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  • Common mathematical framework for real and synthetic aperture by interferometry radiometers

     Bosch Lluis, Xavier; Ramos Pérez, Isaac; Camps Carmona, Adriano Jose; Rodríguez Álvarez, Nereida; Valencia Domenech, Enric; Park, Hyuk
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2014-01
    Journal article

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    This work focuses on the relationship between real and synthetic aperture radiometers giving a general and common mathematical framework for both of them. It will be demonstrated that a real aperture radiometer array can be understood as a synthetic aperture one, with a high level of redundancy. Therefore, all the recent results from synthetic aperture radiometry can be translated to real aperture radiometer arrays. This fact can be used to create beamforming arrays in a new way. To do this, the beamforming array equation will be written in terms of cross-correlations between all pair of antenna signals (visibility samples). By properly combining the visibility samples, a new type of digital beamforming radiometer can be implemented, which will benefit from the high calibration accuracy achieved in synthetic aperture radiometers (e.g., The Y-shaped MIRAS radiometer used in the Soil Moisture and Ocean Salinity mission of the European Space Agency) and the flexibility to electronically steer the beam. © 1980-2012 IEEE.

  • Consolidating the precision of interferometric GNSS-R ocean altimetry using airborne experimental data

     Cardellach, Estel; Rius, Antonio; Martín Neira, Manuel; Fabra Cervellera, Fran; Nogués Correig, O.; Ribó Vedrilla, Serni; Kainulainen, Juha; Camps Carmona, Adriano Jose; d'Addio, Salvatore
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2014-08
    Journal article

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    This paper revises the precision of altimetric measurements made with signals of the Global Navigation Satellite Systems (GNSS) reflected (GNSS-R) off the sea surface. In particular, we investigate the performance of two different GNSS-R techniques, referred to here as the clean-replica and interferometric approaches. The former has been used in GNSS-R campaigns since the late 1990s, while the latter has only been tested once, in 2010, from an 18-m-high bridge in static conditions and estuary waters. In 2011, we conducted an airborne experiment over the Baltic Sea at 3-km altitude to test the interferometric concept in dynamic and rougher conditions. The campaign also flew a clean-replica GNSS-R instrument with the purpose of comparing both approaches. We have analyzed with detail the data sets to extract and validate models of the noise present in both techniques. After predicting the noise models and verifying these with aircraft data, we used them to obtain the precision of altimetric measurements and to extrapolate the performance analysis to spaceborne scenarios. The main conclusions are that the suggested noise model agrees with measured data and that the GNSS-R interferometric technique is at least two times better in precision than a technique based on using a clean replica of the publicly available GPS code. This represents a factor of at least four times finer along-track resolution. A precision of 22 cm in 65-km along-track averaging should be achievable using near-nadir interferometric GNSS-R observations from a low earth orbiter.

  • 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.

  • GNSS-R derived centimetric sea topography: an airborne experiment demonstration

     Carreño Luengo, Hugo; Park, Hyuk; Camps Carmona, Adriano Jose; Fabra Cervellera, Fran; Rius Jordán, Antonio
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
    Date of publication: 2013-06
    Journal article

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    The results of two airborne experiments performed to test the precision and the relative accuracy of the conventional Global Navigation Satellite Systems Reflectometry (GNSS-R) technique employing only the C/A code are presented. The first and the second experiments demonstrate, respectively, a 17 cm precision for a 500 m flight altitude with a 8 km along-track spatial resolution, and a 6 cm precision for a 3000 m flight altitude with a 6.6 km along-track spatial resolution. In both, the Relative Mean Dynamic Topography (RMDT) is compared with results derived from traditional radar altimetry provided by Jason-2. The Root Mean Square (RMS) of the RMDTdifference between both measurement systems is 48 cm for the first flight, and 198 cm for the second flight. During the second flight, the feasibility of the proposed technique to measure the sea slopes is demonstrated by superposing over the aircraft ground track the measured sea surface height with the geoid undulations, which are about 1 meter.

  • Access to the full text
    Designing CDIO capstone projects: a systems thinking approach  Open access

     Alarcon Cot, Eduardo Jose; Bou Balust, Elisenda; Camps Carmona, Adriano Jose; Bragos Bardia, Ramon; Oliveras Verges, Albert; Pegueroles Valles, Josep Rafel; Sayrol Clols, Elisa; Marques Acosta, Fernando
    International CDIO Conference
    Presentation's date: 2013-06-10
    Presentation of work at congresses

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    Given the all-pervasiveness of Systems thinking -which consists of thinking about things as systems- as a way of reasoning, in this work we will describe its application to make an interpretation of how to conceive and design a final year CDIO capstone course. Both the student teamwork structure as well as the complex engineering system itself addressed in the project are described in terms of entities, links, form and function, thereby pointing out their formal and functional interaction. The ultimate goal of the Systems thinking perspective is, given the necessary ingredients, to try maximizing the chances of the emergence of a fruitful capstone course, namely a culminating project that yields a set of students qualified to CDIO complex engineering systems.

    Given the all-pervasiveness of Systems thinking -which consists of thinking about things as systemsas a way of reasoning, in this work we will describe its application to make an interpretation of how to conceive and design a final year CDIO capstone course. Both the student teamwork structure as well as the complex engineering system itself addressed in the project are described in terms of entities, links, form and function, thereby pointing out their formal and functional interaction. The ultimate goal of the Systems thinking perspective is, given the necessary ingredients, to try maximizing the chances of the emergence of a fruitful capstone course, namely a culminating project that yields a set of students qualified to CDIO complex engineering systems.

  • An IBC solar cell for the UPC CubeSat-1 mission

     Ortega Villasclaras, Pablo Rafael; Jove Casulleras, Roger; Pedret, A; Gonzalvez, G.; Lopez Rodriguez, Gema; Martin Garcia, Isidro; Dominguez Pumar, Manuel M.; Alcubilla Gonzalez, Ramon; Camps Carmona, Adriano Jose
    Spanish Conference on Electron Devices
    Presentation's date: 2013-02
    Presentation of work at congresses

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    In this work the fabrication and electrical characterization of interdigitated back contact IBC solar cells is shown. These solar cells have been specifically designed for a CubeSat based satellite under developement at the Universitat Politecnica de Catalunya (UPC). Solar cells incorporate a transparent cover-glass as an extraterrestrial radiation shield. Front surface passivation was achieved using an Al2O3 layer exhibiting surface recombination velocities 100 cmls at the final device. Measurements confirm photovoltaic efficiencies n's-12%, with open circuit voltages Voc's 650 m V and short circuit current densities Jsc's 25 mA/cm 2. A module with 11 IBC solar cells interconnected in series will be integrated in one of the faces of the satellite forming part of the power subsystem. Preliminary results confirm the good electrical performance of the module.

