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Galactic noise model adjustment

Galactic noise model adjustment. Jean-Luc Vergely (ACRI-ST) Jacqueline Boutin (LOCEAN) Xiaobin Yin (LOCEAN). Issue : GN correction. Aim of this study : To better understand rugosity in L band

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Galactic noise model adjustment

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  1. Galactic noise model adjustment Jean-Luc Vergely (ACRI-ST) Jacqueline Boutin (LOCEAN) Xiaobin Yin (LOCEAN)

  2. Issue : GN correction. • Aim of this study : • To better understand rugosity in L band • To estimate the GN corrections for some operating points (WS, theta) and to cross check with the current model implemented in the L2OS processor.

  3. Inversion of the forward model • Data : SMOS Tbgal_refl_X and Tbgal_refl_Y = TB L1c –flat sea and roughness contribution – OTT–atmospheric contribution • Forward model : With b=cos²(a) or b=sin²(a), a being the rotation angle ground->antenna UNKNOWN : and Inversion shall be done at the antenna level : bayesian approach as for SSS retrieval.

  4. SMOS data selection : reprocessed data • 30 descending half orbits in the south pacific in the period 09/2011 – 11/2011=> strong galactic signal is expected. • 11 ascending half orbits in the south pacific in the period 03/2010 – 04/2010=> strong galactic signal is expected. • Selection of data : no contamination by land, TB valid, geometric rotation < 10° : TBH and TBV processed independently.

  5. Inverse scheme • Retrieval : • non parametric approach. • Axisymmetry of the bistatic coefficients. • Add new constraints in the retrieval scheme: • forcing the normalization of the bistatic coefficients. • Possibility to add a bias (as an OTT) • Use of asc and desc orbits

  6. Retrieval results • polar H (ascending) Dynamic only for WS = 3m/s Strong negative bias. OTT issue ? RH around 0.72 as expected

  7. Retrieval results • polar V (ascending) Strong negative bias.

  8. Retrieval results From non parametric approach • Comparison with AUX_GAL2 (ascending) From non parametric approach AUX_GAL2 new AUX_GAL2 new Differences due to the bias (always negative) ?

  9. Retrieval results • polar H (descending)

  10. Retrieval results • polar V (descending) Strong negative bias.

  11. Retrieval results From non parametric approach • Comparison with AUX_GAL2 (descending) From non parametric approach AUX_GAL2 new AUX_GAL2 new Better than ascending for H pol. Difference in V pol due to the bias.

  12. Retrieval results NEW AUX_GAL2 OLD AUX_GAL2 • Comparison with old AUX_GAL2 (descending) From non parametric approach From non parametric approach (old data) AUX_GAL2 new AUX_GAL2 old With normalisation No normalisation

  13. Conclusions • Results depend on OTT. • Chi2 too high. • Strong dynamic for WS=3 m/s only. • Low response for ascending orbits -> to be done with extended selection. Solution is lower than the new AUX_GAL LUT • Better coherence for descending orbits, H pol. • Problem with the normalization and the constant correction ? • Data set to be increased, at least for ascending orbits.

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