Gabarro Prats, Carolina
Total activity: 9
Department
Department of Signal Theory and Communications
E-mail
carolina.gabarroestudiant.upc.edu
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Scientific and technological production
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1 to 9 of 9 results
  • Impact of the local oscillator calibration rate on the SMOS measurements and retrieved salinities

     Gabarro Prats, Carolina; Gonzalez Gambau, Verónica; Corbella Sanahuja, Ignasi; Torres Torres, Francisco
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-09-02
    Journal article

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    The local oscillators (LOs) of the Soil Moisture and Ocean Salinity mission payload are used to shift the operating frequency of the 72 receivers to an optimal intermediate frequency needed for the signal processing. The LO temperature variations produce phase errors in the visibility, which result in a blurring of the reconstructed brightness temperature (Tb) image. At the end of the commissioning phase, it was decided to calibrate the LO every 10 min while waiting for a more in-depth analysis. During short periods of time, the LOcalibration has been performed every 2 min to assess the impact of a higher calibration rate on the quality of the data. In this paper, by means of a decimation experiment, the relative errors of 6- and 10-min calibration interval data sets are estimated using the 2 min as a reference. A noticeable systematic across- and along-track pattern of amplitude ±0.3 K is observed for Tb differences between 10 and 2 min, whereas this is reduced between 6 and 2 min. A simulation experiment confirms that the nature of such systematic pattern is due to the visibility phase errors induced by the LO calibration rate. Such pattern is propagated into the sea surface salinity (SSS) retrievals. Overall, the SSS error increase (relative to the 2min SSS data) is about 0.39 and 0.14 psu for the 10- and 6-min data sets, respectively. This paper shows that a LO calibration rate of at least 6 min would noticeably improve the SSS retrievals.

  • Impact of the local oscillator calibration on the SMOS sea surface salinity maps

     Gabarro Prats, Carolina; Gonzalez Gambau, Verónica; Martínez, J.; Guimbard, Sébastien Arnaud; Gourrion, J.; Piles Guillem, Maria; Portabella, Marcos; Font, J.
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07
    Presentation of work at congresses

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    The Local Oscillators (LO) of the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) onboard the Soil Moisture and Ocean Salinity (SMOS) satellite are used to maintain the operating frequency of the 69 receivers. The phase of the LO drifts over time, in turn blurring the MIRAS brightness temperature (TB) measurements. After a pre-launch assessment, it was decided to calibrate the LO every 10 minutes to reduce the phase drifts. During short periods of the first 2.5 years of SMOS mission, the LO calibration has been performed every 2 minutes to assess the impact of a higher calibration frequency on the quality of the data. In this study, relative differences (10-min TBs versus 2-min TBs) of about 0.3 K are shown, which lead to non-negligible relative differences of about 0.2-0.3 practical salinity units (psu) in the retrieved sea surface salinity (SSS). However, when performing independent validation against Argo float SSS data at Level 3 (spatio-temporally averaged SSS products), no significant differences are found between 10-min and 2-min data. This is due to the fact that current SMOS SSS accuracy (relative to Argo) is about 0.6-0.8 psu, thus masking the relatively smaller LO calibration frequency effect.

  • 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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  • Ocean Monitoring Using L-Band Microwave Radiometry and GNSS-R  Open access

     Valencia Domenech, Enric
    Defense's date: 2012-10-17
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The knowledge of sea surface salinity (SSS) is a key issue to understand and monitor the Earth¿s water cycle. Accurate and systematic measurement of SSS was not possible until the ESA¿s Soil Moisture and Ocean Salinity (SMOS) mission was launched in 2009. The SMOS mission uses L-band microwave radiometry to infer SSS from measurements of the ocean¿s emis- sivity. However, the ocean surface emissivity is not only dependent on SSS, but also on sea surface temperature (SST), incidence angle, polarization, and sea surface roughness (i.e. sea-state). While the dependence on most of these parameters is well-known, and can be properly accounted for, the accurate estimation and correction of the sea surface roughness contribution remains a challenge. The Passive Advanced Unit (PAU) project was born in 2003 with the main objective of studying how to correct ocean L-band brightness temperature for the sea-state effect by using an emerging technology such as reflectome- try of opportunity GNSS signals (GNSS-R). GNSS-R is based on measuring the forward scattered GNSS signals so as to infer geophysical properties of the scattering surface. Particularly, the PAU project proposed to use direct observables from the reflected signal¿s Delay-Doppler Map (DDM) to parame- terize sea surface roughness, and link those observables to the brightness tem- perature variations induced by sea-state, without using scattering/emissivity models. In this line, prior work was performed by J.F. Marchan-Hernandez in his PhD. Thesis (UPC, Barcelona, 2009). In that work, a first version of the PAU GNSS-R receiver was developed, and first experimental results were obtained that supported the hypothesis that direct GNSS-R observables can be used to describe sea-state. This PhD. Thesis follows on that research, and steps into the use of GNSS- R observables for estimation of the sea-state contribution to the ocean L-band brightness temperature. The work presented here was undertaken between 2008 and 2012, and comprises contributions to three main fields: GNSS-R hardware development, experimental results, and theoretical studies. Firstly, the PAU GNSS-R instrument was re-designed and re-implemented for im- proved sensitivity and stability. Secondly, results from ground-based and airborne experiments were obtained, that prove the hypothesis that GNSS-R observables can be used to successfully correct L-band brightness tempera- ture for the sea-state effect, resulting in an improvement in the SSS retrieval accuracy. Finally, theoretical studies to foresee the performance of the PAU concept in a future spaceborne mission were conducted, along with the de- velopment of a new technique to obtain ocean surface scattering coefficient images from measured DDMs.

  • 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.

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

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

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

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

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

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

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

  • Sea surface radiometric observations at L-band: wind speed sensitivity derived from WISE 2000 and 2001

     Camps Carmona, Adriano Jose; Font, J.; Etcheto, J.; Caselles, V.; Weill, A.; Corbella Sanahuja, Ignasi; Vall-llossera Ferran, Mercedes Magdalena; Torres Torres, Francisco; Duffo Ubeda, Nuria; Villarino Villarino, Ramon; Enrique, L.; Miranda Mendoza, Jorge Jose; Arenas, J.; Julià, A.; Gabarro Prats, Carolina; Boutin, J.; Contardo, S.; Niclós, R.; Rivas, R.; Reising, Steve C.; Wursteisen, P.; Berger, M.; Martín Neira, Manuel
    URSI General Assembly and Scientific Symposium
    Presentation of work at congresses

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