High-order wavefront sensing and control 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 was delivered and integrated into the Roman telescope in 2024. CGI’s high-order wavefront sensing and control (HOWFSC) modeling has played an important role throughout CGI development phases, from flight design, component risk assessment, and engineering decision-making support, to predelivery system requirement verification, anomaly resolution, etc. All these hinge on the credibility of HOWFSC models to predict key performance metrics. We outline the main evolution of the RST CGI HOWFSC performance model. We start by briefly summarizing past testbed model validation efforts and results and then focus on more recent modeling results during CGI’s instrument-level thermal vacuum (TVAC) test campaign. We show that our model’s prediction is consistent and in agreement with CGI’s TVAC performance on many key contrast performance metrics, extending the good model validation track record. The model verified a critical anomaly discovered during TVAC and provided a credible assessment of the anomaly’s on-orbit impact both with and without mitigation. The RST CGI model also shows a good correlation between the contrast drifts observed with the deformable mirror creep-like effect we have modeled. The results, experiences, and lessons learned from CGI HOWFSC modeling efforts are valuable to both future CGI operations and future missions to improve coronagraph technology development where there is a need to understand the bottlenecks of testbed raw contrast performance of various promising coronagraph types that are under development or testing.