# Polarization Modeling and Predictions for DKIST Part 1: Telescope and example instrument configurations

## TL;DR

This paper models and predicts the polarization performance of the DKIST telescope and its instruments using optical simulations, providing detailed Mueller matrix estimates across various conditions and validating the models with theoretical and lab comparisons.

## Contribution

It introduces a comprehensive polarization modeling approach for DKIST, including a coating formula and Mueller matrix predictions, validated through Zemax simulations and theoretical limits.

## Key findings

- Mueller matrix varies significantly with wavelength and position.
- Estimated 2% variation in Mueller matrix elements over the CryoNIRSP field.
- Model validation shows good agreement with theoretical and lab measurements.

## Abstract

We outline polarization performance calculations and predictions for the Daniel K. Inouye Solar Telescope (DKIST) optics and show Mueller matrices for two of the first light instruments. Telescope polarization is due to polarization dependent mirror reflectivity and rotations between groups of mirrors as the telescope moves in altitude and azimuth. The Zemax optical modeling software has polarization ray-trace capabilities and predicts system performance given a coating prescription. We develop a model coating formula that approximates measured witness sample polarization properties. Estimates show the DKIST telescope Mueller matrix as functions of wavelength, azimuth, elevation, and field angle for the Cryogenic Near Infra-Red Spectro-Polarimeter (CryoNIRSP) and for the Visible SpectroPolarimeter (ViSP). Footprint variation is substantial. We estimate 2\% variation of some Mueller matrix elements over the 5 arc minute CryoNIRSP field. We validate the Zemax model by show limiting cases for flat mirrors in collimated and powered designs that compare well with theoretical approximations and are testable with lab ellipsometers.