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Isotropic RFI detection

Jean-Luc Vergely (ACRI-ST)Claire Henocq (ACRI-ST)

Philippe Waldteufel (LATMOS)

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Introduction

Principal aims of this study :

Looking for strong isotropic source -> RFI

St1, A3 and A4 analysis.

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Data setData set to be used

2010 and 2011 reprocessed data.

Philosophy:

-> use L1c browse products for global analysis: source detection on ocean and land targets.

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Data set

Land/ocean L1c browse products

L1c browse products over two years (2010 and 2011) : - four polarizations (in FP mode) at the same

geometry- TB at antenna level- TB at 42.5° incidence- TB errors

Allow global analysis on 5 FOV zones

Zone 1 Zone 2

Zone 3

Zone 4 Zone 5

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Introduction

St1,A3 or A4 emission

• Is the signal observed on descending and ascending orbits ?

• Is the signal isotropic?

• Is the signal variable or constant ?

• Is the signal spatially coherent ?

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Isotropic source

Detected in the 5 zones in ascending and descending -> good azimuth coverage.

Normalization to be done because of using zones affected by different OTT correction.

Applying a threshold.

St1 and A4

For A3 : ascending and descending zone 3

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St1 isotropic sourceIsotropic source detection

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St1 isotropic sourceIsotropic source detection

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St1 isotropic source

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A4 isotropic sourcesThreshold of 3 K

Only RFI …

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A4 isotropic sourceIsotropic source detection

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A3 asc/desc sourcesThreshold of 7 K

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A3 isotropic sourceIsotropic source detection

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Principal conclusions

Looking for RFI from St1, A3 and A4 SMOS measurements: isotropic sources

For RFI detection : do not use A4 (correlated with A3).

Only few isotropic sources have been detected. Constant isotropic source for St1 could be RFI.

Distinction between sources and Gibbs effect to be done.

-> further works : play with different thresholds (adaptation of the threshold according to the target (ocean or land).