MODIS polarization ray tracing analysis

On-orbit optical sensors are the primary data source for the remote sensing community. A rigorous pre-flight characterization and calibration is a key to the success of their mission. Indeed, preliminary calibration and correction factors are determined during this process. As part of this process, prior to the launch of NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) its polarization sensitivity was measured. In this work, our goal was to simulate these measurements using computer ray tracing software. Based on that, we could evaluate the evolution of the different coatings (Mirror, Beam splitters, Anti-reflection and Band pass filters) due to degradation over time. We were able to simulate the measurements and obtained what the theoretical polarization sensitivity should be. The results were compared to the pre-launch measurements and an analysis of the whole MODIS optical system was performed in order to explain these differences. A full description of the MODIS polarization ray tracing procedure along with a discussion on the results and their implications on past, present and future work will be given.