Modern Wavefront Control for Space-Based Exoplanet Coronagraph Imaging

Direct imaging of earth-like exoplanets is one of the most timely and important scientific endeavours for future large space telescopes. Typically, an earth-like exoplanet is roughly a billion times dimmer than its host star, so the key for exoplanet imaging is to create extremely high contrast observation regions in the telescope's image plane. One approach to achieving this goal is a cornagraph together with wavefront control, where the coronagraph is used to suppress the diffracted starlight and the wavefront control is used to cancel the wavefront aberrations. In this paper, we present a brief survey of the modern wavefront control techniques for a space-based coronagraph instrument, from the speckle nulling feedback controller to newly developed learning-based controllers. We also describe our implementation of all these controllers on NASA's next large space telescope, the Wide Field Infrared Survey Telescope (WFIRST), to compare their advantages and limitations.