Phase retrieval implementation and test results for Roman CGI

The Coronagraph Instrument (CGI) on the Roman Space Telescope represents a groundbreaking technology demonstration of advanced coronagraphy in space, enabling the detection and characterization of 10−9 contrast exoplanets in reflected light. Phase retrieval is integral to CGI calibration, supporting deformable mirror registration, wavefront flattening, and high-order wavefront sensing and control. By adapting methods proven in the high-contrast imaging testbed at the Jet Propulsion Laboratory, the CGI phase retrieval process mitigated development risks while meeting stringent performance requirements for repeatability, accuracy, and capture range. Extensive testing using the CGISim model confirmed alignment with these requirements, and successful thermal vacuum testing demonstrated robustness in real hardware scenarios. The phase retrieval algorithm, implemented as a Python package, plays a critical role in enabling CGI’s high-contrast imaging capabilities, marking a significant step forward in coronagraph exoplanet imaging.