman filter can be used. The intercalibration time in a real-time instrument is evaluated, and the requirements and performances are compared to offline instruments.

  • Snow thickness monitoring using GNSS measurements

     Rodríguez Álvarez, Nereida; Aguasca Sole, Alberto; Valencia Domenech, Enric; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Ramos Perez, Isaac; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012
    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.

  • Calibration, performance, and imaging tests of a fully digital synthetic aperture interferometer radiometer

     Ramos Perez, Isaac; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Bosch Lluis, Xavier; Rodríguez Álvarez, Nereida; Valencia Domenech, Enric; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
    Date of publication: 2012-06-28
    Journal article

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    This work presents the calibration, characterization, and imaging tests of the Passive Advanced Unit-Synthetic Aperture instrument (PAU-SA). PAU-SA is a fully digital -shaped two-dimensional synthetic aperture interferometric radiometer operating at the Global Positioning System (GPS) L1 band ( GHz), conceived as a test-bed for potential technological improvements in future instruments. Calibration of instrumental offsets is performed by looking to a microwave absorber and the “cold” sky. Since the instrument operates in the GPS L1 band, GPS satellites are imaged therefore, a new way to compute the Flat Target Response (FTR) has been devised. Internal phase/amplitude calibration is performed using a new technique that consists of injecting pseudo-random noise signals. Different paths from the input switch to the antennas are calibrated by means of an external beacon. A near-field to far-field transformation is applied to compensate for differences in the propagation paths. Finally, absolute amplitude calibration is achieved by imaging the GPS satellites constellation when pointing to the zenith. Evaluation of the images’ quality in terms of angular resolution, radiometric resolution and precision, show the goodness of the techniques applied to compensate for instrumental errors, the imaging capabilities of the instrument, and demonstrate their applicability in future missions.

  • 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.

  • Vegetation water content estimation using GNSS measurements

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Ramos Perez, Isaac; Valencia Domenech, Enric; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012-03
    Journal article

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    Global Navigation Satellite Systems (GNSS) opportunity signals reflected at or near the Earth's surface have already shown their potential to perform retrievals of a number of geophysical parameters. Radio occultations using GNSS signals are also used for atmospheric sensing. This letter presents a GNSS technique to retrieve vegetation water content (VWC). This technique measures the received powers of the GPS signals in open sky and under the vegetation layer. From these two powers, the attenuation due to the vegetation is computed, which is related to the VWC. This letter presents the results obtained after deploying the instrument in a walnut-tree stand for 11 months.

  • Enhancing the spatial resolution of SMOS soil moisture data over Spain

     Piles Guillem, Maria; Monerris Belda, Alessandra; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-28
    Presentation of work at congresses

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  • Downscaling SMOS-derived soil moisture using MODIS visible/infrared data

     Piles Guillem, Maria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Corbella Sanahuja, Ignasi; Panciera, Rocco; Rudiger, Chris; Kerr, Yann H.; Walker, Jeff
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-28
    Presentation of work at congresses

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  • Snow monitoring using GNSS-R techniques

     Rodriguez Alvarez, Nereida; Aguasca Sole, Alberto; Valencia Domenech, Enric; Bosch Lluis, Xavier; Ramos Perez, Isaac; Park, Hyuk; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-25
    Presentation of work at congresses

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    GNSS-R techniques are currently being studied to remotely sense a number of geophysical parameters over different types of surfaces [1-6]. The Interference Pattern Technique (IPT) is based on the measurement of the interference pattern of the GPS direct and reflected signals, after reflecting over the surface, as the GPS satellites move. This paper extends previous studies [7-11], in which water level was monitored [7] and land areas were observed retrieving soil moisture, topography and vegetation height for different kinds of crops (wheat, barley and maize) [8-10], to a snowcovered soils studies.

    GNSS-R techniques are currently being studied to remotely sense a number of geophysical parameters over different types of surfaces [1-6]. The Interference Pattern Technique (IPT) is based on the measurement of the interference pattern of the GPS direct and reflected signals, after reflecting over the surface, as the GPS satellites move. This paper extends previous studies [7-11], in which water level was monitored [7] and land areas were observed retrieving soil moisture, topography and vegetation height for different kinds of crops (wheat, barley and maize) [8-10], to a snow- covered soils studies.

