Fine Steering Mirror for Smallsat Pointing and Stabilization

SDL has used internal funds to develop a prototype low-cost 2-axis fine steering mirror (FSM) as an enabling technology for smallsats. The FSM has a lightweight high-reflectance mirror, high angular deflection capability for along-track ground motion compensation and cross-track pointing, and a high bandwidth to help cancel unwanted jitter. Key performance parameters are: Clear aperture, 75 mm; along-track angle, ±30 deg (mechanical); cross-track angle, ±60 deg (mechanical); slew rate, greater than 75 deg/sec; bandwidth, 70 Hz; steadystate average error, as good as 1 arcsec; average power dissipation, 0.4 Watts; and total mechanical mass, 1 kg. The FSM makes use of off-the-shelf components as much as possible. Key components for the along-track (elevation) axis include a rotary voice coil and a unique non-contact feedback sensor. The cross-track (azimuth) axis features a brushless DC motor and a high-resolution optical encoder. Rapid prototyping, autocoding, and real-time hardwarein-the-loop (HIL) testing were used to develop the control algorithms. The cost for the first prototype (including labor and materials) was about $200K.