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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.

  • Using DDM asymmetry metrics for wind direction retrieval from GPS ocean-scattered signals in airborne experiments

     Valencia Domenech, Enric; Zavorotny, Valery; Akos, Dennis M.; Camps Carmona, Adriano Jose
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2014-07
    Journal article

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    Reflectometry of signals of opportunity such as those emitted by a global navigation satellite system, known as GNSS-R, has been developed over the past years as a technique with great potential for ocean scatterometry, among other applications. Different approaches have been proposed to use GNSS-R for remote sensing of ocean surface roughness. One of them is based on deriving some descriptor/metric from the measured delay-Doppler map (DDM) and directly relating it to a geophysical property of the scattering surface. For instance, different descriptors have been proposed in the literature to measure the DDM spreading caused by the increase in ocean surface mean square slopes due to surface winds. In this paper, a new descriptor based on the DDM is proposed for wind direction retrieval. This descriptor, designated as the skewness angle 1,skew, measures the asymmetry in the DDM power distribution along the Doppler frequency axis, and it was modeled as a function of wind direction by means of a simulation study. Then, that model was validated using real GNSS-R data from an airborne experiment. After validation, the DDM skewness model was successfully used for wind direction retrieval, with a resulting rms error on the order of 20°

    Reflectometry of signals of opportunity such as those emitted by a global navigation satellite system, known as GNSS-R, has been developed over the past years as a technique with great potential for ocean scatterometry, among other applications. Different approaches have been proposed to use GNSS-R for remote sensing of ocean surface roughness. One of them is based on deriving some descriptor/metric from the measured delay-Doppler map (DDM) and directly relating it to a geophysical property of the scattering surface. For instance, different descriptors have been proposed in the literature to measure the DDM spreading caused by the increase in ocean surface mean square slopes due to surface winds. In this paper, a new descriptor based on the DDM is proposed for wind direction retrieval. This descriptor, designated as the skewness angle 1,skew, measures the asymmetry in the DDM power distribution along the Doppler frequency axis, and it was modeled as a function of wind direction by means of a simulation study. Then, that model was validated using real GNSS-R data from an airborne experiment. After validation, the DDM skewness model was successfully used for wind direction retrieval, with a resulting rms error on the order of 20°

  • 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: 2014-08-01
    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.

    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.

  • Temperature gradient sensor from pulsed power supply duty cycle in ultra-low-power energy harvesting system

     Jove Casulleras, Roger; Ramos Castro, Juan Jose; Corimanya, H; Camps Carmona, Adriano Jose; Alarcon Cot, Eduardo Jose; Amezaga Sarries, Adria; Bou Balust, Elisenda
    Electronics Letters
    Date of publication: 2014-05-22
    Journal article

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    Directly interfacing sensors that link sensors to micro-controllers without a signal conditioning circuit or an analogue-to-digital converter on the one side and energy harvesting systems on the other side are two key enabling technologies to create self-powered autonomous low-cost and low-maintenance sensor networks. In this reported work, both technologies are concurrently combined in such a way that the duty cycle of the pulsed power supply provided by the harvesting system itself yields in turn a temperature gradient sensor functionality. Originally conceived to power a low-power satellite beacon in a CubeSat project, it has found application, among other applications, in automatic air conditioning and heating systems aiming smart buildings.

  • Contributions to Radio Frequency Interference Detection and Mitigation in Earth Observation

     Forte Veliz, Giuseppe Francesco
    Defense's date: 2014-06-26
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    El problema més comú en els sistemes electrònics de mesura són les interferències electromagnètiques. La presència d'aquests senyals pot danyar les mesures preses per instruments molt sensibles, com radiòmetres de microones o sistemes de navegació. L'exactitud i precisió es veuen compromeses. El primer pas per mitigar aquests efectes no desitjats és estudiar les propietats de les interferències electromagnètiques. Diversos algoritmes han estat proposats per detectar interferències, però no hi ha mètode que funcioni bé en tots els casos .Aquest treball comprèn el disseny, implementació i comprovació de diferents mètodes de detecció i mitigació en temps real. Els estudis i caracterització de les fonts d'interferències són una gran contribució per a optimitzar les tècniques de mitigació actuals. En el tema de mitigació, dos sistemes en temps real han estat implementats en hardware: un sistema que utilitza wavelets per modelar la interferència i mitigar-la, i un circuit que permet a un sistema de navegació continuar funcionant sota els efectes d'un interferidor comercial ( jammer ).

