Space-qualified fast steering mirror for an image stabilization system of space astronomical telescopes

A space-qualified fast steering mirror (SQ-FSM) was designed, built, and tested at the National Astronomical Observatories of the Chinese Academy of Sciences for an image stabilization system of space astronomical telescopes, which is used for the tip-tilt correction of small jitter of the satellite platform; this achieved image stability in a closed-loop manner. Its design primarily faces four challenges involving (1) sustaining the specified sine and random vibration without launch lock, as well as shock response spectrum experiments; (2) surface form error of a clear aperture of ϕ120  mm less than 1/50λ root mean square (RMS, λ=632.8  nm) with a relatively rigid mirror support; (3) resonance frequency of at least 800 Hz and as high as possible; (4) minimum reaction force and torque in order to decrease its unfavorable influence on the satellite platform. To achieve these goals, the global optimizations and compromises have to be made throughout the design process. The study reviews the detailed design of the SQ-FSM with respect to the four challenges, mainly by keeping the mirror and its support lightweight, mirror bonding and solidification, actuator and its stiffness, flexure support of the mirror and its holder, material optimization for weight, stiffness, and coefficient of thermal expansion, as well as finite element analysis on statics and dynamics. The performances are also measured and expatiated, including the surface form, resonant frequency, tip-tilt stroke, vibration and shock response spectrum experiments, etc., which validate the performances of the SQ-FSM.