Investigation on the role of optical filters on the point spread function of the NASA MIDEX solar mission MUSE

The study of the coronal heating problem is one of the main goals of existing extreme ultraviolet (EUV) coronal spectroscopy space missions and future observatories currently under development such as NASA's MIDEX mission MUSE (Multi-slit Solar Explorer). In such missions, the performance of optical filters is a critical aspect for effectively achieving scientific objectives. We numerically model the effects of various optical filter designs-including traditional filters with nickel meshes and novel carbon nanotube-based filters featuring hexagonal mesh structures-on the point spread function (PSF) of the spectrograph (SG) instrument on board the NASA MIDEX solar mission MUSE. The simulations presented here are useful to assess the suitability of such filters also for other EUV space missions. We performed detailed simulations for different filter configurations across the MUSE SG wavelengths (108, 171, and 284 A). Our analyses show that simple models are insufficient for reliably predicting design-dependent PSF properties, and simulations accounting for realistic mirror roughness and mesh patterns are necessary. The simulations reveal that all of the studied designs meet the high angular resolution requirements of missions like MUSE. Carbon nanotube-based filters with optimized mesh designs can reduce the percentage of diffracted light outside of a 0.5" angular window as compared to more traditional filters while maintaining a high core PSF transmittance. Our findings show how using simulations to obtain accurate estimates of the PSF is necessary for the design, development, and optimization of optical components for EUV solar space missions.