  • 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.

    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.

  • 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.

  • 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 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.

  • 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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  • 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.

  • 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.

  • 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).

  • 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.

    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.

  • 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.

    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.

  • 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.

    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.

    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.

  • 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.

  • 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.

  • 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.

  • 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.

    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.

  • The Light Airborne Reflectometerfor GNSS-R Observations (LARGO) instrument: towards soil moisture retrievals

     Alonso Arroyo, Alberto; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano Jose; Park, Hyuk; Pascual Biosca, Daniel; Onrubia Ibañez, Raul
    URSI Commission F Microwave Signatures
    Presentation's date: 2013-10-29
    Presentation of work at congresses

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  • 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.

  • Ocean surface wind vector measurements from high-altitude aircraft using GPS delay-doppler maps

     Zavorotny, Valery U.; Valencia, E.; Akos, Dennis M.; Camps Carmona, Adriano Jose
    US National Committee of URSI National Radio Science Meeting
    Presentation's date: 2013-01
    Presentation of work at congresses

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    Reflectometry of opportunity signals such as Global Positioning Satellites System, known as GNSS-R, has been developed in the last years as a technique with a great potential for ocean scatterometry, among other applications. Different approaches have been proposed to use GNSS-R for remote sensing of the ocean surface roughness. One of them is based on deriving some descriptor/metric from the measured delay-Doppler map (DDM) and directly relating it to a geophysical property of the scattering surface. For instance, different descriptors have been proposed in the literature to measure the DDM spreading caused by increase in ocean surface mean square slopes due to surface winds.

  • 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.

  • 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.

  • Antena multibanda tipo parche con sistema de alimentación cruzada

     Onrubia Ibañez, Raul; Camps Carmona, Adriano Jose
    Date of request: 2013-11-27
    Invention patent

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  • Sistema de estabilización para la compensación del movimiento angular en plataformas LIDAR móviles

     Rocadenbosch Burillo, Francisco; Tiana Alsina, Jordi; Bermejo Sanchez, Sergio; Vall-llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano Jose
    Date of request: 2013-07-22
    Invention patent

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  • 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
    Theses

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    La radiometria de microones ha anat millorant el seu rendiment amb mesures cada vegada més precises, donant lloc a unamajor presència en l'àmbit de la teledetecció. Per realitzar diverses campanyes de mesures, s'han desenvolupat diversosradiòmetres ja siguin embarcats en satèl · lits, avions o a terra. No obstant això, la sensibilitat d'un radiòmetre sovint estàlimitada per emissions de ràdio d'origen terrestre, com ara radars, emissions de televisió i ràdio, comunicacions inalàmbriquesi molts altres sistemes de telecomunicacions basats en ones electromagnètiques, limitant així la precisió obtinguda per undeterminat radiòmetre. Per tant, per tal de mantenir la precisió en les mesures radiomètriques, hi ha una branca d'investigaciófocalitzada en el desenvolupament d'algorismes de detecció i mitigació de les Interferències de radiofreqüència (RFI per lesseves sigles en anglès) per obtenir millores en el camp de la radiometria de microones.L'objectiu d'aquesta tesi doctoral és el desenvolupament i assaig d'algorismes de detecció i mitigació de RFI per tal de millorarles mesures radiomètriques obtingudes amb el Multifequency Experimental Radiometer with Interference Tracking forExperiments over Land and Littoral (MERITXELL). El MERITXELL és un radiòmetre que s'ha desenvolupat durant aquesta tesiamb la idea d'estudiar la presència de RFI en diverses bandes radiomètriques i la forma de mitigar-les, així com per obtenirdades geofísiques a partir de diverses bandes de freqüència i diversos dispositius en una única campanya de mesures.

