As a space power, China hasn't launched a large-size mission driven by scientific objectives yet. For a case study, the paper investigates the development of NASA's next-generation astrophysics mission-wide field infrared survey telescope (WFISRT), a flagship/large-size mission. Despite that WFIRST has been confronted with cancellation in NASA FY budgets during the past few years, the project passed a critical programmatic and technical milestone in March 2020, and was given the official green light to begin hardware development and testing (Phase C). In the following May, NASA renamed the telescope after Nancy Grace Roman, i.e., Nancy Grace Roman Space Telescope, which shows the mission's strong vitality. Roman Space Telescope aims to conduct dark energy research, exoplanet search and near-infrared survey, while demonstrating the coronagraph's technology for direct imaging of Earth-like exoplanets. WFIRST fits for the NASA's Vision and Mission, and will strengthen US leadership in space science, and its development somehow provides lessons learned about flagship missions.

space telescope  /  dark energy  /  exoplanet  /  coronagraph  /  flagship science mission