  • Water level monitoring using the interference pattern GNSS-R technique

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Ramos Perez, Isaac; Valencia Domenech, Enric; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-25
    Presentation of work at congresses

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  • First results of the PAU-SA synthetic aperture radiometer

     Ramos Perez, Isaac; Forte, Giuseppe; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Valencia Domenech, Enric; Rodriguez Alvarez, Nereida; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-28
    Presentation of work at congresses

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  • Vegetation water content estimation using GNSS measurements

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Ramos Perez, Isaac; Valencia Domenech, Enric; Park, Hyuk; Vall-llossera Ferran, Mercedes Magdalena
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-25
    Presentation of work at congresses

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  • Land Geophysical Parameters Retrieval Using the Interference Pattern GNSS-R Technique

     Rodriguez Alvarez, Nereida; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Bosch Lluis, Xavier; Monerris Belda, Alessandra; Ramos Perez, Isaac; Valencia Domenech, Enric; Marchan Hernandez, Juan Fernando; Martinez Fernandez, Jose; Baroncini Turricchia, Guido; Pérez Gutiérrez, Carlos; Sanchez, Nilda
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2011-01
    Journal article

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  • Error Covariance Matrices Characterization in the Ocean Salinity Retrieval Cost Function within the SMOS Mission

     Talone, Marco; Gabarro Prats, Carolina; Camps Carmona, Adriano Jose; Sabia, Roberto; Gourrion, J.; Vall-llossera Ferran, Mercedes Magdalena; Font, J.
    Journal of atmospheric and oceanic technology
    Date of publication: 2011-09
    Journal article

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  • Review of crop growth and soil moisture monitoring from a ground-based instrument implementing the Interference Pattern GNSS-R Technique

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Aguasca Sole, Alberto; Vall-llossera Ferran, Mercedes Magdalena; Valencia Domenech, Enric; Ramos Perez, Isaac; Park, Hyuk
    Radio science
    Date of publication: 2011-10-15
    Journal article

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  • Radio-frequency interference detection and mitigation algorithms for synthetic aperture radiometers

     Camps Carmona, Adriano Jose; Gourrion, J.; Tarongí Bauzá, José Miguel; Vall-llossera Ferran, Mercedes Magdalena; Gutiérrez, A.; Barbosa Torralbo, José; Castro, Rita
    Algorithms
    Date of publication: 2011
    Journal article

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  • 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.

  • Sistemas de teledetección activos y pasivos embarcados en sistemas aéreos no tripulados para la monitorización de la tierra  Open access

