Roman Coronagraph HOWFSC Modeling: Case Study and Raw Contrast Performance Predictions

NASA’s Nancy Grace Roman Space Telescope (RST) mission includes a coronagraph instrument (CGI) to demonstrate space coronagraph with active wavefront sensing and control (WFSC) for future direct imaging of exoplanets mission needs. CGI is entering Integration & Testing phase and is scheduled to be delivered early next year for integration with Roman observatory. Key flight components, such as deformable mirror (DMs) and detectors, have been recently characterized and integrated into the CGI optical system. A series of system level coronagraph requirement verifications in vacuum chamber will take place later this year. Among them is the static raw contrast with a coronagraph stimulus source (CVS). This is the only time CGI will have opportunity for dark hole digging before in-orbit commission (IOC). CGI high order wavefront sensing and control (HOWFSC) modeling has played an important role in assisting many engineering decisions and risk assessment throughout the project phases, including decisions involving these key components when unexpected risks emerged, such as dead actuators, coupled actuator gain, large DM defocus and astigmatism, DM creep, detector smear at low exposure time, detector nonlinearity at high gain, etc. Here we present selected modeling studies involving some of these issues and risks and update our current-best-estimate on static raw contrast for the upcoming performance verification. Contrast performance for IOC phase WFSC with a typical reference star and its brightness is also given. All evaluations are performed with full features of HOWFSC modeling practice (including probing and sensing with flight detector properties and usages).