Hyperpolishing off-axis mirrors with nanoparticles slurries for the next generation of space exoplanets imagers

The stressed-mirror polishing process has been successfully deployed to manufacture Nancy Grace Roman Space Telescope coronagraph mirrors. This process combines a simple warping system with an optimized thickness distribution of the mirror’s substrates, allowing it to warp them into the required Off-Axis Parabola parameters. This way, the polishing process uses full-sized tools, avoiding generating undesired high spatial frequency sub-aperture tool marks. The smoothness of the surface is then worked with a super-polishing process, lowering the roughness to a few Angstroms. <br/> <br/> The research we present is done in the post-RST technology maturation roadmap frame. The Habitable Worlds Observatory requirements are so drastic that the performance of the stressed mirror polishing process needs to be improved to gain surface roughness. <br/> <br/> Therefore, synthesizing nanoparticle slurries seems to be an alternative to aiming for a low roughness value. In this paper, we present the nanoparticle production process, the results obtained on the mirror prototypes we produced, and the roadmap for the production of hyperpolished OAPs.