     Acevo Herrera, René
    Defense's date: 2011-04-04
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    La comunidad científica ha mostrado gran interés por estudiar los fenómenos que ocurren sobre la superficie de la tierra, específicamente los que suceden en la atmósfera, los océanos, o la superficie del suelo, y que afectan el clima o modifican la superficie de la tierra. Para poder analizar y predecir estos fenómenos, se monitorizan parámetros que se relacionan de manera directa o indirecta con procesos biofísicos y geofísicos. Es en este punto donde la teledetección entra en juego, puesto que es la técnica que permite medir tales parámetros de forma remota sin necesidad de entrar en contacto directo con un objeto o una superficie. En particular, la teledetección por microondas permite la detección de energía electromagnética casi bajo cualquier condición climática y a cualquier hora del día, debido a que a esta longitud de onda la energía electromagnética puede penetrar a través de las nubes, polvo, neblina y lluvia, y es menos susceptible a la dispersión atmosférica, que afecta en gran medida a las señales ópticas. Actualmente existen varios sistemas de teledetección por microondas que se han embarcado en satélites, para monitorizar parámetros biofísicos y geofísicos sobre la superficie de la tierra de manera global. También se han desarrollado estos sistemas para ser transportados en plataformas aéreas tripuladas para realizar estudios a nivel local o regional, donde se desea obtener información de una zona en particular en tiempos relativamente cortos. Sin embargo, ambas plataformas representan, entre otras cosas, un alto coste, no solo económico sino de infraestructura, equipo, grupos de trabajo, permisos de operación, y varios requerimientos más. El creciente desarrollo de los sistemas aéreos no tripulados (Unmanned Aerial Vehicle, UAV), ha hecho posible su uso para transportar sensores de teledetección. Los sistemas UAV presentan las mismas ventajas que los sistemas aéreos tripulados, pero además añaden otras ventajas adicionales. Por ejemplo, pueden ser operados durante varias horas de forma autónoma, el coste de explotación y desarrollo puede ser menor que el de un avión tripulado si se emplea un UAV de bajas prestaciones. Por tal motivo en este trabajo se propone el uso de un aeromodelo de control por radio como plataforma UAV para monitorizar diversos parámetros geofísicos y biofísicos de la tierra mediante sensores activos y pasivos de teledetección por microondas. Para realizar las medidas de teledetección pasiva se ha desarrollado el sensor denominado Airborne RadIometEr at L-Band (ARIEL) que es un radiómetro Dicke de bajo peso y pequeñas dimensiones, y que trabaja en Banda L (≈1.4 GHz). En la presenta memoria se muestra el diseño del sensor, las características principales de funcionamiento, y las técnicas de procesamiento de datos. Posteriormente se presentan las campañas de medida realizadas en zonas de cultivo, suelo descubierto, y zonas costeras. En tales campañas se han conseguido generar mapas de temperatura de brillo y de humedad de suelo. Con el fin de llevar a cabo medidas de teledetección activa se ha desarrollado el sistema denominado AiR Based REmote Sensing ARBRES, que consta de dos sensores radar de apertura sintética SAR diseñados a dos frecuencias diferentes, uno en Banda C (≈ 5.3 GHz) y otro en Banda X (≈ 9.65 GHz). Ambos radares son de onda continua FMCW, además son de bajo peso, bajo consumo de potencia y de pequeñas dimensiones. Ambos sensores tienen la capacidad de realizar medidas de interferometría SAR. En esta memoria se muestran las características de funcionamiento del sistema, así como algunos algoritmos de focalización de imágenes SAR, y una técnica para compensar los movimientos de la plataforma de vuelo. Finalmente se presentan medidas en campo para obtener imágenes de reflectividad de un escenario, y se muestran también los resultados para medidas realizadas en configuración de interferometría de simple pasada, la cual está relacionada con la topografía del terreno.

  • Q-00002

     Tiana Alsina, Jordi; Bermejo Sanchez, Sergio; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose; Rocadenbosch Burillo, Francisco
    Participation in a competitive project

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  • Analysis of a Least-Squares Soil Moisture Retrieval Algorithm from L-band Passive Observations

     Piles Guillem, Maria; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose; Talone, Marco; Monerris Belda, Alessandra
    Remote Sensing
    Date of publication: 2011-01-20
    Journal article

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  • Downscaling SMOS-derived soil moisture using MODIS visible/infrared data

     Piles Guillem, Maria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Corbella Sanahuja, Ignasi; Panciera, Rocco; Ruediger, Christoph; Kerr, Yann H.; Walker, Jeffrey
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2011-09
    Journal article

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    A downscaling approach to improve the spatial resolution of Soil Moisture and Ocean Salinity (SMOS) soil moisture estimates with the use of higher resolution visible/infrared (VIS/IR) satellite data is presented. The algorithm is based on the so-called “universal triangle” concept that relates VIS/IR parameters, such as the Normalized Difference Vegetation Index (NDVI), and Land Surface Temperature (Ts), to the soil moisture status. It combines the accuracy of SMOS observations with the high spatial resolution of VIS/IR satellite data into accurate soil moisture estimates at high spatial resolution. In preparation for the SMOS launch, the algorithm was tested using observations of the UPC Airborne RadIomEter at L-band (ARIEL) over the Soil Moisture Measurement Network of the University of Salamanca (REMEDHUS) in Zamora (Spain), and LANDSAT imagery. Results showed fairly good agreement with ground-based soil moisture measurements and illustrated the strength of the link between VIS/IR satellite data and soil moisture status. Following the SMOS launch, a downscaling strategy for the estimation of soil moisture at high resolution from SMOS using MODIS VIS/IR data has been developed. The method has been applied to some of the first SMOS images acquired during the commissioning phase and is validated against in situ soil moisture data from the OZnet soil moisture monitoring network, in South-Eastern Australia. Results show that the soil moisture variability is effectively captured at 10 and 1 km spatial scales without a significant degradation of the root mean square error.

