Random vibration testing of microelectromechanical deformable mirrors for space-based high-contrast imaging

Abstract

Space-based stellar coronagraph instruments aim to directly image exoplanets that are a fraction of an arcsecond separated from and 10 billion times fainter than their host star. To achieve this, one or more deformable mirrors (DMs) are used in concert with coronagraph masks to control the wavefront and minimize diffracted starlight in a region of the image known as the “dark zone” or “dark hole (DH).” The DMs must have a high number of actuators (50 to 96 across) to allow for DHs that are large enough to image a range of desired exoplanet separations. In addition, the surfaces of the DMs must be controlled at the picometer level to enable the required contrast. Any defect in the mechanical structure of the DMs or electronic system could significantly impact the scientific potential of the mission. Thus NASA’s Exoplanet Exploration Program procured two 50 × 50 microelectromechanical DMs manufactured by Boston Micromachines Corporation to test their robustness to the vibrational environment that the DMs will be exposed to during launch. The DMs were subjected to a battery of functional and high-contrast imaging tests before and after exposure to flight-like random vibrations. The DMs did not show any significant functional nor performance degradation at 10 − 8 contrast levels.