    In this work the fabrication and electrical characterization of interdigitated back contact IBC solar cells is shown. These solar cells have been specifically designed for a CubeSat based satellite under developement at the Universitat Politecnica de Catalunya (UPC). Solar cells incorporate a transparent cover-glass as an extraterrestrial radiation shield. Front surface passivation was achieved using an Al2O3 layer exhibiting surface recombination velocities <; 100 cmls at the final device. Measurements confirm photovoltaic efficiencies η's-12%, with open circuit voltages Voc's ~650 m V and short circuit current densities Jsc's ~25 mA/cm2. A module with 11 IBC solar cells interconnected in series will be integrated in one of the faces of the satellite forming part of the power subsystem. Preliminary results confirm the good electrical performance of the module.

  • Wind speed maping from the ISS using GNSS-R? A simulation study

     Camps Carmona, Adriano Jose; Park, Hyuk; Alonso Arroyo, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    Reflectometry using Global Navigation Satellite System's signals of opportunity (GNSS-R) was originally conceived for mesoscale altimetry, but it can be applied to sea state determination (i.e. wind speed), among many other applications. The feasibility to create scattering coefficient and wind speed maps over the ocean using the Delay-Doppler Maps (DDMs) has also been analyzed. In this work a case study is presented to show the evolution of some features of the DDM (shape and peak) as seen from a PAU-like GNSS-R instrument aboard the International Space Station (ISS), while overpassing the Sandy hurricane on October 27th, 2012 in front of the coast of Florida. © 2013 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.

  • Comparison of GPS L1 and Galileo E1 signals for GNSS-R ocean altimetry

     Pascual Biosca, Daniel; Park, Hyuk; Camps Carmona, Adriano Jose; Alonso Arroyo, Alberto; Onrubia Ibañez, Raul
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    In the last years, the GPS signals have been validated as opportunity signals in a wide range of reflectometry-based remote sensing applications for sea, land or ice scenarios. Recently, the first Galileo satellites have started transmitting the new signal E1, which shares the band with the GPS L1 signal. This work compares the performance of both signals in space and airborne scenarios for sea state and altimetry determination. © 2013 IEEE.

  • 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.

  • Digital back-end for RFI detection and mitigation in earth observation

     Forte Veliz, Giuseppe Francesco; Querol Borras, Jorge; Park, Hyuk; 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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    A powerful real time Radio-frequency interference (RFI) mitigation back-end system is presented in this work. The interfering signals are estimated by using the wavelet transform to utilize its effective denoising capability. The estimated RFI signals are then subtracted from the total received signal, and ultimately the RFI-mitigated signal is obtained. Here, the hardware implementation and the system tests are demonstrated, showing sinusoid, chirp, and PRN interference mitigation under different Interference to Noise Ratios (INRs).

  • Comparison of GNSS-R processing techniques for spaceborne ocean altimetry

     Martin Alemany, Francisco; d'Addio, Salvatore; Camps Carmona, Adriano Jose; Martín Neira, Manuel; Park, Hyuk; Pascual Biosca, Daniel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Earth-reflected Global Navigation Satellite System (GNSS) have become an attractive tool to be employed in low-Earth-orbit spaceborne missions, for applications such as ocean mesoscale altimetry and scatterometry. For such techniques, several on-board processing strategies have been proposed, either based on the correlation with on-board generated signal or based on 'blind' interferometric processing, which involves the correlation between received direct and reflected signals. This paper will provide a comparison of these two proposed GNSS-R processing techniques, highlighting the possible achieved performance for a typical spaceborne scenario. The performance comparison will be carried out by analyzing the widely used Cramer-Rao Bound, which takes into account the full statistical properties of the reflected signals and provides accurate comparison.

  • MIR: the microwave interferometric reflectometer, a new airborne sensor for GNSS-R advanced research

     Onrubia Ibañez, Raul; Pascual Biosca, Daniel; Camps Carmona, Adriano Jose; Alonso Arroyo, Alberto; Park, Hyuk
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    The use of Global Navigation Satellite Signals (GNSS) in reflectometric applications (GNSS-R) is highly extended in remote sensing applications, such as sensing sea state, soil moisture or ice layer characterization. There are two main techniques in this field: the conventional GNSS-R, that achieves high SNRs by cross-correlating the received signal with a replica of the transmitted one but, with a low resolution due to narrow bandwidth of the signals, and the interferometric GNSS-R, which achieves better resolutions but with lower SNRs since it directly correlates the direct and reflected signals. The Microwave Interferometric Reflectometer (MIR) is a new sensor that will use high-directivity, multiband and steerable arrays to achieve higher SNRs in the interferometric technique. Additionally, it will also apply the conventional technique. All these capabilities will be applied simultaneously to two beams at each band (L1 and L5 / E1 and E5). This work describes this concept instrument and the first prototypes will be presented at the conference. © 2013 IEEE.

  • Improvement of the PAU/PARIS End-to-end Performance Simulator (P^2 EPS) in preparation for upcoming GNSS-R missions

     Park, Hyuk; Camps Carmona, Adriano Jose; Pascual Biosca, Daniel; Alonso Arroyo, Alberto; Martin Alemany, Francisco; Carreño Luengo, Hugo
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    PAU/PARIS End-to-end Performance Simulator (P2EPS) has been developed for studying and design tools for GNSS-R space mission. For the purpose of accuracy and various scenario, P2EPS has recently improved in many features. Especially, the wide range of the simulation inputs enables to simulate the upcomming GNSS-R space missions. This paper presents the recent improvement of the P2EPS. © 2013 IEEE.

  • Soil moisture mapping using forward scattered GPS L1 signals

     Alonso Arroyo, Alberto; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Park, Hyuk; Pascual Biosca, Daniel; Onrubia Ibañez, Raul; Jove Casulleras, Roger
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    This work presents a novel technique for the determination of soil moisture obtaining 2-D Soil Moisture (SM) information with a single instrument. Both the instrument and the retrieval algorithm used, which is based on inferring the reflection coefficient of the terrain by direct and forward scattering polarimetric measurements of Global Navigation Satellite Systems (GNSS) Signals, are briefly described. Some preliminary results of a field campaign performed on La Pobla de Mafumet (Tarragona, Spain) are presented. This instrument and retrieval algorithm can be used for different applications, such as, an input for the irrigation algorithm (Smart-Irrigation) or forest fire prevention among others.

