Mechanical qualification of metal-coated-carbon-nanotube optical blocking filters developed for the NASA MIDEX solar mission MUSE

The NASA MIDEX mission MUSE (MUlti-slit Solar Explorer), presently under development with a launch scheduled in mid-2027, will focus on high spectral and time resolution imaging of the solar corona by use of two separate EUV instruments, a multislit spectrograph (SG) and a context imager (CI). Both instruments use back-illuminated CCD detectors and thus need optical blocking filters to attenuate the UV/Vis/IR band of the solar spectrum. As part of the Italian contribution to the MUSE mission, funded by the Italian Space Agency, we are investigating an innovative filter technology based on Carbon Nanotubes (CNT) pellicles that exploit excellent EUV/X-rays transmissivity as well as high mechanical and thermal properties. Particularly significant is the capability we recently developed, within a research contract funded by the European Space Agency (AMETEK Finland Oy prime contractor, CANATU Finland Oy manufacturer of the CNT pellicles), to deliver very thin CNT pellicles supported by partially transparent embedded CNT meshes. Fully representative CNT-based filter models of the MUSE SG and CI telescope entrance filters and focal plane filter wheel filters have been manufactured to demonstrate the maturity of the technology and to prove their capability to withstand launch vibroacoustic stresses. We describe the structural design of the developed CNT-based filter demonstration models and discuss the results of vibration qualification tests. We will also discuss future activities to consolidate the mechanical filter design and achieve a reliable and robust structural model with good optical performance.