Segment phasing for giant telescopes using Moving Horizon Estimation

Real-time segment phasing is non-trivial in giant segmented mirror telescopes, as slope-based wavefront sensing methods are blind to segment piston if the gaps between segments are sufficiently large. In the GMT, this is certainly the case, and many solutions have been proposed which require additional wavefront sensing hardware and added optomechanical complexity. We propose a novel sequential phase-diversity method which requires only a time-sequence of closed-loop tip-tilt wavefront sensor images.