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1© ACRI-ST, all rights reserved – 2012
Galactic noise model adjustment
Jean-Luc Vergely (ACRI-ST)Jacqueline Boutin (LOCEAN)
Xiaobin Yin (LOCEAN)
2© ACRI-ST, all rights reserved – 2012
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© ACRI-ST, all rights reserved – 2012
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 :
2
0)sin(,)1(._XYTbgal_refl
sigal
igalsssssvH ddTbgalbbA
With b=cos²(a) or b=sin²(a), a being the rotation angle ground->antenna
Inversion shall be done at the antenna level : bayesian approach as for SSS retrieval.
UNKNOWN : H and V
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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.
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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
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Retrieval resultspolar H
(ascending)
RH around 0.72 as expected
Strong negative bias. OTT issue ?
Dynamic only for WS = 3m/s
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Retrieval resultspolar V
(ascending)
Strong negative bias.
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Retrieval resultsComparison with AUX_GAL2
(ascending)
Differences due to the bias (always negative) ?
From non parametric approach
From non parametric approach
AUX_GAL2 new AUX_GAL2 new
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Retrieval resultspolar H
(descending)
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Retrieval resultspolar V
(descending)
Strong negative bias.
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Retrieval resultsComparison with AUX_GAL2
(descending)
Better than ascending for H pol. Difference in V pol due to the bias.
AUX_GAL2 new AUX_GAL2 newFrom non parametric approach
From non parametric approach
12© ACRI-ST, all rights reserved – 2012
Retrieval resultsComparison with old AUX_GAL2
(descending)
NEW AUX_GAL2 OLD AUX_GAL2
With normalisation
From non parametric approach
AUX_GAL2 new From non parametric approach (old data)
AUX_GAL2 old
No normalisation
13© ACRI-ST, all rights reserved – 2012
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.