  • 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.

  • SAIRPS: a generic simulator for evaluation of synthetic aperture interferometric radiometers

     Camps Carmona, Adriano Jose; Park, Hyuk; Kang, Yujin; Barbosa, José; Bandeiras, J.; Vieira, Paula; Friaças, Ana; d'Addio, Salvatore
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    ESA's SMOS mission has been a cornerstone in passive Earth Observation, since it has provided for the first time ever with global and frequent observations of Soil Moisture and Ocean Salinity (where the mission acronym comes from). SMOS' single payload is MIRAS: the Microwave Imaging Radiometers by Aperture Synthesis in two dimensions. After SMOS' success, today, a number of instruments are planned or under study: the GeoStar instrument is the baseline payload for the Precipitation and All-weather Temperature and Humidity (PATH) mission from NASA (USA), the Geostationary Atmospheric Sounder (GAS) instrument is under study for post-MSG operational satellites observations (Europe), and the Geostationary Interferometric Microwave Sounder (GIMS) instrument from NSSC-CAS (China). The study of the instrument performance in terms of angular resolution and radiometric performance (radiometric sensitivity and accuracy), and the optimization of this new type of instruments is a complex task that requires dedicated ad-hoc tools. In this work the SAIRPS (Synthetic Aperture Interferometric Radiometer Performance Simulator) is presented. This complex simulator allows to analyze arbitrary receiver topologies, arbitrary array geometries, and includes noise injection calibration algorithms, and new external robust calibration algorithms, and image reconstruction algorithms that allow to evaluate the performance of almost any instrument. At present, the full simulator has been coded in Matlab, translated into C++, and integrated in OpenSF. This work summarizes the key aspects of the architecture of this simulator, completing the presentation made in IGARSS 2012, and presents a few examples of the simulation results using different instrument configurations. © 2013 IEEE.

  • Altimetry performance and error budget of the PARIS in-orbit demonstration mission

     Camps Carmona, Adriano Jose; Pascual Biosca, Daniel; Park, Hyuk; Martin Alemany, Francisco; Rius, Antonio; Ribó Vedrilla, Serni; Benito, Javier; Andrés, Ana; Saameno, Paula; Staton, Gavin; Martín Neira, Manuel; d'Addio, Salvatore; Willemsen, Philip
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    Reflectometry using Global Navigation Satellite System's signals of opportunity (GNSS-R) was originally conceived for mesoscale altimetry [1], although its applicability to sea state determination, soil moisture, vegetation, snow monitoring. has already been demonstrated. In December 2012 the Phase A studies of ESA's PAssive Reflectometry and Interferometry System In-orbit Demonstration (PARIS IoD) mission ended. In conventional GNSS-R the GNSS signals scattered over the Earth's surface are cross-correlated with a locally generated replica of the transmitted signal shifted in frequency (¿fd) and in delay (¿t). PARIS is called an interferometric GNSS-R (iGNSS-R) system because the direct and the scattered signals are cross-correlated in order to use the whole signal's bandwidth, and improve the altimetric precision, despite the large bandwidth signals are not publicly available. This work presents a methodology to evaluate the performance of iGNSS-R altimeters. It is then applied to a PARIS IoD-like case, in which the receivers' bandwidths have been optimized in terms of altimetric resolution. © 2013 IEEE.

  • 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.

  • Airborne GNSS-R wind retrievals using delay-doppler maps

     Akos, Dennis M.; Rodríguez Álvarez, Nereida; Zavorotny, Valery U.; Smith, Jeffrey A.; Camps Carmona, Adriano Jose; Fairall, Christopher W.
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-01
    Journal article

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    Global navigation satellite system (GNSS) reflectometry has emerged recently as a promising remote sensing tool to retrieve various geophysical parameters of the Earth's surface. GNSS-reflected signals, after being received and processed by the airborne or spaceborne receiver, are available as delay correlation waveforms or as delay-Doppler maps (DDMs). In the case of a rough ocean surface, those characteristics can be related to the rms of the L-band limited slopes of the surface waves and, from there, to the surface wind speed. The raw GNSS-reflected signal can be either processed in real time by the receiver or recorded and stored on board and postprocessed in a laboratory. The latter approach leveraging a software receiver allows more flexibility while processing the raw data. This work analyzes DDMs obtained as a result of processing of the data collected by the Global Positioning System (GPS) data logger/software receiver on board the National Oceanic and Atmospheric Administration Gulfstream-IV jet aircraft. Thereafter, the DDMs were used to retrieve surface wind speed employing several different metrics that characterize the DDM extent in the Doppler frequency-delay domain. In contrast to previous works in which winds have been retrieved by fitting the theoretically modeled curves into measured correlation waveforms, here, we do not rely on any model for the determination. Instead, the approach is based on a linear regression between DDM observables and the wind speeds obtained in simultaneous GPS dropsonde measurements.

    Global navigation satellite system (GNSS) reflectometry has emerged recently as a promising remote sensing tool to retrieve various geophysical parameters of the Earth's surface. GNSS-reflected signals, after being received and processed by the airborne or spaceborne receiver, are available as delay correlation waveforms or as delay-Doppler maps (DDMs). In the case of a rough ocean surface, those characteristics can be related to the rms of the L-band limited slopes of the surface waves and, from there, to the surface wind speed. The raw GNSS-reflected signal can be either processed in real time by the receiver or recorded and stored on board and postprocessed in a laboratory. The latter approach leveraging a software receiver allows more flexibility while processing the raw data. This work analyzes DDMs obtained as a result of processing of the data collected by the Global Positioning System (GPS) data logger/software receiver on board the National Oceanic and Atmospheric Administration Gulfstream-IV jet aircraft. Thereafter, the DDMs were used to retrieve surface wind speed employing several different metrics that characterize the DDM extent in the Doppler frequency-delay domain. In contrast to previous works in which winds have been retrieved by fitting the theoretically modeled curves into measured correlation waveforms, here, we do not rely on any model for the determination. Instead, the approach is based on a linear regression between DDM observables and the wind speeds obtained in simultaneous GPS dropsonde measurements.

