Polarimetric calibration of a compact multispectral all-sky polarization imager

We describe the calibration of a compact all-sky polarization imaging system developed to assess the capabilities of low-cost commercial polarization cameras for ground-based remote sensing of clouds and aerosols. The system is based on a division-of-focal-plane camera with a fisheye lens and a fore-optics system that creates a collimated space for a filter wheel. This enables simultaneous measurements of the linear Stokes parameters, repeated sequentially in time for wavelengths currently distributed from 440 to 875 nm. In this presentation, we describe the calibration procedure based on a polynomial fit of integrating-sphere images recorded in different portions of the hemispheric field of view. This method results in a linear Mueller matrix for the entire imaging system.