SMOS IN FLIGHT SYSTEM
PERFORMANCES ASSESSEMENT
AVFETER 1 YEAR IN ORBIT
F Cabot, A. AlBitar, , P. Richaume, Y.H. Kerr
Igarss '11 - Vancouver
Reprocessed Data Quality and Stability
L1C assessmentGeometry
Radiometric accuracy
Absolute accuracy
Repeat with new antenna model
Igarss '11 - Vancouver
Reprocessed L1C
The data analysed spans over 1 year of Data (2010)
• Madagascar geometry • Dome Concordia
– Radiometric accuracy– Absolute brightness temperature accuracy
All data have now been processed up to level 2 (SM) and is also investigated over various validation sites
See Monday’s presentation
Igarss '11 - Vancouver
Geolocation assessment
• Method developped and validated before flight with simulated data
• Simple model fit across sharp transition gives access to shift assessment.
• Madagascar coastline selected: long linear coastline.
• Additional checking being conducted using Earth Horizon ceossing the field of view during external calibration manoeuvre.
Igarss '11 - Vancouver
Madagascar Coastline access
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Model fitting results
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Ascending - Descending
• Alternate passes are used to constrain geolocation matrix.
• Depending on the position of the coast within the swath, this constrain can change.
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Temporal evolution of the geolocation over Madagascar
Same technique used as during commissionning, gives less noisy results.
All products being processed with same BFP (and correctly applied)
std(Ascending) = 350m
std(Descending) = 460m
Trend is clearer than at the end of IOCPand slightly degradesfinal RMS
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Acquisitions over DomeC
Selection of closest DGG node and extraction from L1C products.
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Radiometric Accuracy over Dome COver 12 months of data, Dome C has been seen more than 200000
times in full pol, spanning the entire EAF Fov.
Assuming the target has not changed, we can compute radiometric accuracy as the standard deviation of measured brightness temperature within the FoV.
TX TY TXTY T3 T4
Estimated 2.5337 2.3503 4.1970 3.8349 2.8613 3.0761
Computed 2.1181 2.1696 3.4531 3.4724 2.9358 2.9358
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Radiometric Accuracy over Dome C
T3 and T4 show some inconsistencies.• Radiometric accuracy as expected• Average TB shows strange behavior
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Polarisation signature
Dome C only, Hallikainen model (one layer, Tsnow=-54)
Tv Domex-2 operative 2009
Th Domex-2 operative 2009
Th Domex-2 Initial 2009
Tv Domex-2 Initial 2009
Tv domex2010
th domex2010
DomeX data, G. Macelloni
Igarss '11 - Vancouver
Absolute brightness temperature accuracy
SMOS estimates of TB over Dome C although somewhat noisier, compare well with on-ground measurements
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Bias variations within FoV
Different behaviour observed within AF-FoV and EAF-FoV
Clear change around april
Dielectric constants
Igarss '11 - VancouverAntarctica: Re and Im *10 + 220 (magenta) ECMWF temperature (blue)
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Stability and radiometric accuracy over Dome Concordia
Request for additional statistics and analysis :– Within the field of view– With respect to differential long term drift– METRICS understood as linear temporal trend of average
brightness temperature
Analysis of reprocessed data set with new antenna model– 2010 from reprocessing– 2010 from selected subset
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Analysis of acquisitions over Dome C
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Long term stabilityOver 15 months, trends at 42° almost disappears.
But only impact of January. Over 2010, drift was -0.22K/yr, now -0.72K/yr with new data set. Std(TB) slightly increase
TBH shows signs of a seasonal effect, observed on ground
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Long term stability
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Long term stability in ground reference frame
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METRICS
TX TY T3 T4 TX TY T3 T4
TH TV T3 T4 TH TV T3 T4
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Radiometric Accuracy over Dome COver 15 months of data, Dome C has been seen almost 260000 times
in full pol, spanning the entire EAF Fov.
Assuming the target has not changed, we can compute radiometric accuracy as the standard deviation of measured brightness temperature within the FoV.
Old Antenna ModelRadiometric Acc. (K) Antenna (Surface)
X pol(H pol)
Y pol(V pol)
X from XY(H from XY)
Y from XY(V from XY)
T3 T4
Theoretical at boresight 2.12 2.17 3.45 3.47 2.94 2.94
Measured at boresight 2.48(2.48) 2.39(2.38) 4.09(4.07) 3.81(3.84) 2.91(5.75) 3.11(6.22)
Measured in 0.3 circle 2.71(2.79) 2.56(2.61) 4.15(4.17) 4.18(4.18) 3.26(6.11) 3.18(6.37)
Measured in AF FoV 2.82(2.97) 2.70(2.79) 4.29(4.35) 4.34(4.34) 3.39(6.20) 3.29(6.57)
Measured in EAF FoV 3.29(3.74) 3.33(3.62) 5.12(4.76) 5.28(4.78) 4.09(7.07) 4.01(8.01)
New Antenna ModelRadiometric Acc. (K) Antenna (Surface)
X pol(H pol)
Y pol(V pol)
X from XY(H from XY)
Y from XY(V from XY)
T3 T4
Theoretical at boresight 2.08 2.15 3.36 3.47 2.90 2.90
Measured at boresight 2.35(2.36) 2.58(2.36) 4.10(4.08) 3.99(4.00) 2.91(5.73) 3.15(6.29)
Measured in 0.3 circle 2.56(2.65) 2.61(2.68) 4.08(4.12) 4.21(4.19) 3.24(6.08) 3.18(6.35)
Measured in AF FoV 2.67(2.82) 2.73(2.82) 4.21(4.30) 4.36(4.34) 3.37(6.17) 3.28(6.56)
Measured in EAF FoV 3.19(3.66) 3.27(3.56) 4.97(4.66) 5.29(4.72) 4.03(6.99) 3.93(7.85)
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Radiometric performances
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Radiometric performances 3/4
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New antenna model summary
Mixed results for biases correction. – Clear improvement in ground reference frame from may
onwards.– Antenna reference frame results unconclusive.– T3/T4 rather unclear, mostly degrades.
Marginal gain on radiometric accuracy
Conclusions
• Still homework to be done with• Calibration• Stokes 3 and 4
• Variations within field of view still not totally mastered• But overall performances in radiometry and geolocation
out performs specifications• Long term drift starting to be understood ( and thus
correction within reach
Igarss '11 - Vancouver