In-band and out-of-band transmission curves of Al/Zr-carbon nanotube FM filters for the Muse mission

The NASA Multi-slit Solar Explorer mission, scheduled for launch in 2027, will utilize high-performance optical blocking filters to isolate five critical spectral lines in the 40–120 eV range while attenuating out-of-band solar radiation. This work presents the in-band (EUV) and out-of-band (UV-Vis-IR) characterization of the flight model filter wheel filters for the Spectrograph and Context Imager instruments, fabricated by depositing aluminum and zirconium metallic coatings on carbon nanotube membranes. In-band results show that the thin Zr filters successfully meet the requirements at 10.8 nm, while the thin Al variants show performance at 17.1 nm and 19.5 nm close to the requirements, though failing to meet the 28.4 nm and 30.4 nm thresholds. Out-of-band measurements (190–860 nm) confirm that essentially all the filters comply with the rejection requirement (T < 10−6), validating CNT-based technology for solar space missions.