Numerical phase front propagation for a large-baseline space interferometer

We report on numerical studies of phase front propagation for a large-baseline space interferometer. The main objective is to determine the sensitivity of the average phase of the metrology beam with respect to fluctuations in the pointing of the beam. For this purpose, the metrology beam is propagated numerically along the interferometric arm of the instrument. The effects of the obscurations from the secondary mirror and its supporting struts are studied in detail. Further, the effects of wavefront distortions that occur due to imperfections of the optical elements are estimated through a series of Monte Carlo simulations. The results of this study can be used to determine design requirements for the instrument. (C) 2003 Society of Photo-Optical Instrumentation Engineers

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