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SMOS+ polarimetry : Stokes 3

SMOS+ polarimetry : Stokes 3. Jean-Luc Vergely (ACRI-ST) Philippe Waldteufel (ACRI-ST) Eric Anterrieu (IRAP) Ignasi Corbella (UPC) Frédéric Rouffi ( ACRI-ST). Principal aims of SMOS+ polarimetry study : in reponse to ESA ITT ref. ESRIN/AO/1-6704/11/I-AM

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SMOS+ polarimetry : Stokes 3

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  1. SMOS+ polarimetry : Stokes 3 Jean-Luc Vergely (ACRI-ST) Philippe Waldteufel (ACRI-ST) Eric Anterrieu (IRAP) Ignasi Corbella (UPC) Frédéric Rouffi (ACRI-ST)

  2. Principal aims of SMOS+ polarimetry study : in reponse to ESA ITT ref. ESRIN/AO/1-6704/11/I-AM 1/ Which kind of information can we extract from St3 and St4 SMOS data ? 2/ Is it possible to discriminate between physical signal and instrumental contributions ? 3/ How can we use St3 and St4 to improve the calibration or to help to better understand the instrument ? Introduction

  3. 1/ Stokes 3 is sensitive to TEC. So far however, no coherent TEC has been extracted from SMOS Stokes 3. 2/ Is it possible to separate St3 calibration (OTT correction or other) and TEC estimation ? Stokes 3 issues

  4. TB sensitivity to TEC depends on : -location on the FOV -latitudinal position on the orbit -longitude -ascending/descending => Using descending orbits for high TEC contamination. Sensitivity of St3 and other polarizations to TEC

  5. St3 TX TX St3 Sensitivity of St3 to TEC : location on FOV TY TY High TEC sensitivity Low TEC sensitivity Descending orbit dTB/dTEC, 25° latitude north dTB/dTEC, 20° latitude south

  6. No possibility to retrieve TEC here ! (L.O.S perp. to magnetic field) Sensitivity to TEC : latitudinal position St3 is the most sensitive to TEC Pacific descending orbits

  7. Sensitivity of St3 to TEC : descending orbits No possibility to retrieve TEC but good for (descending) OTT estimation ! Pacific descending orbits

  8. Sensitivity of St3 to TEC : ascending orbits No possibility to retrieve TEC but good for ascending OTT estimation ! Pacific ascending orbits

  9. If parts of the orbit or of the FOV with dTB/dTEC close to 0 are used in order to derive TEC: • dTEC/dTB -> infinity • Delta TEC = dTEC/dTB * Delta TB => explose • If moreover OTT on ST3 is biased: • Delta TEC = dTEC/dTB * (Delta TB + OTTbias) => explose • Use only parts of the FOV with dTB/dTEC significantly different from 0 : that is, top of the ST3 FOV But in addition reliable OTT (St3) are required. Next : TEC profile is derived enforcing latitude independent OTT Sensitivity of St3 to TEC

  10. L1c TEC problem Shifted "front" For reliable OTT estimation Derived versus L1c TEC(descending orbits) Reprocessing orbits 20100801 Land contamination TEC insensitive region. Good for OTT !! TEC & OTT are derived simultaneously

  11. SMOS TEC from ST3 Derived vs L1c TEC: descending orbits Derived TEC "Front"=steep lat variation : positions and amplitudes L1C TEC TEC from IRI Reprocessing orbits 20100801

  12. L1c TEC problem Shifted "front" Derived vs L1c TEC: descending orbits, L1c 5XX consolidated TEC ________ ≈ 1000 kml, distance between subsat & top of FOV New reprocessing orbits 20101102 TEC insensitive region

  13. X_swath TEC detection from St3 TEC obtained from St3 front FOV between -0.3<xi<0.3 on 6 xi positions => GOOD COHERENCE between different xi positions !!

  14. X_swath TEC detection (ascending) TEC obtained from St3 front FOV between -0.3<xi<0.3 on 6 xi positions => GOOD COHERENCE between different xi positions but some oscillations

  15. OTT estimation : ascending/descending OTT obtained from St3 front FOV between -0.3<xi<0.3 on 6 xi positions DESCENDING ORBITS ASCENDING ORBITS ξ ξ Classical OTT close to the new one in ascending. New OTTs are similar in ascending/descending

  16. X_swath TEC detection from TX-TY Softer response expected because σ_noise (TX-TY) larger than σ_noise St3 TEC obtained from TX-TY front FOV between -0.3<xi<0.3 on 6 xi positions Same « front » shift than with ST3 => Central xi gives results closer to TEC L1c : because of TB sensitivity to TEC.

  17. TX-TY sensitivity to TEC (front of the FOV)

  18. OTT estimation : ascending/descending OTT obtained from TX-TY front FOV between -0.3<xi<0.3 on 7 xi positions DESCENDING ORBITS ASCENDING ORBITS As expected : no TEC influence at ξ=0 Too much dispersion ? ξ ξ ξ

  19. X_swath TEC detection from TX-TY in eta =-0.2 TEC obtained from TX-TY between -0.55<xi<0.55 on 15 xi positions. « Fronts » not at the same place because eta close to the middle of the FOV (not in front of the FOV) Smaller shifts • Wings of the FOV seem give coherent results with central part of the FOV

  20. X_swath TEC detection from TX-TY in eta =-0.2 Where is realy the information ? OTT at eta=-0.2

  21. 1/ SMOS ST3 is not garbage !! SMOS ST3 carries TEC information: hence possibility to compute TEC from SMOS ST3. • Estimation of TEC from SMOS ST3 is possible only in some parts of the FOV and some part of the orbit. • Since a correct TEC estimation depends on OTT which depends on TEC… • TEC and OTT have to be derived together with OTT set in latitude zones where TBs is not sensitive to TEC. Special care has to be taken for descending orbits. 2/ TEC estimation from SMOS ST3 shows that: -L1c TEC is overestimated (even the consolidated TEC) -L1c TEC "front" is shifted in comparison with SMOS TEC. • Problem of considering constant TEC on the FOV ? • SMOS SELF CONSISTENCY done using TX-TY Possible future impact on TEC management ? Conclusions

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