FR1.L10.2: CALIBRATION OF LOCALIZATION BIASES FOR SMOS

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  • FR1.L10.2: CALIBRATION OF LOCALIZATION BIASES FOR SMOS

    1. 1. Calibration of localization biases for SMOS François Cabot 1 , Yann Kerr 1 , Philippe Richaume 1 and Philippe Waldteufel 2 (1) CESBIO, 18, Av E Belin 31401 TOULOUSE CEDEX 9 FRANCE (2) IPSL/SA, 91371 Verrières le Buisson, FRANCE
    2. 2. Outline <ul><li>System level performances as assessed during commissioning </li></ul><ul><ul><li>Geolocation biases assessment – Best Fit Plane calibration </li></ul></ul><ul><ul><li>although higher bias than expected, calibration has been achieved up to required accuracy </li></ul></ul><ul><ul><li>Geolocation accuracy – impact at soil moisture level </li></ul></ul><ul><ul><li>preliminary assessment shows we are moving in the right direction, but thorough cal/val results will be needed for final analysis </li></ul></ul><ul><ul><li>Equivalent Array Factor – spatial resolution confirmation </li></ul></ul><ul><ul><li>In close agreement with expectations, and validated making use of RFI </li></ul></ul><ul><ul><li>Radiometric accuracy verification for Land scenes </li></ul></ul><ul><ul><li>Consistent with theory, and used as such for soil moisture retrieval </li></ul></ul><ul><ul><li>Absolute accuracy of brigthness temperatures </li></ul></ul><ul><ul><li>Dome C results extremely promising, finer analysis still needed . </li></ul></ul>
    3. 3. Geolocation assessment <ul><li>Challenging requirement wrt SMOS moderate resolution: 400m rms . </li></ul><ul><li>Method developed and validated before flight with simulated data </li></ul><ul><li>Simple model fit across sharp transition gives access to shift assessment. </li></ul><ul><li>Madagascar coastline selected: long linear coastline. </li></ul><ul><li>Spin-off: assessment of synthetic antenna pattern </li></ul><ul><li>Additional checking making use of Earth Horizon crossing the field of view during external calibration manoeuvre. </li></ul>
    4. 4. Madagascar Coastline access
    5. 5. Model fitting results Pre launch simulation
    6. 6. Ascending - Descending <ul><li>Alternate passes are used to constrain geolocation matrix. </li></ul><ul><li>Depending on the position of the coast within the swath, this constrain can change. </li></ul>
    7. 7. Temporal stability <ul><li>Rmse on bias assessment is down to 600m. </li></ul><ul><li>No clear temporal evolution being seen on first 2 months of data. </li></ul><ul><li>At end of IOCP, only noticeable trend is on roll, but uncertainty on this trend still high </li></ul>blue: ascending, red: descending
    8. 8. Earth Horizon <ul><li>Crossing the fov, very sharp contrast </li></ul><ul><li>Must be used with high rate STR data </li></ul><ul><li>Only over ocean usable: 10 ECM analysed </li></ul><ul><li>Proved more noisy than Madagascar, probably due to limb </li></ul><ul><li>Average pitch bias: -0.0809° </li></ul>
    9. 9. Geolocation summary <ul><li>5 months of data have been used, 49 overpasses </li></ul><ul><li>Roll and pitch biases estimated: </li></ul><ul><ul><li>Roll 0.1406 </li></ul></ul><ul><ul><li>Pitch -0.0736 </li></ul></ul><ul><li>Higher biases than expected from satellite budgets </li></ul><ul><ul><li>After correction, residual shift down to 221m/388m (asc/desc) with 319m standard deviation. </li></ul></ul><ul><li>Some issues have been sorted out. </li></ul><ul><ul><li>Snapshot datation is middle of integration time </li></ul></ul><ul><ul><li>Quaternions are interpolated rather than propagated </li></ul></ul><ul><li>Earth horizon crossing during external manoeuvres gives consistent pitch bias assessment. </li></ul>
    10. 10. Geolocation spin-off: ground resolution <ul><li>Instrumental model used for geolocation assessment includes Blackman rmax parameter. </li></ul><ul><li>Retrieved parameter compares well with theoretical resolution, as computed at L1C: </li></ul><ul><li>Retrievals proved to be very stable with time. </li></ul>45.6 46.7 rmax 2.0 3.1 std(rmax) 19.2 18.4 Descending 22.0 18.9 Ascending Semi axis in L1C Semi axis (-3dB) (km)
    11. 11. Ground resolution from RFI sources <ul><li>Madagascar results can be cross validated making use of RFI (assumed to be point sources) </li></ul>From RFI source From L1C 22 43.5 25 31.5 23.1 36.5 24.8 45.6 A2(km) A1 (km)
    12. 12. Geolocation impact on Soil Moisture <ul><li>Same product processed with/without biases correction </li></ul><ul><li>Brightness temperature impact less than 3K </li></ul><ul><li>SM impact low on average </li></ul><ul><li>Coastal zones and high surface variations show higher impacts </li></ul><ul><li>Overall statistics suggest better retrieval. Finer analysis over anchor sites still on-going. </li></ul>Mialon A., 2010
    13. 13. Antarctica around Dome Concordia <ul><li>Antarctic plateau around Dome C appears a very good candidate for stability monitoring and across fov consistency check </li></ul>
    14. 14. System level performances <ul><li>Average brightness temperature over Antarctic Plateau </li></ul>
    15. 15. System level performances <ul><li>Noise level consistent with expectations </li></ul>pre launch simulations
    16. 16. Antarctica around Dome Concordia <ul><li>Averaged over one month, 200km circle around DomeC </li></ul><ul><li>28 overpasses, 20 snapshot segments </li></ul>
    17. 17. Antarctica around Dome Concordia <ul><li>Standard deviation in xi-eta plane, one month </li></ul>
    18. 18. Antarctica around Dome Concordia <ul><li>Dome C only, Hallikainen model (one layer, Tsnow=-54) </li></ul>DomeX data, G. Macelloni Tv Domex-2 operative 2009 Th Domex-2 operative 2009 Th Domex-2 Initial 2009 Tv Domex-2 Initial 2009 Tv domex2010 th domex2010
    19. 19. Summary <ul><li>System level performances as assessed during commissioning </li></ul><ul><ul><li>Geolocation biases assessment – Best Fit Plane calibration </li></ul></ul><ul><ul><li>although higher bias than expected, calibration has been achieved up to required accuracy </li></ul></ul><ul><ul><li>Geolocation accuracy – impact at soil moisture level </li></ul></ul><ul><ul><li>preliminary assessment shows we are moving in the right direction, but thorough cal/val results will be needed for final analysis. Long-term trends will be monitored. </li></ul></ul><ul><ul><li>Equivalent Array Factor – spatial resolution confirmation </li></ul></ul><ul><ul><li>In close agreement with expectations, and validated making use of RFI </li></ul></ul><ul><ul><li>Radiometric accuracy verification for Land scenes </li></ul></ul><ul><ul><li>Consistent with theory, and used as such for soil moisture retrieval </li></ul></ul><ul><ul><li>Absolute accuracy of brightness temperatures </li></ul></ul><ul><ul><li>Dome C results extremely promising, finer analysis still needed . </li></ul></ul>

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