Preliminary results of the Passive Advanced Unit Synthetic Aperture (PAU-SA)

Ramos-Perez, I.; Bosch-Lluis, X.; Camps, A.; Valencia, E.; Marchan-Hernandez, J.F.; Rodriguez-Alvarez, Nereida; Canales-Contador, F.

doi:10.1109/igarss.2009.5417357

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…Furthermore, multi-angular measurements are inherent in the image formation process in synthetic aperture radiometers such as SMOS/MIRAS [8] or PAU-Synthetic Aperture (PAU-SA) [9]. This paper presents a new option to obtain multi-angular measurements combining an L-band radiometer with the concept of digital beamformer (DBF), which is able to steer multiple and simultaneous beams at different incidence angles without mechanical scan.…”

Section: Figurementioning

confidence: 99%

Description and Performance of an L-Band Radiometer with Digital Beamforming

Bosch-Lluis¹,

Ramos-Perez²,

Camps³

et al. 2010

Remote Sensing

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This paper presents the description and performance tests of an L-band microwave radiometer with Digital Beamforming (DBF), developed for the Passive Advanced Unit (PAU) for ocean monitoring project. PAU is an instrument that combines, in a single receiver and without time multiplexing, a microwave radiometer at L-band (PAU-RAD) and a GPS-reflectometer (PAU-GNSS-R). This paper focuses on the PAU-RAD beamformer's first results, analyzing the hardware and software required for the developed prototype. Finally, it discusses the first results measured in the Universitat Politè cnica de Catalunya (UPC) anechoic chamber.

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Section: Figurementioning

confidence: 99%

Description and Performance of an L-Band Radiometer with Digital Beamforming

Bosch-Lluis¹,

Ramos-Perez²,

Camps³

et al. 2010

Remote Sensing

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“…Figure 8 shows the PAU -Synthetic Aperture topology, and two figures taken during the integration. Hardware and simulation details can be found in [ 16 , 17 ].…”

Section: Instrument Developmentsmentioning

confidence: 99%

New Passive Instruments Developed for Ocean Monitoring at the Remote Sensing Lab—Universitat Politècnica de Catalunya

Camps

Bosch-Lluis

Ramos-Perez

et al. 2009

Sensors

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Lack of frequent and global observations from space is currently a limiting factor in many Earth Observation (EO) missions. Two potential techniques that have been proposed nowadays are: (1) the use of satellite constellations, and (2) the use of Global Navigation Satellite Signals (GNSS) as signals of opportunity (no transmitter required). Reflectometry using GNSS opportunity signals (GNSS-R) was originally proposed in 1993 by Martin-Neira (ESA-ESTEC) for altimetry applications, but later its use for wind speed determination has been proposed, and more recently to perform the sea state correction required in sea surface salinity retrievals by means of L-band microwave radiometry (TB). At present, two EO space-borne missions are currently planned to be launched in the near future: (1) ESA's SMOS mission, using a Y-shaped synthetic aperture radiometer, launch date November 2nd, 2009, and (2) NASA-CONAE AQUARIUS/SAC-D mission, using a three beam push-broom radiometer. In the SMOS mission, the multi-angle observation capabilities allow to simultaneously retrieve not only the surface salinity, but also the surface temperature and an “effective” wind speed that minimizes the differences between observations and models. In AQUARIUS, an L-band scatterometer measuring the radar backscatter (σ0) will be used to perform the necessary sea state corrections. However, none of these approaches are fully satisfactory, since the effective wind speed captures some sea surface roughness effects, at the expense of introducing another variable to be retrieved, and on the other hand the plots (TB-σ0) present a large scattering. In 2003, the Passive Advance Unit for ocean monitoring (PAU) project was proposed to the European Science Foundation in the frame of the EUropean Young Investigator Awards (EURYI) to test the feasibility of GNSS-R over the sea surface to make sea state measurements and perform the correction of the L-band brightness temperature. This paper: (1) provides an overview of the Physics of the L-band radiometric and GNSS reflectometric observations over the ocean, (2) describes the instrumentation that has been (is being) developed in the frame of the EURYI-funded PAU project, (3) the ground-based measurements carried out so far, and their interpretation in view of placing a GNSS-reflectometer as secondary payload in future SMOS follow-on missions.

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“…Figure 2.6 shows the PAU-Synthetic Aperture topology, and two pictures taken during the integration. Hardware, details, calibration, and simulations can be found in [18], and in [46].…”

Section: Pau-synthetic Aperturementioning

confidence: 99%

“…Typically, brightness temperature measurements at different incidence angles can be obtained simultaneously using different receivers, or with the same receiver acquiring data at different times ( [15], [16]). Furthermore, multi-angular measurements are inherent in the image formation process in synthetic aperture radiometers such as SMOS/MIRAS [17] or PAU-Synthetic Aperture (PAU-SA) [18]. This PhD dissertation gives a new option to obtain multi-angular measurements combining an L-band radiometer with the concept of digital beamformer (DBF), which is able to steer multiple and simultaneous beams at different incidence angles without mechanical scan of the antenna.…”

Section: Introductionmentioning

confidence: 99%

On the design of microwave radiometers with digital beamforming and polarization synthesis for earth observation.

