The mirror changes shape to correct for the effects of temperature and mechanical changes on a space telescope which improves image quality.
The primary mirror of the DeMi telescope is about an inch wide, and the deformable mirror surface is about the size of a dime. The DeMi payload can observe stars with the telescope and use an internal laser for calibration measurements of the deformable mirror. When the payload observes stars, the deformable mirror will keep the star centered on the imaging camera. The MEMS mirror has 140 actuators, tiny moving surfaces that control the mirror shape. Calibration measurements will track the performance using about 50 actuators over time in the space environment.