  • GNSS-R as a source of opportunity for remote sensing of the cryosphere.  Open access

     Fabra Cervellera, Francisco José
    Defense's date: 2013-05-13
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    This work evaluates the potential use of signals from the Global Navigation Satellite Systems (GNSS) that scatter off the Earth surface for the retrieval of geophysical information from the cryosphere. For this purpose, the present study is based on data collected with a dedicated reflectometry GNSS receiver during two field campaigns, which were focused on two types of characteristic surfaces of the cryosphere: thin sea ice covers and thick dry snow accumulations. During the first experiment, the complete process of formation, evolution and melting of sea ice was monitorized for more than seven months in a bay located in Greenland. This type of ice is typically characterized by its thickness, concentration and roughness. Different observables from GNSS reflections are analyzed to try to infer these properties. The ice thickness is linked to the free-board level, defined as the height of the sea ice surface. Accurate phase altimetry is achieved, showing good agreement with an Arctic tide model. In addition, the long term results of ellipsoidal height retrievals are consistent with the evolution of the ice surface temperature product given by MODIS, which is a key parameter in the rate of growth of sea ice. On the other hand, the presence of salinity in the sea ice modifies its dielectric properties, resulting in different amplitude and phase for the co- and cross-polar components of the complex Fresnel coefficients. The polarimetric measurements obtained show good agreement with visual inspections of ice concentration from an Arctic weather station. Finally, the shape of the reflected signals and its phase dispersion are tested as potential signatures of surface roughness. For comparison, ice charts of the experimental area are employed. In particular, maximums in roughness given by the GNSS observables coincide with fast ice events. Fast ice is defined as ice anchored to the coast, where the tidal movements contribute to the development of strange patterns, cracks, and fissures on its surface, thus consistent with the GNSS-R roughness retrievals. The second experiment took place on Antarctica, monitoring a pristine snow area which is well-known for the calibration of remote sensing instruments. Due to the relative stability of the snow layers, the data acquisition was limited to ten continuous days. Interferometric beats were found after a first analysis of the amplitude from the collected signals, which were consistent with a multipath model where the reflector lies below the surface level. Motivated by these results, a forward model is developed that reconstructs the complex received signal as a sum of a finite number of reflections, coming from different snow layers (a snow density profile obtained from in-situ measurements). The interferometric information is then retrieved from the spectral analysis applied to time series from both real and modeled signals (lag-holograms). We find that the frequency bands predicted by the model are in general consistent with the data and the lag-holograms show repeatability for different days. Then, we attempt a proper inversion of the collected data to determine the dominant layers of the dry snow profile that contribute to L-band reflections, which are related to significant gradients of snow density/permittivity.

    Aquest treball avalua el possible ús dels senyals dels sistemes mundials de navegació per satèl lit (GNSS) que es reflecteixen a la superfície terrestre, per a l’extracció de la informació geofísica de la criosfera. Amb aquest propòsit, el present estudi es basa en dades recollides amb un reflectòmetre GNSS durant dues campanyes experimentals, centrades en dos tipus de superfícies característiques de la criosfera: cobertes de gel marí i gruixudes acumulacions de neu seca. En el primer experiment, el procés complet de formació, evolució i fusió del gel marí va ser monitoritzat durant més de set mesos a una badia situada a Groenlàndia. Aquest tipus de gel es caracteritza típicament amb el seu gruix, concentració i rugositat. Diferents observables de les reflexions GNSS són analitzats per tractar de fer una estimació d’aquestes propietats. El gruix de gel està relacionat amb el nivell de francbord, que a la seva vegada està relacionat amb l’alçada de la superfície de gel marí. S’ha aconseguit altimetria de fase precisa, que mostra correlació amb un model de marea de l’Àrtic. A més, els resultats a llarg termini de l’alçada elipsoidal segueixen l’evolució de les mesures de temperatura de superfície de gel donades per MODIS. La temperatura és un paràmetre clau en el ritme de creixement del gel marí. Per altra banda, la presència de sal a aquest tipus de gel modifica les seves propietats dielèctriques, el que implica variacions d’amplitud i fase per als coeficients de Fresnel complexos amb polaritzacions oposades. Les mesures polarimètriques obtingudes mostren concordança amb els valors de concentració de gel obtinguts des d’una estació meteorològica propera. Finalment, la forma de la senyal reflectida i la dispersió de la seva fase s’evaluen com a potencials indicadors de la rugositat de superfície. Per a la seva comparació, es fan servir mapes del gel de la zona experimental. En concret, els valors màxims a la rugositat estimada a partir pels observables GNSS coincideixen amb el gel fixe, que es refereix a gel ancorat a la costa, on els moviments de les marees contribueixen al desenvolupament de patrons estranys, esquerdes i fissures en la seva superfície. El segon experiment es va dur a terme a l’Antàrtida, monitoritzant una àrea de neu pristina que és ben coneguda per al calibratge d’instruments de teledetecció. A causa de la relativa estabilitat de les capes de neu, l’adquisició de dades es va limitar a deu dies consecutius. Es van trobar pulsacions interferomètriques a partir d’un primer anàlisi de l’amplitud de les senyals recollides, les quals eren compatibles amb un model de propagació multicamí a on el reflector es troba per sota del nivell de superfície. Com a conseqüència d’aquests resultats, s’ha desenvolupat un model que reconstrueix el senyal complexe rebut com la suma d’un nombre finit de reflexions, procedents de diferents capes de neu (determinat per mesures locals). La informació interferomètrica es recupera després de l’anàlisi espectral aplicat a les sèries temporals tant de les senyals reals, com de les modelades (lag-hologrames). Trobem que les bandes de freqüències predites pel model són en general consistents amb les dades i que els lag-hologrames mostren repetibilitat per dies diferents. Posteriorment, es realitza un anàlisi de les dades recollides per determinar les capes dominants del perfil de neu seca que contribueixen a les reflexions en banda L, i que a la seva vegada, estan relacionades amb gradents significatius de densitat/permitivitat.