  • Access to the full text
    Study of maize plants effects in the retrieval of soil moisture using the interefence Ppttern GNSS-R technique  Open access

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Acevo Herrera, René; Aguasca Sole, Alberto; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Ramos Perez, Isaac; Valencia Domenech, Enric
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2010-07-30
    Presentation of work at congresses

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    The use of Global Navigation Satellite Signals Reflections (GNSS-R) techniques to retrieve geophysical parameters from surfaces has been increased in the recent years. These techniques have resulted in suitable tools to obtain information about the sea state of oceans, which is very useful to improve the ocean salinity retrieval, and also, information about the soil moisture of lands. The present work focuses on the use of the Interference Pattern Technique (IPT), a particular type of GNSS-R technique, to study vegetation-covered soils. The IPT consists mainly of the measurement of the interference pattern between the GPS direct and reflected signals (the interference power), after they impinge over the ensemble soil surface and vegetation layer. The measured interference signal provides information on the soil moisture of the surface and also, on the vegetation height.

  • Access to the full text
    Altimetry study performed using an airborne GNSS-reflectometer  Open access

     Rodriguez Alvarez, Nereida; Acevo Herrera, René; Aguasca Sole, Alberto; Valencia Domenech, Enric; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Bosch Lluis, Xavier; Ramos Perez, Isaac
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2010-07-30
    Presentation of work at congresses

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    The Global Navigation Satellite Signals Reflections (GNSSR)techniques have been widely used for remote sensing purposes retrieving geophysical parameters over different types of surfaces. Over the ocean, altimetry or sea state can be retrieved. Over land, soil moisture can be inferred and over ice, altimetry, and ice age are also retrieved. This paper presents the results of using GNSS-R techniques to retrieve altimetry from the measurements of an airborne GNSS-Reflectometer.

  • Determination of the Sea Surface Salinity Error Budget in the Soil Moisture and Ocean Salinity Mission

     Sabia, Roberto; Camps Carmona, Adriano Jose; Talone, Marco; Vall-llossera Ferran, Mercedes Magdalena; Font Ferré, Jordi
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2010-03
    Journal article

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  • Sea surface salinity retrievals from HUT-2D L-band radiometric measurements

     Talone, Marco; Sabia, Roberto; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Gabarro Prats, Carolina; Font Ferré, Jordi
    Remote sensing of environment
    Date of publication: 2010-08-16
    Journal article

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  • Performance of soil moisture retrieval algorithms using multiangular L band brightness temperatures

     Piles Guillem, Maria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Monerris Belda, Alessandra; Talone, Marco; Sabater, J.M.
    Water resources research
    Date of publication: 2010-06-09
    Journal article

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  • Spatial-Resolution Enhancement of SMOS Data: A Deconvolution-Based Approach

     Piles Guillem, Maria; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Talone, M
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2009-07
    Journal article

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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
    Presentation of work at congresses

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  • Soil Moisture Retrieval Using GNSS-R Techniques: Experimental Results Over a Bare Soil Field

     Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Camps Carmona, Adriano Jose; Vall-llossera Ferran, Mercedes Magdalena; Valencia Domenech, Enric; Marchan Hernandez, Juan Fernando; Ramos Perez, Isaac
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2009-11
    Journal article

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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.

  • Simulated SMOS Levels 2 and 3 Products: The Effect of Introducing ARGO Data in the Processing Chain and Its Impact on the Error Induced by the Vicinity of the Coast

     Talone, M; Camps Carmona, Adriano Jose; Mourre, B; Sabia, Roberto; Vall-llossera Ferran, Mercedes Magdalena; Gourrion, J; Gabarro, C
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2009-09
    Journal article

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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.

  • 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
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