Post on 12-Jan-2016
description
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Detector dependency of MODIS Polarization Sensitivity derived from on-orbit
characterization
Gerhard Meistera,b, Bryan A. Franzb,c, Ewa J. Kwiatkoskad, Robert E. Epleee,b, Charles R. McClainb,c
a: Futuretech Corp. b: OBPG (Ocean Biology Processing Group)
c: NASA Goddard Space Flight Center, Code 614.2d: TEC-EEP, ESTEC, ESA
e: SAIC
8/03/09
Earth Observing Systems XIV,
SPIE Optics and Photonics 2009, San Diego
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Optimization process
Lm = M11LTOA + M12Q + M13U
• find best M11
, M12
, M13
per band, detector, and mirror-side
• M11
, M12
, M13
= f (scan angle), cubic (M11) and linear (M12)
• do this for one day per month over the mission lifespan
• optimize over global distribution of path geometries
Lm: MODIS measured TOA radiance (without polarization corr.)
LTOA: modeled (nLw from SeaWiFS, aerosols from MODIS NIR bands)
Q, U: Stokes vector parameters (modeled from Rayleigh)
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M12: MODIS Terra blue band temporal trends
Mirror side 2
Detector 4
Mirror side 1
Space View (lunar) frameNadir frame
Solar Diffuser frame
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443
488
M12 acts onthe Q component
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M13 fixed to pre-launch412
443
488
Blue band RVS & polarization sensitivity MS1, Detector 4
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More microwave sensitivities: to rain
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Aerosol sensitivity to surface albedo
A “critical surface albedo” exists for which sensitivity to aerosol completely disappears!
Seidel & Popp, AMT, 2012
ϖ0
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Aerosol sensitivity to surface albedo
A “critical surface albedo” exists for which sensitivity to aerosol completely disappears!
Seidel & Popp, AMT, 2012
AOD retrieval error at 550 nm. Plus (minus) signs denote an overestimate of surface albedo by 0.01 (-0.01).
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Sensitivity studies: useful for lots of things
• Impact of instrument errors on retrievals
• Best channels to retrieve certain variables
• Qualitative picture of retrieval errors vs. different quantities (e.g. aerosol vs. surface albedo)
• Impact of uncertainties in other variables on retrievals: e.g. cloud temperatures on cloud water path from Vis/NIR.
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2D Gaussian