TH4-TO3_5-smos_in_flight.ppt

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


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


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.


Madagascar Coastline access


Model fitting results


Ascending - Descending

• Alternate passes are used to constrain geolocation matrix.

• Depending on the position of the coast within the swath, this constrain can change.


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


Acquisitions over DomeC

Selection of closest DGG node and extraction from L1C products.


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


Radiometric Accuracy over Dome C

T3 and T4 show some inconsistencies.• Radiometric accuracy as expected• Average TB shows strange behavior


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


Absolute brightness temperature accuracy

SMOS estimates of TB over Dome C although somewhat noisier, compare well with on-ground measurements


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)


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


Analysis of acquisitions over Dome C


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


Long term stability


Long term stability in ground reference frame


METRICS

TX TY T3 T4 TX TY T3 T4

TH TV T3 T4 TH TV T3 T4


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)


Radiometric performances


Radiometric performances 3/4


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


Business

TH4-TO3_5-smos_in_flight.ppt