Optical performance of Aluminum-coated carbon nanotube pellicles for the NASA MUSE space mission

Exploring the mechanisms of coronal heating and the evolution of flares remains an enduring challenge in solar astrophysics. EUV spectroscopy observatories, such as the NASA MUSE (Multi-slit Solar Explorer) mission, are currently being developed to provide the experimental background needed for the future modeling of solar corona dynamics. As part of MUSE, we are developing novel carbon nanotube (CNT)-based optical blocking filters coated with metal to shield the highly sensitive detectors from the solar optical load. CNT pellicles, being sturdy and EUV-transparent, are a very promising candidate for the substrate of choice for the metal coatings. We are investigating different types of CNT pellicles coated with aluminum to assess their optical blocking performance. We report results of UV, Vis, and NIR spectroscopy, performed at the Astronomical Observatory of Palermo (INAF-OAPA) XACT facility, and compare the experimental visible transmittance of such filters with the very demanding out of band attenuation (~10⁻⁶) requirements required by MUSE. This study will improve the filters’ technology readiness level for the MUSE mission and for other future EUV solar physics experiments.