MODIS polarization performance and anomalous four-cycle polarization phenomenon

James B. Young; Ed Knight; Cindy Merrow

doi:10.1117/12.325630

3 October 1998 MODIS polarization performance and anomalous four-cycle polarization phenomenon

James B. Young, Ed Knight, Cindy Merrow

Proceedings Volume 3439, Earth Observing Systems III; (1998) https://doi.org/10.1117/12.325630
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) will be one of the primary instruments observing the earth on the Earth Observing System (EOS) scheduled for launch in 1999. MODIS polarization performance characterization was required for the 0.4 to 0.6 micrometers (VIS), 0.6 micrometers to 1.0 micrometers (NIR), and 1.0 micrometers to 2.3 micrometers (SWIR) regions. A polarized source assembly (PSA) consisting of a collimator with a rotatable Ahrens polarizer was used to illuminate MODIS with a linearly polarized beam. MODIS signal function having two-cycles per 360 degrees prism rotation signal function was expected. However, some spectral bands had a distinct four-cycle anomalous signal. The expected two-cycle function was present in all regions with the four-cycle anomaly being limited to the NIR region. Fourier analysis was very useful tooling determining the cause of the anomaly. A simplified polarization model of the PSA and MODIS was generated using Mueller matrices-Stokes vector formalism. Parametric modeling illustrated that this anomaly could be produced by energy having multiple passes between PSA Ahrens prism and the MODIS focal plane filters. Furthermore, the model gave NIR four-cycle magnitudes that were consistent with observations. The IVS and SWIR optical trans had birefringent elements that served to scramble the multiple pass anomaly. The model validity was demonstrated with an experimental setup that had partial aperture illumination which eliminated the possibility of multiple passes. The four-cycle response was eliminated while producing the same two-cycle polarization response. Data will be shown to illustrate the four-cycle phenomenon.

Citation Download Citation

James B. Young, Ed Knight, and Cindy Merrow "MODIS polarization performance and anomalous four-cycle polarization phenomenon", Proc. SPIE 3439, Earth Observing Systems III, (3 October 1998); https://doi.org/10.1117/12.325630

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