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The AFTA coronagraph instrument

The Astrophysics Focused Telescope Assets (AFTA) study in 2012-2013 included a high-contrast stellar coronagraph to complement the wide-field infrared survey (WFIRST) instrument. The idea of flying a coronagraph on this telescope was met with some skepticism because the AFTA pupil has a large central obscuration with six secondary mirror struts that impact the coronagraph sensitivity. However, several promising coronagraph concepts have emerged, and a corresponding initial instrument design has been completed. Requirements on the design include observations centered 0.6 deg off-axis, on-orbit robotic serviceability, operation in a geosynchronous orbit, and room-temperature operation (driven by the coronagraph’s deformable mirrors). We describe the instrument performance requirements, the optical design, an observational scenario, and integration times for typical detection and characterization observations.