Electro-optical polarimeters for ground-based and space-based observations of the solar K-corona

摘要

Polarimeters based on electro-optically tunable liquid crystals (LC) represent a new technology in the field ofobservational astrophysics. LC-based polarimeters are good candidates for replacing mechanically rotating polarimetersin most ground-based and space-based applications. During the 2006 total solar eclipse, we measured the visible-lightpolarized brightness (pB) of the solar K-corona with a LC-based polarimeter and imager (E-KPol). In this presentation,we describe the results obtained with the E-KPol, and we evaluate its performances in view of using a similar device forthe pB imaging of the K-corona from space-based coronagraphs. Specifically, a broad-band LC polarimeter is plannedfor the METIS (Multi Element Telescope for Imaging and Spectroscopy) coronagraph for the Solar Orbiter mission tobe launched in 2017. The METIS science driver of deriving the coronal electron density from pB images requires anaccuracy of better than 1% in the measurement of linear polarization. We present the implications of this requirement onthe METIS design to minimize the instrumental polarization of the broad-band visible-light (590-650 nm) polarimeterand of the other optics in the METIS visible-light path. Finally, we report preliminary ellipsometric measurements of theoptical components of the METIS visible-light path.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.