Application progress of stressed mirror continuous polishing technology in the segments fabrication of telescope primary mirror

The primary mirrors of several large ground-based astronomical telescopes currently in the research or planning phases, such as TMT (Thirty Meter Telescope), ELT(Extremely Large Telescope) and LOT (Large Optical /infrared Telescope), take the form of a segmented array telescope. The fabrication of hundreds of off-axis aspheric segments is one of the key technologies for their development. Our proposed stressed mirror continuous polishing (SMCP) method combines the stressed mirror polishing (SMP) and continuous polishing (CP) technologies. The combined technologies deliver high-quality surface smoothness of the SMP technique with the high efficiency of continuous polishing. Nanjing Institute of Astronomical Optics & Technology (NIAOT) and TMT have carried out in-depth cooperation in the segment fabrication of the primary mirror. NIAOT is currently working on the development of off-axis aspheric segments. In this article, the progress for the 5m continuous polishing machine and ancillary equipment, the stress loading test on a 1.52 meter segment, the calibration of our 2-dimensional contact-metrology device and the reference mirror calibration are introduced here in detail.