Metrology mount design for Φ28-meter space mirror

As space astronomical exploration missions advance in sophistication, the aperture sizes of primary telescope mirrors have progressively increased. State-of-the-art space telescopes currently in orbit or development now employ primary mirrors exceeding 2 meters in diameter. While launch vehicle constraints drive the need for lightweight designs in larger apertures, this mass reduction exacerbates gravitational deformation effects. The stringent Earth-space performance consistency requirements for space telescopes present substantial challenges in both manufacturing and verification of orbital mirrors. Ground-based replication of zero-gravity conditions with sub-micron precision becomes imperative for accurate surface metrology to guarantee on-orbit imaging performance. To address these challenges for a Φ2.8-meter class space mirror, we developed a 300-actuator pneumatic gravity unloading system incorporating back-mounted metrological compensation technology. Simulated results demonstrate maintained surface accuracy better than λ/100 (λ=632.8nm) across operational conditions, effectively neutralizing gravitational distortion impacts on orbital-terrestrial performance correlation.