The Polarization Optics for the European Solar Telescope

Abstract

EST, the European Solar Telescope, is a 4-m class solar telescope, which will be located at the Canary Islands. It is currently in the conceptual design phase as a European funded project. In order to fulfill the stringent requirements for polarimetric sensitivity and accuracy, the polarimetry has been included in the design work from the very beginning. The overall philosophy has been to use a combination of techniques, which includes a telescope with low (and stable) instrumental polarization, optimal full Stokes polarimeters, differential measurement schemes, fast modulation and demodulation, and accurate calibration, and at the same time not giving up flexibility. The current baseline optical layout consists of a 14-mirror layout, which is polarimetrically compensated and non-varying in time. In the polarization free F2 focus ample space is reserved for calibration and modulators and a polarimetric switch. At instrument level the s-, and p-planes of individual components are aligned, resulting in a system in which eigenvectors can travel undisturbed through the system.