Polarimetric performance of the European Solar Telescope

Ferro Rodríguez, I.; Collados, M.; Sánchez-Capuchino, J.; Quintero Noda, C.; Barreto Cabrera, M.
Referencia bibliográfica

Ground-based and Airborne Telescopes IX

Fecha de publicación:
8
2022
Número de autores
5
Número de autores del IAC
5
Número de citas
1
Número de citas referidas
1
Descripción
Polarization is a fundamental property of the light and is very useful to measure the magnetic field vector of the various features that can be observed in the solar atmosphere. Ideally, a solar telescope should not introduce any polarization to the incoming light that could mask the one coming from the Sun. However, some instrumental polarization is always introduced by the different optical components, because it depends on the coatings used, as well as on the incidence angle and wavelength. The calibration of these instrumental polarization is specially tedious and complicated if it varies with time (as is the usual case for telescopes, when the pointing changes in elevation and azimuth). The European Solar Telescope (EST) has been designed to minimize this spurious temporally-varying instrumental polarization. A numerical model based on geometrical ray tracing has been developed in combination with Zemax Optic Studio (ZOS), in order to estimate the Mueller matrices of the moving optical elements of the telescope. The Mueller matrices have been calculated as a function of wavelength and for different field of view (FoV) positions and telescope (azimuth and elevation) pointing, using generics coatings (aluminium for the primary mirror and silver for the rest of the mirrors). This paper shows the analysis and results of the Mueller matrices that have been obtained, leading to the confirmation that the telescope has an excellent polarimetric performance for all wavelengths, FoVs and pointing directions.