VIIRS polarization sensitivity tolerance and impact on Ocean Color

The Visible/Infrared Imager Radiometer Suite (VIIRS) is a key science instrument on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NPOESS is the nation's next generation operational weather and climate monitoring system. VIIRS is built to deliver 22 Environmental Data Records (EDRs). One of the EDRs, ocean color, requires accurate and precise measurements of water leaving radiances (L_W) in the reflective VNIR bands, which is a small component of the top of the atmosphere (TOA) radiances observed by VIIRS. The accuracy of measuring the total TOA radiance becomes critical, especially when the other large components of the signal due to atmospheric scatter are substantially polarized. Errors due to minor sensitivity of VIIRS to such polarization can be corrected, but the polarization sensitivity characteristics of VIIRS must be known to within a very small uncertainty. The associated uncertainty requirement on VIIRS is shown to be of a 2-D uncertainty bound on the Degree of Linear Polarization (DoLP) and phase components of the polarization sensitivity of VIIRS. The polarization related measurement uncertainties in TOA radiances are limited as required, with VIIRS polarization sensitivity characteristics within the 2-D bound leading to acceptable ocean color performance estimates, as demonstrated with Monte Carlo simulations and statistics with Global Synthetic Data (GSD) scene conditions.