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Estimating terra MODIS polarization effect using ocean data

TitleEstimating terra MODIS polarization effect using ocean data
Publication TypePresentation
Year of Publication2016
AuthorsWald, A., J. Brinkmann, A. Wu, and X. Xiong
ProceedingsProc. SPIE 9827, Ocean Sensing and Monitoring VIII
MCST ConferenceProc. SPIE 9827, Ocean Sensing and Monitoring VIII
Keywordsocean; polarization; terra

Terra MODIS has been known since pre-launch to have polarization sensitivity, particularly in shortest-wavelength bands 8 and 9. On-orbit reflectance trending of pseudo-invariant sites show a variation in reflectance as a function of band and scan mirror angle of incidence consistent with time-dependent polarization effects from the rotating doublesided scan mirror. The MODIS Characterization Support Team [MCST] estimates the Mueller matrix trending from this variation as observed from a single desert site, but this effect is not included in Collection 6 [C6] calibration. Here we extend the MCST’s current polarization sensitivity monitoring to two ocean sites distributed over latitude to help estimate the uncertainties in the derived Mueller matrix. The Mueller matrix elements derived for polarization-sensitive Band 8 for a given site are found to be fairly insensitive to surface brdf modeling. The site-to-site variation is a measure of the uncertainty in the Mueller estimation. Results for band 8 show that the polarization correction reduces mirror-side striping by up to 50% and reduces the instrument polarization effect on reflectance time series of an ocean target.