    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.

  • European GNSS-R Environmental Monitoring

     Camps Carmona, Adriano Jose
    Participation in a competitive project

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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 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.

  • Access to the full text
    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.

  • 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.

  • Characterization of the SMOS instrumental error pattern correction over the ocean

     Gourrion, J.; Sabia, Roberto; Portabella, Marcos; Tenerelli, Joseph; Guimbard, Sébastien Arnaud; Camps Carmona, Adriano Jose
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2012-07
    Journal article

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    The Soil Moisture and Ocean Salinity (SMOS) mission was launched on November 2nd, 2009 aiming at providing sea surface salinity (SSS) estimates over the oceans with frequent temporal coverage. The detection and mitigation of residual instrumental systematic errors in the measured brightness temperatures are key steps prior to the SSS retrieval. For such purpose, the so-called ocean target transformation (OTT) technique is currently used in the SMOS operational SSS processor. In this paper, an assessment of the OTT is performed. It is found that, to compute a consistent and robust OTT, a large ensemble of measurements is required. Moreover, several effects are reported to significantly impact the OTT computation, namely, the apparent instrument (temporal) drift, forward model imperfections, auxiliary data (used by forward model) uncertainty and external error sources, such as galactic noise and Sun effects (among others). These effects have to be properly mitigated or filtered during the OTT computation, so as to successfully retrieve SSS from SMOS measurements.

    The Soil Moisture and Ocean Salinity (SMOS) mission was launched on November 2nd, 2009 aiming at providing sea surface salinity (SSS) estimates over the oceans with frequent temporal coverage. The detection and mitigation of residual instrumental systematic errors in the measured brightness temperatures are key steps prior to the SSS retrieval. For such purpose, the so-called ocean target transformation (OTT) technique is currently used in the SMOS operational SSS processor. In this paper, an assessment of the OTT is performed. It is found that, to compute a consistent and robust OTT, a large ensemble of measurements is required. Moreover, several effects are reported to significantly impact the OTT computation, namely, the apparent instrument (temporal) drift, forward model imperfections, auxiliary data (used by forward model) uncertainty and external error sources, such as galactic noise and Sun effects (among others). These effects have to be properly mitigated or filtered during the OTT computation, so as to successfully retrieve SSS from SMOS measurements.

  • 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.

  • Retracking considerations in spaceborne GNSS-R altimetry

     Park, Hyuk; Camps Carmona, Adriano Jose; Valencia Domenech, Enric; Rodriguez Alvarez, Nereida; Bosch Lluis, Xavier; Ramos Perez, Isaac; Carrero Luengo, Hugo
    Gps solutions
    Date of publication: 2012-10
    Journal article

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  • Altimetry with GNSS-R interferometry: first proof of concept experiment

     Rius, A.; Nogués Correig, O.; Ribó Vedrilla, Serni; Cardellach, Estel; Oliveras, S.; Valencia Domenech, Enric; Park, Hyuk; Tarongí Bauzá, José Miguel; Camps Carmona, Adriano Jose; Van Der Marel, H.; van Bree, R.; Altena, B.; Martín Neira, Manuel
    Gps solutions
    Date of publication: 2012-04
    Journal article

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    The Global Navigation Satellite System Reflectometry (GNSS-R) concept was conceived as a means to densify radar altimeter measurements of the sea surface. Until now, the GNSS-R concept relied on open access to GNSS transmitted codes. Recently, it has been proposed that the ranging capability of the technique for ocean altimetric applications can be improved by using all the signals transmitted in the bandwidth allocated to GNSS, which includes open access as well as encrypted signals. The main objective of this study is to provide experimental proof of this enhancement through a 2-day experiment on the Zeeland Bridge (The Netherlands). In the experiment, we used a custom built GNSS-R system, composed of high gain GPS antennas, calibration subsystem, and an FPGAbased signal processor which implemented the new concepts, an X-band radar altimeter and a local geodetic network. The results obtained indicate that the new approach produces a significant improvement in GNSS-R altimetric performance.

  • 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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  • 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.

  • 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.

  • 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.

  • 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.

  • 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.