Performance improvement of the Giant Steerable Science Mirror prototype: calibration, added-on damping treatment, and warping harness

The Giant Steerable Science Mirror (GSSM), the tertiary mirror of the Thirty Meter Telescope, is designed to meet complicated requirements. Calibration, added-on damping treatment, and warping harness will lower the cost to meet those strict requirements. A laser tracker and sphere-mounted retro-reflector (SMR) were used to calibrate the GSSM prototype (GSSMP). Use of non-uniform distribution SMRs will lower the systematic metrology error. The frequency response function between input excitation and dummy mirror responses is investigated to realize the design of tuned mass damping, which will be added on the GSSMP as a damping treatment to improve settling time and tracing performance. Finally, we utilized the warping harness, combining Zernike mode and bending mode, to relax the requirements of GSSM for low-order mirror figure aberrations. (C) 2017 Optical Society of America