    Este trabajo evalúa el posible uso de las señales de los sistemas globales de navegación por satélite (GNSS) que se reflejan en la superficie terrestre para la extracción de información geofísica de la criosfera. Con este propósito, el presente estudio se basa en datos recogidos con un reflectómetro GNSS durante dos campañas experimentales, centradas en dos tipos de superficies características de la criosfera: capas de hielo marino y gruesas acumulaciones de nieve seca. Durante el primer experimento, el proceso completo de formación, evolución y fusión del hielo marino fue monitorizado durante más de siete meses en una bahía ubicada en Groenlandia. Este tipo de hielo se caracteriza típicamente por su grosor, concentración y rugosidad. Diferentes observables de las reflexiones GNSS son analizados para tratar de estimar dichas propiedades. El espesor de hielo está relacionado con el nivel de francobordo o borda libre, que a su vez está relacionado con la altura de la superficie de hielo marino. Se ha logrado altimetría de fase precisa, mostrando correlación con un modelo de marea del Ártico. Además, los resultados a largo plazo de la altura elipsoidal siguen la evolución de las mediciones de temperatura de superficie de hielo proporcionadas por MODIS. La temperatura es un parámetro clave en el ritmo de crecimiento del hielo marino. Por otro lado, la presencia de sal en este tipo de hielo modifica sus propiedades dieléctricas, lo que implica variaciones en las amplitudes y fases de los coeficientes complejos de Fresnel con polarizaciones opuestas. Los resultados polarimétricos concuerdan con los valores de concentración de hielo obtenidos mediante inspección visual desde una estación meteorológica cercana. Por último, la forma de la señal reflejada y la dispersión de su fase son evaluadas como potenciales indicadores de la rugosidad de superficie. Para su comparación, se emplean mapas del hielo de la zona experimental. En particular, valores máximos de rugosidad estimada por los observables GNSS coinciden con hielo fijo, que se refiere al hielo anclado a la costa, donde los movimientos de las mareas contribuyen al desarrollo de patrones extraños, grietas y fisuras en su superficie. El segundo experimento se llevó a cabo en la Antártida, monitorizando una área de nieve pristina que es bien conocida para la calibración de instrumentos de teledetección. Debido a la relativa estabilidad de las capas de nieve, la adquisición de datos se limitó a diez días consecutivos. Se encontraron pulsaciones interferométricas a partir de un primer análisis de la amplitud de las señales recibidas, las cuales eran compatibles con un modelo de propagación multicamino donde el reflector se encuentra por debajo del nivel de la superficie. Como consecuencia de estos resultados, se ha desarrollado un modelo que reconstruye la señal recibida como la suma de un número finito de reflexiones, procedentes de diferentes capas de nieve (caracterizados por mediciones locales). La información interferométrica se recupera después del análisis espectral aplicado a las series temporales tanto de las señales reales, como de las modeladas (lag-hologramas). Encontramos que las bandas de frecuencias predichas por el modelo son en general consistentes con los datos y que los lag-hologramas muestran repetibilidad para días diferentes. Posteriormente, se realiza un análisis de los datos recogidos para determinar las capas dominantes del perfil de nieve seca que contribuyen a las reflexiones en banda L, y que a su vez, están relacionadas con gradientes significativos de densidad/permitividad

  • Radio Frequency Interference in Microwave Radiometry: Statistical Analysis and Study of Techniques for Detection and Mitigation  Open access

     Tarongí Bauzá, José Miguel
    Defense's date: 2013-03-06
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
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    Microwave radiometry field has been increasing its performance with higher accuracy measurements, leading to a more presence in the remote sensing field. Several space-borne, air-borne and ground-based radiometers have been developed to perform measurement campaigns; however, the actual sensitivity of a radiometer is often limited by man-made radio emissions such as radars, broadcasting emissions, wireless communications and many other communication systems based on electromagnetic waves, limiting the improvement in the radiometers¿ performance. Consequently, in order to maintain the accuracy in the radiometric measurements, it has been researched in the Radio Frequency Interference (RFI) detection and mitigation systems and algorithms for the microwave radiometry field. The scope of this doctoral thesis is the development and testing of RFI detection and mitigation algorithms in order to enhance radiometric measurements performed by the Multifequency Experimental Radiometer with Interference Tracking for Experiments over Land and Littoral (MERITXELL). The MERITXELL has been developed during this thesis with the idea studying the RFI present in several radiometric bands and the way to mitigate it, as well as to obtain data from diverse frequency bands and devices in only one measurement campaign.

  • GNSS Reflectometry for Land Remote Sensing Applications  Open access

     Egido Egido, Alejandro
    Defense's date: 2013-07-05
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Soil moisture and vegetation biomass are two essential parameters from a scienti c and economical point of view. On one hand, they are key for the understanding of the hydrological and carbon cycle. On the other hand, soil moisture is essential for agricultural applications and water management, and vegetation biomass is crucial for regional development programs. Several remote sensing techniques have been used to measure these two parameters. However, retrieving soil moisture and vegetation biomass with the required accuracy, and the appropriate spatial and temporal resolutions still remains a major challenge. The use of Global Navigation Satellite Systems (GNSS) reflected signals as sources of opportunity for measuring soil moisture and vegetation biomass is assessed in this PhD Thesis. This technique, commonly known as GNSS-Reflectometry (GNSS-R), has gained increasing interest among the scienti c community during the last two decades due to its unique characteristics. Previous experimental works have already shown the capabilities of GNSS-R to sense small reflectivity changes on the surface. The use of the co- and cross-polarized reflected signals was also proposed to mitigate nuisance parameters, such as soil surface roughness, in the determination of soil moisture. However, experimental evidence of the suitability of that technique could not be demonstrated. This work analyses from a theoretical and an experimental point of view the capabilities of polarimetric observations of GNSS reflected signals for monitoring soil moisture and vegetation biomass. The Thesis is structured in four main parts. The fi rst part examines the fundamental aspects of the technique and provides a detailed review of the GNSS-R state of the art for soil moisture and vegetation monitoring. The second part deals with the scattering models from land surfaces. A comprehensive description of the formation of scattered signals from rough surfaces is provided. Simulations with current state of the art models for bare and vegetated soils were performed in order to analyze the scattering components of GNSS reflected signals. A simpli ed scattering model was also developed in order to relate in a straightforward way experimental measurements to soil bio-geophysical parameters. The third part reviews the experimental work performed within this research. The development of a GNSS-R instrument for land applications is described, together with the three experimental campaigns carried out in the frame of this PhD Thesis. The analysis of the GNSS-R and ground truth data is also discussed within this part. As predicted by models, it was observed that GNSS scattered signals from natural surfaces are a combination of a coherent and an incoherent scattering components. A data analysis technique was proposed to separate both scattering contributions. The use of polarimetric observations for the determination of soil moisture was demonstrated to be useful under most soil conditions. It was also observed that forests with high levels of biomass could be observed with GNSS reflected signals. The fourth and last part of the Thesis provides an analysis of the technology perspectives. A GNSS-R End-to-End simulator was used to determine the capabilities of the technique to observe di erent soil reflectivity conditions from a low Earth orbiting satellite. It was determined that high accuracy in the estimation of reflectivity could be achieved within reasonable on-ground resolution, as the coherent scattering component is expected to be the predominant one in a spaceborne scenario. The results obtained in this PhD Thesis show the promising potential of GNSS-R measurements for land remote sensing applications, which could represent an excellent complementary observation for a wide range of Earth Observation missions such as SMOS, SMAP, and the recently approved ESA Earth Explorer Mission Biomass.