Bosch Lluís

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Actualment, la comunitat científica ja disposa de les primeres mesures radiomètriques a banda L, polarimètriques i multi-angulars fetes de l’espai. Això és gràcies al recent llançament de la missió de la Eurepean Space Agency (ESA) anomenada Soil Moisture and Ocean Salinity (SMOS). Es sabut que a partir de la temperatura d’antena es possible recuperar salinitat superficial marina (Sea Surface Salinity, (SSS)) i humitat del sòl (Soil Moisture (SM)). Els beneficis de mesurar aquests dos paràmetres geofísics son múltiples, essent especialment profitosos en els camps de la oceanografia i la climatologia. La raó principal que va motivar la presentació del projecte Passive Advanced Unit (PAU) a la European Science Foundantion (ESF) va ser per estudiar la relació entre brillantor de temperatura i observables Global Navigation Satellite System Reflectometry (GNSS/R) per a millorar la recuperació de la SSS i SM. A més a més, els objectius tècnics del projecte PAU incloïen el desenvolupament de nous conceptes de radiòmetres en banda L, com a base tecnològica per a nous sistemes radiomètrics. La present tesi doctoral estén el coneixement adquirit en els últims anys en el desenvolupament del radiòmetre SMOS i és una contribució al desenvolupament d'una nova generació de sensors passius. Per primera vegada – pel que fa els coneixements de l'autor – s’ha desenvolupat amb èxit un radiòmetre amb una agrupació d’antenes capaç de formar feixos en temps real. Aquest sistema és capaç de dirigir múltiples i simultanis feixos en diferents angle d'incidència, sense cap m moviment mecànic, proporcionant així un nou mètode per a obtenir mesures multi-angulars. El projecte PAU ha estat desenvolupat en el Remote Sensing Lab, del Departament de Teoria del Senyal i Comunicacions de la Universitat Politècnica de Catalunya. La present tesi doctoral descriu la tasca realitzada entre 2005 i 2010, tant en aspectes teòrics i de hardware com en el camp de la radiometria de banda L. Aquesta tesi consisteix en un estudi teòric realitzat en radiòmetres correlació amb la formació de feix digital des del punt de vista dels radiòmetres d'obertura sintètica i una anàlisi exhaustiva del impacte del sistema de digitalització. D'altra banda, han estat definits els requisits per a construir un radiòmetre de correlació amb la formació de feix digital en temps real i amb síntesi de la polarització. Un instrument amb aquestes característiques s'ha construït, a nivell intern va igualar per l'amplitud i fase de cada receptor, provat i es caracteritza a la cambra anecoica, i, finalment, s’ha realitzat campanya de camp per obtenir valors de l'emissivitat del sòl per a una gamma d’angles d'incidència. With the recent launch of the ESA’s Soil Moisture and Ocean Salinity (SMOS) mission the scientific community is provided with the first polarimetric and multi-angular L-band radiometric measurements from the space. From the antenna temperature is possible to retrieve Sea Surface Salinity (SSS) and Soil Moisture (SM), which benefits both the oceanographic and climatologic studies. It is well known that it exists angular and polarization dependence for the radiometric measurements. Using this dependence, it is possible to use multi-angular and polarimetric measurements to retrieve geophysical parameters. The main rationale that motivated the submission of the Passive Advanced Unit (PAU) project to the European Science Foundation (ESF) was to study the relationship between the brightness temperatures and some Global Navigation Satellite System Reflectometry (GNSS/R) observables, so as to improve the SSS retrievals. Also, the technical objectives of the PAU project included the development of new L-band radiometer concepts, such as a technological bed for providing new radiometer systems. The present PhD dissertation extends the knowledge acquired in the recent years in the development of the SMOS radiometer, and is a contribution to the development of a new generation of passive sensors. For the first time – to author’s knowledge – real-time digital beamforming and polarization synthesis have been successfully implemented in a real system. The system is able to steer multiple and simultaneous beams in different incidence angles without mechanical scan of the antenna, providing a new method to obtain multi-angular measurements combining an L-band radiometer with the concept of digital beamformer. The PAU project has been developed by the Passive Remote Sensing Group of the Remote Sensing Lab, at the Department of Signal Theory and Communications of the Universitat Politècnica de Catalunya. The present PhD dissertation describes the work undertaken between 2005 and 2010 in both theoretical and hardware issues within the field of L-band radiometry with real-time digital beamforming with polarization synthesis. This dissertation consists of a theoretical study performed on digital correlation radiometers with beamforming from the point of view of the synthetic aperture radiometers and an extended analysis of the impact of the digitization scheme. Moreover, the requirements to build a correlation radiometer with real-time digital beamforming and polarization synthesis have been stated. The new concept instrument has been built, internally equalized for the amplitude and phase of each receiver, tested and characterized in the anechoic chamber, and in a field campaign obtaining soil emissivity values for a range of incidence angles.

show abstract

Preliminary results of the Passive Advanced Unit Synthetic Aperture (PAU-SA)

Cited by 4 publications

References 8 publications

Description and Performance of an L-Band Radiometer with Digital Beamforming

Description and Performance of an L-Band Radiometer with Digital Beamforming

New Passive Instruments Developed for Ocean Monitoring at the Remote Sensing Lab—Universitat Politècnica de Catalunya

On the design of microwave radiometers with digital beamforming and polarization synthesis for earth observation.

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