  The Wide Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument
(CGI) will be the first high-performance stellar coronagraph using active
wavefront control for deep starlight suppression in space, providing
unprecedented levels of contrast, spatial resolution, and sensitivity for
astronomical observations in the optical. One science case enabled by the CGI
will be taking images and(R~50)spectra of faint interplanetary dust structures
present in the habitable zone of nearby sunlike stars (~10 pc) and within the
snow-line of more distant ones(~20pc), down to dust density levels commensurate
with that of the solar system zodiacal cloud. Reaching contrast levels
below~10-7 for the first time, CGI will cross an important threshold in debris
disks physics, accessing disks with low enough optical depths that their
structure is dominated by transport phenomena than collisions. Hence, CGI
results will be crucial for determining how exozodiacal dust grains are
produced and transported in low-density disks around mature stars.
Additionally, CGI will be able to measure the brightness level and constrain
the degree of asymmetry of exozodiacal clouds around individual nearby sunlike
stars in the optical, at the ~10x solar zodiacal emission level. This
information will be extremely valuable for optimizing the observational
strategy of possible future exo-Earth direct imaging missions, especially those
planning to operate at optical wavelengths, such as Habitable Exoplanet
Observatory (HabEx) and the Large Ultraviolet/Optical/Infrared Surveyor
(LUVOIR).