    La humedad del suelo y la biomasa de la vegetaci on son dos parametros clave desde un punto de vista tanto cient co como econ omico. Por una parte son esenciales para el estudio del ciclo del agua y del carbono. Por otra parte, la humedad del suelo es esencial para la gesti on de las cosechas y los recursos h dricos, mientras que la biomasa es un par ametro fundamental para ciertos programas de desarrollo. Varias formas de teledetección se han utilizado para la observaci on remota de estos par ametros, sin embargo, su monitorizaci on con la precisi on y resoluci on necesarias es todav a un importante reto tecnol ogico. Esta Tesis evalua la capacidad de medir humedad del suelo y biomasa de la vegetaci on con señales de Sistemas Satelitales de Posicionamiento Global (GNSS, en sus siglas en ingl es) reflejadas sobre la Tierra. La t ecnica se conoce como Reflectometr í a GNSS (GNSS-R), la cual ha ganado un creciente inter es dentro de la comunidad científ ca durante las dos ultimas d ecadas. Experimentos previos a este trabajo ya demostraron la capacidad de observar cambios en la reflectividad del terreno con GNSS-R. El uso de la componente copolar y contrapolar de la señal reflejada fue propuesto para independizar la medida de humedad del suelo de otros par ametros como la rugosidad del terreno. Sin embargo, no se pudo demostrar una evidencia experimental de la viabilidad de la t ecnica. En este trabajo se analiza desde un punto de vista te orico y experimental el uso de la informaci on polarim etrica de la señales GNSS reflejadas sobre el suelo para la determinaci on de humedad y biomasa de la vegetaci on. La Tesis se estructura en cuatro partes principales. En la primera parte se eval uan los aspectos fundamentales de la t ecnica y se da una revisi on detallada del estado del arte para la observaci on de humedad y vegetaci on. En la segunda parte se discuten los modelos de dispersi on electromagn etica sobre el suelo. Simulaciones con estos modelos fueron realizadas para analizar las componentes coherente e incoherente de la dispersi on de la señal reflejada sobre distintos tipos de terreno. Durante este trabajo se desarroll o un modelo de reflexi on simpli cado para poder relacionar de forma directa las observaciones con los par ametros geof sicos del suelo. La tercera parte describe las campañas experimentales realizadas durante este trabajo y discute el an alisis y la comparaci on de los datos GNSS-R con las mediciones in-situ. Como se predice por los modelos, se comprob o experimentalmente que la señal reflejada est a formada por una componente coherente y otra incoherente. Una t ecnica de an alisis de datos se propuso para la separacióon de estas dos contribuciones. Con los datos de las campañas experimentales se demonstr o el bene cio del uso de la informaci on polarim etrica en las señales GNSS reflejadas para la medici on de humedad del suelo, para la mayor a de las condiciones de rugosidad observadas. Tambi en se demostr o la capacidad de este tipo de observaciones para medir zonas boscosas densamente pobladas. La cuarta parte de la tesis analiza la capacidad de la t ecnica para observar cambios en la reflectividad del suelo desde un sat elite en orbita baja. Los resultados obtenidos muestran que la reflectividad del terreno podr a medirse con gran precisi on ya que la componente coherente del scattering ser a la predominante en ese tipo de escenarios. En este trabajo de doctorado se muestran la potencialidades de la t ecnica GNSS-R para observar remotamente par ametros del suelo tan importantes como la humedad del suelo y la biomasa de la vegetaci on. Este tipo de medidas pueden complementar un amplio rango de misiones de observaci on de la Tierra como SMOS, SMAP, y Biomass, esta ultima recientemente aprobada para la siguiente misi on Earth Explorer de la ESA.

  • European GNSS-R Environmental Monitoring

     Camps Carmona, Adriano Jose
    Participation in a competitive project

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  • Delay Tracking in Spaceborne GNSS-R Ocean Altimetry

     Park, Hyuk; Valencia Domenech, Enric; Camps Carmona, Adriano Jose; Rius, Antonio; Ribó Vedrilla, Serni; Martín Neira, Manuel
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2013-01
    Journal article

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  • Land monitoring using GNSS-R techniques: a review of recent advances

     Camps Carmona, Adriano Jose; Rodríguez Álvarez, Nereida; Valencia Domenech, Enric; Forte Veliz, Giuseppe Francesco; Ramos Pérez, Isaac; Alonso Arroyo, Alberto; Bosch Lluis, Xavier
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Soil moisture is required to improve meteorological and climate predictions. Global soil moisture maps are nowadays produced daily from SMOS satellite data, with a basic spatial resolution of ~50 km. Recently, using data fusion techniques between SMOS and MODIS data, an operational service has been implemented at the SMOS-Barcelona Expert Center to downscale SMOS data down to 1 km over the Iberian peninsula [1]. However, despite SMOS operates in the passive microwave 'protected' band from 1400 to 1427 MHz, radio frequency interference may degrade the quality of the soil moisture (and sea salinity) retrievals or even prevent them [2]. Signals of opportunity transmitted from Global Navigation Satellite Systems (GNSS) can be used for soil moisture, vegetation, snow, water level. monitoring after reflection (GNSS-R) on the Earth's surface. In principle, even though these signals can also be jammed, their structure and the way they are processed, makes them more robust in front of radio-frequency interference, while at the same time -in principle- can achieve also a better spatial resolution. In this work, the few different GNSS-R techniques are first revised, including their pros and cons. Then a few applications are revised, with special emphasis -but not exclusively- in those in which the UPC Remote Sensing Lab has been working.

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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.

  • Interferometric GNSS-R achievable altimetric performance and compression/denoising using the wavelet transform: An experimental study

     Camps Carmona, Adriano Jose; Martin Alemany, Francisco; Park, Hyuk; Valencia Domenech, Enric; Rius, Antonio; d'Addio, Salvatore
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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  • Airborne wind retrieval using GPS delay-Doppler maps

     Zavorotny, Valery U.; Rodríguez Álvarez, Nereida; Akos, Dennis M.; 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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    Global Navigation Satellite System Reflectometry (GNSSR) has emerged recently as a promising remote sensing tool to retrieve various geophysical parameters of Earth’s surface. GNSS-reflected signals, after being received and processed by the airborne or space-borne receiver, are available as delay correlation waveforms or as delay- Doppler maps. In the case of a rough ocean surface, those characteristics can be related to the RMS of L-band limited slopes of the surface waves, and from there to the surface wind speed. The raw GNSS-reflected signal can be processed either in real time by the receiver, or can be recorded and stored onboard and post-processed in a laboratory. The latter approach leveraging a software receiver allows more flexibility while processing the raw data. This work analyzes Delay Doppler Maps (DDM) obtained as a result of processing of the data collected by the GPS data logger/software receiver onboard the NOAA Gulfstream-IV jet aircraft. Thereafter, the DDMs were used to retrieve surface wind speed employing several different metrics that characterize the DDM extent in the Doppler frequency-delay domain. In contrast to previous works in which winds have been retrieved by fitting the theoretically modeled curves into measured correlation waveforms, here we do not rely on any model for the determination. Instead, the approach is based on a linear regression between DDMs observables and the wind speeds obtained in simultaneous GPS dropsonde measurements.

