Hyperpolishing off-axis mirror’s with nanoparticles slurries for the next generation of space exoplanets imagers

The stressed-mirror polishing process has been successfully deployed for the manufacturing of Nancy Grace Roman Space Telescope coronagraph mirrors. This process combines a simple warping system with an optimized (more complex) thickness distribution of the mirror’s substrates allowing to warp them into the required Off Axis Parabola’s parameters. This way, the polishing process uses full-sized tools, avoiding the generation of undesired high spatial frequency sub-aperture tool marks. The smoothness of the surface is then worked with a super-polishing process, lowering the roughness down to a few Angstroms. The research we present is done in the frame of the post-RST technology maturation roadmap. The Habitable Worlds Observatory requirements are so drastic that we must push the performance of the stressed mirror polishing process to gain on the roughness. Together with chemical scientists, we work on the production of nanoparticle slurries with the goal to go below the angstrom in terms of roughness. In this talk, we present the nanoparticles production process, the results obtained on the mirror’s prototypes we produced and the roadmap for the production of hyperpolished OAPs.