PAU-GNSS/R, a real-time GPS-reflectometer for earth observation applications: architecture insights and preliminary results

Marchan-Hernandez, J.F.; Ramos-Perez, I.; Bosch-Lluis, X.; Camps, A.; Rodriguez-Alvarez, Nereida; Albiol, David

doi:10.1109/igarss.2007.4424012

Cited by 9 publications

(8 citation statements)

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“…The amplitude of the peak of the DDM (or the WF), either in absolute terms (scattered power from a given delay Doppler bin), or in relative terms (relative power of the reflected signal vs. direct signal). Due to the limited hardware resources, in the mid 90's the first GNSS-R instruments either used the so-called cGNSS-R technique (see below) in real time with just a few lags [5], or directly record the whole signal for offline processing, and it was not until 2007 [6] that the first instrument capable of measuring true real-time DDMs (not as a series of consecutive waveforms computed for diffe rent Doppler shifts) was fu lly developed.…”

Section: Imentioning

confidence: 99%

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

Camps

Rodriguez-Alvarez

Valencia

et al. 2013

2013 IEEE International Geoscience and Remote Sensing Symposium - IGARSS

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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 fu sion 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 [11. However, despite SMOS operates in the passive microwave "protected" band from 1400 to 1427 MHz, radio fre quency interference may degrade the quality of the soil moisture (and sea salinity) retrievals or even prevent them [21. 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, eventhough these signals can also be jammed, their structure and the way they are processed, makes them more robust in front of radio-frequency interference, while at the same time -in principle-can achieve also a better spatial resolution. In this work, the few different GNSS-R techniques are first revised, including their pros and cons. Then a few applications are revised, with special emphasis -but not exclusively-in those in which the UPC Remote Sensing Lab has been working.

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Section: Imentioning

confidence: 99%

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

Camps

Rodriguez-Alvarez

Valencia

et al. 2013

2013 IEEE International Geoscience and Remote Sensing Symposium - IGARSS

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“…Inside the FPGA a microprocessor, data bus and RAM system is synthetized. Several peripherals are attached to the bus [10]. The most relevant is the DDM generator, which performs the Doppler compensation and the integration (Eqn.…”

Section: Gnss-r Reflectometer Architecturementioning

confidence: 99%

“…The goal of implementing this reflectometer-DDM generator [8, 10] is to obtain quantitative relationships between the sea state (mainly driven by the surface wind and the swell) and the overall DDM shape. It is expected that this would make possible to correct the sea state influence on the L-band brightness temperature to improve the retrieval of the sea surface salinity (SSS).…”

Section: Introductionmentioning

confidence: 99%

PAU/GNSS-R: Implementation, Performance and First Results of a Real-Time Delay-Doppler Map Reflectometer Using Global Navigation Satellite System Signals

Marchan-Hernandez

Camps

Rodriguez-Alvarez

et al. 2008

Sensors

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Signals from Global Navigation Satellite Systems (GNSS) were originally conceived for position and speed determination, but they can be used as signals of opportunity as well. The reflection process over a given surface modifies the properties of the scattered signal, and therefore, by processing the reflected signal, relevant geophysical data regarding the surface under study (land, sea, ice…) can be retrieved. In essence, a GNSS-R receiver is a multi-channel GNSS receiver that computes the received power from a given satellite at a number of different delay and Doppler bins of the incoming signal. The first approaches to build such a receiver consisted of sampling and storing the scattered signal for later post-processing. However, a real-time approach to the problem is desirable to obtain immediately useful geophysical variables and reduce the amount of data. The use of FPGA technology makes this possible, while at the same time the system can be easily reconfigured. The signal tracking and processing constraints made necessary to fully design several new blocks. The uniqueness of the implemented system described in this work is the capability to compute in real-time Delay-Doppler maps (DDMs) either for four simultaneous satellites or just one, but with a larger number of bins. The first tests have been conducted from a cliff over the sea and demonstrate the successful performance of the instrument to compute DDMs in real-time from the measured reflected GNSS/R signals. The processing of these measurements shall yield quantitative relationships between the sea state (mainly driven by the surface wind and the swell) and the overall DDM shape. The ultimate goal is to use the DDM shape to correct the sea state influence on the L-band brightness temperature to improve the retrieval of the sea surface salinity (SSS).

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“…The shape of the DDM is sensitive to the roughness of the scattering surface and, through various empirical models, the ocean surface winds [2], [3]. Ocean winds can be retrieved by fitting a scattering model to DDM observations, or identifying an observable, such as trailing or leading edge slopes or DDM power average exceeding a threshold, [4], [5]. A variety of such methods have been demonstrated with airborne experiments [3], [6], and [7].…”

Section: Introductionmentioning

confidence: 97%