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FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt
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FR2-T04-5_A_synergy_between_smos_and_aquarius.ppt

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  • 1. A synergy between SMOS & AQUARIUS: resampling SMOS maps at the resolution and incidence of AQUARIUS Eric A NTERRIEU , Yann K ERR , François C ABOT , Gary L AGERLOEF and David L E V INE
  • 2.
    • ESA mission for global monitoring of surface Soil Moisture and Ocean Salinity from space.
    SMOS
    • 1 synthetic aperture imaging radiometer
      • L-band 1.413 GHz
      • 69 antennas/receivers
      • diluted apertures (6.75 m)
    • launched November 2 nd 2009
    • http://www.esa.int/smos
    1
  • 3.
    • Partnership between NASA and CONAE for monitoring Sea Surface Salinity from space.
    AQUARIUS
    • 3 radiometers (+ 1 scatterometer)
      • L-band 1.413 GHz
      • parabolic reflector, 3 feed horns
      • filled aperture (2.5 m)
    • launched June 10 th 2011
    • http://www.nasa.gov/aquarius
    2
  • 4.  
  • 5. AQUARIUS in SMOS
  • 6. Why resampling?
    • The spatial resolution achieved by SMOS is always smaller than the footprint of any of the 3 beams of AQUARIUS radiometers.
    • SMOS and AQUARIUS do not share the same sampling grids .
    • There is a need for resampling the temperature maps provided by SMOS down to the ground resolution of AQUARIUS beams so that a synergy between both missions can be properly set.
    3
  • 7. How to interpolate?
    • Resampling: discrete inverse Fourier transform
      • only 1396 terms in the sum ( band-limited reconstruction… )
      • does not introduce any interpolation artifact
    • Resampling + Windowing: filter Gibbs effects
    4 T(  ,  ) =  T( u , v ) e +2j  ( u  + v  ) u , v  H  T (  ,  ) =  W( u , v ) T( u , v ) e u , v  H +2j  ( u  + v  ) w  
  • 8. Kaiser window: 1 parameter s
    • Kaiser windows are widely used for filtering out Gibbs effects.
    • Parameter   0 and constant over all the frequency coverage H (  is the radial distance normalized to the circumscribed circle).
    • For  = 0, the Kaiser window reduces to the rectangle window (no tapering).
    5 u v    = 1 W( u , v ) = I 0 (  ) I 0 (   1    ² ) 
  • 9. Kaiser window: 1 parameter s
    • The shape of the synthesized PSF W(  ,  ) is controlled by the value of  :
     = 3  = 10 spatial domain W(  ,  ) 5 u v    = 1 W( u , v ) = I 0 (  ) I 0 (   1    ² )  Fourier domain W( u , v ) 
  • 10. How to interpolate?
    • Resampling + Windowing: with a single window
      • the same window is attached to each pixel (  ,  )
    • Resampling + Windowing: with multiple windows
      • a unique window is attached to each pixel (  ,  )
    6 T (  ,  ) =  W( u , v ) T( u , v ) e u , v  H +2j  ( u  + v  ) w   T (  ,  ) =  W ( u , v ) T( u , v ) e   u , v  H +2j  ( u  + v  ) w  
  • 11. Kaiser window: 3 parameters
    • Value of  continuously depends on  with the aid of 3 parameters  1 ,  2 and  1 according to the linear relation:
    • It is possible to control the shape of W(  ,  ).
    7 u v  1  2    1  2  = 1   =  1 + (  2   1 )    1  2   1 W( u , v ) = I 0 (  ) I 0 (   1    ² ) 
  • 12. Kaiser window: 3 parameters
    • It is possible to control the shape of W(  ,  ):
     1 = 0°  1 = 3  2 = 10  1 = 30°  1 = 10  2 = 3 spatial domain W(  ,  ) 7 W( u , v ) = I 0 (  ) I 0 (   1    ² )  u v  1  2    1  2  = 1  Fourier domain W( u , v ) 
  • 13. Optimization of the multiple windows
    • Characteristics of the footprint of AQUARIUS beams:
    • Resolution of SMOS is better than that of AQUARIUS for the same incidence angles (50-100 Km).
    8 incidence angle resolution a  b orientation  28.7° 37.8° 45.6° 1 94  76 Km 120  84 Km 156  96 Km  1 9.8°  15.3°  1 6.5° a b 
  • 14. Optimization of the multiple windows
    • Characteristics of the field of view of SMOS:
    9   @ instrument level cross track distance (Km) along track distance (Km) @ Earth surface
  • 15. Optimization of the multiple windows
    • Parameters  1 ,  2 and  1 can be optimized for degrading SMOS pixels down to the resolution of AQUARIUS at the Earth surface (non-linear optimization).
     1  1  2 local azimuth angle (deg) local azimuth angle (deg) local azimuth angle (deg) 10  =  1 + (  2   1 )    1  2   1 W( u , v ) = with I 0 (  ) I 0 (   1    ² ) 
  • 16. Optimization of the multiple windows
    • Non-linear optimization is an heavy task, precluding any real time application.
    • These curves are tabulated in such a way that a linear interpolation does not introduced an error larger than 0.01 Km ( a and b ) and 0.01° (  ) on the final ground resolution.
     1  1  2 local azimuth angle (deg) local azimuth angle (deg) local azimuth angle (deg) 10
  • 17. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 1:
      • T x and T y read from SMOS L1b file
      • and resampled at AQUARIUS resolution/incidence
    T x @ 28,7° T x @ 37,8° T x @ 45,6° 11
  • 18. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 1:
      • T x and T y read from SMOS L1b file
      • and resampled at AQUARIUS resolution/incidence
    T y @ 28,7° T y @ 37,8° T y @ 45,6° 11
  • 19. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 2:
      • geometric rotation angle read from SMOS L1c file (DGG)
      • and interpolated (LSQ) at AQUARIUS incidence
    geometric @ 28,7° geometric @ 37,8° geometric @ 45,6° 12
  • 20. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 2:
      • faraday rotation angle read from SMOS L1c file (DGG)
      • and interpolated (LSQ) at AQUARIUS incidence
    faraday @ 28,7° faraday @ 37,8° faraday @ 45,6° 12
  • 21. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 3:
      • T h and T v computed from T x and T y and rotation angles
      • and written in SMOS L1c file (DGG)
    T h @ 28,7° T h @ 37,8° T h @ 45,6° 13
  • 22. Concrete illustration
    • Orbit 2010 June 6 th 10:56:31 to 11:50:33
    • Step 3:
      • T h and T v computed from T x and T y and rotation angles
      • and written in SMOS L1c file (DGG)
    T v @ 28,7° T v @ 37,8° T v @ 45,6° 13
  • 23. Conclusion
    • How to resample the temperature maps retrieved from SMOS interferometric measurements down to the ground resolution and at the incidence angles of AQUARIUS.
    • Resampling procedure is fast, accurate and operational.
    • A synergy between SMOS and AQUARIUS can be set for the benefit of both missions.
    14

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