HOWFSC performance modeling and model validations with Roman Coronagraph Instrument

After nearly a decade’s development, the Coronagraph Instrument (CGI) built for NASA’s Nancy Grace Roman Space Telescope (RST) mission has been delivered and is being integrated into the Roman telescope. CGI high order wavefront sensing and control (HOWFSC) modeling has played an important role throughout CGI development phases from flight design, component risk assessment, engineering decision making support, to pre-delivery system requirement verification, anomaly resolution, etc. All these hinges on the model’s credibility. Here we outline the main evolution of our HOWFSC performance model. We start by briefly summarizing past testbed model validation efforts and results and then focus on the more recent modeling results during CGI’s instrument-level thermal vacuum (TVAC) test campaign. We show that our model’s pre-test prediction during TVAC extends the good track record of prediction-versus-measurement agreement on many key contrast performance metrics. In fact, it effectively helped the successful TVAC HOWFSC execution itself. The model verified a critical anomaly discovered during TVAC and provided credible assessment of the anomaly’s in-orbit impact with or without mitigation. And lastly, the model shows a good correlation of the contrast drift observed from a stability test to the deformable mirror (DM) creep effect we have modeled. These results, experience, and lessons learned from CGI HOWFSC modeling efforts should be valuable to both future CGI operation and future missions to further coronagraph technology development where there is urgent need to understand the bottlenecks of testbed raw contrast performance of various promising coronagraph types that are under development or under testing on current testbeds.