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Proceedings Paper

SeaWiFS lunar calibration methodology after six years on orbit
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Paper Abstract

The SeaWiFS Project uses monthly lunar calibrations to monitor the on-orbit radiometric stability of SeaWiFS over the course of its mission. Ongoing analyses of the steadily increasing lunar calibration data set have led to improvements in the calibration methodology over time. The lunar measurements must be normalized to a common viewing geometry for the calibration time series to track the radiometric stability of the instrument. Corrections computed from the time and geometry of the observations include Sun-Moon and instrument-Moon distances, oversampling of the lunar image, and variations in the lunar phase angles. The Project has recently implemented a correction for lunar libration that is computed from regressions of the libration angles of the observations against the lunar radiances. Decaying exponential functions of time are fit to the geometry-corrected calibration time series. The observations for bands 1,2,and 5-8 are fit to two simultaneous exponential functions of time, while bands 3 and 4 are fit to single exponential functions of time. The corrections to the radiometric response of the instrument over time are the inverses of these fits. The lunar calibration methodology provides top-of-the-atmosphere radiances for SeaWiFS that are stable to better than 0.07% over the course of the mission, with residual time drifts that are smaller than -0.004% per thousand days. The resulting water-leaving radiances are stable to better than 0.7%, allowing the Project to implement a vicarious calibration of the water-leaving radiances that is independent of time. The calibration methodology presented here will be used to generate the calibration table for the fifth reprocessing of the SeaWiFS global ocean data set.

Paper Details

Date Published: 26 October 2004
PDF: 13 pages
Proc. SPIE 5542, Earth Observing Systems IX, (26 October 2004); doi: 10.1117/12.556408
Show Author Affiliations
Robert E. Eplee, Science Applications International Corp. (United States)
Robert A. Barnes, Science Applications International Corp. (United States)
Frederick S. Patt, Science Applications International Corp. (United States)
Gerhard Meister, Futuretech Corp. (United States)
Charles R. McClain, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 5542:
Earth Observing Systems IX
William L. Barnes; James J. Butler, Editor(s)

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