  • Recent advances in land monitoring using GNSS-R techniques

     Camps Carmona, Adriano Jose; Forte Veliz, Giuseppe Francesco; Ramos, I.; Alonso Arroyo, Alberto; Martinez, Philippe; Crespo, Luis; Alcayde, Antonio
    Workshop on Reflectometry Using GNSS and Other Signals of Opportunity
    Presentation's date: 2012-10
    Presentation of work at congresses

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    Soil moisture and land surface’s temperature are proxys of forest fires risk. In the frame of the DANTE project, ADTelecom (Barcelona, Spain) is working in the design of an instrument: 1) to estimate the risk of forest fires, based on surface temperature and soil moisture measurements, 2) to detect and localize the ignition of forest fires by image processing techniques, and finally, once the forest fire has ignited, 3) to estimate the direction of propagation of the fire based on short- range wind lidars. This paper is focused on the design of the soil moisture remote sensor. To do that, some of the existing techniques for ground-based soil moisture monitoring based on the use of signals of opportunity transmitted from Global Navigation Satellite Systems after reflection on the land surface are first reviewed. Then, some conclusions drawn to design a new and simpler remote sensing instrument for soil moisture monitoring taking the advantages of all each of the individual systems revised before. Finally, the instrument developed is presented together with some preliminary results, pending on the development of more refined retrieval methods through the processing of more experimental data.

  • A generic simulator for aperture synthesis radiometers

     Camps Carmona, Adriano Jose; Park, Hyuk; Barbosa Torralbo, José; Bandeiras, J.; d'Addio, Salvatore
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    ESA's SMOS mission has demonstrated that Synthetic Aperture Interferometric Radiometers can be a useful tool for Earth observation. Today, the NASA's GeoStar instrument (USA), ESA's GAS instrument (Europe), or CSSAR's GIMS instrument (China) are just three examples of planned geostationary millimeter-wave sounders using synthetic aperture interferometric radiometry for continuous atmospheric monitoring with a much improved spatial resolution. The study of the performance in terms of angular resolution and radiometric performance, and the optimization of this new type of instruments is a complex task that requires dedicated ad-hoc simulators. The SAIPRS (Synthetic Aperture Interferometric Radiometer Performance Simulator) is an ESA project aiming at the development of a generic simulator in terms of receiver architecture and array configuration, including moving antennas (and eventually changing polarization reference frames). This work summarizes the key aspects of the architecture of this simulator.

  • Submeter ocean altimetry with GPS L1 C/A signal

     Carreño Luengo, Hugo; Park, Hyuk; Camps Carmona, Adriano Jose; Fabra Cervellera, Fran; Rius, Antonio
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    The ultimate accuracy and precision of conventional1 and interferometric2 Global Positioning Satellite System Rerflectometry (GNSS-R) techniques for mesoscale ocean altimetry are still a matter of debate in the scientific community. The results obtained depend on the techniques used to identify the point of the specular delay in the waveform, and to perform the different delay corrections to derive the geometric delay. Also, the geometric model assumed for the scenario determines the accuracy of the altimeter range. This work presents the results of two ESA-sponsored airborne experiments using conventional GNSS-R showing subdecimeter altimetric precision with the Global Positioning System (GPS) L1 C/A code only. The Relative Mean Dynamic Topography (RMDT) obtained in both experiments is compared with results derived from traditional radar altimetry provided by Jason 2. The Root Mean Square (RMS) of the RMDT difference between both measurement systems is 48 cm for the first flight, and 198 cm for the second flight. Additionally, results from the second flight experiment show the capability of the proposed technique to retrieve sea slope measurements by superposing the ground track with EM96 geoid undulations.

  • Impact of doppler frequency compensation errors on spaceborne GNSS-R altimetry

     Park, Hyuk; Camps Carmona, Adriano Jose; Valencia Domenech, Enric
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    The compensation of the Doppler frequency error is important to accurately estimate the sea height in spaceborne GNSSR altimetry. This work presents the impact of the residual Doppler error on the altimetric performance. The GNSS-R altimetric observables (waveforms) are simulated with various observation parameters, and the degradation is analyzed vs. the Doppler errors. It is shown that the Doppler error causes a bias, a decrease of the waveform value, and consequently the altimetric performance degradation in accuracy and precision.

  • Pycaro's instrument proof of concept

     Carreño Luengo, Hugo; Camps Carmona, Adriano Jose; Perez Ramos, I.; Rius, Antonio
    Workshop on Reflectometry Using GNSS and Other Signals of Opportunity
    Presentation's date: 2012-10
    Presentation of work at congresses

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  • 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.

  • PAU instrument aboard INTA MicroSAT-1: initial results of the FM model from an airborne experiment

     Alonso Arroyo, Alberto; Camps Carmona, Adriano Jose; Pascual Biosca, Daniel; Park, Hyuk; Alcayde, Antonio; Chavero, Sergio; Martinez, Pedro; Crespo, Luis; Angulo, Manuel; Rius, Antonio
    Workshop on Reflectometry Using GNSS and Other Signals of Opportunity
    Presentation's date: 2012-10
    Presentation of work at congresses

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    This work presents the PAU instrument aboard the satellite INTA MicroSAT-1. The PAU instrument is a combination of a Radiometer and a GNSS Reflectometer designed to study the relationship GNSS-R observables (Delay Doppler Maps) and the L-Band brightness temperature measurements to improve the Sea Surface Salinity (SSS) retrievals. This work describes an airborne experiment conducted to preliminary test the PAU instrument GNSS-R observables sensibility to sea state and to explore other applications of the instrument

  • 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).

