The processing of hexagonally sampled signals with standard rectangular techniques: application to 2-D large aperture synthesis interferometric radiometers

Camps, Adriano; Bará, J.; Sanahuja, Ignasi Corbella; Torres, F.

doi:10.1109/36.551946

Cited by 147 publications

(130 citation statements)

References 6 publications

(4 reference statements)

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“…For the hexagonal sampling to be discussed in 4, the support region is either a hexagon or a hexagonally symmetrical figure [Camps et al, 1997a …”

Section: Impulse Responsementioning

confidence: 99%

Angular resolution of two‐dimensional, hexagonally sampled interferometric radiometers

Bará¹,

Camps²,

Torres³

et al. 1998

Radio Science

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Abstract. A theoretical analysis of the angular resolution of two-dimensional interferometric radiometers for Earth observation from low-orbit satellites and its degradation due to spatial decorrelation effects is presented. The analysis extends basic effects known in the context of radio astronomy (application with narrow field of view, very few baselines) and in one dimension (ESTAR L band, few baselines interferometric radiometer) to the wide-field-ofview, many-baseline, high-resolution two-dimensional system required by Earth observation applications and computes beam width, encircled energy (or main beam efficiency), and side lobe level as a function of windowing (apodization) to allow for an optimum angular versus radiometric resolution trade-off. It is found that the extension of the Barlett window (which has a poor performance in one dimensional signal processing) to two dimensions produces high-quality results, comparable or better than those of Gaussian and Blackmann windows. Theory is extended to hexagonally sampled systems based on a A or Y-shaped instrument, with hexagonal-and star-shaped support regions in the visibility space, respectively. The superior performance of the latter over the former for the same number of antennas and correlators is quantified and details of the angular resolution of one instrument of this kind, MIRAS, under development by the European Space Agency, are presented. For this radiometer Gaussian or Barlett windows should be used for good radiometric sensitivity or spatial resolution, respectively. In both cases the effects of decorrelation within the small alias-free field of view are negligible. It is also found that the impact of hardware imperfections which exist within the strict requirements of the specifications have a negligible effect on the angular resolution. Finally, experimental angular resolution results with a laboratory breadboard in a focused near-field setup are presented and compared to the theoretical predictions.

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“…For the hexagonal sampling to be discussed in 4, the support region is either a hexagon or a hexagonally symmetrical figure [Camps et al, 1997a …”

Section: Impulse Responsementioning

confidence: 99%

Angular resolution of two‐dimensional, hexagonally sampled interferometric radiometers

Bará¹,

Camps²,

Torres³

et al. 1998

Radio Science

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“…It assumes a perfect instrument with identical antennas and receivers, thus providing output errors on reconstructed brightness temperatures which correspond to input errors introduced in the forward step; redundant visibility samples are averaged. As Y-shaped arrays consisting of equispaced antennas along each arm lead to visibility functions sampled over an hexagonal grid inside a star-shaped domain [Lannes and Anterrieu, 1994;Camps et al, 1997a] apodization is required to filter out the effect of the sharp frequency cutoff. In this study, the exact Blackman window has been used to perform this.…”

Section: Simulation Methodsmentioning

confidence: 99%

About the effects of instrument errors in interferometric radiometry

Anterrieu

Waldteufel

Caudal³

2003

Radio Science

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[1] The SMOS mission is a European Space Agency (ESA) project aimed at global monitoring of surface soil moisture and sea surface salinity from radiometric L-band observations. The radiometer onboard SMOS uses a 2-D synthetic aperture concept in order to achieve satisfactory spatial resolution performances for a minimal cost in terms of payload mass and volume. As the satellite moves ahead, every area on Earth's surface is seen at a variety of incidence angles. This multiangular capability is used in the retrieval of geophysical parameters. A major issue for obtaining useful measurements of the surface salinity is the radiometric accuracy, since the overall dynamic range resulting from ocean salinity variations only extends over a few Kelvin. To improve instrument performances, it is foreseen that independent retrieved salinity estimates will be averaged over a suitable space/time domain. This should bring random uncertainties due to radiometric sensitivity down to around 0

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“…Note that this expression is valid for both a rectangular grid and a hexagonal grid with a proper definition of the lattices in the (u; v) and ( ; ) spaces [7]. For the sake of simplicity, and without loss of generality, we will assume that N u = N v = N and will omit it in the summations when it is clearly understood.…”

Section: Basic Baseline Equationmentioning

confidence: 99%

The correlation of visibility noise and its impact on the radiometric resolution of an aperture synthesis radiometer

Bará

Camps

Torres

et al. 2000

IEEE Trans. Geosci. Remote Sensing

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Abstract-The correlation between the visibility samples' noise of an aperture synthesis radiometer are required for the computation of the recovered temperature noise of a given pixel and of the improvement introduced by baseline redundance. A general expression for this correlation and noise examples for a linear array are presented.Index Terms-Microwave radiometry, microwave receivers, radio interferometry, radiometry, remote sensing, synthetic aperture imaging.

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The processing of hexagonally sampled signals with standard rectangular techniques: application to 2-D large aperture synthesis interferometric radiometers

Abstract: Abstract-In Earth observation programs there is a need of passive low frequency (L-band)

Cited by 147 publications

References 6 publications

Angular resolution of two‐dimensional, hexagonally sampled interferometric radiometers

Angular resolution of two‐dimensional, hexagonally sampled interferometric radiometers

About the effects of instrument errors in interferometric radiometry

The correlation of visibility noise and its impact on the radiometric resolution of an aperture synthesis radiometer

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