Active maintenance of a segmented mirror based on edge and tip sensing

Area of Science:

• Optical Engineering
• Astronomy Instrumentation
• Adaptive Optics

Background:

• Segmented primary mirrors are crucial for large telescopes like the Chinese Giant Solar Telescope (CGST).
• Active control of these mirrors is essential for maintaining image quality.
• The unique ring aperture of the 8 m ring solar telescope (8 m RST) presents challenges for traditional edge detection in closed-loop control.

Purpose of the Study:

• To investigate the feasibility and performance of a combined edge and tip detection scheme for active maintenance of a segmented ring telescope.
• To validate the proposed active control strategy through experimental analysis.

Main Methods:

• A two-segmented mirror workbench was constructed for experimental analysis.
• Capacitive sensors were employed to measure edge height changes between mirror segments.
• A Shack-Hartmann sensor was utilized to detect segment tip and tilt variations.

Main Results:

• A stable mirror figure was achieved and maintained for a duration of 100 minutes.
• The mirror figure error was successfully controlled and kept below 18.94 nm.

Conclusions:

• The combined edge and tip detection method is a viable approach for the active maintenance of segmented ring telescopes.
• This study provides valuable data and insights for the primary mirror selection and active control implementation for the CGST.