  • GNSS-R altimeter performance: analysis of Cramer-Rao lower bounds

     d'Addio, Salvatore; Martín Neira, Manuel; Martin Alemany, Francisco; Park, Hyuk; Camps Carmona, Adriano Jose
    Workshop on Reflectometry Using GNSS and Other Signals of Opportunity
    Presentation's date: 2012-10
    Presentation of work at congresses

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    Earth-reflected Global Navigation Satellite Systemsignals have become an attractive tool for remote sensing, being proposed as a means to perform ocean altimetry, among many other applications. The technique exploiting navigation signals is widely known as GNSS-R. In this paper the well-known Cramer- Rao lower bound is used to predict the sea surface height estimation precision of a GNSS-R based spaceborne altimeter, exploiting the open-access GPS L1 C/A code signal. Real spaceborne data acquired by the GPS-R receiver on-board UKDMC satellite is used to extract statistical properties of spaceborne GPS reflected signals.

  • Analysis of GNSS-R delay and doppler tracking errors

     Park, Hyuk; Camps Carmona, Adriano Jose; Valencia Domenech, Enric; Carreño Luengo, Hugo; Martin Alemany, Francisco; Alonso Arroyo, Alberto; Pascual Biosca, Daniel
    Workshop on Reflectometry Using GNSS and Other Signals of Opportunity
    Presentation's date: 2012-10
    Presentation of work at congresses

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    The compensation of the delay and Doppler errors using tracking is important to accurately estimate the sea height in spaceborne GNSS-R. This work presents the impacts of the tracking residual errors on the GNSS-R observables, and potential tracking strategies for spaceborne GNSS-R. Tracking error impacts are visually demonstrated by using the P2EPS (PAU/PARIS End-to-end Performance Simulator) spaceborne simulation.

  • 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.

  • PARIS interferometric technique proof of concept: sea surface altimetry measurements

     Rius Carrasco, Antoni; Fabra Cervellera, Fran; Ribó Vedrilla, Serni; Arco Fernandez, Juan Carlos; Oliveras, S.; Cardellach, Estel; Camps Carmona, Adriano Jose; Nogués Correig, O.; Kainulainen, Juha; Rohue, E.; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    We report preliminary results of an aircraft experiment aimed to proof the PARIS Interferometric Technique. The experiment was performed in the Gulf of Finland during a two hours flight. We installed a PARIS Interferometric Receiver together with a GOLD-RTR instrument to collect reflected C/A, P(Y) and M-code GPS signals. The collected data has been analyzed to produce altimetric observables with both techniques.

    We report preliminary results of an aircraft experiment aimed to proof the PARIS Interferometric Technique. The experiment was performed in the Gulf of Finland during a two hours flight.We installed a PARIS Interferometric Receiver together with a GOLD-RTR instrument to collect reflected C/A, P(Y) and M-code GPS signals. The collected data has been analyzed to produce altimetric observables with both techniques.

  • 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.

  • Impact of the observation geometry on the GNSS-R direct descriptors used for sea state monitoring

     Valencia Domenech, Enric; Camps Carmona, Adriano Jose; Park, Hyuk; Rodríguez Álvarez, Nereida; Ramos Perez, Isaac
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    In recent years GNSS-R has been proposed for ocean remote sensing, both for altimetry and scatterometry. For the later, two main approaches are available: fitting the measurements with a model, or using some observable from the measurements (either the waveform or the delay-Doppler Map) to be directly linked to ocean surface's roughness. For ground-based and airborne experiments, several direct observables have been proposed to describe ocean surface's roughness, and they have been used assuming that the observation geometry had little impact on them. However, it may not be true for a spaceborne scenario, since the dynamics are higher. In this work an extensive simulation study is performed, and the first results on how the observation geometry does impact different GNSS-R direct observables is presented

    In recent years GNSS-R has been proposed for ocean remote sensing, both for altimetry and scatterometry. For the later, two main approaches are available: fitting the measurements with a model, or using some observable from the measurements (either the waveform or the delay-Doppler Map) to be directly linked to ocean surface’s roughness. For groundbased and airborne experiments, several direct observables have been proposed to describe ocean surface’s roughness, and they have been used assuming that the observation geometry had little impact on them. However, it may not be true for a spaceborne scenario, since the dynamics are higher. In this work an extensive simulation study is performed, and the first results on how the observation geometry does impact different GNSS-R direct observables is presented.

  • Cubesat-based demonstrator for optical Earth observation

     Jove Casulleras, Roger; Camps Carmona, Adriano Jose; Ramos Castro, Juan Jose
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-26
    Presentation of work at congresses

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    This paper introduces UPCSat-1 , the first project of the Universitat Politècnica de Catalunya to build and launch a pico-satellite. Its main scope is to develop, construct, assembly, test and launch into a Low Earth Orbit a CubeSat that will carry a simple optical payload and some technological demonstrators. On one hand, this is mainly an educational project in which the development of some of the subsystems is carried out by Master Thesis students. On the other hand, the satellite becomes an optimum platform to perform small scientific experiments, and to demonstrate some of the new technologies that it incorporates.

  • 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).

  • Preliminary performance study of different radio-frequency interference detection and mitigation algorithms in microwave radiometry

     Depau, Veronica; Tarongí Bauzá, José Miguel; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose
    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 work presents the preliminary performance study of several RFI detection and mitigation algorithms applied to real data. The used algorithms include statistical analysis in the time and frequency domains and time and frequency domains analysis. The data has been acquired in an urban area using a new experimental radiometer called MERITXELL.

  • SMOS L3 salinity performances at decreasing sea surface temperature

     Sabia, Roberto; Fernández Prieto, D.; Portabella, Marcos; Gourrion, J.; Font Ferré, Jordi; Talone, Marco; Camps Carmona, Adriano Jose
    Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment
    Presentation's date: 2012
    Presentation of work at congresses

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    A study of the latitudinal trend of the retrieved salinity performances along a Southwards transect has been performed, analyzing the trade-off between geophysical effects in cold seawater and the concomitant temporal oversampling under various processing configurations. Quantitative sensitivity with respect to sea surface temperature gradient has been evaluated.

  • Cross-correlation waveform mode: a critical review

     Martin Alemany, Francisco; Park, Hyuk; Camps Carmona, Adriano Jose; d'Addio, Salvatore; Martín Neira, Manuel
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Earth-reflected Global Navigation Satellite System (GNSS) signals have become an attractive tool for remote sensing. Recently it has been proposed as an alternative to the conventional altimetry to estimate the surface height However GNSS-R altimetry offers lower bandwidths and signals power compared to radar altimeters. This implies a poorer altimetry precision, accuracy and resolution per pulse.Also the altimetry precision will be impacted by the impact of the thermal, and speckle noise mainly. This paper gives a critical review of the cross-correlation waveform model.

  • 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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